Download Community Interactions: Competition, Predation and Symbiosis Part

Unit 9: Ecology
Name: ___________________________________
Aim 51: Community Interactions
Date: ________________
Community Interactions: Competition, Predation and Symbiosis
Part I: Competition

Competition- the struggle between organisms for the same limited resources in a particular area
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Resource- any necessity of life, such as water, nutrients, light, food or space.
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Direct competition often results in one species dying out.
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Competitive Exclusion Principle- states that no two species can occupy exactly the same niche in exactly the
same habitat at the same time.
Competition Questions: Write TRUE if the statement is true. If the statement is false change the underlined word or
words to make the statement true.
1) _____________________Competition occurs when organisms attempt to use the same resources.
2) _____________________Direct competition often results in both species surviving.
3) _____________________The competitive exclusion principle states that no two organisms can occupy exactly
the same niche in exactly the same habitat at exactly the same time.
4)
5)
Part II: Predation
Predator-prey interactions help shape communities. A predator is an organism that hunts and kills other
organisms for food. Prey are the organisms hunted or eaten by a predator. Predation is the act of one organism, a
predator, feeding on another organism, its prey. Predator and prey populations influence each other - predators help
control the size of prey populations. As predators kill and eat their prey, they limit the growth of the prey population. If
too many prey animals are killed, predators begin to starve and their population is reduced. With fewer predators, the size
of the prey population begins to recover. When prey populations decrease, the number of predators usually decreases
because less food is available.
Predation Questions:
6) A lion eats a zebra.
Which animal is the predator? ___________________________
Which animal is the prey? _______________________________
7) Explain how predators help control the size of prey populations
8) If the grass that the zebras eat decreases in population, what will happen to the zebra population? Will it
increase or decrease?
________________________________________
9) What will happen to the lion population? Will it increase or decrease _________________________________
10) The zebra population decreases and the lion population decreases because of it. After a while, will the zebra
population start to increase or decrease because of the decrease in lion population? Explain why:
11) Why is it important that there are more prey than predators in an ecosystem?
12)
13) The graph below shows changes in the populations
of two species that interact only with each other
over a period of time
Part III: Symbiosis

Symbiosis- occurs when two species live closely together in one of three ways:
1) Mutualism (+,+) - both species benefit from the
relationship
2) Parasitism (+,-) - one species (parasite) benefits by
living in or on the other species (host) and this other is
harmed
3) Commensalism (+,0) - one species benefits
and the other is neither helped nor harmed
A clownfish and a sea anemone (just like in “Finding Nemo”
have a mutual relationship (both benefit). Sea anemones are mainly sessile (does
not move) animals. Some of them depend on the motile clown fish for their
survival. The clown fish helps to provide food for the sea anemone as it seeks
protection in the anemone's tentacles
Symbiosis Questions: Match the example with the type of relationship or term
A tapeworm living in a person’s intestines
14)
(harming the person)
15)
Microorganisms living in the intestines of
termites break down cellulose, providing food for both the termites
and the microorganisms. This nutritional relationship is known as
16)
Deer ticks are responsible for spreading
Lyme disease. This organism, which feeds on the blood of warmblooded organisms like mice, deer, and humans, is best described as a
Type of relationship/Term
A. Mutualism
B. Commensalism
C. Parasitism
D. Parasite
E. Host
A bee eating a flower’s nectar and picking up the flowers pollen (which helps the
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flower reproduce)
18)
A barnacle living on a whale’s skin (causing no harm)
19)
When a foot fungus grows on a human, the human is considered a
20)
21) The presence of parasites in an animal
usually:
A) an increase in meiotic activity within
structures of the host
B) the inability of the host to maintain
homeostasis
C) the death of the host organism within
twenty four hours
D) an increase in genetic mutation rate in
the host organism