1. Understanding Populations
How Populations Change in Size

2. Objectives Describe the three main properties of a population
Describe exponential population growth
Describe how the reproductive behavior of individuals can affect the growth rate of the population
Explain how population sizes in nature are regulated

3. Population
A group of organisms of the same species that live in the same geographical area
Interbreeding
Refers to size and number

4. Properties of a Population
Density- Number of individuals living in a given unit of area
Dispersion- Pattern of distribution of organisms in an area
Random
Clumped
Even
Describe populations and used to predict changes

5. How do Populations Grow?
Growth rate- Increase in the size of an organism or population over time
Positive- Births outnumber deaths
Negative- Deaths outnumber births
Zero- Births and deaths are equal

6. Reproductive Potential
Reproductive potential- Maximum number of offspring that an organism can produce
Increases:
More offspring produced at a time
Reproduction begins earlier in life
Generation time- Average time it takes to reach age at which members of a population begin reproducing
Biotic potential- Fastest rate at which a population can grow
Limited by reproductive potential
Large organisms
Long generation time
Slow population growth
Small organisms
Short generation time
Fast population growth

7. Exponential Growth
Growth in which numbers increase by a certain factor in successive time periods
Plenty of food and space
No competition or predators

8. What Limits Population Growth?
Carrying Capacity- The maximum population that an ecosystem can support indefinitely
Estimated by observing population crashes
Ex: Rabbits introduced into Australia in 1859

9. What Limits Population Growth?
Limiting resource- Natural resource that is consumed at the same rate at which the ecosystem produces it
Competition
Compete for mates, food, and homes
Territory- An area defended by one or more individuals

10. Two Types of Population Regulation
Density Independent- A certain proportion of a population may die regardless of the population’s density
Severe weather and natural disasters
Density dependent- Deaths occur more quickly in crowded conditions
Limited resources, predation, and disease