Learning outcomes:
4.1
understand the terms population, community, habitat and ecosystem
4.2
explain how quadrats can be used to estimate the population size of an organism in two different areas
4.3
explain how quadrats can be used to sample the distribution of organisms in their habitats.
More lovely definitions for you to learn!

Population: all the individuals of a particular species within a defined area
Community: a group of different populations living in the same area
Habitat: the physical, chemical and biological environment in which an organism lives
Ecosystem: a community of living things and the environment in which they live

quad.GIF
In ecology we usually need to sample (this is because it is not practical to count all of the species we’re interested in e.g. one cannot count all of the grass plants in a field!). Ecologists use quadrats to sample from.

Quadrats can be any size you like (e.g. 5km by 5km sampling zebra heards in Africa, or 5cm by 5cm sampling lichen on a tree), but there are 3 different methods of using a quadrat. You need to be able to explain how you would use quadrats to find out information about specific species in their habitat.