Transcript 3.2 Interactions and Changes Occur in Ecosystems

3.2 Interactions and Changes
Occur in Ecosystems
Science 7
Unit A
Key Terms
Bioinvasion
Competition
predation
predator
prey
Wetlands Case Scenario –p 55
• Read p. 55
• What makes
wetlands special?
• What do you think
happened to make
people reconsider
the importance of
wetlands?
Give It a TRY - TO CHANGE OR
NOT TO CHANGE
Purpose
To infer how an ecosystem will change
over time.
All things change! –p. 56
• Change is a factor for all life and for all
ecosystems on Earth.
• The cycles of matter that they have
already studied illustrate constant change.
• What are examples of changes that are
happening inside you and around you?
Make your own definitions:
• After reading about the following terms,
define in your own words:
• Bioinvasion 
• Competition
• Predation 
This is real; This is Nature!
• In natural communities, living things
compete with each other all the time.
• Living things are trying to survive and are
looking for the resources they need to do
so.
• When you have a limited number of
resources, and many different species
who need those resources, there is
competition.
INQUIRY ACTIVITY
Survival in the Field
Purpose
To explore how
competition might
affect the health
and survival of a
population.
Predation –p 60
• Read paragraph and think of other
examples of predator-prey relationships.
• Look at the photo of the flooded alfalfa
field on this same page (by the Check and
Reflect.) Think about a situation where
weather has affected ecosystems. What
are some of your thoughts?
C & R –p. 60
• Do all questions.
Answers to C & R –p. 60
The introduction of a non-native plant or animal is
called bioinvasion. Bioinvasion can have serious
consequences on ecosystems. Often these
introduced species are stronger than the native
species or they do not have any natural
predators in their new environment. This means
that they compete directly with native species for
the available resources. Populations of native
species are often reduced and sometimes
eliminated.
Answers to C & R –p. 60
2. a) The introduction of a new species can reduce
populations of native species due to competition
for resources, particularly food. Sometimes this
competition leads to the elimination of the native
species so this changes the community.
b) If the availability of food decreases, then this
may severely decrease some or most of the
populations; the competition for food becomes
more difficult.
Answers to C & R –p. 60
3. You should notice the close relationship between the predator (lynx)
and prey (hare) populations.
When the hare population increases, there is lots of food for the lynx to
feed their young, so the young survive. As the hare population
increases, eventually they outstrip their food supply.
Their population declines because of starvation as well as lynx
predation. As the hares decline, there is less for the lynx to eat and
they start to die of starvation.
When the hares are at their lowest level, their food source can recover
and there is more food for the remaining hares, so the cycle starts
again.
The lynx-and-hare population cycle is very well known. Students might
like to know that scientists discovered this cycle by looking at
records of lynx pelts bought by the Hudson’s Bay Company in
northern Canada between 1845 and 1935.
Review Key Terms
Bioinvasion
Competition
predation
predator
prey