1. Factors Affecting Population Change

2. Exponential Vs. Logistic Growth

3. Two Strategies for Growth
1. “r-strategists”: Spawners!
Characterized by exponential growth, which results in temporarily large populations, followed by sudden crashes in population size.
Ex. Insects, bacteria, some plants
live in unpredictable and rapidly changing environments
Reproduce quickly when conditions are favorable
External Fertilization
Many offspring: small, mature rapidly, no parental care

4. Two Strategies for Growth
2. “K-strategists”: Brooders!
Characterized by a high degree of specialization. Ex. Trees, whales, tigers, etc.
Live in stable and predictable environments
Can compete effectively
Reproduce late in life
Internal Fertilization
Few offspring: large, mature slowly, often much parental care

5. Density Dependent Factors
Factors that influence population regulation, having greater impact as population density increases or decreases
Struggle for survival includes factors like competition, predation, disease, and other biological effects

6. Density Dependent Factors
Intraspecific Competition – Ecological interaction where individuals of the same species/population compete for resources in their habitat.

7. Density Dependent Factors
Predation - Consumption of prey by carnivores
-Regulation can occur due to preferred species of prey

8. Density Dependent Factors
Disease –
Pathogens able to pass from host to host in overcrowded populations with greater ease

9. Density Dependent Factors
Allee effect –
Occurs when population cannot survive or fails to reproduce enough to offset mortality once the population density is too low; such populations usually do not survive.
Eg. The extinct passenger pigeon.

10. Density Dependent Factors
Minimum viable population size – Smallest number of individual needed for a population to continue for a given period of time
Small population size can result in inbreeding and loss of genetic variation

11. Density Independent Factors
Factors influencing population regulation regardless of population density
Human intervention - Pesticides
Environment - reproductive success based on temperatures, natural disasters etc

12. Limiting Factors
Any essential resource that is in short supply or unavailable. These factors determine how much the individual or population can reproduce.
Eg. light, space, water, nutrients

13. Homework!
Page 675 1, 2 & 5
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