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. 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
Birth -
Emigration

10. Population Dispersion

11. 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.

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. Mark and Recapture Method
R (marked recaptured) = M (Marked initially) T (total in second sample) N (total population size) SO we can rearrange this to find total population size N = M x T R

14. Mark and Recapture Example
Suppose you took 200 mice out of a forest having an unknown number of mice, put leg bands on them, return them to the forest and let them mix thoroughly. If you then take 250 mice from the forest and find 50 of them to be have leg bands, what is the total population size?

15. Example continued…
M= 200
T= 250
R= 50
200 x = mice 50

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

17. Exponential Growth Curve
Figure 35.3A

18. Logistic Growth Curve

19. Reproductive Strategies
R Strategists
Short life span
Small body size
Reproduce quickly
Have many young
Little parental care
Ex: cockroaches, weeds, bacteria

20. Reproductive Strategies
K Strategists
Long life span
Large body size
Reproduce slowly
Have few young
Provides parental care
Ex: humans, elephants

21. Human Population 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

22. The Human Population Doubled three times in the last three centuries
~ 7.4 billion and may reach 9.3 billion by the year 2050
Improved health and technology have lowered death rates

23. History of the Human Population