2. Populations & Population Growth

3. Populations Population size - number of members in a population 2 ways to estimate population size: 1.Random sampling – used mainly for plants; samples and counts organisms in random plots 2.Mark & recapture – used mainly for animals; captures, marks, and releases animals, then samples the population again Random sampling- take a representative sample

4. Populations Population growth – an increase in the size of a population Exponential growth Beginning growth Leveling off fluctuations

5. Populations Carrying capacity – the maximum number of individuals in a population that an area can support

6. Populations Limiting factor – anything that limits the survival of an organism –Can stop an increase in the size of a population –Ex.: food & shelter availability, climate, temperature, number of predators –Affects carrying capacity (if food increases, carrying capacity increases) Limiting factor – anything that limits the survival of an organism –Can stop an increase in the size of a population –Ex.: food & shelter availability, climate, temperature, number of predators –Affects carrying capacity (if food increases, carrying capacity increases)

7. Population Growth There are 2 types: –Logistic growth Looks like an S-curve Levels off at carrying capacity (K) At K, birth rate = death rate

8. Population Growth –Exponential Growth Looks like a J-curve Population keeps increasing rapidly Birth rate and death rate are constant Limiting factors stop population from growing indefinitely large (ex.: food, space, etc.)