1. Population Ecology

2. Population Dynamics Population:
All the individuals of a species that live together 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.

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
#1 - 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
#2- 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.

6. 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)

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

8. Density-Dependent Factors
limiting resources (e.g., food & shelter)
production of toxic wastes
infectious diseases
predation
stress
emigration

9. Density-Independent Factors
severe storms and flooding
sudden unpredictable severe cold spells
earthquakes and volcanoes
catastrophic meteorite impacts

10. A graphic way of representing population data is a survivorship curve
A graphic way of representing population data is a survivorship curve. This is a plot of the number of individuals still alive at each age. A Type I curve shows a low death rate early in life (humans). The Type II curve shows constant mortality (squirrels). Type III curve shows a high death rate early in life (oysters).

11. Survivorship Curve

12. Three Key Features of Populations
#3- 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.

13. Population Dispersion

14. 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

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

16. Exponential Growth Curve
Figure 35.3A

17. Logistic Growth Curve

18. Carrying Capacity 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.

19. 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

20. How well does the logistic model fit the growth of real populations?
The growth of laboratory populations of some animals fits the S-shaped curves fairly well.
Stable population
Seasonal increase

21. Some of the assumptions built into the logistic model do not apply to all populations.
It is a model which provides a basis from which we can compare real populations.
Severe Environmental Impact

22. “Booms” and “Busts”

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

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