Life Sciences Grade 11 Textbook PDF

LIFE SCIENCES Grade 11 Textbook  Contributors Ms Laura Munnik, Mr Peter Weisswange (editors), Ms Angie Weisswange (illustrator), Mr Wayne Brazier, Mr Jason Field, Ms Michelle Tracy Hagemann, Ms Kathryn Lamarque, Ms Jessica Marais, Ms Laura Munnik, Ms Alydia Monteith,...

LIFE SCIENCES Grade 11 Textbook  Contributors Ms Laura Munnik, Mr Peter Weisswange (editors), Ms Angie Weisswange (illustrator), Mr Wayne Brazier, Mr Jason Field, Ms Michelle Tracy Hagemann, Ms Kathryn Lamarque, Ms Jessica Marais, Ms Laura Munnik, Ms Alydia Monteith, Ms Danielle Stander, Ms Angie Weisswange (all authors), Dr Arnold Johannes, Ms Helena Oosthuizen, Ms Delia Stander, Ms Kerstin Stoltsz Quality Assurance by Life Sciences Subject Advisors, under the direction of Mr Kanthan Naidoo (CES): Ms Wendy Coertze (LP), Mr Jakobus Farmer (WC), Ms Michele Fortuin (WC), Mr Cassius Ditshwedi Makgata (GP), Ms Grace Moepang (GP) Produced for the National Department of Basic Education © DBE TABLE OF CONTENTS Introducing Life Sciences 1 Strand: Diversity, change and continuity 1. Biodiversity and classification of micro-organisms 6 2. Biodiversity of plants 53 3. Biodiversity of animals 77 Strand: Life processes in plants and animals 4. Photosynthesis 109 5. Animal nutrition 133 6. Cellular respiration 162 7. Gaseous exchange 178 8. Excretion in humans 204 Strand: Environmental studies 9. Population ecology 233 10. Human impact on the environment 275 Appendices A Final Word: Assessments 343 Answers to Activities 346 Image Attribution 367 INTRODUCING LIFE SCIENCES The aim of this textbook is to allow you, the learner, to be an active partner in your learning experience. The text has been designed to cover all the content you need for Grade 11, and to provide it in a readable manner that communicates all concepts simply, clearly and in the necessary amount of detail. The next few pages will provide you with a broad overview of Life Sciences and hopefully show you its value as a choice for a school subject. Studying Life Sciences also offers you broader benefits: it will encourage your ability to think critically, to solve problems and seek to understand the world around you. What are the Life Sciences? The term ‘Life Sciences’ indicates clearly the two ideas held together in this subject:  Life refers to all living things – from the most basic of molecules through to the interactions of organisms with one another and their environments.  Science indicates it is necessary to use certain methods in our study of the subject. The two broad aims of any science are to increase existing knowledge and discover new things. We approach this using careful methods that can be copied by others. These include:  proposing hypotheses (the predicted outcome of an investigation) and  carrying out investigations and experiments to test these hypotheses. Scientific knowledge changes over time as more is discovered and understood about our world; as such, Life Sciences is a constantly growing subject. Why choose Life Sciences as a subject?  First, to give you knowledge and skills that are helpful in everyday life, even if you do not pursue Life Sciences after school.  Secondly, to expose you to the wide variety of sub-fields within the subject that could encourage or interest you to pursue a career in the sciences. If you choose to study Life Sciences at school you will be able to study any Life Science specialisations after school - such as microbiology, genetics, environmental studies or biotechnology. 1 What skills will Life Sciences equip you with? This subject will teach you important biological concepts, processes, systems and theories, and provide you with the skills to think, read and write about them. Life Sciences will:  give you the ability to evaluate and discuss scientific issues and processes  provide an awareness of the ways biotechnology and a knowledge of Life Sciences have benefited humankind  show you the ways in which humans have impacted negatively on the environment and organisms within it, and show you how to be a responsible citizen in terms of the environment and conservation  build an appreciation of the unique contribution of South Africa to Life Sciences - both the diversity of the unique biomes within Southern Africa and the contributions of South Africans to the scientific landscape. Life Sciences Strands for Grade 11 Everything you study this year will fit into one of these three broad strands. These knowledge pathways grow over your three years of FET. Within each knowledge strand, ideas should not be studied separately; rather seek to discover the links between related topics so that you grow in your understanding of the inter-connectedness of life. As you study each section or chapter, look for the broad strokes that place it under one of these strands:  Knowledge Strand 2: Life Processes in Plants and Animals  Knowledge Strand 3: Diversity, Change and Continuity  Knowledge Strand 4: Environmental Studies The Purpose of studying Life Sciences There are three broad purposes, which will expand as we continue:  Aim 1 - knowing the content (theory);  Aim 2 - doing practical work and investigations;  Aim 3 - understanding the applications of Life Sciences in society - both present society (indigenous and western) and within the context of history. Aim 1: Knowing the content of Life Sciences Learning content involves understanding and making meaning of scientific ideas, and then connecting these ideas. Theory is not just recalling facts; it is being able to 2 select important ideas, use different sources to learn, and describe concepts, processes and theories important to Life Sciences. Within this you will learn to write summaries, develop your own diagrams and reorganise data you are given into something meaningful. Additionally, you will learn to interpret the data you are working with and link it to theory you have studied. Aim 2: Doing practical work and investigations Life Science is a fascinating subject and one of the best ways to understand it is for you to see it in action. Therefore, it is important for you to know how to do practical investigations. Within this, you will learn many useful skills like how to follow instructions in a safe manner and how to name, recognise and handle laboratory equipment. During a practical investigation it is important for you to be able to make observations. There are many ways this can be done - by making drawings, describing what you see, taking measurements, and comparing materials before and after a certain treatment. After making these observations it is important for you to be able to measure and record them in a useful way. From here you will interpret your data - you will look for the value in what you gathered and discuss the changes, trends, and applications of what you have shown. Finally, you will learn how to design your own investigations and experiments. An investigation is more straightforward; for example, it could involve observing soil profiles or counting animal populations. Planning an experiment would begin with identifying a problem, and then hypothesising a solution. In planning, you would identify variables and consider ways to control them, select apparatus and materials to assist you, and then plan an experiment that could be repeated by someone else. It is also important to consider ways of capturing and interpreting your data. Aim 3: Understanding the history, importance and modern applications of Life sciences The third aim of Life Sciences is to show you that school science can be relevant to your life and that studying provides enrichment to you, even if you do not pursue it past school level. As you study you will be exposed to the history of science and indigenous knowledge systems from other times and other cultures. As you learn a certain section of work, you will be introduced to how that knowledge was developed by various scientists across the ages as they pursued a deeper understanding of the world around them. 3 Our search of knowledge is shaped by our world view. Therefore, an important concept to be aware of is that modern science (and technology) and traditional, indigenous knowledge systems will sometimes differ in their approach to science. These seemingly opposite views can be held together as both bring a certain dynamic; they should not be seen as opposing forces. Finally, there are many possible career fields branching out of Life Sciences and, as you learn, some of these will be shown through examples. Different sections would open up different careers choices- in the past (for example palaeontology), the present (like horticulture, game ranch management and preservation) and the future (such as biotechnology and genetic engineering). A final word on using this textbook The best way to use this textbook to increase your understanding and thereby results would be as follows:  Remember, good learning begins in the classroom so always pay careful attention as your teacher works through it with you  Take note of sections you do not understand and revisit them  Ask questions to make sure you understand  Consider the end-of-chapter summaries and build on them to create your own point-form summary note  Practice re-sketching the given diagrams  Work through all the given questions and answers at the end of the chapter. 4 5 1: Biodiversity and classification of micro-organisms Introduction Rabies The classification of organisms HIV / AIDS Viruses Influenza Structure and characteristics Diseases caused by bacteria of viruses Blight Bacteria Cholera Characteristics of bacteria Tuberculosis Structural characteristics Anthrax Nutrition of bacteria Diseases caused by Protista Reproduction of bacteria Malaria Protista Diseases caused by fungi Characteristics of Protista Rusts Three groups of Protista Thrush Fungi Ringworm Characteristics Athlete’s foot Activity 1: Kingdoms Activity 4: Diseases Activity 2: Practical Immunity investigation The response of plants against an The role that micro-organisms play in infecting micro-organism maintaining a balance in the The response of animals against environment an infecting micro-organism … in food chains Lymphocytes … as decomposers Phagocytes … in the nitrogen cycle Vaccinations Symbiotic relationships The use of drugs to fight infecting Lichens micro-organisms The relationship between nitrogen Antibiotics fixing bacteria and plants Biotechnology The relationship between E. coli The making of antibiotics and the human intestine The making of insulin Mycorrhizal fungi and the roots of higher plants Traditional technology Activity 3: Nitrogen use Diseases caused by micro-organisms End of topic exercises Diseases caused by viruses 6 CHAPTER 1: BIODIVERSITY AND CLASSIFICATION OF MICRO-ORGANISMS Introduction Biodiversity in general, refers to the wide variety of plants, animals and micro- organisms on Earth. Organisms which are too small to be seen with the naked eye are referred to as micro-organisms. Micro-organisms can be unicellular or multicellular. Some are harmful and cause diseases whilst others are very useful in the environment and to humans e.g. yeasts are used to make bread. Key terminology unicellular an organism consisting of only one cell multicellular an organism made up of many cells biodiversity the variety of organisms found in an area or on Earth The classification of organisms Scientists have placed all the organisms into specific groups so that it is easier to study them. There are five groups called kingdoms (Figure 1):  Kingdom Monera – bacteria  Kingdom Protista  Kingdom Fungi  Kingdom Plantae  Kingdom Animalia A scientist who is responsible for the placing of an organism within a specific group is called a taxonomist. Figure 1: The 5 Kingdoms of Life 7 Viruses Viruses are placed in a separate group and not in a kingdom because they display some non-living as well as living characteristics. Key terminology capsid a protein coat surrounding the nucleic material of a virus acellular non-cellular obligate = forced; a parasitic organism that cannot complete its obligate life-cycle without exploiting a suitable host (if an obligate parasite parasite cannot obtain a host it will fail to reproduce) host an organism that harbours a parasite pathogenic an organism that causes disease a type of virus that infects bacteria; the word "phage" means to bacteriophage eat” an irregularly shaped region within the cell of a prokaryote that nucleoid contains all or most of the genetic material Structure and characteristics of viruses Introduction to viruses: https://www.youtube.com/watch?v=8FqlTslU22s  Viruses are microscopic (20 – 300 nm) and can only be studied using an electron microscope.  Viruses consist of a core of either DNA or RNA enclosed by a protein coat called a capsid (Figure 2). Envelope DNA or RNA Protein coat Figure 2: Structure of a typical virus 8   Viruses occur in a variety of shapes,  cannot respire, feed or excrete waste,  do not have a cytoplasm and do not have any membrane bound organelles such as mitochondria or nuclei.  Viruses have either DNA or RNA which is surrounded and protected by an outer protein coat or capsid. All other living organisms have both DNA and RNA.  Viruses are acellular.  Viruses do not have chlorophyll and are therefore unable to make their own food by photosynthesis.  All viruses are obligate internal parasites. This means that they cannot multiply without infecting another living organism or host.  Viruses can infect bacteria, protists, plants and animals. Viruses that infect bacteria are called bacteriophages.  Viruses cause diseases and are said to be pathogenic.  In humans, viruses are responsible for diseases such as HIV/AIDS, poliomyelitis, chickenpox, herpes and influenza.  If a virus cannot find a host, they can become dormant. Bacteria Bacteria belong to the Kingdom Monera. Bacteria are found everywhere on earth. Some are pathogenic and cause diseases such as tuberculosis, while most are useful. Key terminology an organism where the nuclear material is not enclosed in a prokaryotic membrane any single or multicellular group of organisms that have a eukaryotic membrane-bound nucleus containing genetic material a whip-like, protruding filaments that help cells or micro- flagellum organisms move; plural of flagellum is flagella organisms which can synthesize their own food e.g. green autotrophic plants, algae and some bacteria any organism that sources food from its environment because heterotrophic it cannot make its own food, e.g. animals, fungi, most bacteria plant or fungal microorganisms that feeds on dead or decaying saprophytic tissues of other organisms 9  asexual reproduction of a single cell in which divides by binary fission mitosis; the cell regenerates as two or more separate cells having the same chromosomal identities as the parent cell a tough, protective, non-reproductive bacteria structure that contains DNA and cytoplasm and lies dormant to survive endospore unfavourable environmental conditions in order that it can germinate once conditions improve a plasmid is a small, circular, double-stranded DNA molecule plasmid that is distinct from a cell's chromosomal DNA Characteristics of bacteria Bacterial cell structure: https://www.youtube.com/watch?v=4DYgGA9jdlE  Bacteria are unicellular (one celled) organisms.  Bacteria are larger than viruses and can be seen using a light microscope.  Bacteria are distinguished from one another by their shape (Figure 3). These shapes include: coccus – round, bacillus – rod-shaped, spirillum – spiral- shaped, and vibrio – comma-shaped. Cocci Bacilli Others coccus diplococci spirilla coccobacillus coryne- sarcina bacterium tetrad bacillus diplobacilli streptococci vibrios staphylococci palisades spirochete Figure 3: Bacterial shapes 10 Structural characteristics All bacteria have the following structural characteristics (Figure 4):  A cell wall made up of polysaccharides.  Some bacteria have a slime capsule to protect them from drying out.  Cytoplasm surrounded by a cell membrane.  No membrane-bound organelles.  The DNA is in the form of an irregular loop and is called a nucleoid. Since there is no membrane around the nuclear material, bacteria are said to be prokaryotic.  A plasmid, small, circular, double-stranded DNA molecule is also found in the cytoplasm of bacteria.  Many bacteria have a whip-like flagellum which they can use to move in a liquid. The flagella can rotate to propel the organism forwards. slime layer cell wall cell membrane ribosomes nucleoid plasmid flagella Figure 4: Basic structure of a bacillus shaped bacterium 11 Nutrition of bacteria Autotrophic bacteria can manufacture their own food.  Photosynthetic bacteria use sunlight energy, while  Chemosynthetic bacteria get their energy from chemical processes. Heterotrophic bacteria cannot manufacture their own food. This includes:  Parasitic bacteria that obtain their food from other living organisms.  Saprotrophic bacteria that play an important role as decomposers. They obtain their food from dead organic plants and animals.  Mutualistic bacteria that form a relationship with another organism. Both organisms benefit from the relationship. Reproduction of bacteria Bacteria multiply very quickly under favourable conditions. This simple form of cell division is called binary fission (Figure 5). Figure 5: Binary fission in bacteria Bacteria form endospores when conditions are unfavourable for example, when there is a lack of food, extreme heat or a lack of moisture. Protista The Kingdom Protista is a collection of eukaryotic organisms. Protists do not fit into the plant, animal or fungi kingdoms. 12 Key terminology aquatic living in or around water phytoplankton very small plants (algae) that float on or near the surface of water zooplankton consisting of small animals and the immature stages of larger animals which float on or near the surface of the water sessile organisms are usually permanently attached to sessile something and can cannot move on their own but can move through outside sources (such as water currents) Characteristics of the Protista  simple unicellular or multicellular eukaryotic organisms  no tissue differentiation  found mainly in water  autotrophic or heterotrophic  usually microscopic but can be several meters in length for example the seaweeds  some are sessile or free-floating while others can move using flagella (e.g. Euglena) or move using false feet called pseudopodia (e.g. Amoeba)  they can reproduce both sexually and asexually Three groups of Protista are recognized: Plant-like Protista:  mainly unicellular organisms found in aquatic (water) environments  most are autotrophic  free floating aquatic plant-like protists are called phytoplankton (Figure 6) Figure 6: Phytoplankton 13  Animal-like Protista:  mainly heterotrophic free-living unicellular animals living in an aquatic environment e.g. Amoeba  some are parasitic and cause diseases such as malaria  free-floating aquatic animal- like protists are called zooplankton (Figure 7) Figure 7: Zooplankton Algae  multicellular, macroscopic organisms commonly called seaweeds (Figure 8)  seaweeds contain various photosynthetic pigments which give them a green, red or brown colour  seaweeds may be free-floating Figure 8: A species of red seaweed or sessile (attached to a (Gelidium pristoides) harvested along the substrate) South African coast to produce agar Fungi The Kingdom Fungi includes moulds, yeasts, mildews, rusts, toadstools and mushrooms (Figure 9 – 12). Key terminology a fibrous substance consisting of polysaccharides, which is the chitin major constituent in the exoskeleton of arthropods and the cell walls of fungi a network of multi-celled threadlike filaments forming the hyphae mycelium of a fungus a vegetative mass or network of fungal hyphae found in and mycelium on soil or organic substrates 14  multinucleate cells that have more than one nucleus per cell, i.e., multiple nuclei shared in one common cytoplasm threadlike structures that anchor lower plants and fungi to a rhizoids surface a form of asexual reproduction which involves the pinching off budding of offspring from the parent cell; the offspring cell is genetically identical to the parent Figure 9: Toadstools Figure 10: Mushrooms Figure 11: Bracket fungi Figure 12: Breadmould Characteristics Fungi have the following characteristic in common:  Some are unicellular (yeasts) while others are multicellular (mushrooms).  Eukaryotic (i.e. have a nuclear membrane).  Heterotrophic since they lack chlorophyll. Fungi that live off dead organic matter are said to be saprotrophic. Parasitic fungi live off living organisms. Fungi cause diseases such as thrush, ringworm and athlete’s foot. 15   Cell walls which contain chitin. Plants have cellulose in their cell walls.  The bodies of multicellular fungi are made up of threads called hyphae. All the hyphae together form a mycelium.  The hyphae are often multinucleate (have many nuclei).  Fungi reproduce both sexually and asexually.  Asexual reproduction in unicellular fungi such as yeasts is by budding.  In multicellular fungi asexual reproduction is by means of spores. Activity 1: Kingdoms 1. Name the five kingdoms which represent all living organisms (5) 2. Make a labelled diagram to show the internal structure of a bacterium. (6) 3. Name one important characteristic which distinguishes fungi from algae. (2) 4. Explain why viruses are not placed into one of the five kingdoms. (2) 5. Complete the following table: (12) Unicellular/ Prokaryotic / Mode of Organism Multicellular Eukaryotic nutrition Viruses acellular neither Bacteria Phytoplankton autotrophic Zooplankton Fungi (27) Activity 2: Practical investigation Aim: Investigating the growth of bread mould under different temperature conditions A Grade 11 learner investigated the optimum (ideal) temperature for growth of bread mould. The learner used the following method:  The learner selected four black plastic containers with lids.  A slice of bread was placed in each container.  Before closing the containers, 30 ml of water was sprinkled over each slice.  Container A was placed in a fridge (cold), container B was placed in a cupboard (cool), container C was kept at room temperature (mild) and container D was placed on a window sill (warm).  After a week the slices of bread were removed from the containers and placed next to each other. 16 The results of the investigation are depicted below. 1. Formulate a hypothesis for the investigation. (2) 2. Name: (a) the dependent and (b) the independent variable in this investigation. (2) 3. State the relationship between the growth of bread mould and temperature. (2) 4. State three ways in which the learner made sure the results were valid. (3) 5. How could the learner have ensured that the results were reliable? (2) 6. Use the following scale to determine the percentage of bread mould growing on the slices of bread. Record the estimations in a table. (5) 7. Plot a bar graph to show the relationship between temperature (cold, cool, mild and warm) and the growth of breadmould using the table. (6) (22) The role that micro-organisms play in maintaining a balance in the environment Micro-organisms play an essential role in the natural recycling of living materials. Key terminology organisms that break down dead plant and animal (organic) decomposers material e.g. bacteria and fungi saprophytes organisms that live off dead organic matter 17 Micro-organisms as producers in food chains Autotrophic bacteria, phytoplankton and algae can manufacture their own food by photosynthesis. The carbohydrates they produce are available to consumers. These organisms form the first link in a food chain. Oxygen, the waste product of photosynthesis, is made available to other organisms for respiration. The role of micro-organisms as decomposers  Bacteria and fungi are the main decomposers.  They break down dead plant and animal remains and return the nutrients to the soil.  Organisms which break down dead organic matter to obtain nutrients are called saprophytes. The role of bacteria in the nitrogen cycle Bacteria play an important role in the nitrogen cycle.  Free living bacteria can convert atmospheric nitrogen to ammonia and nitrates.  Higher plants can only use nitrogen when it is in the form of nitrates, so they rely on bacteria for the conversion.  Some plants form special relationships with nitrogen fixing bacteria.  When plants and animals die, de-nitrifying bacteria return nitrogen to the atmosphere by a process called denitrification. Symbiotic relationships Symbiosis refers to the living together of two or more species of organism. A symbiotic relationship may benefit one or both members or it can be beneficial to one but harmful to the other one. Key terminology mutualism a symbiotic relationship where both organisms benefit a symbiotic relationship where one organism benefits without commensalism harming or affecting the other organism 18  a symbiotic relationship where parasitic organisms benefit parasitism while causing harm to their hosts composite organisms made up of fungi that grow symbiotically lichens with algae or cyanobacteria an even-toed mammal that chews the cud regurgitated from its ruminant rumen e.g. cattle, sheep, antelopes, deer, giraffes, and their relatives. mycorrhiza The symbiotic association of fungi with the roots of trees. Three types of symbiosis occur:  mutualism – both organisms benefit e.g. lichens  commensalism – one species benefits whilst the other does not benefit, nor is it harmed  parasitism – one species benefits whilst the other is harmed Lichens Algae need a moist environment to survive and cannot live on dry land. They can, however, form a mutualistic relationship with a fungus and this called a lichen (Figure 13). The fungus provides the alga protection from the environment. Fungi however cannot produce food for themselves. They in turn obtain nutrients from the algae which can produce food by photosynthesis. In this way, both the alga and the fungus benefit. Figure 13: Lichens are often the first organisms to occupy a habitat 19 The relationship between nitrogen fixing bacteria and plants  Higher plants require nitrogen to manufacture proteins.  Plants cannot use nitrogen directly from the atmosphere.  Plants require nitrogen in the form of nitrates.  Some soil bacteria can convert free nitrogen to nitrates that can be used by plants. Some nitrogen-fixing bacteria live in special nodules in the roots of leguminous plants (i.e. pod producing plants such as beans and peas). They produce nitrates for the plant while the plant provides the bacterium with a place to live, carbohydrates and water. Both the plant and the bacteria benefit in this relationship. The relationship between E. coli and the human intestine  Not all the bacteria found in our intestines are harmful.  Mutualistic bacteria such as Escherichia coli (E. coli) (Figure 14) live on the undigested remains of food in the gut and in turn make vitamin K which can be used by humans.  Vitamin K plays an important role in blood clotting. Both humans and the bacteria benefit from the relationship. Figure 14: E. coli bacteria Mutualistic bacteria are also found in the digestive tracts of ruminants and termites where they are responsible for the digestion of cellulose into simple sugars. 20 Mycorrhizal fungi and the roots of higher plants Filamentous fungi known as mycorrhizas can penetrate and become associated with the roots of higher plants. The fungi increase the absorption surface area of the roots. The fungus in turn, gets sugars from the plant. Symbiosis in general: https://www.youtube.com/watch?v=zTGcS7vJqbs Activity 3: Nitrogen use 1. Name the form of nitrogen which higher plants use. (1) 2. Describe three ways in which nitrogen becomes available to higher plants. (3) 3. What is a lichen? (3) 4. Describe the role bacteria play in maintaining the nitrogen balance in an ecosystem. (6) 5. The photograph below (Figure 15) shows a seedling without mycorrhizal fungi (left-hand side) and one with mycorrhizal fungi (right-hand side). The seedlings are the same age. Study the photograph and answer the questions that follow. without & with mycorrhizae Figure 15: Seedlings with and without mycorrhizal fungi. 5.1 What is a mycorrhiza? (2) 5.2 Explain why the seedling on the right-hand side is bigger than the seedling on the left-hand side. (3) (18) 21 Diseases caused by micro-organisms Organisms that cause diseases are called pathogens. You are required to study only one disease from each of the four groups of micro-organisms discussed below. Key terminology pathogen Infectious biological agent or organism that causes disease An agent who carries and transmits an infectious pathogen vector into another living organism. Living cell in which a virus (or foreign molecule or host microorganism) multiplies or hides. Refers to a sudden increase in the number of cases of a epidemic disease above what is normally expected. Refers to an epidemic that has spread over several countries pandemic or continents, usually affecting a large number of people Diseases caused by viruses Rabies Rabies affects both domestic and wild animals such as dogs (Figure 16), jackal and mongooses. The rabies virus is passed from one animal to another in saliva. Humans usually get infected when they are bitten by a rabid animal. Figure 16: Dogs infected by rabies often foam at the mouth. After a person has been bitten by a rabid animal, there is an incubation period of up to 60 days during which time the victim shows no symptoms. After this period the victim may show one or more of the following symptoms:  headaches and fever  sore throat 22   nausea  fatigue or tiredness These symptoms are followed by an agitated phase where the victim has convulsive seizures, salivates and fears water (hydrophobia). They also have difficulty in swallowing and breathing. Once the symptoms of the disease appear, there is no cure and the patient dies within 10 days from heart failure or breathing difficulties. Rabies can be managed as follows:  vaccination of dogs and livestock in areas where the disease is found  immunization of people with high-risk occupations such as veterinarians  immunization of travellers going to areas where the disease is found  training of health workers and veterinarians  destroying of animals infected with the disease Treatment of rabies  It is difficult to treat the disease, so it is important to avoid being bitten by animals infected by rabies.  Wild animals which suddenly appear to be tame should not be touched.  If there is contact with an animal which is behaving suspiciously, the person should seek medical attention immediately. HIV / AIDS Acquired Immune Deficiency Syndrome (AIDS) is a sexually transmitted disease caused by the Human Immunodeficiency Virus (HIV) (Figure 17). The virus weakens the immune system by infecting and destroying the immune cells which are known as the CD4 – cells. Figure 17: HIV virus in the blood stream 23 The HI virus is spread mainly through the transfer of body fluids such as semen and blood from an infected person to another person by one of the following ways:  sexual intercourse  blood transfusions of untested blood  sharing contaminated syringes (e.g. drug users)  from an infected mother to the foetus The virus in not transferred in the air, in saliva or by shaking hands with an infected person. The effects of HIV/AIDS on an individual include:  A lack of symptoms during the first phase of infection which can last years.  Flu like symptoms which include headaches, fever, tiredness, and the swelling of lymph glands in the armpits, throat or groin can occur.  As the immune system weakens symptoms such as repeated cold-sore infections, prolonged fevers, night sweats, chronic diarrhoea (runny tummy), etc. occur. Extreme weight loss can also occur.  A weakened immune system allows secondary or opportunistic infections to occur. These include respiratory infections, pneumonia, epilepsy, dementia, skin cancers, lymph cancer and tuberculosis.  In the final phase of HIV infection, the disease is known as AIDS. Death can occur in this phase due to secondary infections. HIV/AIDS affects families in the following ways:  If the breadwinner becomes ill there is no income and a family may become poverty stricken.  The virus is transmitted to an unborn child during pregnancy.  If both parents are infected and die, their children become orphans.  Brothers and sisters may be separated from each other if the parents die. The economy of a country is also affected by HIV/AIDS:  The disease is more common in young working people and reduces the labour force especially in the mining industry.  The costs of treatment and care are high. 24 Management of HIV/AIDS requires:  Testing for the virus in people who are at high risk (e.g. health workers, prostitutes, drug users).  Counselling and treatment for infected people with antiviral drugs.  Strengthening the immune system of infected persons.  Treatment of secondary infections.  Education and the prevention of infection by not having sexual intercourse (casual sex) or using protection such as a condom. Influenza Influenza is commonly called “flu” and is caused by the influenza virus. The virus spreads through the air when a patient coughs or sneezes (Figure 18). It can also spread through contact with bird droppings or contaminated surfaces. Symptoms include:  a sore throat  muscular pain  headaches  coughing. Symptoms usually only last a few days, but some strains of the virus can be deadly. Figure 18: Flu viruses can be spread by coughing 25 Viruses do not respond to antibiotics. Flu is best managed with the use of vaccines. Flu viruses mutate rapidly to form new strains which means that a new flu vaccine must be developed each year. To avoid catching flu, people must wash their hands regularly. People who are already infected should not cough or sneeze without covering their mouths. Diseases caused by bacteria Blight Blight is the term given to plants which suddenly wilt (droop) and die. It is caused by several different bacteria. Blight is a significant problem for commercial farming as it affects crops such as apples, grapes and tomatoes (Figure 19). Figure 19: Tomatoes affected by blight Symptoms of blight include:  drooping or dried up shoots and stalks  lesions (‘sores’) on the leaves  flowers that turn black and die  death of the whole plant if not treated Blight must be managed as follows:  only disease-free stock should be planted  pruning tools must be disinfected  cutting back should only be done on dry windless days  affected plant material should be burnt to avoid spores from spreading 26 Cholera Cholera is commonly found in areas where there is overcrowding, unsafe drinking water and a lack of proper sanitation (Figure 20). Cholera is caused by the bacterium Vibrio cholerae. Figure 20: Cholera breeds in unhygienic places Symptoms of cholera include:  watery diarrhoea (runny tummy) which leads to dehydration  vomiting Note that some people do not show any symptoms of cholera but can become carriers of the disease. Management of the disease should include:  access to clean drinking water or water purification tablets  preventing the spreading of the disease by proper sanitation and disposal of sewerage  infected people must be given fluids with added electrolytes to drink  severely infected people will have to be put on a drip  the bed linen and clothes of infected people must be disposed of  anything which cholera patients have touched must be washed in hot water and sterilized using chlorine bleach  people living in cholera areas should be educated about the importance of hygiene and be encouraged to boil water before drinking. 27  Treatment of cholera involves:  rehydration  antibiotic treatment Tuberculosis The bacterium, Mycobacterium tuberculosis causes the lung disease tuberculosis (TB) (Figure 21). The bacterium can also attack other parts of the body such as the kidneys, brain and spinal cord. TB is spread through the air when infected people cough or sneeze. The bacterium spreads quickly in confined, overcrowded spaces where there is poverty and poor sanitation. mycobacterium tuberculosis Figure 21: TB commonly infects the lungs TB can infect anyone who breathes in the bacterium but usually only develops in people with weak immune systems such as babies, young children, HIV positive people, drug users, diabetics and poverty-stricken people. The effect of TB on infected persons includes:  extreme tiredness and weakness  loss of appetite and weight  chills, fever and sweating at night  excessive coughing 28   chest pains  coughing up blood Management of TB requires:  identification of infections through X-rays, skin tests or tissue cultures.  educating the patient regarding the completion of treatment. Treatment of TB involves:  Treatment with a number of drugs over a period of about 6 months. When patients do not complete their treatment, they can develop a drug-resistant form of TB which is very difficult to treat. Patients are often kept in a TB hospital for treatment and to make sure they take their medication.  DOTS (Directly Observed Treatment Short Course) was developed so that someone makes sure that the patient completes their treatment. Anthrax Anthrax is caused by the bacterium Bacillus anthracis. It affects goats, cattle, sheep and horses. The spores are either inhaled by the animal or they enter through wounds. Once inside the body, the bacterium enters the bloodstream and multiplies very rapidly. It releases very strong toxins and causes tissues to breakdown, bleeding and eventually death. Humans become infected when they are exposed to infected animals or their products. The following symptoms appear in humans:  severe breathing problems and shock,  inflammation of the gastro-intestinal tract,  a painless skin ulcer with a black necrotic area in the middle (Figure 22). Figure 22: A typical symptom of an anthrax infection 29 Anthrax can be managed by:  Vaccination of stock animals.  If there is an outbreak of anthrax, animals showing signs of infection must be isolated and treated with antibiotics. All the other animals that have been in contact with the infected animals must be vaccinated.  The bodies of dead animals must be burned to destroy spores which could survive for up to 90 years.  Humans that have come into contact with anthrax must wash with antimicrobial soap and their clothes must be burned.  The bodies of humans that have died from anthrax should be cremated to avoid the disease spreading further. Diseases caused by Protista Malaria Introduction to Malaria: https://www.youtube.com/watch?v=f5XKob0lc2A  Malaria is a life-threatening disease found mainly in tropical and sub-tropical areas of the world.  Malaria is caused by the protozoan Plasmodium vivax and is spread by the female Anopheles mosquito.  The female Anopheles mosquito is called the vector.  A vector carries a disease-causing organism from an infected host to a new host.  The malaria parasite requires two hosts (mosquitoes and humans) to complete its life cycle. Symptoms of malaria include:  early symptoms that can be mistaken for flu  fever and shivering  headache  joint pain  vomiting  convulsions  anaemia 30 If left untreated, malaria may lead to the infected person falling into a coma, followed by death. The effects of malaria on the economy include:  Loss of income if the breadwinner cannot work or dies, resulting in poverty.  Malaria treatment is expensive. Poor people in undeveloped countries cannot afford treatment. The best way to manage malaria is to avoid being bitten by mosquitoes in areas where malaria occurs. This can be done by:  staying indoors between sunset and sunrise.  covering doors and windows with gauze to stop mosquitoes from entering rooms.  sleeping under mosquito nets.  applying insect repellents to exposed skin.  wearing long sleeves and pants if you need to be outdoors at night.  drain places where there is standing water e.g. drains, ponds, gutters, old tyres etc., as mosquitoes breed in standing water. Anti-malarial drugs can be taken before entering a malaria area. Drugs are available to treat people infected with malaria. Governments in malaria areas need to provide health-care facilities like clinics. They also control the breeding of mosquitoes by spraying with DDT, an insecticide. Diseases caused by fungi Rusts  Rusts are a group of fungi that infect crop plants (tomatoes, beans etc.), grasses and flowering plants such as roses, hollyhocks, and snapdragons.  The hyphae of the fungus burrow into the plant tissue and destroy it.  Bright orange raised areas can be seen on the surface of the plant leaves which resemble rusted metal when infected (Figure 23). 31  Figure 23: Rust is commonly seen on the underside of leaves Management and treatment of rust include:  planting of rust-resistant crops or plants  keeping plants healthy by adding nutrients to the soil or their water  sterilizing of equipment, especially pruning (cutting) tools  spaying with fungicides (chemicals which kill fungi)  burning of affected plant material to prevent the spores from spreading Thrush  Thrush is caused by a yeast (fungus) called Candia albicans.  Thrush can grow on any part of the body but favours moist areas such as the mouth, vagina and upper parts of the digestive tract. Oral thrush (in the mouth) is characterised by white sores on the tongue and in the mouth (Figure 24). Symptoms include difficulty with eating and an uncomfortable burning in the mouth. Thrush is common in bottle- and breast-fed babies and in people with false teeth. 32  Figure 24: Oral thrush Vaginal thrush commonly occurs in pregnant women and women using oral contraceptives (birth control tablets). Tight-fitting pants and underwear can encourage thrush to develop. Vaginal thrush is characterised by severe itching, a burning sensation when urinating and a greyish-white vaginal discharge. Other factors that contribute to the development of thrush include:  a weakened immune system caused by HIV / AIDS or chemotherapy  diabetes – candida thrives on high blood sugar  moist skin folds in overweight people  babies with wet nappies for a prolonged period  poor health as a result of stress, lack of sleep, poor diet rich in sugars  excessive use of antibiotics Thrush can be managed by reducing the factors that the fungus favours for example:  wear loose-fitting clothes and cotton underwear especially when it is hot  do not use perfumed soaps and bubble baths  eat a well-balanced diet that is low in refined sugars  probiotics should be taken if antibiotics are taken over a long period of time  treat oral thrush with an antifungal mouthwash. Antifungal creams can be applied to the affected areas. In extreme cases, systemic treatment in the form of tablets may be necessary  dentures (false teeth) must fit well and be sterilized often 33 Ringworm Ringworm is caused by a fungus and not a worm. Fungal spores can live and spread on the skin of both humans and animals (Figure 25). Ringworm is often spread by contact with affected pets in a home. Figure 25: Ringworm affects both humans and animals. Symptoms include itchy sores (often circular-shaped) on the skin. Management and treatment include:  treatment of the skin with antifungal ointments  treatment of pet animals in the home  avoid sharing clothes with an infected person Athlete’s foot Athlete’s foot is a fungal infection found mainly between the toes and on the arches of feet (Figure 26). It is caused by the fungus Tinea pedis. The fungus feeds on the keratin (protein) in the skin and results in flaky and cracked skin. The cracks allow bacteria to enter. This fungus thrives in warm, moist places. It may be contracted by walking barefoot in public places such as showers, public swimming pool areas and changing rooms 34  Figure 26: Athlete’s foot Athlete’s foot can be treated and managed as follows:  keep the affected areas dry  wear open sandals when it is hot  wear clean, cotton socks if you need to wear closed shoes. avoid nylon socks  wash feet well and dry well between the toes  apply fungal ointments or powders to feet if they are infected  avoid infections by wearing slip-slops in public showers The following videos give a short introduction to these diseases: Tuberculosis https://www.youtube.com/watch?v=202hkf43HXQ HIV/AIDS https://www.youtube.com/watch?v=FDVNdn0CvKI Ringworm https://www.youtube.com/watch?v=ryzwWnsBmXg Cholera https://www.youtube.com/watch?v=jG1VNSCsP5Q Rabies https://www.youtube.com/watch?v=kxBIJvNHZg4 Influenza https://www.youtube.com/watch?v=yhhJfT86Bgg Thrush https://www.youtube.com/watch?v=UiTLpa_LoFw Activity 4: Diseases Complete the following table: 35  Organism Management and Disease Symptoms responsible cure rabies AIDS influenza cholera tuberculosis anthrax malaria thrush ringworm athletes foot rusts blight (36) Immunity Immunity refers to the way in which a plant or animal is able to fight an infection. Key terminology lymphocyte white blood cell type which fight infection a complex molecule that induces an immune response (or antigen disease reaction) in the body a protein made by the immune system to target and combine antibody with a specific antigen (invader) and make it useless the process by which a cell engulfs a solid particle to form an phagocytosis internal compartment known as a phagosome (phago – eat, cyto – cell) an organelle containing digestive enzymes to break down lysosome bacterial or viral cell walls 36  a biological preparation made from damaged virus or bacteria vaccine particles used to stimulate an immune response by the body's immune system against viral and bacterial infectious diseases medicine e.g. penicillin which is developed from living antibiotic organisms e.g. bacteria or fungi and used to fight infections caused by either bacteria or fungi hormone made in the pancreas and released into the blood to insulin help convert glucose to glycogen The response of plants against an infecting micro- organism The first line of defence in plants includes the waxy cuticle, bark and the closely packed epidermal cells which protects them from invading micro-organisms. If a plant is injured, it can produce sticky gums and resins in an attempt to seal the wound and prevent infection. The second line of defence occurs when a plant becomes infected by a pathogen and its natural immune response is activated. It releases chemical compounds such as salicylic acid which are transported in the phloem to cells which are not affected. The unaffected cells respond by producing various chemical defences to protect themselves. The response of animals against an infecting micro- organism Animals have two types of immunity:  Natural immunity which is present at birth, and  Acquired immunity which develops after exposure to pathogens. The body has many ways to prevent pathogens from entering. This is called the first line of defence. It includes:  a multi-layered skin  antiseptic tears  mucus lined air passages which trap pathogens  enzymes (lysozyme) in the saliva  ear wax in the ear canal  hydrochloric acid and enzymes in the stomach 37 The second line of defence involves two responses should pathogens gain entry: (i) Primary response – this response tries to destroy the pathogen and prevent it from spreading. This is brought about by inflammation (swelling and redness) of local areas and fever which raises the body temperature. (ii) Secondary response – this activates the immune system which:  destroys the invading pathogens  holds a memory of pathogens that have been destroyed, to reduce or prevent re-infection. The immune system involves two groups of white blood cells viz. lymphocytes and phagocytes. These are discussed in the following sections. Lymphocytes Lymphocytes are found in the tonsils, lymph glands, spleen and in the blood. Two types of lymphocytes occur: B-lymphocytes and T-lymphocytes. B-lymphocytes Special proteins called antigens are found on the surface of pathogens (Figure 27). B-lymphocytes recognise the antigens and make special proteins called antibodies. Antibodies destroy germs and when they encounter the same germs again, they respond quickly. This is known as natural immunity. antigen antibody B-lymphocyte lymphocyte bacteria bacteria Figure 27: Antibody – antigen relationship 38 Antibodies destroy germs by:  causing bacterial cells to burst.  labelling the germs so that phagocytes can ingest them (Figure 27).  making germs clump together so that they are easy to recognize.  neutralising bacterial toxins. T-lymphocytes T-lymphocytes are found mainly in the lymph glands. Two types occur: 1. CD4 cells – helper cells which start the response. 2. Killer T-cells which destroy body cells infected with viruses or parasites. Phagocytes Macrophages, which are a type of phagocytic cells, are able to identify bacteria. They produce pseudopodia (false feet) which flow around the bacteria and engulf them. This process is known as phagocytosis. Vacuoles filled with enzymes called lysosomes fuse with the vacuole containing the bacteria and destroy them. The process of phagocytosis: https://www.youtube.com/watch?v=7VQU28itVVw Vaccinations A vaccine is a suspension of dead, weakened or fragmented micro-organisms or their toxins, that will stimulate the production of antibodies by the lymphocytes. Vaccinations or immunisation is the process of giving a vaccine either by injection or orally (by mouth) to prevent disease. The antibodies stay in the blood and give long- lasting protection against disease. This type of immunity is called artificially acquired active immunity. Children are usually vaccinated against measles, mumps and rubella. How do vaccines work: https://www.youtube.com/watch?v=rb7TVW77ZCs 39 The use of drugs to fight infecting micro-organisms Antibiotics Antibiotics are drugs that fight infections caused by bacteria. Antibiotics cannot fight infections caused by viruses because viruses do not feed and therefore do not ingest the antibiotics. The best-known antibiotic is penicillin which is produced by the fungus Penicillium (Figure 28). Penicillin was discovered by Alexander Fleming in 1929 (Figure 29). Figure 28: Penicillium fungus Figure 29: Alexander Fleming growing on an agar plate Antibiotics usually target a specific part of a bacterium. For example, they:  prevent cell walls from forming.  damage cell membranes.  stop protein synthesis. Bacteria are able to build up a resistance to antibiotics which is why it is important to always complete a course of antibiotics. The first dose of antibiotics usually kills all the weak bacteria. If the course is not completed, the stronger bacteria that are left behind multiply and become drug resistant. 40 Biotechnology Biotechnology refers to the use of micro-organisms to make substances which are useful to humans. These include medicines such as antibiotics and insulin as well as foods such as maas (fermented milk), bread, wine and cheese. The making of antibiotics Natural antibiotics are made by fungi such as Penicillium, a mould (Figure 28), which is found on the skins of fruits. When the mould is collected and put in a vat at about 25°C with sugar and amino acids, it grows and multiplies rapidly. After about five days the penicillin produced by the mould can be removed and purified. The making of insulin The pancreas in the human body produces insulin to regulate the blood glucose content of the blood. If the pancreas does not function properly the person is said to have diabetes mellitus. People with diabetes need to control their intake of sugars and must inject themselves daily with insulin. Bacteria can be used to make insulin (Figure 30). plasmid removed from a chromosome bacterium enzymes used to cut open the plasmid DNA fragment recombinant DNA Figure 30: The modification of bacteria to make insulin 41   a plasmid is removed from a bacterium  the plasmid is cut open using an enzyme  a piece of DNA containing the gene for making insulin is extracted from a chromosome taken from a human pancreas cell  the DNA is joined to the plasmid from the bacterium to form recombinant DNA  the recombinant DNA is inserted into a bacterium  the genetically engineered bacteria are grown in large vats containing nutrients  the DNA in the bacteria instructs the bacteria to make insulin  the insulin is then extracted and purified. The most commonly used bacterium is E.coli. Traditional technology Micro-organisms such as yeast can undergo alcoholic fermentation (see respiration chapter later) in the absence of oxygen. During this process glucose is changed into ethyl alcohol, carbon dioxide and energy. Humans use this process to manufacture:  Beer – beer is made from maize, sorghum, millet, barley or rice and hops.  Wine – wine is traditionally made from grapes. Yeasts found on the skins of fruit ferment the grape sugar after the grapes are crushed.  Bread – yeasts are used to make bread dough rise. The carbon dioxide given off during alcoholic fermentation expands when heated in the oven creating air pockets. The alcohol produced evaporates when the bread is baked.  Cheese – Lactobacillus bacteria can be used to convert milk sugar called lactose into lactic acid. Lactic acid curdles the milk and forms a solid mass known as curds. Curds are pressed and separated from the watery whey to make cheese.  Maas – maas is similar to yoghurt and is made by bacterial fermentation of milk. Lactic acid thickens the milk and acts as a preservative. 42 Biodiversity and classification of micro-organisms: End of topic exercises Section A Question 1 1.1 Various options are provided as possible answers to the following questions. Choose the correct answer and write only the letter (A – D) next to the question number (1.1.1 – 1.1.5) on your answer sheet, for example 1.1.6 D 1.1.1 Antibodies are proteins that A break down pathogens. B catalyse biochemical reactions. C are produced by T-cells that kill disease carrying viruses. D bind with specific antigens. 1.1.2 Which organism does not belong to a kingdom? A virus B fungus C bacterium D protozoan 1.1.3 The following is a list that describes viruses: i) They play an important role as decomposers. ii) They are major pathogens of humans. iii) They are parasites. iv) They reproduce within a host cell. Which of the following are of biological importance in viruses? A (i), (ii) and (iii) B (ii), (iii) and (iv) C (i), (iii) and (iv) D (ii) and (iv) 1.1.4 The cell walls of most fungi are mainly composed of: A chitin B cellulose C protein D lignin 43  1.1.5 The use of antibiotics is an effective treatment for… A bacterial and viral infections B bacterial infections only C viral infections only D neither viral nor bacterial infections (5 × 2) = (10) 1.2 Give the correct biological term for each of the following descriptions. Write only the term next to the question number. 1.2.1 Microbes which cause disease. 1.2.2 Viruses that attack bacteria. 1.2.3 A relationship between two organisms which live together for the benefit of one or both of the organisms. 1.2.4 The ability to produce antibodies. 1.2.5 The use of micro-organisms to make useful substances. 1.2.6 An organism that transfers a pathogenic organism from one host to another. 1.2.7 Plant-like Protista. 1.2.8 The mutualistic relationship between a fungus and an alga. 1.2.9 Organisms that have a definite nucleus. 1.2.10 The process used by lymphocytes to engulf bacteria. (10 × 1) = (10) 1.3 Indicate whether each of the descriptions in Column I applies to A ONLY, B ONLY, BOTH A AND B or NONE of the items in Column II. Write A only, B only, both A and B or none next to the question number. Column I Column II 1.3.1 Organisms that feed on dead A: saprophytes organic matter. B: parasites A: DNA 1.3.2 Genetic material found in viruses. B: RNA A: bacterium 1.3.3 Malaria is caused by a… B: virus 1.3.4 Whip-like structures used for A: flagella locomotion in bacteria. B: cilia (4 x 2) = (8) 44 1.4 The diagram below is that of a bacterial cell. Study it carefully and then answer the questions that follow. 1.4.1 Provide labels for the parts labelled A to D. (4) 1.4.2 State the function of the part labelled E. (1) 1.4.3 Describe how the structure labelled F can be used in the manufacturing of insulin for diabetics. (5) 1.4.4 Briefly explain how bacteria develop resistance to antibiotics and how humans can contribute to this phenomenon. (3) 1.4.5 Identify the structure labelled G and state its function. (2) (15) 1.5 Study the graph below, which gives the body’s response to a vaccination given by an injection and a booster injection. Answer the questions that follow. 45  Primary and secondary responses to an injection containing dead or weakened germs Amount of antibodies in serum / antibody units A – First injection B – Second A B injection 0 40 80 120 160 200 240 280 Time after immunisation / days 1.5.1 What happened to the antibody level after the first injection? (2) 1.5.2 What would happen to the person if they encountered the disease organism after the second injection? (1) 1.5.3 Mention two common ways of receiving vaccines. (2) 1.5.4 From what is a vaccine made? (1) 1.5.5 Which cells in the immune system produce the antibodies? (1) (7) Section A: Section B: Question 2 Use the graph below to answer the following questions: Percentage prevalence of malaria in Tanzania over 12 years 4 3.5 Prevalence of malaria (%) 3.5 3.1 3 2.6 2.4 2.5 2.2 2.1 2 2 2.1 2 1.6 1.6 1.4 1.5 1 0.5 0 1 2 3 4 5 6 7 8 9 10 11 12 Year 46 2.1 In which year was the percentage of malaria the highest? (1) 2.2 Calculate the percentage increase in malaria infections from year 3 to year 6. Show all working. (3) 2.3 Name two precautionary methods that can be implemented to prevent contracting malaria when travelling in a malaria infested area. (2) 2.4 Give two symptoms of malaria. (2) 2.5 Give two possible reasons for the decline in the number of malaria cases after year 7. (2) Question 3 3.1 During the holidays a learner forgot to take his lunch box out of his school bag. Inside were some uneaten sandwiches. At the beginning of the following term his mother found black, furry patches growing on the left-over bread. bread black patches 3.1.1 Identify the organism most likely to be responsible for the growth on the bread. (1) 3.1.2 Name three conditions which made the lunch box a suitable environment for the organism mentioned in 3.3.1 to grow. (3) 3.1.3 Name three ways in which this type of growth on bread and other foods can be prevented. (3) (7) 3.2 A student investigated the number of bacteria on the skin of people’s hands after they washed and dried it. The same washing method was employed, but hands were dried either by using hot air from a hot air blower or by using paper towels. Swabs were used to take samples from the dried skin and bacteria were cultured from the swabs. The table below shows the number of bacteria that was cultured. Study the table below and answer the questions that follow. 47  Number of bacteria (×108) per square centimetre Samples (cm2) on hand skin following washing and drying Air-dried skin Towel-dried skin 1 8,91 1,11 2 9,75 0,98 3 6,14 0,42 4 8,72 1,02 3.2.1 Write down the aim for this investigation. (1) 3.2.2 Suggest three factors that must be kept constant in this investigation to make this a valid test. (3) 3.2.3 Write down the conclusion the student could make based on the results of this investigation. (3) (7) 3.3 A type of bacterium called Escherichia coli (E.coli) normally lives in the large intestine of humans. To determine whether E.coli is present in water, a chemical indicator is used. If the chemical indicator changes from a clear red colour to a cloudy yellow colour, this indicates that E.coli is present. In an investigation conducted by a group of Grade 11 learners, samples taken from three rivers (X, Y and Z) were investigated for the presence of E.coli. Samples were taken from each river and put into glass bottles, which contained the clear red indicator solution. The bottles were then incubated at 37°C for two days. Only river Y showed presence of E.coli. 3.3.1 Explain two safety precautions that the learners should take when conducting this investigation. (2 × 2) = (4) 3.3.2 Suggest one reason for incubating the sample at 37°C. (1) 3.3.3 State how E.coli could have entered river Y. (1) (6) Section B: Total marks: 48  2: Biodiversity of plants Introduction Pollination The four major plant divisions Adaptation of flowers for pollination Division Bryophyta … through insects Division Pteridophytes … through birds Division Gymnosperms … through wind Division Angiosperms Activity 1: Pollination The decreasing dependence on water and parts of flowers for reproduction The significance of seeds Asexual and sexual reproduction Seed banks The advantages of asexual reproduction Activity 2: Seed banks The disadvantages of asexual reproduction Seeds as a food source The advantages of sexual Endemic seeds as a food reproduction source The disadvantages of sexual reproduction End of topic exercises Flowers as reproductive structures 49 CHAPTER 2: BIODIVERSITY OF PLANTS Introduction All plants are thought to have evolved from simple unicellular algae. Four major plant groups exist namely:  Division Bryophyta.  Division Pteridophyta.  Division Gymnospermae (Gymnosperms)  Division Angiospermae (Angiosperms) A cladogram illustrating the relationship between these divisions is illustrated in Figure 1. mosses ferns conifers flowering plants Bryophytes Pteridophytes Gymnosperm Angiosperm non-vascular seedless pollen and flowers and land plants vascular plants ‘naked’ seeds fruit flowers & fruit pollen and seeds Time vascular system common ancestor Figure 1: Cladogram showing the evolutionary relationship between the major plant divisions 50 The four major plant divisions Key terminology multicellular an organism made up of many cells. any single or multicellular group of organisms that have a eukaryotic membrane-bound nucleus containing genetic material organisms which can synthesize their own food e.g. green autotrophic plants, algae and some bacteria. phylogenetic a diagram which shows the evolutionary relationship between diagram/ organisms cladogram a plant body that is not differentiated into stem and leaves and thallus lacks true roots and a vascular system; thalli are typical of algae, fungi, lichens, and some liverworts a filamentous outgrowth or root hair on the underside of the thallus in some lower plants, especially mosses and liverworts, rhizoids serving both to anchor the plant and (in terrestrial forms) to conduct water gametophyte the gamete-producing generation sporophyte the spore-producing generation sporangium spore producing structure zygote formed by the union of the sperm cell and the egg cell haploid is the term used when a cell has half the usual number haploid of chromosomes having two sets of chromosomes or double the haploid diploid number of chromosomes in the germ cell The four groups (divisions) of plants belong to the Kingdom Plantae. They have the following in common:  multicellular  eukaryotic (cells have a membrane bound nucleus)  cell walls are made of cellulose  most are autotrophic and have chloroplasts for photosynthesis  a life cycle involving two generations: a diploid, spore producing generation called a sporophyte and a haploid, gamete producing generation called a gametophyte – referred to as an alternation of generation 51 The characteristics used to place a plant into one of the four groups depends on:  the presence or absence of true conducting tissues such as xylem and phloem  the presence or absence of true, roots, stems and leaves  the type of reproduction and reproductive structures formed  the degree of dependence on water for reproduction Characteristics of the Kingdom Plantae: https://www.youtube.com/watch?v=gJrOATCtV-k The biodiversity of plants specifically for grade 11: https://www.youtube.com/watch?v=jINRLEYp3ck Division Bryophyta Bryophytes are the most primitive terrestrial plants. The division Bryophyta includes mosses, liverworts and hornworts. Mosses are commonly found in damp shady areas (Figure 2). Figure 2: Mosses growing in a shady area Characteristics of Bryophytes  Mosses are generally small (< 20 cm).  They do not have true roots, stems or leaves. For this reason, the plant body is referred to as a thallus. 52   Water can be absorbed directly through the leaves because there is not a waxy cuticle covering the leaves.  The leaves are not true leaves and are often referred to as ‘leaflets’.  The size of mosses is limited because they do not have any conducting tissues i.e. no xylem or phloem (vascular tissue) is present.  Rhizoids at the base of the plant are responsible for anchoring the plant to a substrate.  Bryophytes can reproduce either asexually or sexually.  The gametophyte generation is the dominant generation and consists of a green leafy plant, capable of photosynthesis.  No fruits or seeds produced. Division Pteridophytes The division Pteridophyta includes all ferns. There are approximately 12 000 different species of ferns. They range in size from tiny plants of only 1 cm in height to tree ferns which can grow to 25 m in height. Most ferns require a warm, damp, shady habitat (see Figure 3). Figure 3: Ferns growing on a forest floor Key terminology frond the leaf of a fern usually with many divisions rhizome a stem which grows horizontally adventitious roots roots which arise at the nodes of stems sori a cluster of sporangia found on the underside of fern leaves 53 Characteristics of Pteridiophytes  Ferns have true leaves, roots and stems.  Fern leaves are covered by a waxy cuticle to prevent excessive loss of water.  The leaves are often divided into smaller leaflets. A leaf which is divided into smaller leaflets is called a compound leaf. Fern leaves are referred to as a frond.  The presence of vascular tissues allows ferns to grow taller than mosses. They have both xylem and phloem which transport water and photosynthetic products respectively.  The stems of most ferns grow horizontally and are called rhizomes. The rhizomes are usually protected by brown scale-like leaves.  Adventitious roots grow from the nodes of the horizontal stem. These are true roots because they have xylem and phloem and absorb water for the plant. The roots also anchor the plant in the soil.  Ferns reproduce both sexually and asexually. The dominant generation in ferns is the sporophyte generation. Spores are produced in sporangia arranged in sori under the leaf (Figure 4).  No fruit or seeds are produce. Figure 4: Sori on the under-surface of a fern frond Division Gymnosperms The division Gymnosperms includes cycads, Gingko biloba, Welwitschia and pine trees (Figures 5A to 5D). Gymnosperms all produce seeds which develop into cones. 54  Figure 5A: Cycad Figure 5B: Gingko biloba Figure 5C: Welwitschia Figure 5D: Pine Characteristics of Gymnosperms In gymnosperms the sporophyte generation is dominant and the most visible e.g. the pine tree.  Gymnosperms have true roots, stems and leaves.  Vascular tissues, namely xylem and phloem are present. Unlike higher plants, the xylem in pine trees does not have vessel elements. Only xylem tracheids are present to transport water. This is the reason why the wood of pine trees is softer than the wood of higher plants.  The leaves of pine trees are needle-like (Figure 6) and have a cuticle to reduce the loss of water through evaporation.  The natural habitat of a pine tree is very cold in winter. The reduced volume of the leaves, prevents ice crystals from forming which would damage the leaves internally. The shape of the tree also stops snow from collecting on the branches. 55  Figure 6: The needle-like leaves of a pine tree  Pine trees have well developed root systems.  Gymnosperms do not produce flowers. They form both male and female cones. It is important to note that fertilization is not dependent on water. Pollen is carried by the wind from a male cone to the female cone.  The seeds of the pine are said to be “naked” because they are not protected by a fruit. The seeds are carried on the exposed scales of the female cone. When the seeds are ripe, they fall out of the cone and are carried by wind to another location. Each seed has a wing to help with wind dispersal (Figure 7). It is important for the survival of the species that the seed does not fall under the tree. If it germinates under the mother tree it will be in the shade and in competition with the mother tree for water and nutrients.  Pine trees are not indigenous to South Africa and are able to make better use of available water than the natural vegetation because of their extensive root system. 56  Figure 7: Pine seeds Did you know? Pine trees are commercially very important. Pine trees are cultivated in South Africa in huge plantations. The wood is used to make paper and furniture. Pine nuts are the seeds of pine trees. They are used to flavour drinks and make pesto. Division Angiosperms Angiosperms are commonly referred to as “flowering plants” and are the most varied and successful group of plants. Most angiosperms are autotrophic, but some are parasitic, while others are saprophytes. Angiosperms typically produce seeds which are found inside fruits. Key terminology fibrous/ formed by many thin, moderately branching roots growing from the adventitious stem – common in monocotyledons root system tap root characterized by a main root or primary root system, growing system vertically downward – common in dicotyledonous plants Characteristics of Angiosperms  The sporophyte generation is the dominant generation in angiosperms. It consists of true roots, stems and leaves.  Xylem and phloem are responsible for transporting water and photosynthetic products, respectively. The structure of a typical angiosperm sporophyte is illustrated in Figure 8. 57  flower fruit leaves stem taproot Figure 8: The structure of a typical angiosperm  Angiosperms have either fibrous (adventitious) root systems or tap root systems. The roots are capable of absorbing water and dissolved mineral salts.  The stems of angiosperms are divided into nodes and internodes. Leaves form at the nodes on the stem. The leaves are covered in a waxy cuticle to prevent excessive loss of water by evaporation.  Angiosperms produce seeds protected by fruit. The life cycle of angiosperms is similar to that of gymnosperms except that the seeds in angiosperms are protected by a fruit. Angiosperms produce flowers instead of cones. 58 Decreasing dependence on water for reproduction As plants have increased in size over millions of years, they have become progressively less dependent on water for their survival and for the completion of their life cycles. Of the four groups studied, the bryophytes are the least adapted to surviving dry conditions for the following reasons:  they have no cuticle, no supporting tissues and no vascular tissues  plant body is a thallus because there are no true roots, stems or leaves  the gametophyte is the dominant generation  the sporophyte is totally dependent on the gametophyte for both food and water  the male gametes are motile (capable of motion) and require water to swim to the female gamete The pteridophytes are more evolved than the bryophytes but are still dependent on water for fertilization. They have the following adaptations which enable them to grow larger than bryophytes:  leaves with a cuticle to prevent desiccation (drying out)  vascular tissue to transport food and water  the sporophyte is the dominant generation and is not dependent on the gametophyte for water and food once mature Both the gymnosperms and angiosperms are well adapted to life on land. Adaptations include:  leaves with a cuticle  true roots, stems and leaves  an embryo enclosed in a seed to prevent drying out  pollen grains to protect and transfer the sperm cells i.e. water is not needed for fertilization Asexual and sexual reproduction Both animals and plants are capable of asexual and sexual reproduction. In asexual reproduction only one parent is required, and the new organism is produced by mitosis. In sexual reproduction a haploid sperm cell fuses with a haploid egg cell to 59 produce a diploid zygote. The zygote divides by mitosis to form an embryo and later, a new organism. The advantages of asexual reproduction  Only one parent is required.  Asexual reproduction is quicker because the parent does not need to find a mate.  All the offspring are identical and if conditions are favourable, they can crowd out any competition.  Asexual reproduction does not rely on pollinators or dispersion agents. The disadvantages of asexual reproduction  All the offspring are genetically identical. If conditions become unfavourable, they will all die.  Poor characteristics in the parents will be passed on to the offspring.  Rapid multiplication by asexual reproduction may lead to overcrowding. The advantages of sexual reproduction  The offspring are genetically different and are able to withstand a variety of conditions.  Farmers can select organisms with desirable characteristics and cross-breed with them. The disadvantages of sexual reproduction  Two parents are required.  Plants that reproduce sexually rely on pollinating agents and dispersal agents to spread their seeds. Flowers as reproductive structures Flowers have the following functions:  contain and protect the reproductive organs  attract pollinators 60 Key terminology formed by the green structures around the petals (the sepals) calyx together; serves to protect the flower and its reproductive organs corolla all the petals of a flower together form the corolla receptacle the thickened part of a stem from which the flower organs grow the non-reproductive part of the flower; the calyx and corolla that perianth form a protective envelope surrounding the sexual organs male part of the flower consisting of a filament and pollen stamen producing anthers female part of the flower consisting of a stigma, style and an ovary pistil where ovules are produced a fleshy, often sweet layer, formed around the seeds in fruit angiosperms following fertilization All the parts of a flower are actually modified leaves arranged in whorls (circles around a central point). Each whorl is specialized to perform a specific function. The four whorls are the:  calyx  corolla  androecium  gynoecium In a typical plant, the outermost whorl is called the calyx and consists of a number of green sepals. All the floral parts are attached to a receptacle. The corolla is made up of coloured petals to attract pollinators (Figure 9). The calyx and corolla are known collectively as the perianth. stigma anther stamen male style filament pistil – female ovary petal ovule sepal pedicel receptacle Figure 9: A longitudinal section through a typical dicotyledonous flower 61 The stamens are the male part of the flower. Each stamen consists of a filament and a bi-lobed anther with four pollen sacs or microsporangia. Pollen grains (microspores) are haploid and produced by meiosis. The female part of the flower usually consists of carpels fused together to form one or more pistils. Each pistil consists of a stigma, style and ovary. Ovules are formed inside the ovary by meiosis. When a pollen grain lands on the stigma, it germinates by growing down the style towards the ovule carrying the male gametes to fertilize the ovule. The fertilized ovule forms a seed and the ovary wall thickens to