Lesson Overview
Objectives 4.2
Niches and
Community
Interactions
Niches and Community Interactions
-Define niche.
-Describe the role competition
plays in shaping communities.
-Describe the role predation
and herbivory play in shaping
communities.
-Identify the three types of
symbiotic relationships in
nature.
Lesson Overview
Niches and Community Interactions
Habitat or Niche???
Habitat ~ the place
where an organism
lives.
Niche ~ describes not
only where it lives, but
how it interacts with
biotic and abiotic
factors in the
environment.
Lesson Overview
Niches and Community Interactions
Resources
A resource is anything necessary for
life, such as water, nutrients, light,
food, mates or space.
Lesson Overview
Niches and Community Interactions
Competition
Competition occurs when two or more
organisms attempt to use the same limited
resource in the same place at the same
time.
Lesson Overview
Niches and Community Interactions
The Competitive Exclusion Principle
The competitive exclusion principle states that no
two species can occupy exactly the same niche in
exactly the same habitat at exactly the same time.
Lesson Overview
Niches and Community Interactions
Dividing Resources
Instead of
competing for
similar
resources,
species usually
divide them.
Lesson Overview
Niches and Community Interactions
Predator-Prey Relationships
An interaction in which
one animal (the
predator) captures and
feeds on another animal
(the prey) is called
predation.
Predators can in affect
the size of prey
populations a community
and determine the
places prey can live and
feed.
Lesson Overview
Niches and Community Interactions
Keystone Species???
Sometimes
changes in the
population of a
single species,
often called a
keystone species,
can cause
dramatic changes
in the structure
of a community.
Lesson Overview
Niches and Community Interactions
Symbioses
Any relationship in which two species
live closely together is called
symbiosis, which means “living
together.”
The three main classes of symbiotic
relationships in nature are mutualism,
parasitism, and commensalism.
Lesson Overview
Niches and Community Interactions
Mutualism
When both species involved benefit
from the relationship, it is called
mutualism.
Lesson Overview
Niches and Community Interactions
Parasitism
When one
species benefits
and the other
one is harmed,
the relationship
is called
parasitism.
Lesson Overview
Niches and Community Interactions
Commensalism
When one organism benefits and
the other one is neither helped
nor harmed, the relationship is
called commensalism.
Lesson Overview
Niches and Community Interactions
True or False
1. An organism’s niche includes the way the organism
gets what it needs to survive and reproduce.
_________________________
2. Two kinds of birds eat the same food and nest in the
same area. These two species of birds are in
symbiosis. _________________________
3. If too many herbivores live in a community, the
predator population will decrease rapidly.
_________________________
4. A symbiotic relationship between organisms in which
one species benefits and the other is neither helped
nor harmed is mutualism.
______________________________
Lesson Overview
Niches and Community Interactions
Answers
1. An organism’s niche includes the way the organism
gets what it needs to survive and reproduce. True
2. Two kinds of birds eat the same food and nest in the
same area. These two species of birds are in
symbiosis. False, competition
3. If too many herbivores live in a community, the
predator population will decrease rapidly. False,
producer
4. A symbiotic relationship between organisms in which
one species benefits and the other is neither helped
nor harmed is mutualism. False, commensalism