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DIGITAL PROJECT

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RESOURCE BANK DIGITAL BOOK

N O I T A C U D E Y R A D EC O N

Y G O BIOL O GY L O E G D N A g . Domín A , e t n e S. Clem A. B. Ruiz

uez,

Building

Blocks

this is

your book

ch unit

f ea The opening pages o

Reading and listening We listen to and read about the contributions of women in the development of the sciences, and discover some of the difficulties they had to overcome.

to study a Leakey was able school meant could achieve Leaving convent As a result, she her truly happy. subject that made incredible things. to do in her Leakey was able talk about what 3 With a partner onal life. personal and professi

Leakey travelled a lot as a child, so she could…

ering history. Mary Leakey. Uncov the Cro-Magnon

Writing

Yes, and because she was a skilled artist, she was able to…

site called s is a fascinating human skeleton In France there five 30,000-year-old sparked rock shelter where I was 11 and it I visited it when were discovered. ric man. As a my interest in prehisto in London in 1913. Leakey. I was born who was a My name is Mary with my father, around Europe But res. travelled I adventu child d was full of inspiring I hated it painter. My childhoo convent school. I was sent to a when Dad died, in trouble. there and was always University archaeology at left, I studied it off When I finally Leakey. We hit There, I met Louis year he had College London. in 1936. That same marrying up a new and ended . I was happy for a dig in Tanzania a huge project, packed my bags! adventure, so I kept the dig running and there team the I coordinated the discoveries, like some important the smoothly. We made ancestral ape; and ul africanus, a rare we skull of Procons opus boisei, which hominid, Paranthr remains of a new his strong jaw. Man’ because of called ‘Nutcracker my work, so I carried I couldn’t give up Louis died in 1972. In the Laetoli desert, find. le an incredib hominids on. Then I made d footprints of bipedal fossilise be the to ed we uncover It was amazing million years ago. from about 3.6 n. steps of our evolutio staring at the first the the questions on again and answer 1 Read the text context? language used. in this and why is it used a) What is a ‘spark’ verbs can be verbs. What other b) Find two phrasal used instead? on to school but went do well at convent 2 Leakey didn’t field. What lessons ive career in another have an impress this? from away can we take

Writing

Education. Goal 4: Quality e to run, on are expensiv ones Leakey worked a result, Projects like the immediately. As generate money and normally don’t research. obstacles in their ed a scientists face many that has announc read a news article cancelled You have just projects have been research to the number of scientific a persuasive letter cut of funding. Write they must not because of lack why g n explainin Minister of Educatio . projects the funding for ion on: Include informat nt. like these are importa ➜ Why projects to learn from them. ➜ What we are able lead to in the future. ➜ What they can you develop 4 goals to help individual SDG Read through the your ideas.

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CONTENT DEVELOPMENT

Create In this section we create a cross-curricular project that joins Biology and Geology with other subjects.

Unit 4

Understand, think, search...

5.2 Our ancestors

5.1 The hominisation process

pelvis 4 million years ago. They were short (1.3 metres tall) but their and and limbs show that they stood and walked upright. Their skull jaws brain were small, and they had a prominent nose and large which helped them to eat fruit, seeds and roots.

➜ Homo habilis. The humanisation process began with this species.

us different to other primates.

crude, They were able to manufacture tools which, whilst African demonstrated conceptual thinking. They lived in the around savannah between 2.3 and 1.6 million years ago. They were and 1.5 metres tall and their cranial capacity was now between 600

Characteristics of hominids 1 Bipedalism or standing upright implied

800 cm3.

anatomical changes. The spine took on an S shape; the pelvis became wider and shorter; the femur became more robust and leaned inwards, and the bones in the feet adapted in order to provide balance and to

➜ Homo erectus. They appeared 1.6 million years ago and continued

and to exist until around 100 000 years ago. They lived in both cold cranial warm climates. They were taller (1.7 metres tall) and had a 3 more capacity of up to 1 100 cm . They could make fire and had

support body weight.

the ➜ Homo antecessor. These were the ancestors of both

helped detect prey and predators.

2 An increase in cranium size and an increase

in the volume and complexity of the brain (encephalisation) especially at the front, allowed intelligent thinking. The human brain is seven times larger than that of other mammals of a similar size.

3 Development of language. Anatomical traits

developed that permitted the articulation of a wide variety of complex sounds, as well as the association of these sounds to objects and thoughts.

TODAY’S 4 Neoteny. We are born in an immature state of development, particularly in terms of the EVOLUTIONARY THEORIES brain, because the pelvis is narrow. We are dependent for a long period of time.

An example of Neo-Darwinism 1st generation

Understand, think, search… 1 Spain is home to one of the most important

archaeological sites in Europe for studying different species of hominids and their habits: Atapuerca. Do some research into Atapuerca. Name the species of hominids found there, and describe at least one important discovery related to the habits of one of the species.

of bipedalism for 2 What were the advantages Aa hominids?

AA of an opposable thumb was The presence aa another great evolutionary advantage. Find out is and why it was useful. what this trait Aa Aa aa

4 What do you think were the advantages of language acquisition and development for the first hominids? AA

2nd ‘Atapuerca’ anayaeducacion.es Go to generation in your resource bank.

102

Working with pictures

Neo-Darwinism tackled* these matters successfully.

3.1 Neo-Darwinism Neo-Darwinism, also known as the synthetic theory, is a revised version of the theory of natural selection and is based on the following:

➜ The evolutionary unit is not the individual, but the population itself. There are variations in genotypes in the population and these are represented by the frequencies of the different alleles in each gene.

and recombination processes that take place during sexual reproduction.

AA AA

➜ Natural selection acts on genetic variability. As

Develop your abilities to observe and interpret pictures.

in Neanderthals and modern humans. The remains uncovered lived Atapuerca, Burgos, are 850 000 years old and show that they in temperate climates. They were hunters and cannibals. had ➜ Homo neanderthalensis. They appeared 166 000 years ago. They a very strong body and significant cranial capacity. They were hunters, years used tools and buried their dead. They became extinct 28 000 they ago and did not leave descendants. There are indications that lived alongside Homo sapiens but the latter ended up overtaking them since they were better adapted to the environment. in ➜ Homo sapiens. They appeared around 200 000 years ago skull Africa and moved from there to all the other continents. Their have all modern traits. They used to live in caves. and skeleton Darwin’s theory of natural selection provided no ability to think that they left in them indicates their The artwork explanation for how characteristics were passed on a result of the complexity of their brains. abstractly, from one generation to the next nor what the origin of thestages variability hominisation individuals in a population of between The was. There was insufficient understanding Homo in order Homo Homo Australopithecus to explain the inheritancehabilis antecessor of characteristics, erectusso a afarensis new or revised theory needed to be formed.

➜ This genetic variability is the result of mutations

such, those individuals that are best adapted have a greater chance of surviving and transmitting their genetic traits to offspring.

AA Aa

Understand, think, search…

elaborate tools.

Bipedalism provided several advantages, such as freeing the hands to pick up and transport objects. Being able to see from higher up also

Gorilla skeleton

C REATE Cave paintings were the earliest artform which have been studied in order to understand the life of prehistoric man. Make a cave painting that could be used to help others understand what life is like for the most modern human that has ever existed, you.

➜ Australopithecus. They lived in small groups in the savannah

specific Hominisation led to the acquisition of a number of The characteristics that differenciate us from our primate relatives. that make following picture also includes some of the characteristics

Human skeleton

History and Visual Arts

Fossils tell us that our earliest ancestors belong to the Australopithecus included genus. They were followed by the Homo genus, which The different species. Only one of these is a direct ancestor of humans. others disappeared and do not have any modern-day descendants.

referred Human beings (Homo sapiens) are classified in the group Whilst to as hominids; we are the only living species in that group. to the it remains unclear, our earliest ancestor is thought to belong of other Australopithecus genus. Thanks to the discovery of fossils hominid species, it has been possible to reconstruct the phylogenetic history of modern humans.

Activities that expand on the contents and inspire curiosity about scientific investigation.

We write a variety of different styles and types of text about a subject matter in the unit. By practising different styles of writing, we will improve the writing skills we need to do well in our studies.

about the experiences. Talk your own past you were 4 Now think about younger, and what when you were things you did you do today? result. What can able to do as a

HUMAN EVOLUTION

We speak about the different issues that will be learnt about throughout the unit.

Speaking

The originS of life and evolution

The audios of each unit’s content are available at www.anayaeducacion.es

Speaking

➜ Changes will gradually take place in the population as a result of this natural selection process. These will eventually give rise* to the creation of a new species.

3rd generation

5 Explain the difference between Austhralopithecus erectus.

and

Homo

The Prediction. Imagine it is 250 000 years in the future. Through a process of speciation, a new species of hominid has appeared. Explain the process and describe the traits that make the new species different from Homo sapiens. See the resource on anayaeducacion.es to learn how to Neutralism use this thinking technique.

Unit 4

Motoo Kimura proposed this theory in 1968. It suggests that most mutations are neutral. Whether they remain or are eliminated from a population’s genetic Homo Homo makeup is down to a question sapiens of chance. When genes persist neanderthalensis and are inherited, phenotypic variations can develop. Under certain isolated conditions, they can lead to new species.

F ocus on English Tackle – to deal with a difficult problem, (in sports) to take the ball away from someone Give rise – to be the reason why something happens

The main evolutionary mechanism would be genetic drift. In other words, dramatic changes in populations that affect a population’s genetic variability both randomly and rapidly.

Schools of thought – a specific opinion or way of thinking that a group of people share on a subject matter

3.3 Speciation The most common speciation model, as proposed by Darwin, is speciation as a result of geographical isolation. According to this model, speciation takes place in the following stages:

➜ The population becomes geographically 103 isolated due to a natural barrier such as the sea, a mountain or a desert. This impedes reproduction with individuals from other populations of the same species.

➜ Gradual genetic changes appear in the population over time; the population is acted on by the specific environmental conditions in its surroudings.

➜ The new species appears when all these changes mean that reproduction is no longer possible with the original species.

Speciation is the evolutionary process through which new species are generated from a population of a particular species.

Understand, think, search… 1 Explain what Neo-Darwinism contributes to Darwin’s theory of evolution.

2 Is the theory of punctuated equilibrium compatible with Neo-Darwinism or not? Explain your answer.

Ideas pool. Choose an animal species and invent a speciation process that results in two different species. Describe the traits that differentiate the two species, and give each species a name.

AA AA

AA AA AA

AA AA

Working with pictures A gene determines wing colour in this population of moths. Allele A gives the moth dark wings, and allele a gives it light wings. The individuals with dark wings are better camouflaged and less visible to predators than those with white wings. What do you think has happened to the population in the illustration? Use an example to explain how an environmental change could cause the frequency of individuals with white wings to increase.

The icons included with some activities indicate the keys to the project.

3.2 Other evolutionary theories Neo-Darwinism provides an explanation for the mechanisms of evolution that is widely accepted by most scientists. However, in recent years, several schools of thought* have made slight changes to it or criticised its proposals.

An example of speciation 1

Focus on English Do you think Biology and Geology and English have anything in common? Discover how language, biology and geology are linked so you can learn them together.

1 Hills do not stop the living beings from one side and the other coming together and reproducing. They are individuals of the same species.

Punctuated equilibrium This theory, which was proposed by Gould and Eldredge in 1972, suggests that there are specific periods of intense speciation. These follow significant events such as geological disasters and cause an imbalance in the normal natural selection adaptation process. In other words, it suggests that the evolutionary process can jump forward. anayaeducacion.es Go to ‘The relationship between genetics and evolution’ in your resource bank.

2 When the natural barrier is larger, populations become isolated. Over time, they evolve separately and become two different species.

anayaeducacion.es Go to ‘Was Lamarck right about epigenetics and evolution?’ and ‘Speciation’ in your resource bank.

Visual aids to support your understanding of the contents.

KEY

PROJECT

SDG SDG Commitment Discover the Sustainable Development Goals and be an active part of our commitment to make a more equal and liveable world.

Developing thinking Work on strategies for thinking: reflect on the content you are learning, generate ideas, organise them, debate them, explain them…

Cooperative learning Get involved in your learning and participate in the group’s learning; you will find that cooperating improves performance and harmony in the class.

Emotional education Get to know yourself; identify the situations that bring up complicated emotions and manage them with constructive, self-affirming experiences.

Research Project This book contains three research projects.

glossary We learn a clear definition of the relevant terms within the unit.

They are divided into steps that you will find at the end of each unit.

Unit 1

ect

research proj

Glossary

Researching the transmission of hereditary traits PROJECT INTRODUCTION Problems human with studyingics: genet

variation in • Huge genetic humans. many polygenic • There are ted by several traits (regula genes) between offspring. • A long time and few generations traits, such as • Interesting es, are expressed diseas rare infrequently.

UNIT 4

Living beings transfer their traits to their offspring through DNA, their genetic material. A gene is a fragment of DNA that contains the information required for a specific biological trait to manifest. Genetics is the part of biology that studies how these genes are transferred during the reproduction process.

step 1

In order to study the transmission of human genetic traits, we create pedigree charts, which are graphic representations of the inheritance of a family trait. These charts represent each individual with a symbol, which is usually a circle for a woman, or a square for a man.

Adaptation Living beings ability to change to suit the environment in which they live

Organising your work

Allopatric speciation Speciation that takes place when a population is geographically seperated from the rest of the species and develops in isolation

Your teacher will put you in groups of 3 or 4. In your groups, discuss the project and the biological traits you are going to study (each group should choose four traits to investigate), the methodology you are going to use and the steps to follow to carry out the project. Divide the work between the team members.

These individuals are linked with lines to indicate the family relationships. The members of the pedigree chart are organised into rows that represent the different generations. Individuals are identified by two numbers: a Roman numeral that shows the generation, and an Arabic numeral that distinguishes between the individuals in the same generation. Individuals that have the trait being studied are coloured in.

Straight hairline

B Biogeography Scientific discipline which studies the distribution of animals and plants

Searching for information and analysis

Bipedalism The ability of some animals to walk upright

There are some monogenic human traits that are easy to identify and which you can study in this project. They include:

F Fossil Remains of an organism or its biological activity that have been preserved in sedimentary rocks

• Straight hairline or widow’s peak. 1

• Tongue rolling.

• Direction of hair whorl.

PROJECT STEPS

N Natural selection Evolutionary mechanism proposed by Darwin, which states that individuals that are favourably adapted to their environment are more likely to survive and reproduce

• Bent little finger.

III

PROJECT OBJECTIVE

P Palaeontology The scientific study of living beings that inhabited the planet in the past and whose remains are, for the most part, fossils

Mutation Any genetic change which affects a trait

Neo-darwinism A development of the theory of natural selection which includes evidence from scientific advances in the fields of genetics and molecular biology in order to explain the evolutionary process. This theory is also known as the synthetic theory of evolution

• Earlobe shape. II

M Mass extinction Events in which, as a result of natural catastrophes, numerous species disappear globally in a relatively short period of time

Evolution Living beings change and adapt progressively in response to the environment. Evolution leads to the appearance of distinct species from a shared ancestor

Biodiveristy All the species which inhabit an ecosystem

Before starting work, share your ideas with the class. It will be more interesting if your class studies a number of traits, but also if each trait is studied by more than one group, so that you can compare the results.

Widow’s peak

I 1

Organising your work and searching for information

Endosymbiotic theory Theory that hypothesises that eukaryotic cells originate from a series of symbiotic processes between prokaryotic organisms. Mitochondria, for example, would have developed from a symbiotic relationship between a larger amoeboid prokaryote and an aerobic bacteria introduced into its cytoplasm

Dimples in cheeks

In this research project, you are going to study some human traits that are controlled by a single, easily-identifiable gene. You are going to collect data about these traits and create family trees. These will tell you how the trait you are studying has been transmitted in the family. You can study your own family or any other. You will need to prepare a presentation to present the results of your research to your class.

• Relative length of index finger.

No dimples in cheeks

• Dimples in cheeks.

presentations so that you can recognise them in your study.

➜ Gather information about the human genome and how it is found in cells. Remember that all human cells, except gametes, contain two sets of 23 chromosomes, one set from the father, and another from the mother.

information you need for your study.

➜ Step 2 (in unit 2). Proposing the hypothesis for the study, doing the

Free earlobes

research and collecting experimental data.

Human skeleton

Catastrophism Fixist theory which states that some species disappear following big catastrophes and are replaced by new species through divine intervention

They can be dominant (they always manifest when they are present in one of the two chromosomes), or recessive (they only manifest if they are present in both chromosomes – maternal and paternal).

➜ Step 3 (in unit 3). Analysing and interpreting the results, drawing conclusions and presenting your study in a presentation. 42

Gorilla skeleton

➜ Lastly, investigate how the genetic traits manifest in individuals.

Attached earlobes

Punctuated equilibrium Evolutionary theory that hypothesises that there are specific periods of intense speciation which can interrumpt the normal processes of adaption through natural sollection. They suggest that the evolutionary process takes place through big jumps forward

Recombination The process that occurs during meiosis which produces the random crossing and segregation of genetic material between homologous chromosomes

• Hair on the second phalanges of the fingers.

➜ Step 1 (in this unit). Organising your work and searching for the

Population A group of organisms of the same species that live the same geographical area at the same times

• Dimple in chin.

➜ Look for information about these traits and their phenotypical

The suggested stages or steps for this project are:

Phylogenetic sequences Groups of fossils which can be ordered by age and show the gradual changes of a particular characteristic

G Genetic drift Sudden changes experienced by populations that randomly and rapidly affect their genetic variability

Nuetralism Evolutionary theory which proposes that the majority of mutations are neutral. As long as these mutations don’t affect the ability to reproduce successfully, they are inherited randomly. In this theory, genetic drift is the main evolutionary mechanism

Specie Population of similar individuals which can reproduce together and have fertile offspring Spontaneous generation An ancient belief that organisms could come from inert matter

232

233

REVIEW AND PRACTISE Applying your knowledge to choose Remember o. your portfoli

this resources from

Pictures to practice analysing images.

unit for

Unit 2

TISE

review and PRAC

Organising your ideas 1

Attribute wheel. In your notebook, copy and complete the following chart on the DNA molecule. Visit anayaeducacion.es to learn how to use this graphic organiser. Formed by two chains of nucleotides twisted ? into a

Visual organisers to help you remember the content.

Base nitrogenada

Grupo fostato

Each nucleotide

? is made up of ? and ?

questions:

• • •

to DNA or RNA molecules? Explain your answers.

? ? ? ?

? ?

Thymine bonds with

and cytosine bonds with

The chains are It is the base for the

Summarising 2 Use these guidelines to create your own summary of the unit.

• Explain the composition and structure of DNA. • Name the different types of RNA and list their functions.

b) Using the genetic code, translate it into a sequence of amino acids.

following DNA sequence: ATA CCG CAC CCC ATG TCG AT.

11 Explain whether a prokaryotic cell can undergo mitosis? What about meiosis?

a) What types of nucleic acid do they show? b) How are these two biomolecules similar? How are they different? c) What function(s) do they perform in cells?

4 What process is taking place in the picture below? Which molecules are involved? Explain it step by step.

the prophase of mitosis.

13 What type of division will a human hepatic (liver) cell undergo? How many chromosomes will the mother cell have? And the daughter cell?

14 Explain what spermatogenesis is. Where does it take place? meiosis:

involved in the process.

MITOSIS

MEIOSIS

Type of cells it takes place in

are involved in it.

• Explain what the genetic code is and what it is for. • Give a short explanation of the different phases of the cell cycle.

• Explain step by step how DNA replication takes place.

• Indicate the main events of each of the phases of mitosis.

• Explain the biological significance of mitosis. • Establish the difference between cytokinesis in plant and animal cells.

• Define meiosis and explain its biological significance. • Describe the main events of each of the phases anayaeducacion.es Go to the science workshop ‘Observing mitosis’ in your resource bank.

Sustainable Development Goals 17 The genes that regulate the cell cycle are affected by mutagenic agents resulting from contamination, and this can cause cancer. Target 3.9 of the sustainable development goals aims to reduce the number of deaths and diseases caused by harmful chemical products, and air, water and soil pollution. Although all politicians agree on this goal, they have difficulty agreeing on how to achieve it. This is because the economic interests of energy, transport and tourism companies are involved. a) Find out which three European cities have imposed traffic restrictions to reduce pollution and compare their regulations. What do you think about this? Who is opposed to it?

No. of divisions

No. of daughter cells

No. of chromosomes in the daughter cells.

b) Should air travel be restricted and other types of transport, such as trains, be promoted? What negative effects would this measure have?

Is there genetic recombination?

c) Find out whether cars with petrol or diesel engines pollute more. Do electric cars cause pollution?

of meiosis. 62

Trust in your skills and knowledge, develop creativity, adapt to changing situations and have a proactive and responsible attitude.

5 In this diagram you can see a cell in anaphase. Look at the chromosomes and explain whether it is in mitotic anaphase, meiotic anaphase I or meiotic anaphase II. Explain your answer.

Using the scale, calculate the magnification used to take the photo. What type of microscope was used to observe the image?

12 Explain why prophase I of meiosis is longer than

15 Complete the following chart about mitosis and

• Define translation and name the molecules that

Enterprising culture

10 μm

a) Transcribe it into a complementary mRNA molecule.

9 Explain why DNA replication is semiconservative. 10 Write the complementary chain or strand for the

• Define transcription and name the molecules

Questions about the essential parts of the unit so that you can write your own summary.

below. Which phases of mitosis are they in?

8 Look at this DNA sequence:

Nitrogenous bases

and

16 Look closely at the tissue cells in the micrograph

a) ACCGGAUCUAGAUCGAUC

TACCCCACTGAGATC

Nitrogenous bases are located

6 Draw a nucleotide and explain the difference 7 Do the following chains of nucleotides correspond

B G

b) ACTTAGGCAATCGACGGAT

DNA MOLECULES

do not join

Moving forward

between DNA nucleotides and RNA nucleotides. A C

Azúcar: ribosa o desoxiribosa

•

3 Look at the following diagrams and answer the

, There are four types of nitrogenous bases

Both chains are joined

Applying your knowledge

Interpreting pictures

anayaeducacion.es Go to ‘Key concepts’ and ‘Learn by playing’ in your resource bank.

d) Some regions charge a tourist tax. How could this be invested to reduce pollution?

SDG. Reflect and suggest actions that could help achieve the goal mentioned in each unit.

Academic and professional

ICT

orientation

Assessment

Linguistic Plan

Learn how to obtain information, select it and apply it; to plan, manage and work on projects; and to collaborate online in an ethical and safe manner.

Evaluate your personal skills, discover and awaken your calling, train yourself to make decisions and learn to choose between different options.

Discover different strategies to analyse what you have learnt and how you learnt it; train yourself to take responsibility or overcome difficulties.

Use your communication skills in the different types of text that you will see. Language is always present, communicate!

Resource

Bank

Register at www.anayaeducacion.es to access your resource bank or download your digital book. You just need an email address, the code from the inside cover this book and permission from your parent or legal guardian.

www.anayaeducacion.es

Digital Book Resource bank

A digital version of your book to be used online or offline. It offers access to your digital resources which are grouped by type or linked to unit content.

A space with resources, techniques and activities, designed to strengthen your knowledge. More about the keys

Resources related to THE project keys ODS

SDG Commitment with short videos that will help you understand the targets for reaching the Sustainable Development Goals worked on in this project. Linguistic Plan with infographics that will give you models to work with the four linguistic skills, using different text types (descriptive, narrative, explanatory, etc.).

Developing thinking with explanations on how to apply the different thinking techniques proposed in the project.

Cooperative learning which includes descriptions of the cooperative learning techniques proposed in the project. Emotional education with resources to help you overcome any worries that may arise in different situations at school (beginning the school year, taking a test, etc.). ICT resources to help you use information and communication technology in a healthy, correct and safe way.

Academic and professional orientation with information on different professions linked to the subject content.

0:40/1:33

Assessment which includes resources for your portfolio, as well as rubrics and targets that will help with your self-assessment.

Resources

Subject key concepts What you need to know Scientific texts Science workshops Key concepts Learn by playing

0:40/1:33

Resources classified

by unit

All the resources are classified by unit so that you can find them more easily.

0:40/1:33

Course Contents The Scientific method

Page 8

1. Science and the scientific method ................................ 10 2. Laboratory research ........................................................... 14 3. Scientific fieldwork .............................................................. 18 4. Searching for information ................................................ 22 Review and practise ............................................................... 24

Biological inheritance

Page 64

1. From traits to genes ........................................................... 66 2. Mendel’s experiments ........................................................ 68 3. Mendel’s laws ........................................................................ 70 4. Exceptions to Mendel’s laws ............................................ 74 5. Mutations ................................................................................. 77 6. Genetic engineering techniques .................................... 78 7. Applications of genetic engineering ............................ 82 Research project STEP 3 Researching the transmission of hereditary traits ............................................................................................... 84 Review and practise ............................................................... 86

Cells: the building blocks of life

Page 26

1. The composition of living matter .................................. 28 2. Cells ........................................................................................... 30 3. Prokaryotic cells ................................................................... 32 4. Eukaryotic cells ..................................................................... 34 5. The nutrition function in eukaryotic cells ................... 38 6. The interaction function in eukaryotic cells .............. 40 7. The reproduction function in eukaryotic cells .......... 41 Research project STEP 1 Researching the transmission of hereditary traits........ 42

The origin of life and evolution

Page 88

1. The origin of biodiversity ............................................... 90 2. Early theories about the origin of biodiversity ...... 92 3. Today’s evolutionary theories ....................................... 96 4. Proof of evolution .............................................................. 98 5. Human evolution ................................................................ 102 6. Hypotheses on the origin of life .................................. 104 Research project STEP 1 Investigating proboscideans ............................................... 108 Review and practise ............................................................. 110

Review and practise ............................................................... 44

Genetic information

Page 46

1. Nucleic acids ......................................................................... 4 8 2. Gene expression. Protein synthesis .............................. 5 0 3. The transmission of genetic information .................... 52 4. Mitosis and cytokinesis ...................................................... 5 4 5. Meiosis and sexual reproduction ................................... 5 6 Research project STEP 2 Researching the transmission of hereditary traits ............................................................................................... 6 0 Review and practise ............................................................... 62

The Earth’s interior and its dynamics

Page 112

1. The composition and structure of the Earth’s interior .................................................................... 114 2. The Earth’s dynamics ....................................................... 116 3. The theory of plate tectonics ....................................... 122 4. The consequences of lithospheric dynamics .......... 126 5. The evolution of the Earth’s relief ............................... 130 6. How we study the relief: topographic maps and profiles .......................................................................... 134 Research project STEP 2 Investigating proboscideans ............................................... 136 Review and practise .............................................................. 138

The history of the Earth

Page 140

1. Recording the Earth’s history ........................................ 1 42 2. Dating the Earth’s historical records ........................... 1 46 3. Geological time: a history of changes ........................ 1 50 Research project STEP 3 Investigating proboscideans ............................................... 1 56 Review and practise ............................................................... 158

Ecosystem dynamics

Page 178

1. Trophic levels ........................................................................ 180 2. The circulation of matter and energy in an ecosystem ................................................................... 182 3. Food chains and food webs ........................................... 184 4. Trophic parameters and ecological pyramids ......... 186 5. Biogeochemical cycles ..................................................... 188 6. Ecological succession ...................................................... 192 7. Ecosystems are self-regulating ..................................... 194 Research project STEP 2 Investigating the waste that we produce ....................... 196 Review and practise .............................................................. 198

The ecosystem and its components

Page 160

1. The ecosystem and environmental factors ............... 162 2. Abiotic factors and adaptations ................................... 164 3. Biotic factors: populations .............................................. 168 4. Biotic factors: relationships ............................................ 170 Research project STEP 1 Investigating the waste that we produce ....................... 174 Review and practise .............................................................. 176

Human beings and the environment

Page 200

1. The environment and its situation today ................. 2. The sustainable management of biosphere resources .............................................................................. 3. Sustainable water management ................................. 4. Sustainable energy management ............................... 5. Sustainable waste management .................................

202 206 210 212 218

Research project STEP 3 Investigating the waste that we produce ..................... 220 Review and practise ............................................................ 222

Andalusian content Tectonic plates in Andalucía Natural resources in Andalucía Conservation in Andalucía

Glossary

232

The origin of life and evolution Mary Leakey. Uncovering history. In France there is a fascinating site called the Cro-Magnon rock shelter where five 30,000-year-old human skeletons were discovered. I visited it when I was 11 and it sparked my interest in prehistoric man. My name is Mary Leakey. I was born in London in 1913. As a child I travelled around Europe with my father, who was a painter. My childhood was full of inspiring adventures. But when Dad died, I was sent to a convent school. I hated it there and was always in trouble. When I finally left, I studied archaeology at University College London. There, I met Louis Leakey. We hit it off and ended up marrying in 1936. That same year he had a huge project, a dig in Tanzania. I was happy for a new adventure, so I packed my bags! I coordinated the team there and kept the dig running smoothly. We made some important discoveries, like the skull of Proconsul africanus, a rare ancestral ape; and the remains of a new hominid, Paranthropus boisei, which we called ‘Nutcracker Man’ because of his strong jaw. Louis died in 1972. I couldn’t give up my work, so I carried on. Then I made an incredible find. In the Laetoli desert, we uncovered the fossilised footprints of bipedal hominids from about 3.6 million years ago. It was amazing to be staring at the first steps of our evolution.

1 Read the text again and answer the questions on the language used. a) What is a ‘spark’ and why is it used in this context? b) Find two phrasal verbs. What other verbs can be used instead?

2 Leakey didn’t do well at convent school but went on to have an impressive career in another field. What lessons can we take away from this?

Speaking Leaving convent school meant Leakey was able to study a subject that made her truly happy. As a result, she could achieve incredible things.

3 With a partner talk about what Leakey was able to do in her personal and professional life.

Leakey travelled a lot as a child, so she could….

Yes, and because she was a skilled artist, she was able to… 4 Now think about your own past experiences. Talk about the things you did when you were younger, and what you were able to do as a result. What can you do today?

Writing

Goal 4: Quality Education.

Projects like the ones Leakey worked on are expensive to run, and normally don’t generate money immediately. As a result, scientists face many obstacles in their research. You have just read a news article that has announced a number of scientific research projects have been cancelled because of lack of funding. Write a persuasive letter to the Minister of Education explaining why they must not cut funding for the projects. Include information on

➜ Why projects like these are important. ➜ What we are able to learn from them. ➜ What they can lead to in the future.

NK E BANK A B E G A ANGU LANGUAG L ANK ANK GE BANK B B E E G G A A U U GUA K LANG ANG N L A L AN GE BANK 91 ANK GE BANK B B E E G G A A U U G A LAN LANG LANGUA LANGU Read through the individual SDG 4 goals to help you develop your ideas.

1 THE ORIGIN OF BIODIVERSITY

Biodiversity or biological diversity is the variety of species that inhabit or have ever inhabited the Earth. Biodiversity is one of Earth’s greatest gifts. It provides us with resources and is essential to the planet’s stability.

1.1 Biodiversity and adaptation Living beings inhabit all Earth’s known environments. Those that live on land do so in all regions from the coldest to the most arid, whilst aquatic living beings inhabit both seawater and freshwater environments. Species have survived in each of these habitats due to their ability to adapt to them.

Adaptation is the accumulation of changes in living beings in order to suit the environment in which they live. The three main types of adaptations are structural, physiological and behavioural adaptations.

Structural adaptations Structural adaptations are those that affect certain organs in a living being’s body and that allow them to do specific things. For example, birds feed using their beaks, and the shape of their beaks is suited to the way in which they eat: splitting seeds, getting insects out of holes, filtering tiny organisms from water, etc.

Physiological adaptations Physiological adaptations affect the function of an organism. For example, the metabolism of dromedaries turns accumulated fat in their hump into water.

Behavioural adaptations Behavioural adaptations are actions that organisms carry out and which provide them with some sort of advantage. For example, some birds migrate in the winter in order to avoid low temperatures; others use a courtship dance in order to attract females and reproduce.

Understand, think, search… 1 What is an adaptation? 2 Antarctica has one of the most extreme climates on the planet. However, many animals live there. Think carefully and write down at least five adaptations to the cold.

I think, I’m interested, I investigate. Choose an animal and give a detailed description of a structural, a physiological and a behavioural adaptation for it. Learn how to use this thinking technique on anayaeducacion.es.

Unit 4

1.2 Biodiversity and evolution The adaptations to conditions in the environment that occur in living beings take place slowly over millions of years. During this process, species evolve. That is, they change and turn into other new species that are better adapted to the environment in which they live.

The slow and gradual changes that have taken place in living beings over millions of years is called biological evolution. As we will see in this unit, theories that aim to explain the origin of biodiversity have been put forward throughout history. They range from those based on religious beliefs to those that include genetic variability as an explanation for the process of evolution. Studying evolution has taught us that:

➜ The Earth’s huge biodiversity exists as a result of evolution from a common universal past. ➜ Species originate from others and, as such, those that live on Earth today are different to those that lived on Earth in the past.

Working with pictures In the picture you can see a tree with some of the main groups of living beings and their evolutionary relationships. In which position are the kingdoms that contain the organisms with the simplest structure? Is the same true of organisms in the same kingdom? Why do you think they are organised this way?

Angiosperms Mushroom-forming fungus

Mosses

Reptiles Echinoderms Molluscs Cnidaria Arthropods

PLANTS Gymnosperms

Yeasts

Annelids

Moss

Nematodes

FUNGI Flatworms

ANIMALS

Ferns Porifera

Algae MONERA PROTOCTISTA

Protozoa Common ancestor

anayaeducacion.es Go to ‘Phylogenetic trees’ in your resource bank.

2 EARLY THEORIES ABOUT THE ORIGIN OF BIODIVERSITY George Cuvier

People used to believe that species maintained the same characteristics they had when they were created. Later, when it was discovered that some species had become extinct, and thanks to the scientific revolution in the 18th century, early theories on the origin of species were put forward. In the 19th century, naturalists were divided into two lines of thought*:

➜ Those such as Linnaeus and Cuvier who believed that all organisms existed from the very beginning of time (fixist theories);

➜ And those such as Lamarck and Darwin who believed that organisms evolved. In other words, they changed as time went by (evolutionary theories).

2.1 Fixist theories Fixist theories upheld* that species could not change in any way and had been created in order to occupy a specific place in nature. Influenced by the Church, many believed that all species had existed from the very beginning of time as a result of divine creation (they were the so-called creationists).

George Cuvier is thought of as the founding father of comparative anatomy and palaeontology. He was also able to reconstruct previously unknown fossilised species from just a few fragments of bones. He used the theory of catastrophism to explain why some of them disappeared. According to Cuvier, species had not changed since the Creation.

However, some palaeontologists realised that certain species had become extinct and that others had appeared later on in time. They then had to propose new lines of thought in order to explain what they had discovered. They proved that organisms changed over time and this is how the first evolutionary theories appeared. However, George Cuvier, who is considered the founder of palaeontology, gave a different explanation. He thought that organisms had changed as a result of a series of catastrophes that had extinguished species and replaced them with others by means of divine creation (catastrophism).

Understand, think, search… 1 Describe

fixism and explain how Cuvier’s prosopsals contributed to it. What kind of catastrophes do you think he referred to in his theory?

Look up Cuvier and explain why he is considered the father of palaeontology.

Unit 4

2.2 Lamarck’s evolutionary theory John Baptiste de Lamarck was the first scientist to propose an evolutionary theory in his book, Zoological Philosophy, published in 1809. According to Lamarck’s theory, species transform over time through a mechanism he called inheritance of acquired characteristics. It was based on the following ideas:

➜ Organisms have a natural tendency towards perfection. ➜ When the environment changes, organisms need to use their organs to a greater or lesser extent. This leads to changes in them through either development or atrophy. In other words, use creates or eliminates the organ.

➜ Acquired characteristics (organ development or elimination) that are brought on by* the environment are passed on to offspring. Lamarckism is considered to be the first-ever evolutionary theory. Lamarck was the first to believe that species were not invariable, and that they developed in response to changes to the environment.

F ocu s on Eng lish Brought on by – caused by something e.g. His failure in the exam was brought on by not studying. Line of thought - a way of thinking that is typical of an individual or group Uphold – to keep or defend a belief or law.

Understand, think, search… 3 When we say organisms have a natural tendency towards perfection, what does that mean in evolutionary terms?

However, Lamarck’s theory was rejected because he was not able to demonstrate how the environment was responsible for changes in individuals.

Thinking hats. Choose a living being and one of its traits. How would Lamarck have explained the development of this trait?

The evolution of giraffes according to Lamarck’s theory

Today’s giraffes have evolved from early giraffes with short necks that fed on the leaves on the lowest branches.

When those leaves became less readily available, they began to stretch their necks and forelegs in order to reach leaves that were higher up.

This characteristic was passed on to their offspring and they also stretched their necks and forelegs. These gradually became longer until they reached their current size.

2 EARLY THEORIES ABOUT THE ORIGIN OF BIODIVERSITY Charles Darwin

2.3 Darwin’s theory: natural selection

Two English naturalists, Charles Darwin and Alfred Russel Wallace, independently came to the same conclusions on the evolution of species. Darwin published them in his book, The Origin of Species, in 1859.

Background Charles Darwin developed his theory of natural selection based on the different scientific understandings of the time:

➜ On a five-year journey around the world on board the Beagle, he carried out many observations and collected large quantities of fossil, flora and fauna samples from the regions he visited. These provided him with a wealth of information on which to base his hypotheses.

➜ Geologist Charles Lyell’s actualism theory made Darwin think that the world was not static and that species were continuously transforming. Changes in a species take place gradually and continuously over long periods of time rather than as a result of catastrophes. Throughout the time when he was developing his theory on evolution, and even following its publication, Darwin remained at home. The scientist did not enjoy controversy and arguments, and he was aware of the uproar that his theory on the origin of species would cause. Whilst various British publications printed caricatures of him with the body of an ape, he continued to move forward with his research and tried hard not to make the situation worse. Meanwhile, his theory began to gain ground and followers.

➜ Farmers carried out artifical selection when selecting and crossbreeding animals, and this generated individuals with the traits they wished to strengthen. This technique gave Darwin a clue to how nature works: through natural selection, the mechanism that led species to evolve.

➜ Thomas Malthus’s theory that resources increase at a slower rate than the human population, led Darwin to observe that there is a struggle between the individuals in all populations to access the necessary resources for survival.

Understand, think, search… 5 Use an example to explain Darwin’s theory about

8 How are artificial selection and natural selection

the process of natural selection.

Use the Internet to search for information about Darwin’s expedition on the Beagle, and list its main destinations.

7 From Darwin’s point of view, who is more successful in evolutionary terms: an animal which lives a long time, or an animal which has a lot of offspring?

similar?

Time and space travel. Imagine the species that replaces Homo sapiens in the future. What do you think it will look like? Will it be a species that has evolved from Homo sapiens? Will both species be alive at the same time, like Homo sapiens and Homo neanderthalensis? Visit anayaeducacion.es to learn how to use this technique.

anayaeducacion.es Go to ‘A very productive journey’ in your resource bank.

Unit 4

The theory of natural selection According to Darwin, natural selection is based on the following:

➜ Variability between individuals, which gives some of them advantages over others. In any population, there are variations between individuals that occur randomly. Some of these increase the probability of survival and the reproductive success of an individual; others reduce it. These characteristics need to be inherited and not produced by the environment in order for them to have an impact on the evolutionary process.

➜ The struggle for existence between organisms in a population. Limited resources lead to a struggle to survive, which means individuals have to compete for the resources they need to stay alive.

➜ Survival of the fittest, or best-suited. Individuals with advantageous variations survive and reproduce more successfully. The next generation then has those same traits. Less well-suited individuals with a disadvantageous trait do not mature, or leave fewer descendants. As a result, those traits disappear from the population.

➜ The origin of species as a result of adaptation of organisms to the environment. With time, an accumulation of modifications leads to new breeds and varieties, which eventually results in new species.

Understand, think, search… 10 Do you think it is right to summarise Darwin’s theory of evolution as ‘the survival of the fittest’? Explain why or why not.

11 Choose an animal species that you think is perfectly adapted to an extremely cold climate. Do you think it will be equally well adapted to a tropical climate? Explain your answer.

The evolution of giraffes according to Darwin’s theory

Within the giraffe populations, there were individuals with short necks and others with slightly longer necks. These characteristics were passed on from generation to generation. Since giraffes fed on grass, a short or long neck was no advantage when searching for food.

With time, a huge drought killed off all the vegetation on the ground and the only available food was the leaves on trees. Therefore, the characteristic of a long neck was an advantage in comparison with a short neck. Since they were better adapted to these conditions, the giraffes with long necks reproduced more than those with short necks, many of which died of starvation.

Many generations later, all the individuals in the giraffe population had long necks. Therefore, the giraffes that were best adapted to the new circumstances survived and left descendants with the same traits; in this case, a long neck.

3 TODAY’S EVOLUTIONARY THEORIES

Darwin’s theory of natural selection provided no explanation for how characteristics were passed on from one generation to the next nor what the origin of the variability between individuals in a population was. There was insufficient understanding in order to explain the inheritance of characteristics, so a new or revised theory needed to be formed.

An example of Neo-Darwinism 1st generation

Neo-Darwinism tackled* these matters successfully. Aa

3.1 Neo-Darwinism

AA AA

Neo-Darwinism, also known as the synthetic theory, is a revised version of the theory of natural selection and is based on the following:

aa Aa

➜ The evolutionary unit is not the individual, AA

but the population itself. There are variations in genotypes in the population and these are represented by the frequencies of the different alleles in each gene.

2nd generation

➜ This genetic variability is the result of mutations

and recombination processes that take place during sexual reproduction.

AA AA

➜ Natural selection acts on genetic variability. As

such, those individuals that are best adapted have a greater chance of surviving and transmitting their genetic traits to offspring.

AA AA

AA Aa

➜ Changes will gradually take place in the population as a result of this natural selection process. These will eventually give rise* to the creation of a new species.

3rd generation

AA AA

AA AA AA

AA AA

Unit 4

Neutralism Motoo Kimura proposed this theory in 1968. It suggests that most mutations are neutral. Whether they remain or are eliminated from a population’s genetic makeup is down to a question of chance. When genes persist and are inherited, phenotypic variations can develop. Under certain isolated conditions, they can lead to new species. The main evolutionary mechanism would be genetic drift. In other words, dramatic changes in populations that affect a population’s genetic variability both randomly and rapidly.

3.3 Speciation

F ocu s on Eng lish Tackle – to deal with a difficult problem, (in sports) to take the ball away from someone Give rise – to be the reason why something happens Schools of thought – a specific opinion or way of thinking that a group of people share on a subject matter

The most common speciation model, as proposed by Darwin, is speciation as a result of geographical isolation. According to this model, speciation takes place in the following stages:

➜ The population becomes geographically isolated due to a

Understand, think, search…

natural barrier such as the sea, a mountain or a desert. This impedes reproduction with individuals from other populations of the same species.

1 Explain what Neo-Darwinism contributes

➜ Gradual genetic changes appear in the population over time;

2 Is the theory of punctuated equilibrium

the population is acted on by the specific environmental conditions in its surroudings.

➜ The new species appears when all these changes mean that reproduction is no longer possible with the original species.

Speciation is the evolutionary process through which new species are generated from a population of a particular species.

to Darwin’s theory of evolution. compatible with Neo-Darwinism or not? Explain your answer.

Ideas pool. Choose an animal species and invent a speciation process that results in two different species. Describe the traits that differentiate the two species, and give each species a name.

An example of speciation 1

ills do not stop the living beings from one side 1 H and the other coming together and reproducing. They are individuals of the same species.

hen the natural barrier is larger, populations 2 W become isolated. Over time, they evolve separately and become two different species.

anayaeducacion.es Go to ‘Was Lamarck right about epigenetics and evolution?’ and ‘Speciation’ in your resource bank.

4 PROOF OF EVOLUTION

There is sufficient evidence from different fields of science for us to demonstrate that modern-day biodiversity is the result of the evolution of species.

4.1 Palaeontological evidence Fossils provide evidence of animals and plants from the past that became extinct and which are different to modern-day species. Fossils provide us with the following evidence of evolution:

➜ The species in fossils are the predecessors of modern-day species since all living beings come from another earlier living being.

➜ Phylogenetic sequences are groups of fossils that can be ordered by age and that are evidence of gradual changes to a particular characteristic, such as those of equids.

➜ Transitional fossils are fossils that exhibit the traits of two different species or taxonomic groups and which show us how they progressed from one to the other. For example, the Archaeopteryx fossil exhibits characteristics of reptiles such as teeth, a tail and claws as well as characteristics of birds such as feathers, wings and a beak.

➜ A tendency towards greater complexity, as the oldest fossils are of very simple invertebrates, and then different types of vertebrates such as fish, amphibians, reptiles, etc. gradually begin to appear.

4.2 Biogeographical evidence The study of the geographical distribution of modern animals or fossils provides us with proof of evolution:

➜ Living beings that live in areas that are close to each other are similar. The differences increase as they move further away from each other. This proves that species did not originate on their own. On the contrary, there is a relationship between them.

➜ Similar fossils have been found on the coasts of South America and Africa. The two continents used to be geographically united.

➜ Flora and fauna can be found today on the continents in the

Understand, think, search… 1 Explain what a phylogenetic sequence is.

2 What biogeographical evidence provides proof of evolution.

100

Do some research and name two species whose fossils have been found in South America and Africa.

southern hemisphere that have characteristics that suggest a common origin, but which have evolved independently following the separation of the continents. For example, ratites (rheas, emus and ostriches). The modern-day distribution of these birds may be explained based on the idea that their common ancestor lived on the continent which used to occupy the southern hemisphere. When the continents became separated from each other, each evolved individually. Nowadays, we can see how these types of phenomena started to happen; African elephants are an example. Although traditionally these were thought to be only one species, recent studies have divided them into two different species: Loxodonta cyclotis and Loxodonta Africana. The separation is largely biogeographical, as the first species live in wooded areas and the second in the savannah. Currently, there are hybrids in a small area in which both species still have some contact. anayaeducacion.es Go to ‘Coevolution and the arms race’ in your resource bank.

Unit 4

Proof of the evolution of elephants

Elephas maximus

Loxodonta africana Loxodonta cyclotis

Mamuthus

Holocene 0.01 Ma Pleistocene 2 Ma

Stegodon

Mammut

Pliocene 5.5 Ma

Primelephas Deinotherium Anancus

Platybelodon

Miocene 24 Ma

Current distribution of African elephants

Moeritherium

Palaeomastodon

Barytherium

L. africana

L. cyclotis

Eritherium

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4 PROOF OF EVOLUTION

4.3 Evidence from comparative anatomy The analysis of the internal anatomy of different species provides us with the following evidence of evolution:

➜ Related species have homologous organs that differ in shape depending on their function. For example, the limbs of tetrapod vertebrates. This gives added value to the concept of evolution through adaptive divergence in which a primitive organ modifies its morphology in order to adapt to life on land, in water or in the air.

➜ Nature also provides us with examples of analogous organs that evolve through adaptive convergence. Different organs develop similar ways of carrying out the same function. One example would be the wings on birds, insects or mammals such as the bat.

Evidence provided by comparative anatomy Homologous organs

Cetacean

Reptile

Horse

Human being Bat

Analogous organs

Dragonfly Bat

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Bird

anayaeducacion.es Go to ‘Homologous, analogous and vestigial organs’ in your resource bank.

Unit 4

4.4 Embryological evidence

Embryonic development

Embryo development in a living being is like a rapid summary of its evolution, and certain traits of its ancestor’s embryos can be observed. We are able to see the following when we observe embryo development in several species:

Fish

Bird

With pharyngeal arches and tail.

Mammal

➜ The embryos in some groups of related animals are very similar in their early stages. For example, those of vertebrates.

➜ In some animals, there are organs that are present in the embryo but which disappear in the adult. However, they remain in the adults of other related animals. For example, the tail and pharyngeal arches (gill slits).

With pharyngeal arches and tail.

4.5 Biochemical evidence Biochemical evidence has meant we have been able to determine that:

With pharyngeal arches and tail.

➜ All

living beings are made from similar biomolecules such as proteins, carbohydrates, lipids, etc.

The pharyngeal arches disappear, but not the tail.

The pharyngeal arches and tail disappear.

➜ Metabolic pathways are common to a wide variety of organisms.

➜ Cell structures are similar in all cells, etc. Additionally, DNA and protein sequencing techniques have also allowed scientists to compare the traits of these molecules in different species and work out their evolutionary history. They could then create phylogenetic trees that show how closely different species are related, how long they have been separate, and which are their common ancestors. The more similar the DNA and protein sequences of two species are, the less time has passed since they separated from a common ancestor.

Understand, think, search… 4 Using different examples from those in the picture,

7 According

to biochemical evidence, what parameters allow us to suggest that all living beings come from common ancestors? What do scientists use to differentiate between them and to create phylogenetic trees?

explain what analogous and homologous organs are.

5 Define

adaptive divergence.

convergence

and

adaptive

6 What principles of embryology are used to support the theory of evolution?

Choose two living beings that you think are related, and use the Internet to find out what percentage of DNA they have in common.

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5 HUMAN EVOLUTION

5.1 The hominisation process Human beings (Homo sapiens) are classified in the group referred to as hominids; we are the only living species in that group. Whilst it remains unclear, our earliest ancestor is thought to belong to the Australopithecus genus. Thanks to the discovery of fossils of other hominid species, it has been possible to reconstruct the phylogenetic history of modern humans. Hominisation led to the acquisition of a number of specific characteristics that differenciate us from our primate relatives. The following picture also includes some of the characteristics that make us different to other primates.

Characteristics of hominids 1 Bipedalism or standing upright implied

Bipedalism provided several advantages, such as freeing the hands to pick up and transport objects. Being able to see from higher up also helped detect prey and predators.

2 An increase in cranium size and an increase

in the volume and complexity of the brain (encephalisation) especially at the front, allowed intelligent thinking. The human brain is seven times larger than that of other mammals of a similar size.

3 Development of language. Anatomical traits developed that permitted the articulation of a wide variety of complex sounds, as well as the association of these sounds to objects and thoughts.

4 Neoteny. We are born in an immature state Human skeleton

of development, particularly in terms of the brain, because the pelvis is narrow. We are dependent for a long period of time.

Gorilla skeleton

Understand, think, search… 1 Spain is home to one of the most important archaeological sites in Europe for studying different species of hominids and their habits: Atapuerca. Do some research into Atapuerca. Name the species of hominids found there, and describe at least one important discovery related to the habits of one of the species.

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2 What were the advantages of bipedalism for hominids?

The presence of an opposable thumb was another great evolutionary advantage. Find out what this trait is and why it was useful.

4 What do you think were the advantages of language acquisition and development for the first hominids?

anayaeducacion.es Go to ‘Atapuerca’ in your resource bank.

Unit 4

5.2 Our ancestors Fossils tell us that our earliest ancestors belong to the Australopithecus genus. They were followed by the Homo genus, which included different species. Only one of these is a direct ancestor of humans. The others disappeared and do not have any modern-day descendants.

➜ Australopithecus. They lived in small groups in the savannah 4 million years ago. They were short (1.3 metres tall) but their pelvis and limbs show that they stood and walked upright. Their skull and brain were small and they had a prominent nose and large jaws which helped them to eat fruit, seeds and roots.

➜ Homo habilis. The humanisation process began with this species.

C RE AT E

History and Visual Arts

Cave paintings were the earliest artform which have been studied in order to understand the life of prehistoric man. Make a cave painting that could be used to help others understand what life is like for the most modern human that has ever existed, you.

They were able to manufacture tools which, whilst crude, demonstrated conceptual thinking. They lived in the African savannah between 2.3 and 1.6 million years ago. They were around 1.5 metres tall and their cranial capacity was now between 600 and 800 cm3.

➜ Homo erectus. They appeared 1.6 million years ago and continued to exist until around 100 000 years ago. They lived in both cold and warm climates. They were taller (1.70 metres tall) and had a cranial capacity of up to 1 100 cm3. They could make fire and had more elaborate tools.

➜ Homo antecessor. These were the ancestors of both the Neanderthals and modern humans. The remains uncovered in Atapuerca, Burgos, are 850 000 years old and show that they lived in temperate climates. They were hunters and cannibals.

➜ Homo neanderthalensis. They appeared 166 000 years ago. They had a very strong body and significant cranial capacity. They were hunters, used tools and buried their dead. They became extinct 28 000 years ago and did not leave descendants. There are indications that they lived alongside Homo sapiens but the latter ended up overtaking them since they were better adapted to the environment.

➜ Homo sapiens. They appeared around 200 000 years ago in Africa and moved from there to all the other continents. Their skull and skeleton have all modern traits. They used to live in caves. The artwork that they left in them indicates their ability to think abstractly, a result of the complexity of their brains.

Understand, think, search… 5 Explain the difference between Austhralopithecus erectus.

and

Homo

The stages of hominisation Australopithecus afarensis

Homo habilis

Homo erectus

Homo antecessor

Homo neanderthalensis

Homo sapiens

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6 HYPOTHESES ON THE ORIGIN OF LIFE

Life on Earth began around 3 800 million years ago. There are several hypotheses that attempt to explain the origin of life but it is still a scientific mystery.

6.1 The early hypotheses

Redi’s experiment If we place some meat in an open jar and some in a closed jar ...

Supernatural creation Throughout history, there have been many supernatural origin of life theories. Some had a magical element. Others were based on ideas such as the possession of a ‘vital spirit’ or ‘vital force’ of an unknown or unnatural nature.

Spontaneous generation This belief had already been outlined by Aristotle and had a large following for a very long period of time. The theory suggested that life originated spontaneously from remains of inert matter. For this reason, flies appeared on rotten meat, worms appeared in mud and parasites in sweat.

... after a few days ...

In the 17th century, the Italian scientist Francesco Redi used the scientific method to demonstrate that maggots appeared in rotten meat because flies had previously laid eggs there.

... there are maggots in the open jar and flies around it ...

... there are neither maggots nor flies in the closed jar.

Later on, in the 19th century, Louis Pasteur demonstrated that not even microorganisms appeared spontaneously. In fact, they are in the air and develop on the organic matter on which they feed. In order to demonstrate this, he used a culture medium that was rich in nutrients, free of microbes and isolated from the environment.

Pasteur’s experiment 1

The broth in the flask is brought to a boil. Steam comes out from the tube.

2 Nutrient broth is poured into a flask.

Heat

The neck of the flask is bent into an S shape. 4 As the broth slowly cools, the air in the flask contracts and drags more air in from outside. Dust particles and microorganisms are deposited in the neck of the flask.

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Dust and bacteria become trapped here.

Unit 4

6.2 Oparin and Haldane’s hypothesis In the 1930s, two scientists, the Russian Alexander Oparin and the Englishman John Haldane, suggested that life began from inorganic molecules following a period of biochemical evolution. According to their hypothesis, biomolecules could have formed as a result of chemical reactions between gases in the Earth’s primitive atmosphere, which they believed was made of water vapour (H2O), hydrogen (H2), methane (CH4) and ammonia (NH3). The energy for these reactions might have come from solar radiation and electrical charges in storms. This would form simple sugars, amino acids, fatty acids and nucleotides that would fall into the primitive seas and create a ‘primordial soup’. These simple molecules would interact and form other, more complex ones, such as proteins and nucleic acids. As they became more complex, these molecules acquired the capacity to selfreplicate or, in other words, to continue to exist by making copies of themselves.

Understand, think, search… 1 Review

Redi’s experiment and explain why, in spite of no flies growing, the meat ended up rotting.

2 Write the name and formula of the gases in the primitive atmosphere of Oparin and Haldane’s theory.

3 Explain why Miller and Urey’s experiment was important for Oparin and Haldane’s theories.

In 1953, the scientists Stanley Miller and Harold Urey tested Oparin’s hypothesis in an experiment using the apparatus you can see in the picture below. Into one of the flasks, they put a mixture of gases similar to what they believed the primitive atmosphere consisted of. To this they added two electrodes in order to generate electrical charges to replicate lightning and serve as an energy source. They simulated the primitive ocean in the other flask. When they analysed the water a few days later, they found small quantities of amino acids.

The Miller-Urey experiment

Electrodes H2 CH4 Gas valve

H2O NH3

Coolant

Condensation of steam Heat

The scientists Miller and Urey built an apparatus which they used to reproduced the conditions Operin thought existed on primitive Earth; in other words, an atmosphere without oxygen that was, fundamentally, rich in hydrogen, ammonia, methane and water. 1 They introduced the gases Oparin believed existed in the primitive atmosphere into a chamber. 2 Then they ran electric currents through it using electrodes to simulate the energy from lightning. 3 The products created by the chemical reactions that took place in the chamber collected in a container that imitated the ‘primitive ocean’. 4 When they extracted the liquid of the ‘primitive ocean’ and analysed it, they observed biomolecules that had formed from the simple inorganic products.

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6.3 The evolution of cells

6 HYPOTHESES ON THE ORIGIN OF LIFE

To be able to say a thing is alive, it must meet a series of requirements:

➜ It must consist of a closed compartment, which is able to exchange substances with the environment.

➜ It must have molecules that can process substances in A

chemical reactions to obtain energy, and other molecules that allow it to maintain its own structures.

➜ It must have molecules that can store information to replicate the whole system. The precursors of living beings were pre-cellular structures. These were organic molecules similar to modern carbohydrates, lipids, proteins and nucleaic acids, but much simpler. Scientists believe that around 3 800 million years ago, these structures evolved and transformed to meet the requirements for life, forming prokaryotic organisms: bacteria. Later, after a process that lasted around 2 000 million years, eukaryotic cells appeared.

Heterotrophic prokaryotes

In an atmosphere that had no oxygen, the first prokaryotic cells obtained nutrients and energy from the fermentation of organic matter in the environment.

Autotrophic prokaryotes When organic matter began to become scarce, a mass death of many bacteria took place. However, some of them, the cyanobacteria, were able to survive because they could synthesise organic matter through photosynthesis. Thanks to this process, the atmosphere became enriched with oxygen. Some chemosynthetic prokaryotes began to use this oxygen, obtaining energy from the oxidation of inorganic substances.

Aerobic heterotrophic prokaryotes

Working with pictures Picture A shows chains of cyanobacteria today, and picture B shows stromatolites, which are rocky structures formed by fossilised colonies of cyanbacteria. If you cut into these stromatolites and observed them under a microscope, you would see the chains of cyanobacteria. Some of these remains are more than 3 700 years old. Explain why they are used as proof of the origin and evolution of cells. 108

The presence of oxygen also facilitated the emergence of organisms that were capable of carrying out cellular respiration, a process that is highly effective for obtaining energy. As resources in the environment disappeared, these heterotrophs learned how to obtain the nutrients that had been synthesised by autotrophs.

Eukaryotes These emerged around 1 800 million years ago from prokaryotic cells. Today, the most commonly accepted hypothesis amongst scientists to explain their origin is endosymbiotic theory.

Unit 4

6.4 Endosymbiotic theory Endosymbiotic theory was proposed by Lynn Margulis in 1967 and aims to explain the origin of eukaryotic cells. This theory suggests that some eukaryotic cell organelles, particularly chloroplasts and mitochondria, originated from prokaryotic organisms that were taken inside another organism. This established a symbiotic relationship between the two. Mitochondria are considered to have developed from heterotrophic bacteria and chloroplasts from cyanobacteria. The main basis for this theory is that mitochondria and chloroplasts have the following traits:

➜ Mitochondria are of a similar size to some bacteria. ➜ Mitochondria and chloroplasts have a circular DNA that is similar to the chromosome in bacteria instead of the lineal DNA found in the cell nucleus.

➜ Both mitochondria and chloroplasts have ribosomes that are similar to prokaryotic ribosomes that carry out their own protein synthesis.

➜ The presence of a double membrane in these organelles backs up the idea that they entered the cell by means of phagocytosis. The internal membrane would be the original membrane from the bacteria. The one on the outside would be the membrane from the vesicle that surrounded it.

F ocu s on Eng lish The word endosymbiosis is easier to remember if you know that it is a word made up of endo, a prefix meaning within, used in the formation of compound words, and the Greek syn- (together) + bios (life).

The theory of endosymbiosis Aerobic bacteria (take in O2)

Prokaryote amoeboid organism

Formation of mitochondria

Spirochaetes

Flagellum Towards animals Nucleus Towards plants Cyanobacteria cells (photosynthesis) Formation of chloroplasts

According to endosymbiotic theory (the most commonly accepted theory nowadays), a large prokaryotic, anaerobic cell with phagocytic ability engulfed, over time, another prokaryote. Instead of being digested, it survived in symbiosis inside its captor until it became dependent on it. Finally it ended up generating different organelles in an aerobic eukaryotic cell.

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ject

research pro

Investigating proboscideans project presentation

Loxodonta cyclotis

There are currently three species of elephants in existence: the African elephant (Loxodonta africana), the African forest elephant (Loxodonta cyclotis) and the Asian elephant (Elephas maximus). Elephants, and their extinct relatives the woolly mammoths and the mastodons, belong to the order Proboscidea, a Greek term for nose. As a student interested in palaeontology, you are interested in investigating the evolutionary line of this order and, in particular, their relationship to the woolly mammoths (Mammuthus primigenius) and the mastodons (Mammut americanun).

Loxodonta africana

Elephas maximus

project Objective

In this research project you are going to study the phylogenetic tree of the proboscideans. To do this, you will need to collect data on existing species in the line (Loxodonta africana, Loxodonta cyclotis and Elephas maximus) and find out about the fossils of their ancestors that have been found. To report the results of your investigation, you will need to prepare a model of the proboscidean phylogenetic tree, and supplement it with small sculptures, drawings and photographs of the different species.

project steps

The suggested steps for this project are:

➜ Step 1 (in this unit). Organising your work and searching for the information you need.

➜ Step 2 (in unit 5). Proposing the hypotheses for the study, doing the research and collecting the data.

➜ Step 3 (in unit 6). Analysing and interpreting the results, drawing conclusions and presenting your study with a model. 110

Unit 4

STEP 1

Organising your work and searching for information Organising your work Your teacher will put you in groups of 3 or 4. In your groups, discuss the project and what you know about proboscideans. Each group should choose four species of living or extinct proboscideans to investigate. For each species, create a model using modelling clay, potter’s clay, recycled materials, etc. Divide the work between the team members. Before you start, share your ideas with your class. It will be more interesting if your class studies a number of species, but also that each species is studied by more than one group. This way you can compare the results.

Searching for information and analysis Look for general information about the different species of current and extinct proboscideans: Fragment of jawbone from Eritherium.

➜ Scientific and common names of the different species, accompanied by full photographs or diagrams of the body with labels.

➜ Anatomical information and the different traits of each species of proboscidean.

unit for an See section 4 of this lp you with your he ill w t a th on ti ra st illu investigation.

➜ Geographical distribution of current elephants and extinct proboscideans.

➜ Causes of the disappearance of the extinct species and threats to the populations of current elephants.

➜ Look for news in the press about the different palaeontological discoveries that have to do with proboscideans.

➜ Research the appearance of frozen mammoths and find out whether DNA samples have been well preserved.

Barytherium

Moeritherium

Paleomastodon

111

m this resources fro r to choose be em m Re lio. your portfo

unit for

TISE

AC review and PR

Organising your ideas

Interpreting pictures

3 Look at the pictures on the evolution of the giraffe’s

Concept map. In your notebook, complete this concept map on Darwin’s theory of evolution. Visit anayaeducacion.es to learn how to use this organiser.

Variability between individuals:

The struggle for ?

Survival of the ?

The origin of species as a result of adaptation of ?

neck and do these exercises: A

• In any population, there are variations between individuals that ... • Some increase the ? and the ? Others reduce it. • These characteristics need to be ? • A struggle to survive is created by • It means individuals have to ?

• Individuals with advantageous variations ? Then the next generation has those same traits. • Individuals with disadvantageous traits ? • With time, the accumulation of modifications leads to: – New ? – New ?

Summarising 2 Use these guidelines to create your own summary of the unit.

• Define

biodiversity and adaptation and describe the types of adaptations that exist. Explain the relationship between biodiversity and evolution.

• List the differences between Cuvier’s fixist theory and the theory of natural selection.

• Explain what Neo-Darwinism is and name the premises on which it is based.

• Explain the differences between neutralism and punctuated equilibrium (punctualism).

a) Match each picture to the evolutionary theories of Lamarck and Darwin. b) Which evolutionary mechanism is at work in each case? c) Explain the differences between the two interpretations of this evolutionary change.

4 Look at the following pictures and answer the questions: a) Which of the organs are homologous? Which are analogous? b) What evolutionary information does each one provide? A

• Define speciation and explain the phases in the case of geographical isolation.

• Give some examples of evidence for evolution. • Explain what hominisation is and list the characteristics of hominids. Name the most prominent species and when they lived.

C D

• Explain the hypotheses about the origins of life and how the first cells evolved into modern ones.

• Explain the basics of endosymbiotic theory. 112

anayaeducacion.es Go to the science workshop ‘Interpreting a phylogenetic tree’ in your resource bank.

Unit 4

Applying your knowledge

Moving forward

5 Moles, which live underground and dig tunnels, have adapted front paws like spades and are practically blind. What types of mutations are these? Explain the appearance of these adaptations from fixist, Lamarckist and Darwinist points of view.

16 Read the following text and answer: In evolutionary theory, scientists say a population goes through a ‘bottleneck’ when circumstances cause it to drastically reduce in size. It then undergoes a ‘founder effect’: the population evolves from a small segment of individuals, whose genetic variability does not represent the diversity of the original population. These evolutionary events have affected many species, such as sealions. Their population shrank to the brink of extinction at the end of the 19th century as a result of indiscriminate killing.

6 Could natural selection exist without genetic variability? Where does genetic variability come from?

7 From a modern point of view, what are the main gaps in Darwinism?

8 Explain the difference between: a) Palaeontological evidence and biogeographical evidence. b) Homologous organs and analogous organs. c) Adaptive convergence and adaptive divergence. d) Embryological evidence.

evidence

and

biochemical

9 Create a timeline showing our hominid ancestors and their main traits.

10 Explain the difference between hominisation and humanisation.

11 Explain the advantages of neoteny for humans. 12 Why does mould grow on damp bread? Where does this mould come from?

13 Imagine you have to show a friend that life is not generated spontaneously. How would you do it?

14 How did the first photosynthetic organisms impact life on Earth?

15 Indicate the main ideas of endosymbiotic theory and give some supporting evidence. anayaeducacion.es Go to the sections ‘Key concepts’ and ‘Learn by playing’ in your resource bank.

a) What is a bottleneck? Why does it happen? b) Which evolutionary mechanism and evolutionary theory would you relate to this event?

Sustainable Development Goals 17 Homo habilis appeared in Africa, and was able to make tools. However, the limitations of the infrastructure in many modern African countries have reduced productivity up to 40 %. Target 9.a of the Sustainable Development Goals aims to develop sustainable, resilient infrastructures in countries with low levels of economic development, through financial, technological and technical support. a) Several NGOs are providing schools with tablets and access to the Internet in order to encourage digital education in some African countries. What impact do you think this will have on their future economic development? Look up some examples of projects and discuss them as a group. b) The SAAM Project (Supporting Alliance for African Mobility) is a pilot initiative to foster the exchange of teachers and student teachers between Africa and Europe. Find out what it consists of and write your opinion.

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Glossary

UNIT 4

A Adaptation Living beings ability to change to suit the environment in which they live Allopatric speciation Speciation that takes place when a population is geographically seperated from the rest of the species and develops in isolation

B Biodiversity All the species which inhabit an ecosystem Biogeography Scientific discipline which studies the distribution of animals and plants Bipedalism The ability of some animals to walk upright

Human skeleton

Evolution Living beings change and adapt progressively in response to the environment. Evolution leads to the appearance of distinct species from a shared ancestor

F Fossil Remains of an organism or its biological activity that have been preserved in sedimentary rocks

Gorilla skeleton

C Catastrophism Fixist theory which states that some species disappear following big catastrophes and are replaced by new species through divine intervention

232

G Genetic drift Sudden changes experienced by populations that randomly and rapidly affect their genetic variability

Mass extinction Events in which, as a result of natural catastrophes, numerous species disappear globally in a relatively short period of time

Palaeontology The scientific study of living beings that inhabited the planet in the past and whose remains are, for the most part, fossils

Mutation Any genetic change which affects a trait

N Natural selection Evolutionary mechanism proposed by Darwin, which states that individuals that are favourably adapted to their environment are more likely to survive and reproduce Neo-darwinism A development of the theory of natural selection. It includes evidence from scientific advances in the fields of genetics and molecular biology in order to explain the evolutionary process. This theory is also known as the synthetic theory of evolution

Phylogenetic sequences Groups of fossils which can be ordered by age and show the gradual changes of a particular characteristic Population A group of organisms of the same species that live in the same geographical area at the same times Punctuated equilibrium Evolutionary theory that hypothesises that there are specific periods of intense speciation which can interrupt the normal processes of adaption through natural selection. They suggest that the evolutionary process takes place through big jumps forward

R Recombination The process that occurs during meiosis which produces the random crossing and segregation of genetic material between homologous chromosomes

S Nuetralism Evolutionary theory which proposes that the majority of mutations are neutral. As long as these mutations don’t affect the ability to successfully reproduce, they are inherited randomly. In this theory, genetic drift is the main evolutionary mechanism

Species Population of similar individuals which can reproduce together and have fertile offspring Spontaneous generation An ancient belief that organisms could come from inert matter 233

e d

a c r ce

biolo gía y geolo gía

4 ESO

Building

Blocks

Building Blocks es un proyecto educativo de Anaya para la Educación Secundaria. Este libro ha contado con la colaboración de:

CONTENIDO: Berta Gallego (adaptación de los materiales del libro Biología y Geología 4). Equipo editorial: Almudena Alcón, Esther Fernández, Mª Isabel García, Marco Sánchez, Jorge Torres y Paloma Rodríguez Esteban.

Diseño, mapas y dibujos técnicos: Patricia G. Serrano, Juan Carlos Quignón, Miguel A. Castillejo, Miguel A. Díaz-Rullo and Miriam Arribas.

Ilustración:

Sara Mateos, Celia López Bacete, Santi Martín, Alicia Posada, M.ª Carmen Fuente, David

Menéndez.

Maquetación: Óscar Latorre. Corrección: Sergio Borbolla, Miguel Ángel Alonso. Fotografía:

Age Fotostock (STEVE GSCHMEISSNER, SZ Photo/Süddeutsche Zeitung Photo), Alamy/ Cordon Press (Adam Major, Photonesia, Susan E. Degginger, Yakov Oskanov), Archivo Anaya (Candel, C.; Canto, M.; Cosano, P.; González Grande, J. L.; Gragera, R. & Muñiz, E.; Lezama, D.; Martínez, C.; Moreno, C.; Ortega, Á.; Padura, S.; Ruiz, J. B.; Sánchez, J.; Valls, R.; Vázquez, A.), Dreamstime (Piyaphun Juntraverot, Steve Ball, Sue Feldberg), Getty Images (Martin Ruegner), iStock/Getty Images (AndreAnita, aopsan, branex, Cheryl Ramalho, dr322, Elif Bayraktar, Josep Sala Francas, kingkidton, McIninch, micro_photo, Noemi Braña, scanrail, sonatali, Tom Strudley, Tramper2, travelview, Zach Etheridge), 123RF (Achim Prill, angellodeco, Dan Barbalata, jenifoto, Kevin Wells, Roman Fedin, sergiitrofymchuk, ssilver, Анастасия Короткова).

compromiso Nuestras publicaciones mantienen el rigor en el uso y en la selección de los contenidos, en las imágenes y en el lenguaje, para cumplir con la no discriminación por razón de género, cultura u opinión. Grupo Anaya considera la responsabilidad social y medioambiental uno de sus valores fundamentales. Por ello, se compromete a: · mejorar nuestros resultados en materia de medio ambiente, · reducir nuestras emisiones de carbono, · hacer uso de los recursos naturales de manera responsable y · eliminar cualquier impacto negativo de nuestra actividad en los bosques en peligro. Dichos compromisos, entre otros, hacen que el 100 % del papel utilizado en nuestros libros tenga el sello PEFC.

Importante: Las actividades propuestas en este libro deben ser realizadas en cuadernos u hojas sueltas; nunca en el propio libro. Los enlaces a las páginas web que aparecen en este libro han sido revisados en la fecha de su impresión. La editorial no se hace responsable de las modificaciones o las anulaciones que se produzcan en ellos con posterioridad a dicha fecha.

Biología y geología 4 De cerca - cóDigo 3100566 - Bl001186 (caSTellaNo) © Del texto: Silvia Clemente Roca, Mª Aurora Domínguez Culebras, Ana Belén Ruiz García, 2021. © Del conjunto de esta edición: GRUPO ANAYA, S.A., 2021 - C/ Juan Ignacio Luca de Tena, 15 - 28027 Madrid Printed in Spain. Reservados todos los derechos. El contenido de esta obra está protegido por la Ley, que establece penas de prisión y/o multas, además de las correspondientes indemnizaciones por daños y perjuicios, para quienes reprodujeren, plagiaren, distribuyeren o comunicaren públicamente, en todo o en parte, una obra literaria, artística o científica, o su transformación, interpretación o ejecución artística fijada en cualquier tipo de soporte o comunicada a través de cualquier medio, sin la preceptiva autorización.

Biology aND geology 4 aNDalucía - Bl001186 - 3100566 © Text: Silvia Clemente Roca, Mª Aurora Domínguez Culebras, Ana Belén Ruiz García, 2021.

ÍNDICE EL MÉTODO CIENTÍFICO .................................................... 4

5 LA TIERRA Y SU DINÁMICA .........................................40

1 Como es el método científico • 2 La investigación en el laboratorio • 3 El trabajo científico en el campo • 4 La búsqueda de información

1 La dinámica terrestre • 2 La teoría de la tectónica de placas • 3 Consecuencias de la dinámica terrestre • 4 La evolución del relieve terrestre • 5 El estudio del relieve. Mapas y perfiles

1 LA CÉLULA: LA BASE DE LA VIDA ............................ 10 1 La composición de la materia vida • 2 La célula • 3 Las células procariotas • 4 Las células eucariotas • 5 La función de nutrición en las eucariotas • 6 La función de relación en las eucariotas • 7 La función de reproducción en las eucariotas

2 LA INFORMACIÓN GENÉTICA ........................................18 1 Los ácidos nucleicos • 2 La expresión de los genes. Síntesis de proteínas • 3 El ciclo celular y la replicación • 4 La mitosis y la citocinesis • 5 La meiosis y la reproducción sexual

3 LA HERENCIA BIOLÓGICA ...............................................24 1 De los caracteres a los genes • 2 Los experimentos de Mendel • 3 Las leyes de Mendel • 4 Excepciones a las leyes de Mendel • 5 Las mutaciones • 6 Las técnicas de ingeniería genética

4 EL ORIGEN Y LA EVOLUCIÓN DE LA VIDA ..........32 1 El origen de la biodiversidad • 2 Teorías evolutivas actuales • 3 La evolución humana • 4 Las hipótesis sobre el origen de la vida

6 LA HISTORIA DE LA VIDA EN LA TIERRA ............52 1 El registro de la historia de la Tierra • 2 La datación del registro • 3 El tiempo geológico. Una historia de cambios

7 LA COMPOSICIÓN DE LOS ECOSISTEMAS ..........58 1 Ecosistemas y factores ambientales • 2 Los factores abióticos y las adaptaciones • 3 Los factores bióticos. Las poblaciones • 4 Los factores bióticos. Las relaciones

8 LA DINÁMICA DEL ECOSISTEMA ...............................62 1 Los niveles tróficos • 2 Las circulación de la materia y la energía en el ecosistema • 3 Cadenas y redes tróficas. Parámetros tróficos • 4 Las pirámides ecológicas • 5 Los ciclos biogeoquímicos • 6 Las sucesiones ecológicas • 7 El ecosistema se autoregula

9 EL MEDIOAMBIENTE Y EL SER HUMANO .......... 70 1 El medioambiente y su situación actual • 2 La gestión sostenible de los recursos de la biosfera • 3 La gestión sostenible del agua • 4 La gestión sostenible de la energía 5 • La gestión sostenible de los residuos

GLOSARIO....................................................................................78

D iDA

EL ORIGEN Y LA EVOLUCIÓN DE LA VIDA

1 EL ORIGEN DE LA BIODIVERSIDAD La biodiversidad o diversidad biológica es la variedad de especies que habitan o han habitado la Tierra.

La biodiversidad y la adaptación La adaptación es la adecuación de los seres vivos a las condiciones del medio en el que viven. Las adaptaciones son: • Estructurales: afectan a determinados órganos del cuerpo. • Fisiológicas: afectan al funcionamiento del organismo. • De comportamiento: son acciones que llevan a cabo los organismos y que les permiten obtener algún beneficio.

La biodiversidad y la evolución

George Cuvier, considerado el padre de la paleontología, pensaba que las especies no habían cambiado desde la Creación.

Se denomina evolución biológica a los cambios lentos y graduales que han ocurrido en los seres vivos a lo largo de millones de años. Hoy en día sabemos que la gran biodiversidad de la Tierra ha surgido por evolución a partir de un antepasado común, y que las especies se originan unas a partir de otras.

Primeras teorías del origen de la biodiversidad Teorías fijistas Las teorías fijistas defendían que todas las especies eran inalterables y existían desde el principio de los tiempos. Los creacionistas pensaban que las especies habían aparecido por creación divina. Sin embargo, los paleontólogos, al estudiar los fósiles, se dieron cuenta de que había especies que se habían extinguido y otras habían aparecido con posterioridad. Para explicar estos hechos surgieron las primeras ideas evolucionistas. Sin embargo, George Cuvier consideraba que ese hecho era consecuencia de una serie de catástrofes que provocaban la extinción de unas especies, que eran entonces sustituidas por otras que aparecían por creación divina (catastrofismo). 240

Comprende, piensa, investiga... 1 En parejas, explicad a qué condición del medio se adaptan estos animales: a) Aves que migran en invierno a zonas cálidas. b) Aves con pico fuerte con forma de gancho. c) Dromedarios que producen agua a partir de la grasa de su joroba. d) Animales que hibernan.

2 ¿Qué tipo de adaptación presentan los animales de la actividad anterior?

3 ¿Quién propuso la teoría denominada catastrofismo? ¿Qué hechos buscaba explicar con esa teoría?

4 ¿El catastrofismo es una teoría fijista o evolucionista? Justifica tu respuesta.

Teorías evolucionistas La teoría de la evolución de Lamarck Jean Baptiste de Lamarck fue el primer científico que propuso una teoría evolucionista, en su obra Filosofía zoológica, publicada en 1809. Según su teoría, las especies se transforman a lo largo del tiempo mediante la herencia de los caracteres adquiridos:

Evolución de las jirafas según Lamarck

• Los organismos tienden hacia el perfeccionamiento. • Cuando se producen cambios en el ambiente, los organismos se ven obligados a utilizar sus órganos en mayor o menor medida, lo que provoca su modificación por desarrollo o atrofia. Es la función la que crea o anula el órgano (la función que desempeña este hace que se desarrolle o termine por desaparecer). • Las modificaciones adquiridas, inducidas por el ambiente, se transmiten a su descendencia. Su teoría fue rechazada porque no pudo demostrarse que el ambiente fuera el responsable de los cambios de los individuos. La teoría de la selección natural de Darwin Los naturalistas Charles Darwin y Alfred Russel Wallace llegaron, de forma independiente, a las mismas conclusiones sobre la evolución de las especies. Fue Darwin quien las expuso en su libro El origen de las especies, en 1859. La selección natural se basa en las siguientes premisas: • La variabilidad de caracteres, por la que algunos individuos presentan ventajas frente a otros. Los individuos de una población presentan variaciones producidas al azar, algunas de las cuales aumentan su probabilidad de supervivencia y el éxito reproductivo, y otras lo reducen. Estas características deben ser heredables y no producidas por el ambiente.

Evolución de las jirafas según Darwin

• La lucha por la existencia entre los organismos de una población que se genera debido a que los recursos son limitados. • Selección de los más aptos. Los individuos que tienen variaciones favorables sobreviven y se reproducen con más éxito, por lo que la siguiente generación presenta sus rasgos. • El origen de las especies por adaptación de los organismos al ambiente. Con el tiempo, la acumulación de modificaciones origina la aparición de nuevas razas y variedades, y, por último, la aparición de nuevas especies.

Comprende, piensa, investiga... 5

Lee el texto «Antecedentes de la teoría de la selección natural» disponible en el banco de recursos de anayaeducacion.es y escribe cuáles fueron las cuatro ideas que inspiraron a Darwin para desarrollar la teoría de la selección natural.

6 Observa las imágenes de la evolución de las jirafas según Lamarck y según Darwin y escribe un párrafo que explique lo que se observa en cada una de las escenas.

241

2 TEORÍAS EVOLUTIVAS ACTUALES. PRUEBAS DE LA EVOLUCIÓN

Un ejemplo de neodarwinismo 1.a generación

El neodarwinismo También conocido como teoría sintética de la evolución, es una revisión de la teoría de la selección natural que se basa en las siguientes premisas: • La unidad evolutiva no es el individuo, sino la población. En ella se producen variaciones genotípicas.

Aa AA AA

aa Aa

• Esta variabilidad genética procede de las mutaciones y de los procesos de recombinación durante la reproducción sexual.

2.a generación

• La selección natural actúa sobre la variabilidad genética. aa

• Como consecuencia de la selección natural, irán apareciendo cambios graduales en la población que dan lugar a la aparición de una especie nueva.

AA AA

La especiación

AA AA

AA Aa

La especiación es el proceso evolutivo por el cual, a partir de una población de una especie, se generan nuevas especies. El modelo de especiación más común, propuesto por Darwin, se produce por aislamiento geográfico: un obstáculo natural produce el aislamiento de las poblaciones y, con el tiempo, estas evolucionan por separado y se convierten en especies diferentes.

3.a generación AA

AA AA

Las pruebas de la evolución Las pruebas paleontológicas El registro fósil muestra especies extintas distintas a las actuales y permite extraer las siguientes pruebas: • Las especies fósiles son antecesoras de las actuales. • Las series filogenéticas, que son conjuntos de fósiles que se pueden ordenar por antigüedad, muestran los cambios progresivos en una determinada característica. • Las formas intermedias, que son fósiles con características de dos especies o grupos taxonómicos distintos, nos muestran su progresión de uno a otro.

Un ejemplo de especiación por aislamiento geográfico Individuos de una misma especie.

explica cómo se ha producido según el neodarwinismo.

242

Un gen determina el color de las alas en esta población de polillas. El alelo A, el color oscuro, y el a, el color claro. Los individuos con alas oscuras se camuflan mejor y sufren menos depredación que los que tienen alas blancas. Se ha marcado en azul los individuos que se reproducen de cada generación.

1 Observa la ilustración superior de la evolución de las polillas y Lee el texto «Otras teorías evolucionistas» disponible en el banco de recursos de anayaeducacion.es y explica cuál es el mecanismo fundamental de la evolución según el neutralismo. ¿Es el mismo que propone el neodarwinismo?

AA AA

Comprende, piensa, investiga...

Las colinas producen el aislamiento geográfico de las poblaciones. Con el tiempo, se forman dos especies diferentes.

Las pruebas biogeográficas

Unidad 4

El estudio de la distribución geográfica de animales actuales o fósiles aporta las siguientes evidencias:

Órganos homólogos

• Los seres vivos de regiones cercanas se parecen y sus diferencias aumentan cuanto más alejados están. • Se han hallado fósiles comunes en las costas de Sudamérica y África. • Existe flora y fauna actual en los continentes del hemisferio sur cuyas características indican un origen común, que han evolucionado de forma independiente tras la separación de los continentes, como las aves rátidas (ñandús, emús y avestruces).

Las pruebas de la anatomía comparada

Caballo

Cetáceo

• Existen órganos homólogos en especies emparentadas, cuya forma difiere según la función que desempeñan, lo que apoya la idea de la evolución por divergencia adaptativa, en la que un órgano evoluciona para adaptarse.

Ser humano

• Los órganos análogos son aquellos que adquieren formas semejantes para realizar la misma función, pero sin tener un origen común. Evolucionan por convergencia adaptativa.

Murciélago

Las pruebas embriológicas

Reptil

• Los embriones de algunos grupos de animales emparentados se parecen mucho en sus primeros estadios. • En algunos animales existen algunos órganos en los embriones que desaparecen en la forma adulta, pero que permanecen en otros grupos de animales emparentados.

Las pruebas bioquímicas • Todos los seres vivos estamos formados por biomoléculas similares. • Existen rutas metabólicas comunes a muchos organismos. • Las estructuras celulares son similares en todas las células. Además, las técnicas de secuenciación de ADN y proteínas han permitido comparar estas moléculas entre las diferentes especies y averiguar su historia evolutiva. Esto ha hecho posible crear árboles filogenéticos que permiten conocer el parentesco entre especies.

Desarrollo embrionario Pez

Con arcos branquiales y cola.

Ave

Mamífero

Con arcos branquiales y cola.

Desaparecen los arcos branquiales, pero no la cola.

Desaparecen los arcos branquiales y la cola.

Comprende, piensa, investiga... 1 Observa la imagen de las extremidades superiores de varios animales y explica en qué se parecen esas estructuras. ¿En qué se diferencia la extremidad de un murciélago de la de un cetáceo? ¿Se te ocurre algún órgano análogo al ala del murciélago?

Con arcos branquiales y cola.

2 En parejas, explicad las semejanzas y diferencias en el desarrollo embrionario de peces, aves y mamíferos. ¿Qué prueban esas características?

3 Según las pruebas bioquímicas, ¿qué parámetros nos permiten suponer que todos los seres vivos provienen de ancestros comunes? ¿Qué se utiliza para diferenciarlos y construir árboles filogéneticos?

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3 LA EVOLUCIÓN HUMANA

El proceso de hominización Los seres humanos (Homo sapiens) pertenecemos al grupo de los homínidos y somos la única especie viva de este grupo. Aunque no está claro, se cree que nuestro antecesor más antiguo pertenecía al género Australopithecus. Gracias al hallazgo de restos fósiles de otras especies de homínidos, se ha podido reconstruir la historia filogenética de los seres humanos.

Esqueleto gorila

El proceso de hominización supuso la adquisición de una serie de características que nos diferencian de nuestros parientes primates.

Las características de los homínidos • El bipedismo o postura erguida supuso una serie de ventajas, como la liberación de las manos, que pueden utilizarse para transportar o coger objetos. La visión más elevada puede ayudar a detectar presas y depredadores. Sin embargo, la postura erguida implica varios cambios anatómicos: — La columna vertebral adquiere forma de S. — La pelvis se hace más ancha y corta. — El fémur es más robusto e inclinado hacia el interior. — Los huesos del pie se modifican para equilibrar y soportar el peso corporal. • El aumento de la capacidad craneal, acompañado del aumento de volumen y complejidad del cerebro (encefalización) sobre todo de su parte frontal, permite un pensamiento inteligente. El encéfalo humano es siete veces mayor que el de otros mamíferos con un tamaño similar al nuestro. • La adquisición del lenguaje. Se desarrollan las características anatómicas que permiten articular una gran variedad de sonidos complejos, así como la capacidad de asociar esos sonidos a objetos y pensamientos. • La neotenia. Nacemos en un estado inmaduro, sobre todo del encéfalo, debido a que el orificio de la pelvis es estrecho, y tenemos un largo período de dependencia infantil.

Comprende, piensa, investiga... 1 En parejas, observad las imágenes superiores y comentad qué diferencias existen entre el esqueleto del chimpancé y el esqueleto humano.

2 Escribe una definición para las siguientes características: neotenia, bípedo, pulgar oponible, hominización.

3 ¿Qué cambios anatómicos implicó el bipedismo y qué ventajas proporcionó esa condición?

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Esqueleto humano

Nuestros antepasados

Unidad 4

Los fósiles nos indican que nuestros parientes más lejanos pertenecen al género Australopithecus. Tras ellos, apareció el género Homo, con diferentes especies. • Australopithecus. Vivían en pequeños grupos en la sabana hace más de 4 millones de años. Eran de baja estatura (1,3 m), pero su pelvis y extremidades indican que ya caminaban erguidos. El cráneo y el cerebro eran pequeños, y tenían grandes mandíbulas. • Homo habilis. Es la especie más primitiva del género Homo. Son capaces de fabricar herramientas toscas que demuestran un pensamiento conceptual. Vivieron hace entre 2,3 y 1,6 millones de años en África. Medían alrededor de 1,5 m y tenían una capacidad craneal de entre 600 y 800 cm3. • Homo erectus. Vivieron hace entre 1,6 millones de años hasta hace 100 000 años. Eran de mayor estatura, 1,70 metros, y con capacidad craneal de 1 100 cm3. Usaban el fuego y sus herramientas eran más elaboradas. • Homo antecessor. Fueron antecesores tanto de los neandertales como de los humanos actuales. Los restos hallados en Atapuerca, Burgos, tienen una antigüedad de 850 000 años, y demuestran que vivieron en ambientes templados. Eran cazadores y caníbales. • Homo neanderthalensis. Los restos más antiguos encontrados son de hace unos 166 000 años. Tenían un cuerpo muy robusto y una elevada capacidad craneal. Eran cazadores, usaban herramientas y enterraban a sus muertos. Se extinguieron hace 28 000 años. Parece que convivieron con los Homo sapiens, que acabaron desplazándolos. • Homo sapiens. Los primeros restos tienen unos 200 000 años y se han encontrado en África, desde donde se desplazaron al resto de continentes. Su cráneo y su esqueleto tienen ya todos los rasgos modernos. Vivían en cuevas, donde dejaron muestras de su arte, lo que demuestra un pensamiento abstracto, fruto de su complejidad cerebral.

Comprende, piensa, investiga... 4 ¿A qué género corresponden los fósiles de los primeros bípedos verdaderos?

Elige una de las especies del género Homo y escribe un texto explicando sus características. Puedes encontrar información en las miniguías educativas del Museo de la Evolución Humana.

Nuestros antepasados Australopithecus afarensis

Homo habilis

Homo erectus

Homo antecessor

Homo neanderthalensis

Homo sapiens

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4 LAS HIPÓTESIS SOBRE EL ORIGEN DE LA VIDA

Experimento de Pasteur

Las primeras hipótesis

1 Se añade una infusión o un caldo

La vida apareció en la Tierra hace unos 3 800 millones de años. Las primeras teorías sobre el origen de la Tierra tenía contenidos mágicos o se basaban en fuerzas desconocidas.

por el cuello del matraz.

La generación espontánea Esta teoría defendía que la vida se originaba espontáneamente a partir de la materia inerte. En el siglo xvii, Francesco Redi demostró que en la carne podrida surgían gusanos porque las moscas, previamente, habían puesto allí huevos.

Calor

Más tarde, en el siglo xix, Louis Pasteur demostró que ni siquiera los microorganismos surgen de forma espontánea, sino que se encuentran en el aire y se desarrollan sobre la materia orgánica, que les sirve de alimento.

2 El cuello se dobla en forma de S.

Las hipótesis de Oparin y Haldane En la década de 1930, Alexander Oparin y John Haldane propusieron que la vida surgió a partir de moléculas inorgánicas. Según su hipótesis, las biomoléculas se pudieron formar por reacciones químicas entre los gases de la atmósfera primitiva de la Tierra, que pensaban que estaba formada por vapor de agua (H2O), hidrógeno (H2), metano (CH4) y amoniaco (NH3). La energía para esas reacciones procedería de las radiaciones solares y de las descargas eléctricas de las tormentas. Así, se formarían azúcares sencillos, aminoácidos, ácidos grasos y nucleótidos, que caerían en los mares y formarían un «caldo primitivo». Estas moléculas interaccionarían y formarían otras más complejas, como las proteínas o los ácidos nucleicos. A medida que se hicieron más complejas, estas moléculas adquirieron la capacidad de autorreplicarse. En 1953, los científicos Stanley Miller y Harold Urey comprobaron experimentalmente la hipótesis de Oparin.

3 El caldo del

matraz se hace hervir con fuerza. El vapor sale por el extremo del tubo.

4 Polvo y bacterias atrapados aquí.

A medida que el caldo se enfría, el aire del matraz se contrae, arrastrando más aire del exterior hacia dentro. Las partículas de polvo y los microorganismos se depositan en el codo del cuello.

Comprende, piensa, investiga... 1 Observa la ilustración de la derecha, que representa el experimento realizado por Francesco Redi, y explica en qué consiste. ¿Crees que se basa en el método científico?

2 ¿Cómo demostró Pasteur que los microorganismos no surgían de la nada? 3 Observa la imagen del experimento de Pasteur y explica qué pasaría en el caldo si el matraz se inclina y pueden pasar el polvo y las bacterias retenidos.

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Busca información en Internet sobre el experimento de Miller y Urey y explica qué demostró ese experimento.

Carne

… pasados unos días…

La evolución de las células

Unidad 4

Los precursores de los seres vivos eran estructuras precelulares, es decir, moléculas orgánicas más sencillas que las actuales. Hace unos 3 800 millones de años evolucionaron y dieron lugar a los organismos procariotas: las bacterias. Posteriormente, tras un proceso que duró alrededor de 2 000 millones de años, surgieron las células eucariotas. • Procariotas heterótrofos. En una atmósfera sin oxígeno, las primeras células procariotas obtenían los nutrientes y la energía de la fermentación de la materia orgánica presente en el medio. • Procariotas autótrofos. Cuando la materia orgánica comenzó a escasear se produjo la muerte de muchas bacterias. Pero las cianobacterias fueron capaces de sobrevivir, ya que eran capaces de sintetizar materia orgánica mediante la fotosíntesis. Gracias a ese proceso, la atmósfera comenzó a enriquecerse en oxígeno. Algunos organismos procariotas quimiosintéticos comenzaron a usarlo para obtener energía en reacciones de oxidación de sustancias inorgánicas. • Procariotas heterótrofos aerobios. La presencia de oxígeno permitió la aparición de organismos capaces de llevar a cabo la respiración celular. A medida que las reservas de materia del medio se fueron agotando, estos heterótrofos adquirieron la capacidad de obtener los nutrientes sintetizados por los autótrofos. • Eucariotas. Surgieron hace unos 1 800 millones de años a partir de células procariotas.

La teoría de la endosimbiosis Bacterias aeróbicas (respiran O2)

Organismo procariota ameboide

Espiroquetas

Formación de mitocondrias Hacia los animales

Formación de flagelos

La teoría endosimbiótica Esta teoría, postulada por Lynn Margulis en 1967, trata de explicar el origen de las células eucariotas. Según esta teoría, algunos orgánulos de la célula eucariota, especialmente los cloroplastos y las mitocondrias, tienen su origen en organismos procariotas que habrían sido absorbidos por otro organismo, estableciéndose entre ellos una relación de simbiosis. Se cree que las mitocondrias procederían de un tipo de bacterias heterótrofas, y los cloroplastos, de las cianobacterias.

Hacia los vegetales

Núcleo

Células de cianobacterias (fotosíntesis)

Formación de cloroplastos

Comprende, piensa, investiga... 1

Lee «Los principales fundamentos de la teoría endosimbiótica» disponible en el banco de recursos de anayaeducacion.es y escribe cuáles son los cuatro que se mencionan.

2 En parejas, observad la imagen superior y explicad cómo se formaron las mitocondrias, los flagelos y los cloroplastos según la teoría endosimbiótica.

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