What factors can
make
Populations
Increase or
Decrease in Size?
Let’s suppose….
• We have two mice…:
and they
produce the
standard 56
“pups”
(baby mice)
each year.
and each of
these mice
goes on to
have 56
babies each
year….
Soon…..
• We’d be over-run with mice on the planet!!
Why doesn’t this occur?
Populations can change in size when new
members JOIN the population or when members
LEAVE a population. This is called BIRTH RATE and
DEATH RATE.
What could have caused the
deer population to increase
from months 1 through 6?
What could have caused the
deer population to decrease
in months 6 through 7?
Why did the population seem
to balance from months 8
through 12?
When the adult female deer had their fawns, this is known as BIRTH
RATE. This means they INCREASED their population by giving birth to
newborn deer. What else can increase the deer population?
So, from months one through 6 what could
have made the deer population increase?
Populations increase due to the following:
 Births
 Immigration: Moving INTO a new
population
There are several things that can cause the DEATH RATE to increase.
Can you think of some factors that may cause the population of deer to
decline due to an increase in deaths?
Predators hunt and kill fawns and adult
deer for energy.
Predation
There are several things that can cause the DEATH RATE to increase.
Can you think of some factors that may cause the population of deer to
decline due to an increase in deaths?
When food runs out or scarce due to
human activities or natural disasters.
Predation
Starvation
There are several things that can cause the DEATH RATE to increase.
Can you think of some factors that may cause the population of deer to
decline due to an increase in deaths?
Emigration occurs when deer leave their
population in search of food, water, or
shelter.
Predation
Starvation
Emigration
There are several things that can cause the DEATH RATE to increase.
Can you think of some factors that may cause the population of deer to
decline due to an increase in deaths?
Predation
Starvation
Emigration
Disease
Disease and sickness affects all
organisms within populations.
There are several things that can cause the DEATH RATE to increase.
Can you think of some factors that may cause the population of deer to
decline due to an increase in deaths?
Predation
Starvation
Emigration
Disease
Over Hunting
Hunting within government guidelines help keep
many populations in balance, however over hunting
can cause populations to decrease to an unhealthy
size.
To finish the lesson:
1. Read pages 68 through 72
2. Complete the following activities:
a. Do the Math page 69
b. Figure 1 page 70
c. Figure 2 page 71
d. Apply It! Page 72
3. Go to Canvas to complete the following assignments
a. Vocabulary definitions