Populations of different species interact ecologically in communities. Ecological interactions like competition, predation, and mutualism can affect species' distributions, abundances, and evolution. These interactions include competition for limited resources, one species feeding on another, mutually beneficial relationships, and cases where one species benefits while the other is not affected.

1. Population – group of individuals of the same species
living in the same area, potentially interacting
Community – group of populations of different species
living in the same area, potentially interacting
What are some ecological interactions?

2. Why are ecological interactions important?
Interactions can affect distribution and abundance.
Interactions can influence evolution.
Think about how the following interactions can affect
distribution, abundance, and evolution.

3. Types of ecological interactions
competition
predation
parasitism
mutualism
commensalism
symbiosis

5. Competition – two species share a requirement for a
limited resource  reduces fitness of one or both species

6. Predation – one species feeds on another  enhances
fitness of predator but reduces fitness of prey
herbivory is a form of
predation

7. Parasitism – one species feeds on another  enhances
fitness of parasite but reduces fitness of host

8. Mutualism – two species provide resources or services
to each other  enhances fitness of both species

9. Commensalism – one species receives a benefit from
another species  enhances fitness of one species; no
effect on fitness of the other species

10. Symbiosis – two species live together  can include
parasitism, mutualism, and commensalism

11. Organizing ecological interactions
effect on species 1
+
+
effect on
species 2
mutualism
0
0
-
commensalism
predation
herbivory
parasitism
commensalism
-
predation
herbivory
parasitism
competition
competition
competition