1. Ecology Population Problems
You will be able to determine population sizes of organisms in an ecosystem
You will be able to determine the health of an ecosystem and recognize potential problems

2. What are populations?
Population is a group of organisms of the same species living in a precise area of an ecosystem
Populations are used to determine the health of ecosystems using a quantity known as POPULATION DENSITY
POPULATION DENSITY = #of organisms
Unit Area

3. 4 Ways to Determine Population Size
1. Direct Observation – Counting each organism within an ecosystem. Most Accurate but most inefficient
2. Indirect Observation- counting each organism by signs they leave in environment. Foot tracks, nests, burrows, holes…
3. Sampling- Taking small area of ecosystem and converting findings to size of entire ecosystem. Most Time Efficient, but prone to errors since organism’s distribution may not be random
Mark and Capture- Capture Organisms and Mark them. Return after time has passed and recapture in same area. Best Way ecologists use to estimate populations of organisms

4. Mark and Capture Formula
Total Pop = Number Marked X Total Number Captured
Number Recaptured (with Marks)
MOST COMMON METHOD USED BY ECOLOGISTS

5. What Affects Population Sizes
Birth Rate- number of Births in Population
Death Rate- number of Deaths in Population
Immigration Rate – number of organisms moving INTO the ecosystem
Emigration Rate- number of organisms leaving ecosystem

6. Population Sizes If BR > DR Population is growing
If IM > EM Population is growing
If BR<DR Population is in decline
If EM < IM Population is in decline

7. Population limits

8. Populations are limited in Size
Limiting Factors- control size of an organism’s population
Food- amount available to organism
Space- amount of living space an organism needs
Weather/Seasons- Natural Events which alter conditions in Ecosystem
The maximum number of an Organism within an Ecosystem is known as the CARRYING CAPACITY of the Ecosystem or the K0 Factor

9. REMINDER
When Estimating populations of Organisms you must ROUND whole numbers. (.anything of any organism can not exist!)