1. Ch 5 Populations
Students know how to analyze changes in an ecosystem resulting from changes in climate, human activity, introduction of nonnative species, or changes in population size.
Students know how fluctuations in population size in an ecosystem are determined by the relative rates of birth, immigration, emigration, and death.

2. Content Objectives
What characteristics are used to describe a population?
What factors affect population size?
What are exponential growth and logistic growth?
What factors limit population growth?

3. Population Characteristics
Three important characteristics of a population are its geographic distribution, density and growth rate.
Population Density:
The number of organisms per unit area 3

4. Population Growth How fast a given population grows
Factors that influence this are:
Birth Rate
Death Rate
Emigration (the number of individuals moving _________ a population)
Immigration (the number of individuals _________ a population)
away from
moving to 4

5. Exponential Growth
Under ideal conditions with unlimited resources, a population will grow exponentially.
Populations reproduce at a constant rate.
J-shaped curve

6. Understanding Exponentials6

7. Logistic Growth
As resources become less available the growth of a population slows or stops.
Occurs when a population’s growth slows of stops following a period of exponential growth.
Populations stop growing when the birth rate=death rate.
S-shaped curve

9. Population Limiting Factors
Population Ecology: Population Growth Models
Population Limiting Factors
Population growth models
Logistic Growth Model
Often called the S-shaped growth curve
Occurs when a population’s growth slows or stops following exponential growth.
Growth stops at the population’s carrying capacity
Populations stop increasing when:
Birth rate is less than death rate (Birth rate < Death rate)
Emigration exceeds Immigration (Emigration > Immigration) 9

10. Population Limiting Factors
Population growth models
Limits to exponential growth
Competition follows as nutrients and resources are used up
The limit to population size that a particular environment can support is called carrying capacity (k) 10

11. Population Limiting Factors
Density-independent factors
Factors that limit population size, regardless of population density.
These are usually abiotic factors
They include natural phenomena, such as weather events
Drought, flooding, extreme heat or cold, tornadoes, hurricanes, fires, etc. 11

12. Population Limiting Factors
Density-dependent factors
Any factor in the environment that depends on the number of members in a population per unit area
Usually biotic factors
These include
Predation
Disease
Parasites
Competition 12

13. Biodiversity What is Biodiversity?
Biodiversity and Conservation: What is biodiversity?
Biodiversity
What is Biodiversity?
The variety of life in an area that is determined by the number of different species in that area.
There are 2 main types:
Genetic Diversity
Species Diversity

14. Community Ecology: Communities
Review:
A community is a group of interacting populations that occupy the same area at the same time.

15. Communities Limiting Factors
Community Ecology: Communities
Communities
Limiting Factors
Any abiotic or biotic factor that restricts the numbers, reproduction, or distribution of organisms.

16. Ecological Succession
Community Ecology: Ecological Succession
Ecological Succession
Ecological Succession
The change in an ecosystem that happens when one community replaces another as a result of changing biotic and abiotic factors