Transcript Chapter 2 Lesson 3

How do organisms interact?
Chapter 2 Lesson 3
In an ecosystem, organisms compete for space,
light, food, water, air, and nutrients
• Competition is the struggle among organisms
for limited resources in an area.
• Population density is a measure of a
population’s size in relation to the size of
where the population lives.
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The predator prey relationship
• A predator is an animal
that feeds on other
living animals.
• Prey is an animal that
predators eat.
What would happen if there are too many
predators?
What would happen if there aren’t enough
prey for the predators to eat?
But we don’t like to compete…
– Not all organisms in an ecosystem compete. Some live
together in a relationship called symbiosis.
• Symbiosis is a close relationship between organisms
of different species in which one or both of the
organisms benefit.
– There are three types of symbiosis
• Parasitism is a relationship where one species
benefits while the other is harmed.
– A parasite is an organism that lives in or on another
organism
– The organism that a parasite lives in or on is called the
host.
• Parasites are usually smaller than the host and don’t usually kill
them, but can make them weaker
• In this relationship, both organisms benefit.
• In this relationship, one organism benefits and
the other is neither helped, nor harmed.
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