1. Ecology of Populations
Chapter 46

2. Chapter Outline Scope of Ecology Population Density and Distribution
Population Growth Models
Survivorship Curves
Age Distributions
Regulation of Population Size
Life History Patterns
Human Population Growth
Environmental Impact

3. Scope of Ecology Ecology – what is it? Definitions:
Habitat - Place where an organism lives.
Population - All the organisms within an area belonging to the same species.
Community - All various populations interacting at same locale.
Ecosystem – A collection of communities

4. Ecological Levels

5. Density and Distribution of Populations
Population Density - Number of individuals per unit area or volume.
Population Distribution - Pattern of dispersal of individuals within the area of interest.

6. Uniform Distribution
EXAMPLE

7. Random Distribution
EXAMPLE

8. Clumped Distribution
EXAMPLE

9. Characteristics of Populations
They tend to grow
Intrinsic Rate of Natural Increase (r)

10. Population Growth Models
Exponential Growth
Biotic Potential
Environmental Resistance

11. Exponential Growth Curve

12. Logistic Growth Logistic growth—indicated by an S-shaped curve
Difference between logistic and exponential due to environmental resistance

13. Logistic Growth

14. Carrying Capacity
Carrying Capacity is the maximum number of individuals of a given species the environment can support.
The closer the population to the carrying capacity, the greater the environmental resistance.
Biotic potential is having full effect and birthrate is a maximum during exponential growth.

15. St. Paul Island Reindeer Population

16. Mortality Patterns
Cohort --- all the members of a population born at the same time.
Survivorship---the probability of newborn individuals of a cohort surviving to particular ages.
Illustrated by Survivorship Curves
A cohort is composed of all the members of a population born at the same time.
Survivorship is the probability of newborn individuals of a cohort surviving to particular ages.
Survivorship Curves

17. Survivorship Curves
NOTE: Looks at life expectancy as a percentage of maximum life span.
Type I---long lived, die older, later in reproductive cycle
EX?
Type II—die at a constant rate
Type III—Die young

18. Survivorship Curves
Some examples

19. Age Distributions What proportion of population is in each cohort?
Age Structure Diagrams
Populations differ according to what proportion of the population falls in each age category.
At least three structures possible.
Increasing
Stable
Decreasing

20. U.S. Age Distributions
The United States –note the Baby Boomers

21. Regulation of Population Size
Density - Dependent Factors
Density - Independent Factors

22. Factors That Affect Population Size
Density Dependent Factors
1. Competition
Intraspecific
Interspecific
Predation
Parasitism
4. Disease

23. Factors That Affect Population Size
Density Independent Factors
Abiotic factors
2. Unpredictable, catastrophic events

24. Life History Patterns r - Strategists (Opportunistic)
Remember r=reproduction

25. Life History Patterns k - Strategists (Equilibrium)
Remember k=Karrying kapacity

26. Human Population Growth
Human population has had an exponential growth pattern.
Doubling time currently estimated at 53 years.
Population Size
Billion
Billion
Billion
Billion

27. World Population Growth

28. Country Development More-Developed Countries (MDCs) GR=0.1%
Less-Developed Countries (LDCs) GR= 1.6%
LDC population expected to increase from 5-8b by 2050

29. Age Distributions
Age Structure Diagrams divide populations into three age groups.
Pre-Reproductive
Reproductive
Post-Reproductive

30. The Demographic Transition
Stage I: high birthrates and death rates
Stage II: continued high birthrates, declining death rates
Stage III: falling birthrates and death rates, eventually stabilizing

31. More-Developed Countries

32. Less-Developed Countries

33. Age Distribution of the World’s Population
Population Structures by Age and Sex, 2005
Millions
Less Developed Regions
More Developed Regions
Age
0-4
Male
Female
Male
Female
Source: United Nations, World Population Prospects: The 2002 Revision (medium scenario), 2003.

35. Figure 7.2 World Population Distribution by Region, 1998 and 2050

37. Environmental Impact Measured in terms of: Population Size
Resource Consumption Per Capita
Resultant Pollution

38. Environmental Impact

39. Review Scope of Ecology Population Density and Distribution
Population Growth Models
Survivorship Curves
Age Distributions
Regulation of Population Size
Life History Patterns
Human Population Growth
Environmental Impact