1. How Populations Grow
Ecology

2. POINT > Identify ways we describe populations
POINT > Describe ways that populations change
POINT > Examine population growth patterns
POINT > Define carrying capacity
POINT > Identify density-dependent and density-independent population factors

3. POINT > Identify ways we describe populations
1. Geographic Range: Area inhabited by a population
Habitat of Canis lupis (Gray wolf) shown in red

4. POINT > Identify ways we describe populations
2. Density & Distribution
Density:
Distribution:
Number of individuals per unit area
Higher
Lower
How individuals are spaced out
Random
Uniform
Clumped

5. a) is the same as population distribution
WB CHECK:
Population density
a) is the same as population distribution
b) depends on how individuals are spaced in an area
c) depends on the number of individuals in an area
d) is equal to the number of individuals

6. Population distribution a) is the same as population density
WB CHECK:
Population distribution
a) is the same as population density
b) depends on how individuals are spaced in an area
c) depends on the number of individuals in an area
d) is equal to the number of individuals

7. POINT > Identify ways we describe populations
3. Growth rate: Positive growth rate means population is getting bigger; negative growth rate means population is shrinking
Growth rate determines whether a population increases, decreases, or remains constant
4. Age Structure: Number of males/females at each age

8. POINT > Describe ways that populations change
1. Birth & Death Rate
Birth > Death 
Birth = Death 
Birth < Death 
Population Grows
Population Constant
Population Shrinks

9. The age structure of a population
WB CHECK:
What happens to a population when the birth rate is higher than the death rate?
The age structure of a population
is the average age of males and females
describes how long individuals live
is determined by the birth rate
describes number of male and females at each age

10. POINT > Describe ways that populations change
2. Immigration & Emigration
Immigration:
Individuals move INTO a population range from elsewhere. This causes the population to grow

11. POINT > Describe ways that populations change
Immigration & Emigration
Emigration:
Individuals move OUT of a population’s range. This causes the population to shrink

12. Birth
Immigration
Death
Emigration

13. POINT > Describe two population growth patterns
1. Exponential population growth
2. Logistic population growth

14. POINT > Examine population growth patterns
1. Exponential growth: Each generation of offspring is larger than the one before it
The larger the population gets, the faster it grows

15. POINT > Examine population growth patterns Exponential Growth:
Number of Individuals
Time

16. POINT > Examine population growth patterns
Populations grow exponentially only under ideal conditions with unlimited resources

17. POINT > Examine population growth patterns
2. Logistic Growth: Period of exponential growth, followed by slower growth, and finally growth levels off

18. POINT > Examine population growth patterns Logistic growth:
Number of Individuals
Time

19. POINT > Examine population growth patterns
Three phases of logistic growth
Phase I – Exponential growth: population size & rate of growth increase rapidly

20. POINT > Examine population growth patterns
Number of Individuals
Time

21. POINT > Examine population growth patterns
Three phases of logistic growth:
Phase II – Growth slows
Pop. size increases, but rate of growth decreases

22. POINT > Examine population growth patterns
Number of Individuals
Time

23. POINT > Examine population growth patterns
Three phases of logistic growth:
Phase III – Growth Stops
Pop. size remains constant, rate of growth is zero

24. POINT > Examine population growth patterns
Number of Individuals
Time

25. What happens in stage I of logistic growth?
WB CHECK:
What happens in stage I of logistic growth?
What happens in stage III of logistic growth?
What happens in stage II of logistic growth?
When can exponential growth occur?

26. POINT > Define carrying capacity
Carrying capacity is the maximum number of individuals of a species a particular environment can support
Carrying capacity may change based on many factors (biotic or abiotic factors)

27. is constant for a given ecosystem
WB CHECK:
Carrying capacity
is constant for a given ecosystem
can change if biotic or abiotic factors change
is determined by birth rate
is determined by death rate

28. Homework:
Read Ch 5.1 pages
Assess #1-4 page 135
Workbook pages 324, 327, 334