Levels of Organisation (Ecosystem) & Competition & Interdependence

What is an organism?

An individual living thing.

What is a population?

All the organisms of one species living in a particular area.

What is a community?

All the populations of different species living and interacting in a particular area.

What is an ecosystem?

The interaction of a community of living organisms (biotic components) with the non-living (abiotic) parts of their environment.

What is a habitat?

The place where an organism lives.

Put the ecological levels of organisation in order.

Organism → population → community → ecosystem.

Why do organisms compete?

Organisms require resources to survive and reproduce, and these resources may be limited.

What do plants compete for?

Light, space, water and mineral ions from the soil.

What do animals compete for?

Food, mates and territory.

How can competition affect population size?

Organisms that are better able to compete for limited resources are more likely to survive and reproduce, whereas unsuccessful competitors may die or fail to reproduce.

What is interdependence?

The dependence of different species on each other within a community.

What might species depend on each other for?

Food, shelter, pollination and seed dispersal.

Why can removing one species affect an entire community?

Other species depend on it, for example as a food source, predator, pollinator or seed disperser, so its removal can cause changes in other population sizes.

What is a stable community?

A community in which all the species and environmental factors are in balance, so population sizes remain fairly constant.