1. Populations

2. Population Dynamics
Population: a group of the same species that interbreed and live in the same area at the same time

3. Population Characteristics
Density
How many egrets are there in an area of 2km²
Dispersion
Uniform
Clumped
Random

4. Principles of Growth How fast do populations grow?
What are the limitations?
Do organisms show patterns in their growth?

5. Population Ranges What determines which animals live where?
A Bit of Review…
Two Major Factors
Limiting Factors
Tolerance Ranges
Other influencing factors:
Competitors
Predators
Parasites

6. What limits population growth?
Types of Limiting Factors
Density Independent
Any factor in the environment that does not depend on the number of members in a population per unit area
Usually abiotic
May cause a total wipeout
Examples of natural events:
Examples of Human alterations:

7. Types of Limiting Factors
Density Dependent
Any factor in the environment that depends on the number of members in a population per unit area.
Usually biotic factors
Predation
Disease
Competition
Occurs between same species and different species
Causes starvation or emigration to decrease competition
Parasites

8. Effects of Competition
When populations are low, resources are plentiful
When populations increase, resources become scarce-

9. What is the relationship of the hare and the lynx?
What might happen to the lynx if the producers in the area suffered a major decline? Explain.

10. Explain the relationship between the three populations of organisms and how their growth or decline rate are related to each other. Explain what density dependent factor might have influenced the two animal populations.

11. Population Trends
Hurry up already. I am already two weeks old. We have to have as many kids as possible before we are ancient!
No worries….let’s travel and see the Savannah before we have kids. I’m not ready yet. I need to be able to support my family first.

12. How fast can a population grow?
Small Organisms
Large Organisms
Elephant - k-strategist
Adapted to a stable environment
Long life span – no hurry
Few offspring
Mosquito - r-strategist
Adapted to an unstable environment
short life span – hurry up
many offspring
Why the differences???

13. How fast can a population grow?
Populations grow exponentially when resources are unlimited.
An exponential Growth Curve

14. Population Growth Limited by carrying capacity:
carrying capacity: the number of one species an area can support
Limitations include: oxygen, nutrients, water, energy
Causes a logistic growth
curve to occur
Logistic Growth Model