Download File - Mr. Jensen`s Science

COMMUNITY INTERACTIONS IN AN ECOSYSTEM
Predator/Prey Interactions
What does the tree get?
You may remember that a predator is an
animal that hunts and kills other animals
for food. Prey is a term used to describe
animals that are hunted and killed by
predators. Predators share a
relationship due to competition for prey
and other resources. Predation is a
strong, selective pressure that drives
prey organisms to find ways to avoid
being eaten. Some defensive strategies
are pretty obvious, and top among the
list of strategies is running away.
Gazelle, deer, small mammals and
lizards often rely on their speed and
quickness to escape predators, and
many birds rely on flight as their primary
defensive strategy. Some organisms,
like armadillos, tortoises, porcupines
and thorny plants, use armor, quills and
thorns to defend themselves against
predators.
Quite a lot actually, you see the ants are
very territorial and aggressive. They will
attack anything and everything that
touches the tree - from grasshoppers
and caterpillars to deer and humans.
They will even climb onto neighboring
trees that touch their tree and kill the
whole branch and clear all vegetation in
a perimeter around their tree's trunk, as
well.
Symbiosis
The word symbiosis literally means
'living together,' but when we use the
word symbiosis in biology, what we're
really talking about is a close, long-term
interaction between two different
species. There are many different types
of symbiotic relationship that occur in
nature.
In many cases, both species benefit
from the interaction. This type of
symbiosis is called mutualism. An
example of mutualism is the relationship
between bullhorn acacia trees and
certain species of ants. Each bullhorn
acacia tree is home to a colony of
stinging ants. Acacia tree also provides
the ants with food sources in the form of
nectar.
Parasitism
Now, let's say by some chance, a
bacteria does manage to establish itself
in a person's large intestine. The host
provides a habitat and food for the
bacteria, but in return, the bacteria
cause disease in the host. This is an
example of parasitism or an association
between two different species where
one organism benefits and the host is
harmed. Not all parasites have to cause
disease. Lice, ticks, fleas, and leeches
are all examples of parasites that don't
usually cause disease directly, but they
do suck blood from their host, and that
is causing some harm, not to mention
discomfort to their host.
Commensalism
Commensalism is an association
between two different species where
one species benefits and the other is not
significantly affected. For example, the
cattle egret follows cattle, water buffalo,
and other large herbivores as they
graze. The herbivores flush insects from
the vegetation as they move, and the
egrets catch and eat the insects when
they leave the safety of the vegetation.
In this relationship the egret benefits
greatly, but there is no apparent effect
on the herbivore.
Name/Period: __________________________________________________
COMMUNITY INTERACTIONS IN AN ECOSYSTEM
What is a predator?
Give an example.
Explain the relationship between predators.
What is prey?
Give an example.
How do prey combat predators? Give two examples.
Define symbiotic relationship.
Define mutualism and give an example.
Define parasitism and give an example.
Define commensalism and give an example.