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LIFE SCIENCES STUDY GUIDE Grade 11

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Life Sciences

Study guide

Grade 11

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Study Guide G11 ~ Life Sciences

CONTENTS STRAND 1: DIVERSITY, CHANGE AND CONTINUITY. ............................................... 3 UNIT 1: UNIT 2: UNIT 3: UNIT 4: UNIT 5: UNIT 6: UNIT 7: UNIT 8: UNIT 9: UNIT 10: UNIT 11: UNIT 12: UNIT 13: UNIT 14: UNIT 15: UNIT 16: UNIT 17: UNIT 18: UNIT 19:

Biodiversity and classification of micro-organisms.......................................... 4 Viruses and bacteria ....................................................................................... 8 Fungi ............................................................................................................ 21 Protista ......................................................................................................... 31 Diseases caused by micro-organisms .......................................................... 45 The prevention and treatment of diseases ................................................... 55 Biodiversity of plants..................................................................................... 60 Bryophytes (Mosses) .................................................................................... 63 Pteridophytes (Ferns) ................................................................................... 69 Gymnospermae (Naked seeds) .................................................................... 75 Angiosperms (Flowering plants) ................................................................... 81 The significance of seeds ............................................................................. 89 Biodiversity of animals .................................................................................. 94 Porifera and Cnidaria.................................................................................. 100 Platyhelminthes .......................................................................................... 104 Annelida ..................................................................................................... 108 Arthropoda .................................................................................................. 113 Chordata ..................................................................................................... 117 Role of invertebrates in agriculture and ecosystems .................................. 121

STRAND 2: LIFE PROCESSES IN PLANTS AND ANIMALS ................................... 124 UNIT 1: UNIT 2: UNIT 3: UNIT 4: UNIT 5: UNIT 6: UNIT 7: UNIT 8:

Photosynthesis ........................................................................................... 125 Animal nutrition – Mammals ....................................................................... 140 Chemical digestion and absorption............................................................. 158 The relationships between food intake, energy, growth and health requirements .............................................................................................. 166 Tooth decay and drug abuse ...................................................................... 179 Cellular respiration...................................................................................... 187 Gaseous exchange..................................................................................... 200 Excretion by humans ................................................................................. 219

STRAND 3: ENVIRONMENTAL STUDIES..................................................................232 UNIT 1: UNIT 2:

Population ecology ..................................................................................... 233 Human impact on the environment ............................................................. 257

REFERENCES:........................................................................................................... 282

Study Guide G11 ~ Life Sciences

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STRAND 1: DIVERSITY, CHANGE AND CONTINUITY

Life consists of a wide variety of organisms that live in a variety of niches. This strand introduces learners to different life forms ranging from micro-organisms to macroscopic plants and animals. They are organised according to a manmade classification system that is based on the visible features. The role of organisms in an ecosystem will be discovered, including micro-organisms that are the main cause of diseases. This strand also includes the evolutionary development of plant- and animal phyla. In this strand you will study the following: • The basic structure and general characteristics of viruses, bacteria, fungi and protista. • The role of micro-organisms in maintaining balance in the environment. • Symbiotic relationships such as nitrogen fixing bacteria in plants and E.Coli in the human intestines. • The effect and management of one disease from each of the four groups of micro-organisms. • The immune response of plants and animals against the infecting microorganisms as well as vaccinations. • The use of medication such as antibiotics and the effect of them on microorganisms. • The use of micro-organisms to produce medicine. • The traditional use of technology to produce beer, wine and cheese. • The grouping of Bryophytes, Pteridophytes, Gymnosperms and Angiosperms in accordance with the presence or absence of vascular tissue, true leaves and roots, seeds or spores and fruit. • Asexual and sexual reproduction in plants. • The biodiversity of invertebrate animals

Study Guide G11 ~ Life Sciences

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UNIT 1: BIODIVERSITY AND CLASSIFICATION OF MICROORGANISMS There are a large number of living organisms. The number of species on earth today varies from as little as three million to a 100 million or more. Living organisms are divided into two main groups, plants and animals. What do you know? You already know that organisms consist of cells. The simplest organisms consist of single cells and complex organisms consist of many cells.

What do you have to know? The use of the electron microscope has discovered two types of cellular organisms: prokaryotes and eukaryotes. The prokaryotes have very small cells with no true nucleus. The eukaryotes have a true nucleus that is separated by a membrane from the cytoplasm.

Challenge! 1. Which micro-organisms are both beneficial and essential for our survival? 2. Which micro-organisms are responsible for our deaths?

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Study Guide G11 ~ Life Sciences

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Living organisms are classified into five groups. The main kingdoms are: ♣ Monera ♣ Protista ♣ Fungi ♣ Plantae (plant kingdom) ♣ Animalia (animal kingdom)

Did you know? If only one page were to be used to describe every specie, then it would have covered a total of 6,03 km of book shelving

Micro-organisms refer to those organisms that cannot be seen with the naked eye. This includes examples of all the Prokaryotes, some Protozoa and Fungi, as well as viruses. Even though micro-organisms share the feature of being small organisms, they have little in common and differ greatly in structure and function. Did you know? You cannot see the Micro-organisms vary in structure and function. Micromillions of virusses organisms can be both beneficial and harmful to the and bacteria leave environment. Decomposition and recycling is necessary your nose everytime for life. Micro-organisms benefit man economically in the you sneeze. Flu, production of bread, wine, beer and cheese. pneumonia and even tuberculosis can Micro-organisms cause diseases such as cholera, yellow spread by sneezing. fever, malaria, tuberculosis, flu and Aids. They are the cause of diseases in plants and play a role in the spoiling of food. The name “prokaryotes” is derived from the Greek word pro (which means before) and karyon (which means core/nucleus). These organisms are characterised by the absence of a true core (nucleus) in cells. The use of the electron microscope indicates that the cells of the prokaryotes: • do not have a distinct nucleus. • have a single round chromosome composed of DNA in the cytoplasm. • do not have mitochondria, chloroplasts or structured flagellae. • contain a cell wall composed of a compound from a protein-like origin. • are extremely small. (1 to 10 μm in diameter). Prokaryotes

Study Guide G11 ~ Life Sciences

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The name is derived from the Greek word eu (good) and karyon (nucleus). This group includes the fungi, plants and animals. The electron microscope has made it possible to observe the following features of eukaryotes: • The cell has a nucleus that is separated from the cytoplasm by a nuclear membrane. • The nucleus contains chromosomes. • The cytoplasm contains membrane bound structures called organelles such as endoplasmic reticula and mitochondria. • Some cells have flagellae or cilia. • When a cell wall is present it usually consists of cellulose and/or chitin. • Cells are 10 to 100 μm in diameter. Eukaryotes

The prokaryotes and simple eukaryotes Kingdom Monera

This kingdom consists of all bacteria and cianobacteria. The genetic material of these organisms consists of circular DNA that is unprotected in the cytoplasm. The cytoplasm contains a few organelles. Not one of these organelles is surrounded by a double membrane, as in the eukaryotes. The cell wall is a firm structure, consisting of polysaccharides. Some organelles have the ability to convert atmospheric nitrogen to organic compounds. More about Monera: • These organisms are mostly prokaryotes, because they do not have a true nucleus. Nutrition takes place through absorption or photosynthesis. Monera do not reproduce sexually. • Bacteria are the best known example of this kingdom which was discovered in 1676 by Anton van Leeuwenhoek. They are microscopic and the cell is surrounded by a cell wall. Many bacteria secrete mucus that forms an external sheath around the cell. Some forms move using flagellae while other small forms move passively in water or air. • Bacteria are unicellular. • Reproduction is asexual by a process known as binary fission where the cells divide into two or through conjugation those results in genetic recombination. • Bacteria are widely spread in nature. They are found in air, water, soil, in or on food, within or on the bodies of organisms and in sewage. • Bacteria decompose dead organisms to prevent the build-up of these organisms. They also play an important role in the maintaining of soil fertility in the nitrogen cycle. • Some bacteria are pathogenic and cause diseases such as tuberculosis in humans, spleen sickness in cows and rotting in plants.

Study Guide G11 ~ Life Sciences

Kingdom Protista

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This kingdom consists of unicellular eukaryotes and the multi-cellular organisms that are closely related to them.

The sub-kingdom, Protozoa, consists of a large variety of small, eukaryotic organisms. Most of them are unicellular, animal-like organisms. Nutrition is mostly heterotrophic. Most protozoa are parasitic. Organisms that are parasitic feed off living organisms. They have complicated life cycles that include more than one host. Plasmodium falciparum is a protozoan that causes malaria in humans and uses the adult mosquito as a vector. Fig.1.1.The following diagram indicates the distribution of malaria in the world.

TEST YOUR KNOWLEDGE! 1. What are micro-organisms? 1) 2. Discuss the ecological and economic importance of micro-organisms. (7) 3. In table form name the two kingdoms under which micro-organisms are classified and give two differences between the organisms in each of the kingdoms. (6) [14]

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Study Guide G11 ~ Life Sciences

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UNIT 2: VIRUSES AND BACTERIA What do you know? You should know by now that viruses and bacteria are microscopic organisms that can cause disease.

What should you know? In this unit you will learn about: • The adaptation of viruses and bacteria to their environment and their diversity. • The necessity of virus and bacteria to the environment.

Challenge: 1. Do some research using reputable resources on diseases people can contract from viruses. 2. Name the viral diseases plants are susceptible to? 3. What diseases can animals contract from viruses? 4. What human diseases are caused by bacteria? 5. What diseases can animals contract from bacteria? 6. Name the bacterial diseases plants are susceptible to? 7. What benefit do bacteria have on the ecosystem?

VIRUSES • • •

Studying viruses will enable you to:

Discover the structure and biological importance of viruses. Find out about the replication of viruses. Learn about the general characteristics of viruses.

Remember: Viruses have a very simple structure. They are dependent on plant, animal or bacterial cells for their survival. They often cause disease. They are extremely small – between 10 nm and 200 nm. Do you know what a nanometre (nm) is? If you don’t know, look it up and write it in your exercise book.

Structure of viruses:

Viruses usually are rod-shaped or spherical in shape with a large number of triangular facets on the surface. They are often symmetrical. Viruses contain a nucleic acid enclosed within a protein coat or capsid. In plant viruses the nucleic acid is usually RNA, and in animal viruses the nucleic acid could either be RNA or DNA, but never both.

Did you know? Viral diseases of plants are usually carried by insects, but also by contaminated shears and other garden tools.

Study Guide G11 ~ Life Sciences

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The only life function of a virus is reproduction. A virus cannot be regarded as a cell, as it does not have a nucleus with chromosome material, it does not feed, it does not move, and there is no regulation of osmosis or exchange of gases. Therefore it is regarded as non-living.

The external structure of a bacteriophage (left) and an influenza virus (right)

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Fig 1.2: The external structure of a bacteriophage (left) and an influenza virus (right) Fig 1.3: The Rota virus Activity: Look up the definition of the words “cylindrical”, “spherical” and “symmetrical" in a dictionary.

Find out: What is a pathogen and a vector?

Study Guide G11 ~ Life Sciences

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Biological importance of viruses

“Virus” is a Latin word for “poison”. Viruses cause disease and are therefore the main pathogens of plants as well as animals and humans. They are host specific. The virus could even be tissue specific within the same organism, for example the polio-virus only affects the nerve tissue, but not the intestines. Viruses are obligate parasites that replicate within their host cells by changing the nucleic acid of the host cell to that of their own, and cause the host cell to die. Since viruses reproduce within host cells, it is very difficult to control them. Antibiotics do not work, and vaccines aren’t always successful, therefore, the best way to control viruses is by prevention. Viruses can spread from one person to the next through direct contact, sneezing, coughing or vectors. Fig. 1.4: The MI-virus Tip: When a plant is affected by a virus, remove the contaminated plant material to avoid further contamination, as there are no antidotes against viral infections.

The spread of viruses: Replication of viruses:

Viruses can spread through food, by direct contact or through carriers/vectors. Viruses replicate within living cells only. A virus that replicates within bacteria is termed a bacteriophage.

A bacteriophage attaches itself firmly to the wall of a single bacterial cell or bacterium (attachment), thereafter the nucleic acid content of the bacteriophage is injected into the cell (insertion), leaving the capsid behind. The DNA of the bacterium is used to replicate the viral DNA and form proteins for the new capsids (latent phase). When many bacteriophages have formed, the wall of the bacterium bursts releasing the new bacteriophages (lysis).

General Characteristics of viruses: • • • •

A virus contains either DNA or RNA. Viruses cannot grow or replicate by cell division Viruses are obligate parasites, using living host cells to generate new viruses. A virus is host-specific and can even be tissue-specific.

Study Guide G11 ~ Life Sciences

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BACTERIA Do it yourself!

To examine bacteria cultures you will require the following apparatus: • nutrient agar (feeding agar) • 250 ml conical flask • a pressure cooker • sterilised Petri dishes • cotton wool and aluminium foil • sterile wire loops Fig. 1.5: Apparatus for activity

Conical flask

Petri dish

Fig. 1.6: Microbiological loop

Tip: You can make your own sterile wireloop by bending a loop in nichrome wire, and sticking the other end into a wooden handle. Mix of 40g nutrient agar in water. Pour the mixture into the conical flask. Close the neck of the flask with cotton wool and cover it with aluminium foil. Sterilise the mixture by boiling it in the pressure cooker for 15 minutes. Gently lift the aluminium foil and remove the cotton wool. Pour the mixture into the base of the petri dish and cover with the top half. Allow the medium to cool. You now have a medium on which bacteria can be cultivated. Sterilise the microbiological loop by heating it with a Bunsen burner. Dip the loop into a liquid or scrape it across any surface to pick up bacteria. Open the petri dish for approximately 20 seconds and scrape the loop across the agar medium. Find a clean location, where you expect to find little or no bacteria and scrape the microbiological loop across the surface. Use another petri dish to scrape the loop across the agar medium. Label the petri dishes and store in a dark place or inside a cupboard for a few days.

Study Guide G11 ~ Life Sciences

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Remove the petri dishes after a few days and examine them. What do you observe? Are some of the dishes clean? What can you deduce from this?

What have you discovered? Beware! Some bacteria can be dangerous, and you should handle the petri dishes with great care! When you have completed your examination, you have to decontaminate your Petri dishes and its content by sterilising it in a pressure cooker.

Bacteria are microscopic, single-celled organisms, varying in size from 5 µm to 1 µm, that reproduce quickly and form visible colonies.

Structure of bacteria:

Every bacterial cell is surrounded by a cell wall consisting of polysaccharides. The cell wall is enveloped by a capsule or slimy sheath. The cell content is a mass of grainy protoplasm, contained within its membrane. Bacteria are prokaryotes, meaning that they do not have a true nucleus. The cell has whole strands of DNA called a nucleoid. Small circular pieces of DNA called plasmids float around in the cytoplasm. Bacterial cells have nutrient granules of fats, proteins and glycogen in the protoplasm, and are generally colourless, although some can be coloured.

Fig. 1.7: The structure of a bacteriophage

Study Guide G11 ~ Life Sciences

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Fig 1.8: Line diagram of a bacterium cell.

A – pili C – capsule E – flagellum G – vacuole I – nucleoid

B – ribosome D – cell wall F – cytoplasm H – plasmid J - cytoplasmic membrane

Some bacteria move around using flagella, which are long, thin hair-like fibrils. Bacteria are classified according to their shape, namely bacilli (rod-shaped), cocci (spherical or ellipsoid), vibrio (comma-shaped) and spirillium (spiral-shaped). •

Bacteria are able to reproduce in various ways, for example budding, spore form, segmentation, conjugation (temporary fusion), and binary fission (asexual reproduction).

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Bacteria reproduce asexually when conditions are favourable. These conditions include the availability of enough food and water, it is dark and the temperature is optimal.

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During binary fission the DNA duplicates and divides into two and moves apart.

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A membrane forms across the middle of the cell to separate the cytoplasm. A new cell wall develops on the cell membrane.

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Binary fission can happen every 20 to 30 minutes.

Study Guide G11 ~ Life Sciences

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Fig. 1.9: The life cycle of a bacteriophage

Fig. 1.10: Various forms of bacterial cells A. Bacilli (rod-shaped) B. Cocci (Round-shaped) C. Cocci in bundles D. Cocci in pairs E. Spirillium (spiral-shaped) F. Vibrio (Comma-shaped)

Ecological importance of bacteria: Pathogenic bacteria:

The word pathogen comes from the Greek words “pathos” meaning suffering and “genesis” that means origin. A pathogen therefore relates to the origin of diseases. Pathogenic bacteria, in other words, are bacteria that cause disease.

Did you know? The chronic Respiratory Disease in chickens is caused by Mycoplasma gallisepticum, causing gurgling sounds when chickens go to sleep. A chicken that recovers from this disease remains a carrier of the disease and it could be present in the eggs of infected hens, and the day-old chickens.

Disease causing bacteria can be controlled by using antibiotics manufactured from certain fungi and bacteria. Most antibiotics,

Study Guide G11 ~ Life Sciences

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however, do not kill bacteria, but inhibit the production of proteins that form the bacteria. Broad-spectrum antibiotics are nonspecific and kill many different types of bacteria. Did you know? The bacteria Narrow-specific antibiotics will only kill specific causing bacterial wilt in pathogens. potatoes, beans and tomatoes, (Pseudomonas), can stay active Pathogenic bacteria penetrate the body in various ways. Diseases like tuberculosis, pneumonia and in the ground for years, and diphtheria spread through the air and when an increase the spread of the infected person coughs, sneezes or spits the disease during wet weather. disease can be spread. The bacteria block the tissue that transports water inside Food poisoning (botulism), gastro-enteritis and cholera are transmitted through food and water that the plant, and the plant starts comes in contact with contaminated faeces, or to wilt. through flies that pass the bacteria on from contaminated faeces to food. To prevent these diseases, water should be kept clean, and drinking water should be boiled. All vegetables and fruit should be washed. Did you know? Corynebacterium species, that cause abscesses in sheep, cattle and goats are transmitted through contaminated shears, filthy shearing pens, contaminated clothing of shearers, contaminated dipping troughs and so forth and can penetrate their bodies through lesions caused by tick bites, thistles, and thorns from trees, castration and even the umbilical cords of new-born lambs.

Bacteria causing tetanus, boils, abscesses and acne, can penetrate the body through lesions of the skin. Your skin should be washed regularly and wounds should be disinfected to prevent the spread of these bacteria. Diseases like bubonic plague are transmitted by vectors such as fleas on rats.

Venereal diseases like syphilis and gonorrhoea are transmitted by sexual contact. These and other similar diseases can be prevented through a chaste lifestyle as intended by our Creator. Conversely there are good bacteria like decomposition bacteria in the ground which are responsible for breaking down dead plant and animal material. Even in food bacteria could be beneficial, like in the production of cheese, yoghurt, vinegar, sauerkraut and gherkins by means of fermentation. Bacteria also play a significant role in the manufacture of silage. Some bacteria live symbiotically with other organisms. Various mutualistic bacteria can be found, such as nitrogen-fixing bacteria in the nodules on the roots of legumes, as well as rumen bacteria in ruminants that provide vitamin B12 to the animal.

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