Download Populations and Communities Section 2 Predator

Populations and Communities
Section 2
Section 2: Interactions in Communities
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Bellringer
Key Ideas
Predator-Prey Interactions
Other Interactions
Summary
Populations and Communities
Section 2
Bellringer
Animals, like people, live in communities. Make a list of
different jobs that are done by people in your community
that keep the community running. Keep in mind that some
people may have more than one function in a community.
Populations and Communities
Section 2
Key Ideas
• How do predator-prey interactions influence both
predators and prey?
• What are two other types of interaction in a community?
Populations and Communities
Section 2
Predator-Prey Interactions
• One of the most common interactions in communities is
that between predators and their prey. Predation is the
act of one organism killing another for food.
• Species that involve predator-prey or parasite-host
relationships often develop adaptations in response to
one another.
• Back-and-forth evolutionary adjustment between two
species that interact is called coevolution.
Populations and Communities
Visual Concept: Predation
Section 2
Populations and Communities
Section 2
Visual Concept: Coevolution
Populations and Communities
Section 2
Predator-Prey Interactions, continued
• In parasitism, one organism feeds on another organism
called a host.
• The host is almost always larger than the parasite and is
usually harmed but not killed.
• Parasites often live on or in their host. Therefore, the
parasite depends on its host not only for food but for a
place to live as well.
Populations and Communities
Section 2
Predator-Prey Interactions, continued
• Hosts try to keep parasites from infecting them. Hosts
can defend themselves with their immune systems or
behaviors such as scratching.
• In response, parasites may evolve ways to overcome the
host’s defenses.
Populations and Communities
Section 2
Predator-Prey Interactions, continued
• Herbivores are animals that eat plants.
• Unlike predators, herbivores do not often kill the plants.
But plants do try to defend themselves.
• Plants defend themselves from herbivores with thorns
and spines or with bad tasting chemical compounds.
These chemical compounds may even cause sickness
or death.
• Some herbivores have evolved ways to overcome plant
defenses.
Populations and Communities
Section 2
Visual Concept: Plant Protection
Mechanisms
Click on the thumbnail to learn more.
Populations and Communities
Section 2
Other Interactions
• Not all interactions between organisms result in a winner
and a loser.
• Symbiosis is a relationship in which two species that
live in close association with each other. In some forms
of symbiosis, a species may benefit from the
relationship.
• Mutualism and commensalism are two kinds of symbiotic
relationships in which at least one species benefits.
Populations and Communities
Section 2
Other Interactions, continued
• A relationship between two species in which both
species benefit is called mutualism.
• In commensalism, two species have a relationship in
which one species benefits and the other is neither
harmed nor helped.
Populations and Communities
Visual Concept: Symbiosis
Section 2
Populations and Communities
Section 2
Summary
• Species that involve predator-prey or parasite-host
relationships often develop adaptations in response to
one another.
• Mutualism and commensalism are two types of symbiotic
relationships in which one or both of the species benefit.