Competition in a community

Within an ecosystem there are many communities of different organisms. Each of the organisms is trying to survive in the ecosystem.

Animals must get access to:

  • food
  • water
  • space (territory)

Plants need access to:

  • sunlight for photosynthesis
  • water
  • mineral salts
  • space

All of the communities of organisms within the ecosystem compete for resources that they need to survive. There are only a set amount of resources in an ecosystem.

If an organism cannot access the resources that it needs to survive, then it will die. Animals can try moving to another habitat to find more resources, but plants cannot move to another location.

Changes to the numbers of organisms could be due to a change in the abiotic factors, like water or sunlight, or biotic factors, like a new predator or pathogen.


The introduction of a new species into an ecosystem can result in it out-competing another native species.

Japanese Knotweed is a bamboo-like plant which, as its name suggests, is a species native to Japan. It was introduced into the UK in the early 19th century as an ornamental plant for gardens. Because of competition from other native plants, in Japan its growth is controlled and the plant can only grow to a height of around 40 cm. However, in the UK it has no plants that can compete with it so Japanese Knotweed is able to grow at a rate of 2 cm per day and reach heights of over 3 m. This fast growth means that as it spreads it out-competes and destroys all other plants in its path.