Populations

1.1 Populations and EcosystemsEcosystems Made up of all the interacting biotic and abiotic features in an area. Self-contained units. 2 major processes: flow of energy through the system, the cycling of elements within the system. E.g. pond - has its own community of plants to collect the necessary sunlight energy to supply organisms. Nutrients are recycled in the pond. Contains a number of species. Populations A group of interbreeding organisms of one species in a habitat. Populations of different species form a community. CommunityAll the populations of different organisms living and interacting in a particular place at one time.Habitat Where a community of organisms lives. Many inside an ecosystem. Contain microhabitats. Ecological niche A niche describes how an organism fits into the environment. Where an organism lives and it's role. Includes all the biotic and abiotic conditions required for an organism to survive and reproduce. No two species occupy exactly the same niche.

1.2 Investigating PopulationsQuadrats3 factors to consider: Size of quadrat - depends on size and distribution of organisms Number of quadrats - the larger the number, the more reliable the results. Need balance between validity and time available. Position of quadrat - Random sampling Random SamplingImportant to avoid bias (e.g. muddy areas) Lay out two long tape measures at right angles, along two sides of the study area. Obtain a series of coordinates by using random numbers taken from a table or generated by a computer. Place a quadrat at the intersection of each pair of coordinates and record the species within it. Systematic sampling along transects Sometimes more informative to measure abundance and distribution in a systematic rather than a random manner. Particularly important where some form of transition in the communities of plants and animals takes place. Line transect - tape stretched along ground, any organism on the line is recorded. Belt transect is a strip, 1m wide, marked by putting a second line parallel to the first, species within the lines are recorded. Measuring abundance The number of individuals of a species within a given space. Can be measured in a number of ways including: Frequency -

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