1. Ecology

2. Populations Population
The number of individuals of a species in a specific habitat

3. Characteristics of Populations
Three important characteristics of a population are its
geographic distribution,
describes the area inhabited
density, and
number of individuals per unit area
growth rate.

4. Factors that change population size
Birth: leads to an increase
Death: leads to a decrease
Needs to be balanced for population size to remain constant
Immigration: leads to an increase
Coming into a habitat
Emigration: leads to a decrease
Leaving a habitat

5. Exponential Growth
individuals in a population reproduce at a constant rate
Under ideal conditions with unlimited resources, a population will grow exponentially

6. Logistic Growth
a population's growth slows or stops following a period of exponential growth
resources become less available
Population growth may slow down when the birthrate decreases, when the death rate increases, or when both events occur at the same rate
population growth may slow down when the rate of immigration decreases, the rate of emigration increases, or both

7. Carrying Capacity
size of the population when the average growth rate reaches zero
That number, in turn, represents the largest number of individuals that a given environment can support

8. Quick Assessment Prompts:
Answer the following using complete sentences:
What factors can change a population size?
What is the difference between exponential growth and logistic growth?
Define Carrying Capacity.

9. Limits to Growth Limiting Factors
factor that causes population growth to decrease

10. Density-Dependent Factors
limiting factor that depends on population size
Density-dependent limiting factors include competition, predation, parasitism, and disease.

11. Density-Independent Factors
Unusual weather, natural disasters, seasonal cycles, and certain human activities are all examples of density-independent limiting factors
Many species show a characteristic crash in population size

12. Quick Assessment Prompts:
Answer the following using complete sentences:
If an entire lynx population disappears, what is likely to happen to the hare population on which it preys?
How does a limited resource affect the size of a population?

13. Changes in Pop. Size and Biodiversity
Speciation and Extinction are influenced by:
Natural causes (mutations, evolution)
Changes in climate (adaptations needed)
Human activity (deforestation, pollution)
Introduction of invasive species
Non-native species that move into a habitat and has devastating effects

14. Example of Invasive Species
Kudza Vine
Introduced from Japan for erosion control (1876) and has been growing uncontrollably ever since
Has no competitors for resources or predators
Grows (in summer) almost a foot a day

16. Australia and Its Rabbits
Rabbits were brought to Australia in for hunting and food ~ 1880s
No natural predators
Plenty of resources
Within 6 years, there hundreds of thousands
There are now about 300 million
Destroying habitats
Digs up root systems
Developing deserts

17. Rabbit Solutions Hunting Rewards Fumigation (spraying poisons)
Dynamite
Plowed
2000 mile fence
All Failed

18. Rabbit Solutions Introduced virus in 1951 (2nd invasive species)
Killed millions
But some were naturally resistant
They survived and reproduced
Bunnies are also resistant to virus (genetics)
1991, 1996: Introduced new viruses and killed many but same as above
Decision to release a new virus every two years to lessen the population (or at least keep it in check)

19. Australian Rabbits
Besides acting as an invasive species, the rabbits serve to demonstrate a second point:
Co-evolution
Two species that evolve in response to each other
Rabbits obtain immunity to virus (through genetics)
Virus evolves and begins killing again
Rabbits again obtain immunity to virus (through genetics)
This continues…