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