1. Chapter 1.2
STUDYING POPULATIONS

2. Review the term “population”
Population – is a group of animals or plants in a specific area.

3. Numbers of populations
Scientists like to know the number of populations. They want to know if the number went up or down . OR if the number is the same as 50 years ago.
There are different ways to figure out the number of populations.

4. Ways to figure out the number of populations:
Direct observation
Indirect observation
Sampling
Mark-and-recapture studies

5. Direct observation:
Counting all the members of population.

6. Indirect observation:
Counting the “homes” or signs of animals than animals themselves.

7. Sampling:
To make an estimate- it is an approximation of a number, based on reasonable assumptions. Counting number of organisms in a small area, then multiplying to estimate number in larger area.

8. Mark-and-Recapture Studies:
Scientists catch animals, count and mark them (first time)
Then, second time in 2 weeks, scientists catch again, count how many animals have marks and how many are unmarked.
They use a special formula to figure out the number of population.

9. Changes in Population Size
Population changes when new people move in (immigrate) or move out (emigrate)
Discussion: Why do people immigrate or emigrate?
Answer:
Scientists look at population to:
Make sure it does not grow TOO BIG
HARD to find food
DESTROY environment
RUN OUT of water
POPULATION is not disappearing

10. 1. Births and Deaths
Birth rate – number of organisms born in a specific time.
Death rate – number of organisms die in a specific time
Example of birth rate: rabbits make 600 babies a year.
Example of death rate: 400 rabbits die in a year

11. 2. The Population Statement
IF birth rate > death rate THEN population increases
IF birth rate < death rate THEN population decreases

12. Math Skills – Inequalities p. 16
< LESS THAN
> MORE THAN
½ < TRUE/FALSE?
TRUE
Practice problems: /5
-2-(-8)

13. Immigration and Emigration
Immigration - moving in the population and increasing that population
Emigration - moving out of population and decreasing that population
WHY?
Food, water, space

14. Graphing changes in population
How to show population changes?
USE a GRAPH (see figure 7 on p. 17)
What do the vertical axis of the graph show?
Answer: Number of rabbits
What do the horizontal axis of the graph show?
Answer: Year of study
In what year was rabbit population largest?
Year 4
What was the size of the population that year?
850,000

15. Figure 7 Graph p. 17
From year 0 to 4, more rabbits __________ (joined/left) so population increased.
From year 4 to 8, more rabbits __________ (joined/left) so population decreased

16. Calculating Growth Rate p. 17
Birth rate – number of organisms born in a specific time
Death rate – number of organisms that die in a specific time
If 1600 geese die and 1400 geese are born, what is the growth rate that year if growth rate = birth rate – death rate?
-200
What negative number mean?
Answer: Population decreases

17. 5. Population Density
Definition: Number of organisms in an area of specific size. See figure 8
FORMULA to know population density:
Population density= Number of organisms/ area

18. More dense vs. less dense
Less dense population
More dense population

19. Population is the U.S.A.

20. Population density= Number of organisms/ area Example: 20 per
What is the population density?
Population density= 20 butterflies/10 square meters (show on board)
Population density=2 butterflies per square meter
10 square meters (area)

21. Matching Population density __X axis
Organism __number die in specific time
Count __move out
Mark and recapture __evidence of population
Sampling __count in small area first
Direct observation __one, two, three, four…
Indirect observation __number in a specific area
Immigrate __living thing
Emigrate __mark and count
Birth rate __count one by one
Death rate __move in
Vertical axis __# born in specific time
Horizontal axis __Y axis

22. Limiting Factors Definition
Something that limits the growth of the population
What can limit?
food
water
living space
weather
Carrying Capacity
Definition: maximum number land can support
Example: population cannot increase more than 10 animals

23. Questions: When might an ecologist use indirect observation to estimate a population?

24. What does the word “population density” mean?

25. What is the limiting factor? List the limiting factors.

26. What is carrying capacity?

27. What are 4 ways to determine a population size?

28. What is immigration and emmigration?

29. What is an estimate and what method uses estimate?

30. Section 2 Assessment pg 20
1a. What are 4 methods of determining population size? 1b. Which method would you use to determine the number of mushroom growing on the floor of a large forest? Explain. 2a. Name two ways organisms join a population and two ways organisms leave a population.

31. Con’t.
2b. Suppose a population of 100 mice has produced 600 young. If 200 mice have died, how many mice are in the population now? 2c. Suppose that you discovered that there were actually 750 mice in the population? How could you account for the difference? 3a. Name 3 limiting factors for populations 3b. Choose one of the limiting factors and describe how it limits population growth. 3c. How might the limiting factor you chose affect the pigeon population in your town?

32. 1. 2. 3. 4. 5. 6. WHAT is Mark and Recapture? Each square is a turtle
Copy the data table
Data table shows first three years 1.
Year 4 shows 15 turtles marked in data table
Select 1 turtle from box X10 2.
Record 10 under Total Number Captured column 3.
WHAT is Mark and Recapture?
Each square is a turtle
Each square with a dot is a marked turtle
From the 10 that you captured, count how many were marked 4.
Record number of marked turtles under Number Recaptured column 5.
Formula for last column is number marked x total number captured /number recaptured (#1 p. 21) 6.

33. Year
Number Marked
Total Number Captured
Number Recaptured
Estimated Total Population 1 32 28 15 60 2 25 21 11 3 23 19 4
Estimated Total Population = Number marked x Total number captured
Number Recaptured
Example using Year 1: 32x28
= 59.7 or 60 turtles 15

34. Make a graph: x axis is year and y axis is population size7.
Explain how turtle population changed and why you think it changed 8.
Predict what will happen in year 5. Why you think that way? 9.
Write a paragraph explaining why mark and recapture is a good way to track turtles
10.