1. Population Dynamics Unit 4: The Biosphere
Let them know about the quiz. Four day unit, three days of notes (but short). We’re going outside next class!!!

2. Species Occur in Groups Called Populations
Population density – the number of organisms per unit area
Species distribution (dispersion patterns)
Based on the availability of resources (food)
Population – all the members living in the same place at the same time.
Pattern of spacing within an area (based on the organism’s needs). Examples
Clumpted – American bison
Uniform – black bears
Random – White-tailed deer

3. Population Growth
Population growth rate explains how fast a population grows
Birth rate
Reproductive potential – the maximum number of offspring each member of the population can produce
Different generation times
Death rate
Emigration – moving away from a population
Immigration – moving into a population

4. Exponential Growth – J-Shaped
No limits placed on a population by its environment
Numbers
Time

5. Logistic Growth – S-shaped
Most populations
Growth slows when the carrying capacity is approached
The maximum number of individuals that an environment can support in the long-term
Limited by energy, water, oxygen, and nutrients available

7. Population-limiting Factors
Both of these types control population numbers, but in different ways
Density-independent factors – do not depend on the number of organisms per unit area
Abiotic factors – weather events like drought, flooding, extreme temperature, or tornadoes
Forest fires – crown v. controlled fires

9. Density-dependent factors
Any factor that depends on the number of members per unit area
Usually biotic factors
Disease – outbreaks occur when population density is high
Competition – increases when population density is high
Parasites – can limit the population size when population density is high

10. Lemmings – Competition
Population grows exponentially until food become limited and the population sizes decreases significantly