Download Which Factors Affect Ecosystems

Chapter 3
Lesson 2
What Factors Affect Ecosystems?
SPI’S: Science: 7.2.3, 7.5.2, 7.2.2, 7.2.3
Reading: 5.1.12, 5.1.3, 5.1.14, 5.1.16, 5.1.20
Language: 1.1.5, 1.1.13, 1.5.2
Main Idea
 The size of any population can vary over
time. It responds to change in climate
and resources.
In This Lesson:
We’ll learn how a decrease in food supply,
changes in climate, and relocated species
can upset the balance of an ecosystem.
Vocabulary:
It’s journal time folks!!!
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Extinction
Population
Predator
Prey
Extinction:
 When all members of a species die out
Population:
 All the organisms of a given species that
live together in the same area
Predator:
 Animal that hunts and eats other animals
Prey:
 Animal that is hunted and eaten by
predators
Hey, did you catch that?
Predator and Prey are…
Antonyms!!!
(opposites)
Let’s Talk Population…
 Remember, a population is all the
organisms of a given species that live
together in the same area.
Let’s Talk Population…
 Population size responds to changes in
climate and resources.
How do you think the birds on the previous
slide would respond to the 3 climate examples
listed below?
Let’s Talk Population…
 In a healthy ecosystem, the population of
predators and prey are balanced.
Changes in Population…
 Every ecosystem supports many populations.
That means many different species live in the
same ecosystem.
 A population is all the organisms of a given
species that live together in the same area.
 Any change in one part of an ecosystem can
upset the balance.
For Example:
 Suppose a fungus kills many of the
plants that rabbits eat. Such an event
could lower the rabbit population. This
would affect the hawks, owls, and other
animals that eat the rabbits.
 How would this affect the hawks, owls,
and other animals that eat the rabbits?
Answer…
The hawks, owls, and other animals would
not have the rabbits to eat; therefore,
they might go hungry. Or, they would
have to find another food source which
might cause another species to go
hungry.
Can you see how a change in population
could upset the balance of an
ecosystem?
Question…
 What would happen if a population of
rabbits became too large?
Answer:
They would crowd out the other
species in that area!!
Why would that be a bad thing?
Answer
Ecosystems have limited
resources, and can only support
a limited number of living things.
Hey…that makes sense!!!
Did you know…
In an ecosystem, populations are
ALWAYS changing.
 Old animals die, and new ones are born.
 When a tree falls, plants that thrive in
sunlight can begin to grow.
These are good changes!!!
Consider the relationship
between
predators and their prey
Predators are animals that hunt and eat
other animals.
Prey are animals hunted and eaten by
predators.
(I’d rather be a predator!)
In a healthy ecosystem…
The population densities of predators and
prey are balanced. But remember, we
said certain factors can upset this
balance.
For example: Predators and prey are two
factors that affect the balance of an
ecosystem.
Let’s Read About It:
May I have a volunteer to begin
reading on P. 95, please?
How might a decrease in
predators affect prey?
Answer:
The prey population
could grow.
Did you know…
Once an ecosystem is changed it may take
hundreds of years to recover!
In some cases, it is changed FOREVER!!
Let’s Review:
What factors affect ecosystems?
Answer:
Population
Predators
Prey
Review:
What factors can cause the size of
a population of living things to
change?
Answer:







Climate change
Volcanic eruptions
Fires
Droughts
Floods
Alien species
Lack of resources
Review:
(Cause and Effect)
Why do alien species often thrive
in their new ecosystems?
Answer:
Often the alien species have no
natural predators in the new
ecosystem.
Way To Go!!!
This is the end of Chapter 3 Lesson 2.
Now it’s YOUR time to shine…
In your journal write everything you’ve
learned about the factors that affect
ecosystems.
Make me proud champs!!!