Biology Notes as Essay

7303 WordsSep 27, 201530 Pages
A2 Biology notes – AQA unit 4: Populations and Environment Populations and Communities: - The area of the earth inhabited by living organisms is known as the biosphere. This encompasses land (to a depth of several metres), bodies of water, and the atmosphere to a height of a few kilometres. - The biosphere is divided into large sub-units known as biomes. Examples of biomes include deserts, tundra, and aquatic environments. Terrestrial biomes (i.e. on land) correspond roughly to climatic regions, as the climate is often the defining factor of a biome. - Within biomes are ecosystems. These are stable, self-sustaining communities of organisms which interact with each other and their surroundings – the term ‘ecosystem’ describes both biotic (living) and abiotic (non-living) aspects of an environment. - A population is a group of individuals of the same species inhabiting an area. A community is a group of interacting populations (comprising all the living things) within an area. - An organism’s environment is made up of two types of factor; o Biotic factors: these are the result of other living organisms. Biotic relationships include mutualism, disease and predation. o Abiotic factors: non-living factors, such as temperature, wind or oxygen level. Ecological Niches: - A species’ ecological niche is defined by the sum of the biotic and abiotic conditions that a member of the species needs to survive and reproduce. This includes resources and physical space. - The potential environments in which a species is capable of living form its fundamental niche. Geographical barriers or interspecific competition can prevent a species from occupying the entire of its fundamental niche: the part that is occupied in reality is known as the realised niche. - As members of the same species will share a niche, intraspecific competition will occur in a habitat where resources are scarce.

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