4.1 – Understand the terms population, community, habitat and ecosystem.
– Population: All the organisms of a particular species found in an ecosystem at any
one time.
– Community: The populations of all species found in a particular ecosystem at any
one time.
– Habitat: Places where specific organisms live in an ecosystem.
– Ecosystem: A distinct, self-supporting system of organisms interacting with each
other and with a physical environment.
4.2 – Explain how quadrats can be used to estimate the population size of an organism
in two different areas.
– A quadrat is a square with dimensions of one metre.
– Place random quadrats at a numbered grid corresponding to the habitat.
• The numbers are generated randomly using the random number function on a
calculator.
– The number of each species is counted within the quadrat.
– The number of species in the quadrat (1m2) is multiplied to obtain the number of
species in the area (A m2).
4.3 – Explain how quadrats can be used to sample the distribution of organisms in their
habitats.
– Quadrats can be used to estimate the distribution of organisms, a sample.
• Animals that do not move much (e.g. snails) or plants are sampled.
– The sample size must be sufficient and representative (i.e. able to represent the whole
area), multiple samples may be necessary.