1. Interactions in ecosystems

2. Interactions in Ecosystems
3 main ways organisms interact with each other:
1. Competition
2. Predation
3. Symbiosis

3. 1. Competition
interaction between 2 or more organisms competing for the same resource in a given habitat
in order to coexist in an area, species need slightly
different niches to feed off the same land
Competition can occur between the same species
eg. bulls compete to determine who will mate with the female

4. 2. Predation Occurs when 1 organism eats another to obtain food
Animals use camouflage to
avoid predators
eg. this toad is hardly distinguishable
from its surroundings

5. Predation
monarch butterflies defend by having an awful taste and bright colors
species sometimes use mimicry (looking like another organism) to avoid predators and survive
eg. Viceroy butterfly looks like a monarch

6. 3. Symbiosis
close interaction between 2 different species in which members of 1 species live in, on, or near members of another species
eg. the clownfish and the anemone
3 types:
A. Mutualism
B. Commensalism
C. Parasitism

7. A. Mutualism Mutualism – both species benefit from the partnership
eg. the caterpillars have nectar organs which the ants drink from and the acacia
tolerates the feeding caterpillars. The ants provide protection for both the plant
and the caterpillar

8. B. Commensalism
Commensalism – one species benefits from the relationship and the other lives without any harm or benefit
eg. the bird gets food from the cow’s back but the cow is unaffected

9. C. Parasitism
Parasitism – one species benefits at the expense of another (a parasite lives in or on another organism)
ex. the tick feeds off the dog’s blood

10. Homework
1. Classify the following interactions as mutualism, commensalism, or parasitism.
A yucca moth caterpillar feeds on the yucca plant and pollinates the yucca plant.
Lice feed harmlessly on the feathers of birds.
A cowbird removes an egg from a robin’s nest and replaces it with one of its own.
An orchid plant grows on the branch of a tree. The tree remains healthy.
2. When similar species live in the same habitat, explain how competition between these species is reduced. 
3. When a predator catches its prey, it may appear that the prey species suffers. But there are benefits to this type of interaction for the prey species as well. What are two ways in which the prey species may benefit from the predator hunting them?