1. Describing Populations What is a population? Members of a species that live in the same area at the same time

2. Determining Population Population size The number of individual organisms present in a given population at a given time Population density The number of individuals within a population per unit area Differing densities High population densities: can be susceptible to higher predation due to vulnerability, can spread diseases easier, can suffer from lack of space and resources due to increased competition Low population densities: animals have more space and resources, harder to find mates

4. Population Distribution Random Organisms arranged in no particular pattern Uniform Organisms evenly distributed Clumped Organisms arrange themselves according to available resources

6. Population Changes Immigration Arrival of individuals from outside a given area Emigration Departure of individuals from outside a given area Migration Seasonal movement into and out of an area

8. Calculating Population Growth Rate (individuals added) – (individuals subtracted) Or (birth rate + immigration) – (death rate + emigration) Example: if birth rate is 18/1000 and death rate is 10/1000; immigration is 5/1000 and emigration is 7/1000, then: (18+5) – (10+7) = 6. Multiplied by 100 to get a percent = 0.6%

9. How Populations Grow Exponential Growth When a population undergoes a fixed percent of growth per year due to the right conditions A “J” shaped curve on a graph Logistic Growth Shows initial growth as exponential but is then stopped or slowed by limiting factors Limiting factors: Determine carrying capacity; which is the largest population an environment can support

10. How populations grow cont. If birth rate exceeds death rate the population will increase If birth and death rate remain the same then population stays the same If death rate exceeds birth rate the population will decrease

11. Limiting Factors for Biotic Potential Density-dependent factor Limiting factors that are influenced by density: Predation Disease Competition Food Water Space Density-independent factor Limiting factors whose influence is not affected by density Climate change Natural disasters Cause a dramatic decrease in population size

13. Biotic Potential An organisms maximum ability to produce offspring in ideal conditions 2 types: 1.High biotic potential: cockroaches having 100s of babies 2.Low biotic potential: Orangutans, don’t reach sexual maturity for 10yrs and only have one baby every 8 years