
3 main ways organisms interact with
each other:
 1. Competition
 2. Predation
 3. Symbiosis
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
 Occurs when 1 organism eats another to obtain
food
 Animals use camouflage to
avoid predators
 eg. this toad is hardly distinguishable
from its surroundings
 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
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
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
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
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
1. Classify the following interactions as mutualism, commensalism, or
parasitism.
a) A yucca moth caterpillar feeds on the yucca plant and pollinates the
yucca plant.
b) Lice feed harmlessly on the feathers of birds.
c) A cowbird removes an egg from a robin’s nest and replaces it with
one of its own.
d) 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?