1. Population Ecology

2. Population Dynamics Population:
All the individuals of a species that live together in an area
Demography:
The statistical study of populations, allows predictions to be made about how a population will change
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

3. Three Key Features of Populations
Population Dynamics
Three Key Features of Populations
Size
Density
Dispersion
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

4. Three Key Features of Populations
Size: number of individuals in an area
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

5. Three Key Features of Populations
Growth Rate:
Birth Rate (natality) - Death Rate (mortality)
How many individuals are born vs. how many die
Birth rate (b) − death rate (d) = rate of natural increase (r)
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

7. Three Key Features of Populations
Density: measurement of population per unit area or unit volume
Pop. Density = # of individuals ÷ unit of space
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

8. How Do You Affect Density?
Immigration: movement of
individuals into a population
Emigration: movement of
individuals out of a population
Density-dependent factors: Biotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites)
Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)

9. Factors That Affect Future Population Growth
Immigration + + -
Population
Mortality
Natality -
Emigration

10. Three Key Features of Populations
Dispersion: describes the spacing of organisms relative to each other
Clumped
Uniform
Random
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

11. Population Dispersion

12. How Are Populations Measured?
Population density = number of individuals in a given area or volume
Count all the individuals in a population
Estimate by sampling
Mark-Recapture Method

13. How Do Populations Grow?
Idealized models describe two kinds of population growth:
Exponential Growth
Logistic Growth

14. Exponential Growth Curve
Figure 35.3A

15. Logistic Growth Curve

16. Carrying Capacity (k):
The maximum population size that can be supported by the available resources
There can only be as many organisms as the environmental resources can support
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

17. What keeps a population from growing exponentialy?
Limiting factors=Factors that are biotic or abiotic that keep a population from continuing to increase indefinitely
2Types:
Density-independent factors
Density-dependent factors

18. Factors Limiting Growth Rate
Declining birth rate or increasing death rate are caused by several factors including:
Limited food supply
The buildup of toxic wastes
Increased disease
Predation

19. Density- independent Factors
Density-independent factors = Any factor in the environment that does not depend on the number of members in a population per unit area
Usually abiotic (natural phenomena)
Ex:
Weather events (tornadoes, floods, hurricanes)
Fire
Human alterations of the landscape
Air, land, and water pollution

20. Density-Dependent Factors
Density-dependent factor = Any factor in the environment that depends on the number of members in a population per unit area
Usually biotic
Ex:
Predation
Disease- (high population density--> disease quickly spreads)
Parasites
Competition – food, space limitations

21. “Booms” and “Busts”

22. Human Population Growth
J curve growth
Grows at a rate of about 80 million yearly
r =1.3%
Why doesn’t environmental resistance take effect?
Altering their environment
Technological advances
The cultural revolution
The agricultural revolution
The industrial-medical revolution

23. The Human Population Doubled three times in the last three centuries
About 6.1 billion and may reach 9.3 billion by the year 2050
Improved health and technology have lowered death rates

24. History of the Human Population