Biology Revision notes Ecology:
1) Ecosystems, sampling and population studies
Population: All the individuals of a given species living together in the same area and at the same time. Community: Community: all the individuals of all the species living together in the same area and at the same time. Habitat: The area in which an organism lives within an ecosystem Niche: describes where an organism lives, what it does (its role), what it feeds on and how it interacts with other organisms and the environment. Biotic factor: A living factor which can affect the distribution of an organism Abiotic factor: A non-living factor which can affect the distribution of an organism Abundance: the total number of population size of each species being estimated
1) Must be unbiased, so samples must be collected at random. 2) Must be reliable (repeated by another scientist), representative and suitable for statistical analysis (large enough) 3) Must be an appropriate technique depending on species e.g. quadrat only for immobile or slowly moving organism.
Quadrat used to assess abundance when measuring by:
Percentage cover: amount of species found in the quadrat recorded as an estimated % of total area. However, over-layering may cause % cover to be > 100% Frequency: proportion of quadrats (more than 1) containing species is recorded and percentage is calculated of total quadrats. Reliability, accuracy, precision and speed of data
POP DENSITY- TIME CONSUMING AND SOME SPECIES MAY BE DIFFICULT TO COUNT (GRASS IN CLUMPS) % COVER- AREA OF QUADRT COVERED BY 1 SPECIES IS RECORDED AS A % OF TOTAL AREA, STRATIFICATION MAY OCCUR SO % COVER WILL BE GREATER THAN 100%. FREQUENCY- PROPORTION OF QUADRATS THAT CONTAIN A PARTICULAR SPECIES, OUT OF ALL THE QUADRATS, THE ONES THAT CONGAIN IT ARE CALCULATED AS A PECENTAGE. Random quadrating:
Done to find out what species are present and their relative abundance Compare the species abundance in 2 different areas...
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