Populations in a Community

Food Webs

Population: all the organisms of the same species that live in the same place at the same time

  • A group of frogs living in a pond

Community: multiple populations that live in the same place at the same time

  • Groups of fish, frogs, ducks, and lily pads that live in a pond

Food web: a diagram that shows what eats what in a community

Levels of a food web:

Producers: take in the sun’s energy and make their own food (examples: plants, algae)


  • Primary consumers: herbivores that eat producers for energy (examples: rabbits, cows, deer)

  • Secondary consumers: carnivores that eat primary consumers (examples: lions, tigers)

  • Tertiary consumers eat secondary consumers and so on

  • Animals can belong to multiple levels of a food web: omnivores eat both producers (plants) and consumers (animals) (examples: foxes, bears)

Decomposers: an organism that breaks down dead bodies of organisms at every level (examples: mushrooms, bacteria)

Niche: the function that an organism performs in the food web of that community, as well as everything the organism does and needs in its environment

  • No two types of organisms occupy exactly the same niche in a community

Relationships Between Organisms

A symbiotic relationship may exist between two organisms of different species when they live and work together.

Mutualism: both organisms benefit

  • Clownfish and anemones: the clownfish gets a safe habitat in the anemone while the anemone gets food because the clownfish’s bright colors attract other fish

Commensalism: one organism benefits and the other is unaffected

  • Barnacles and humpback whales: barnacles get a ride on the whales, but the whales are not affected

Parasitism: one organism benefits and the other is harmed

  • Tapeworms and humans: tapeworms attach themselves to human intestines and get food, but humans are harmed

Predator-prey relationship: the interaction between a consumer that hunts for another consumer for food (for example: a fox, the predator, eating a rabbit, the prey)

Competition: two populations both use a resource, so they must fight for it

Cooperation: two populations work together to get a resource

Communities are interdependent because organisms and populations depend on other organisms and population for food or other resources. Energy resources of a community are shared through the interactions of producers, consumers, and decomposers.


Sources Used and Helpful Links