#### Transcript Determining Population Size

```Daily Response
1)
2)
3)
4)
What is the difference between immigration and emigration?
What is a limiting factor?
Name 3 limiting factors.
What happens to a population when the birth rate is bigger
than the death rate?
5) What happens to a population when the death rate is bigger
than the birth rate?
Determining Population Size
4 different techniques scientists use
to estimate the size of populations
Direct Observation
What is the population of penguins?
Count them.
Direct Observation
What is the population of seagulls?
Count them.
Indirect Observation
What is the population of rabbits?
Since you can not see the rabbits you have to count the
number of rabbit holes. Next, estimate how many rabbits you
think live in each hole. Multiply the numbers to get the
population size.
Indirect Observation
What is the population of birds?
Since you can not see the birds you have to count the number
of nests. Next, estimate how many birds you think live in each
nest. Multiply the numbers to get the population size.
Sampling
What is the population of ants?
Take a small section of the ant hill and count the ants. Find
the total area of the ant hill. Follow the equation below to
find the total population of ants.
There are 20 ants in one square cm.
The ant hill is 100 square cm.
20 ants
1 cm
=
?
100 cm
Sampling
A biologist collected 1 gallon of pond water
and counted 50 paramecium. The pond holds
2,000 gallons of water. What is the population
of paramecium?
50 paramecium =
?
1 gal
2,000 gal
Mark and Recapture
This method is most useful when dealing with
an animal population that moves around
1)individual organisms are captured (unharmed)
2) They are counted and marked or tagged and
then released back into the environment
3) After some time some are recaptured and we
count how many have the mark and how
many do not
Mark and Recapture
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rk/arctic/wildlife/polar_bear/tracker/
Journal Entry
Explain the four ways we determine population size.
Then write your own example for each one.
(It may not be the examples from the book , outline or power point.)
Direct
Observation
Indirect
Observation
Sampling
Mark and
Recapture
Explanation -
Explanation -
Explanation -
Explanation -
Example -
Example -
Example -
Example -
```