1. National 5 Biology Course Notes Unit 3 : Life on Earth Part 1 : Biodiversity and distribution of life

2. Biodiversity Biodiversity is the number of different types of organisms in an area – the more different species there are, the greater the biodiversity. What affects biodiversity? Biodiversity is affected by: Biotic factors Abiotic factors Human influences Biotic factors Biotic factors are related to living organisms. Biotic factors can affect the number of other living organisms in an area and where they are found. Examples of biotic factors are: Predators Grazing Disease Availability of food Competition between organisms

3. Abiotic factors Abiotic factors are non-living features of an area that can affect the number of different species (biodiversity) and where the organisms are found (distribution). Examples of abiotic factors are: Temperature – e.g. many animals and plants could not survive in a desert Light – e.g. plants cannot grow in the absence of light pH – e.g. many plants cannot grow in acidic soil, fish are killed when acid rain lowers the pH of the water Human influences Examples of human influences that reduce biodiversity are: Habitat destruction – e.g. felling tropical rainforests Over-grazing of farm animals leading to soil erosion Over-fishing Pollution Human activities that help to maintain biodiversity are: Setting up conservation areas Captive breeding programmes for endangered species

4. Biomes Biomes are regions of the earth that have their own characteristic plants (flora) and animals (fauna) and their own climate. Examples of biomes are: Desert Grassland Tropical rainforest Polar Marine (sea) Aquatic (freshwater) Biomes and abiotic factors Which biomes occur in which parts of the earth (the global distribution of biomes) is affected by the abiotic factors in that area, for example tropical rainforest occurs only where there is high rainfall and high temperature whereas deserts are found where the temperature is high but the rainfall low.

5. Habitat and community An organism’s habitat is the place where it lives. The community is all the organisms (plants and animals) in an area. Ecosystem An ecosystem consists of all the organisms in an area and their non-living environment (all the abiotic factors in the environment. Therefore ECOSYSTEM = COMMUNITY + HABITAT Niche The word niche describes an organism’s role within it’s community. This includes which other organisms it eats, it’s predators, organisms it competes with, its parasites and the abiotic factors that affect it.

6. Revision of meaning of terms WordMeaning BiodiversityThe variety of different species in an area Biotic factor A factor related to living organisms that affects the number and distribution of living things in an area, e.g. predators, disease Abiotic factor A factor that is not living but affects the number of living things and where they are found (their distribution), e.g. temperature, pH Biome A large region of the earth with its own characteristic plants and animals and its own characteristic climate, e.g. deserts, tropical rainforests HabitatThe place where a plant or animal lives CommunityAll the plants and animals in an area Ecosystem The plants and animals (community) and their physical environment (habitat) Niche The role an organism plays in it’s ecosystem including it’s predators, prey, parasites, competitors and the abiotic factors that affect it

7. National 5 Biology Course Notes Unit 3 : Life on Earth Part 2 : Energy in Ecosystems

8. Food chain A food chain shows how energy is passed from an organism that is eaten to the organism that eats it e.g. GRASS Rabbit Fox The arrows show the direction of energy flow. Energy stored in the grass passes to the rabbit when the rabbit eats the grass. Energy stored in the rabbit passes to the fox when the fox eats the rabbit. Energy losses Most of the energy that the rabbit gets from the grass is not passed to the fox. Only energy stored in the rabbit’s body passes to the fox. By the time the fox eats the rabbit, the energy it got from the grass has been lost by: The rabbit producing heat The rabbit using energy to move Energy lost from the rabbit's body as undigested food. In any food chain, only 10% of the energy is passed to the next level. 90% of the energy is lost in these three ways: 1.As heat 2.In movement 3.As undigested material

9. Producers and consumers Producer – A green plant that is able to produce its own food – food chains begin with a producer Primary consumer - An animal that feeds on (consumes) the producer Secondary consumer – An animal that feeds on (consumes) the primary consumer Tertiary consumer – An animal that feeds on the secondary consumer e.g. Algae Water flea Stickleback Pike (producer) (primary consumer) (secondary consumer) (tertiary consumer)

10. Pyramids of numbers, biomass and energy For most food chains, the number of organisms, their biomass (total mass of all the organisms) and the energy stored in all the organisms decrease at each level of the food chain. i.e. there are more producers than primary consumers, more primary consumers than secondary consumers and more secondary consumers than tertiary consumers The producers have a greater total biomass and more stored energy than the primary consumers, the primary consumers have a greater biomass and more energy than the secondary consumers and the secondary consumers have a greater biomass and more energy than the tertiary consumers The decrease in these three features Number or organisms Biomass Energy at each level of the food chain can be represented as a pyramid of numbers, a pyramid of biomass or a pyramid of energy: Decreasing numbers Producers Primary consumers Secondary consumers Tertiary consumers Pyramid of numbers Decreasing biomass Producers Primary consumers Secondary consumers Tertiary consumers Pyramid of biomass Decreasing energy Producers Primary consumers Secondary consumers Tertiary consumers Pyramid of energy

11. Pyramid of numbers that don’t have the usual pyramid shapes The pyramid of numbers is shaped like this: When the producer is a large plant like a tree that has many primary consumers feeding on it The pyramid of numbers is shaped like this: Producer Primary consumer Secondary consumer Producer Primary consumer Tertiary consumer Secondary consumer When the food chain includes a parasite as the secondary or tertiary consumer e.g. Grass Rabbit Fox Fleas The pyramid is this shape since many parasites can feed on a single animal Even when the pyramid of numbers have these unusual shapes, the pyramids of biomass and of energy for the same food chains still have the usual pyramid shape Since the biomass and total energy stored both decrease at each higher level for all food chains including these ones.

12. Nitrogen cycle Plant and animal proteins contain nitrogen. Plants get nitrogen from nitrate absorbed from the soil. This nitrogen is used to produce protein. Animals get protein by eating plants so their protein also depends on nitrate absorbed by plants. Organisms involved in the nitrogen cycle and what they do Decomposers These include soil fungi and bacteria. They decompose proteins in dead organisms and nitrogen compounds in animal wastes to produce ammonium and nitrate. Nitrifying bacteria Nitrifying bacteria change ammonium into nitrite and nitrite into nitrate. This is called nitrification. Nitrification by nitrifying bacteria ammonium nitrite nitrate

13. Nitrogen fixing bacteria These bacteria are able to use nitrogen gas in the air. Some nitrogen fixing bacteria live in the soil, they change nitrogen gas into nitrate. – this is called nitrogen fixation. Other nitrogen fixing bacteria live in swellings called root nodules in the roots of a particular group of plants called legumes. (This group of plants includes clover, beans and peas) Legume root Root nodules Nitrogen fixing bacteria in root nodules change nitrogen gas into a form that can be used by the plant to make protein. Denitrifying bacteria Denitrifying bacteria change soil nitrates into nitrogen gas which escapes into the atmosphere – this process is called denitrification. Lightning Nitrogen gas can also be changed to soil nitrates during lightning storms

14. Summary of nitrogen cycle Nitrates Absorbed by plant roots Plant protein (made using nitrogen atoms in nitrate Animals eat plants Animal protein Dead bodies of plants and animals broken down by decomposers, e.g. bacteria and fungi Ammonium Nitrite Nitrification by nitrifying bacteria Nitrogen gas (in the air) Nitrogen fixation by nitrogen fixing bacteria (free living in soil and in root nodules of legumes Denitrification by denitrifying bacteria

15. ProcessOrganisms involvedReactions involved in the process Summary of processes in the nitrogen cycle Decomposition Decomposers, e.g. soil bacteria and fungi proteins ammonium Nitrification Nitrifying bacteria ammonium nitrite nitrite nitrate Nitrogen fixationNitrogen fixing bacterianitrogen gas nitrate DenitrificationDenitrifying bacterianitrate nitrogen gas

16. Competition Competition between organisms occurs when they need the same resources, for animals they might feed on the same prey, for plants they compete for light and soil water. Interspecific competition This is competition between animals or plants from different species for the same resources. For example, lions and cheetahs belong to different species but they both feed on gazelle. Intraspecific competition Intraspecific competition is animals or plants belonging to the same species competing with each other, for example two cheetahs competing with each other. This competition is more intense because members of the same species need exactly the same resources, whereas members of different species use different resources. Members of the same species can show behaviour that reduces competition, e.g. Territorial behaviour – male members of the species establish territories where they do not allow other males to feed – this can be seen in gardens with male blackbirds Pecking order – for animals that live in groups, dominant individuals get first choice of resources.

17. National 5 Biology Course Notes Unit 3 : Life on Earth Part 3 : Sampling techniques and measuring abiotic factors

18. Quadrat It is used to sample the abundance of plants or very slow moving animals in an area The number of squares containing the organism is counted to give a measure of its abundance. The quadrat must be thrown at random and the results from several quadrats are taken and an average taken to make the result more reliable. Pitfall trap A pitfall trap is a container, for example a plastic cup which is buried in the soil with it’s rim level with the soil surface. A quadrat is a square frame divided into smaller squares It is used to collect and sample invertebrates crawling on the soil surface Several pitfall traps should be set up to make the result more reliable. Errors may occur when using pitfall traps because: Insects that can fly may escape from the traps Some predators that are trapped may eat other trapped invertebrates

19. Measuring abiotic factors Abiotic factorInstrument used to measure abiotic factor Steps taken to reduce error when measuring Light intensityLight meter Hold the meter away from your body to ensure you are not shading the meter Soil moistureMoisture meter Wipe the meter probe dry after each measurement Make sure the probe is deep enough in the soil pH meter Soil pH Clean the meter probe between readings

20. National 5 Biology Course Notes Unit 3 : Life on Earth Part 4 : Adaptation, natural selection and the evolution of species

21. Mutations A mutation is a change to an organism’s genetic material. Mutations are random. They are the only way in which new alleles can arise in a population. Mutations are usually harmful but some mutations can result in genes that give characteristics that give an individual a survival advantage. Mutations are rare but the frequency with which they happen can be increased by mutagenic agents- these include radiation, e.g. X-rays and UV radiation, and some chemicals, e.g. mustard gas. Adaptations An adaptation is an inherited characteristic that makes an organism more able to survive in it’s environment. e.g. adaptations of camel to survival in the desert Can store large amounts of water in the gut Fat in hump releases water when broken down Copes with 30% water loss (most animals die at 10%) Can drink up to 30% of its body weight when it finds water (200L in 3 minutes) Low levels of sweat Can tolerate body temperature changes more than 3 times level that would kill us Low volume of urine Adaptations of a cactus to survival in the desert Leaves are spines to reduce water loss. Stores water. Thick waxy cuticle reduces water loss Extensive roots to absorb as much water as possible

22. Natural selection Most organisms produce more offspring than the environment can sustain. Since there is variation within a species, some individuals have characteristics that make them better able to survive than others, e.g. taller individuals might see predators sooner, faster individuals may be more able to outrun predators, individuals with a certain colour may be better camouflaged. The best adapted individuals have a selective advantage and are more likely to survive, breed and pass on the genes that gave them the best characteristics to the next generation. This process where the best adapted survive at the expense of the others (survival of the fittest) is called natural selection.

23. Examples of natural selection 1.The peppered moth There are two forms of the moth: a light coloured speckled form a dark form These differences are caused by two different alleles of a gene Peppered moths are active at night and during the day rest on surfaces such as tree trunks. The moths are eaten by birds. In unpolluted areas, the tree trunks are covered by light coloured lichens that camouflage the light forms – in these areas, the light forms have a selective advantage so less are eaten and more survive and pass on the light gene. Dark moth Light moth On lichen covered tree trunk In polluted areas, the lichens are killed and tree trunks are stained with soot – in these areas dark moths are camouflaged and given a selective advantage so more dark moths survive and pass on the dark gene. Light moth Dark moth On soot covered tree trunk

24. Examples of natural selection 2. Antibiotic resistance When an antibiotic is applied to a population of bacteria, most are killed but some will have genes that make them resistant to the antibiotic. The resistant bacteria survive antibiotic treatment and pass on the resistance genes to offspring. Since bacteria reproduce quickly and asexually (needing only one parent and producing offspring genetically identical to the parent), antibiotic resistance spreads quickly. Overuse of antibiotics has led to many bacteria becoming resistant.+

25. Speciation Speciation is the formation of one or more new species from an already existing species. The first step in speciation is a population being isolated from the rest of the species. The isolated population gradually becomes totally different from the rest of the species because: 1.Different mutations occur in the two groups so their gene pools become more and more different 2.Since they live in different environments, their selection pressures are not the same so the genes that give survival advantage and are passed on are different for the two groups. Eventually the two groups become so different they can no longer interbreed to produce fertile offspring – the isolated group has now become a new species. An example of speciation – Galapagos island finches These finches arrived from mainland South America and were isolated from the main population by the sea. A number of new species developed from the ancestral seed eating finches to fill niches occupied by other bird species on the mainland. Their beaks became adapted to eat different food sources as shown on the diagram.

26. National 5 Biology Course Notes Unit 3 : Life on Earth Part 5 : Human impact on the environment

27. Increasing human population The graph shows the human population explosion that has taken place in recent centuries. This increase in population leads to a need to produce more and more food The use of fertilisers to supply necessary plant nutrients and of pesticides to destroy pests that damage crops helps to produce high crop yields. However, these chemicals can cause damage to ecosystems.

28. How fertilisers can damage ecosystems Fertilisers can be washed by rain from farm fields into lakes where they increase the growth of surface microscopic plants called algae. The increase in growth of these algae leads to large numbers of them coating the water surface in what are called algal blooms When the algae die, they provide food for bacteria which rapidly multiply and use up oxygen leading to the death of aquatic animals, like fish Algal bloom on a lake surface The flow chart outlines this process: Fertiliser is leached into the water Fertiliser causes increased growth of algae (algal bloom) Bacteria feed on dead algae and use up oxygen in the water Water animals such as fish die due to lack of oxygen

29. Accumulation of pesticide (DDT) in a food chain Accumulation of pesticides in food chains Pesticides are sprayed on crops to kill pests like insects that damage the crops. Predators of these pests eat a lot of them and so accumulate pesticides in their bodies. This trend continues along a food chain with predators at each level accumulating more pesticides in their bodies. The problem is made worse by the fact that organisms often cannot get rid of the pesticide and store it in their bodies. Predators at the top of the food chain can have levels of pesticide that are damaging or lethal. The diagram shows the accumulation of the now banned insecticide DDT in an aquatic food chain in concentrations of parts per million (ppm) after it had been washed into water from farmland,

30. Indicator species Indicator species are organisms whose presence or absence from an area indicates the level of pollution. For some organisms, e.g. bloodworms in water, the fact that they are present indicates pollution while for others, e.g. lichens, the fact that they are absent from trees indicates air pollution. Rivers can be polluted with organic waste, e.g. sewage. Bacteria feed on this and use up oxygen causing death of other organisms such as fish. Some of the invertebrate indicator species whose presence indicates polluted or clean water are shown below: Indicator species present Stonefly or mayfly Freshwater shrimp Water louse Bloodworms Rat-tailed maggot Level of pollution Very low Low Moderate High Very high Increasing level of pollution Absence from water indicates pollution Presence in water indicates pollution

31. Indicators of Air Pollution Lichens are plants that grow in exposed places such as tree bark. Tree trunk covered in lichens Air pollutants like sulphur dioxide from burning fossil fuels dissolves in rainwater and damages lichens preventing them from growing. This makes lichens natural indicators of air pollution. In places where no lichens are growing, this is often a sign that the air contains pollutants such as sulphur dioxide. Tree trunk stained with soot and having no lichens due to pollution

32. Biological control Biological control is a way of controlling pests that doesn’t use pesticides. Instead, natural predators of the pest are used to kill them. For example aphids (also called greenfly) feed on crops and garden plants damaging them and killing them. Ladybirds are natural predators of aphids and can be put on infected plants to control the aphid population Ladybirds feeding on aphids Myxomatosis in rabbits Myxomatosis is a fatal virus disease of rabbits. It has been used to control the rabbit population in countries such as Australia. However those rabbits surviving the disease had genetic resistance and resistance in rabbit populations has been growing GM crops GM crops can be genetically modified to contain genes that produce chemicals lethal to pests so that pesticides do not have to be used or to produce crops that don’t need as much fertiliser.