1. Unit 2: Ecology
2.8 Population Growth

2. Population
Population: all the individuals of a species that live together in one place at one time.
Populations grow because an individual tends to have multiple offspring over their lifetime.

3. Population
Demography: the study of the composition of a population and how the size of the population will change.

4. 3 Key Features of Populations
Population size: the number of individuals in a population.
Population density: the number of individuals that live in a given area
Dispersion: how the individuals are arranged in a given space.
Random: location of individuals determined by chance
Even: located at regular intervals
Clumped: individuals bunched together into groups

5. Population Growth There are 3 factors that affect population size:
The number of births
The number of deaths
The number of individuals that enter (immigration) or leave (emigration) the population.
Population Growth can be modeled by comparing any of these factors.

6. Modeling Population Growth
Growth rate: shows the difference between birth rate and death rate
Growth rate and population size: shows an exponential growth curve
a. Limited by: predators, disease, and the availability of resources
b. Carrying capacity: the population size the environment can sustain

7. Modeling Population Growth
Carrying Capacity

8. Resources and population size:
Logistics model: takes into account that resources are limited and will depend on population size
Density-dependent factors: factors that are limited like food and water
The rate at which they are depleted depends on population size
Assumes birth and death rates will vary with population size
When a population is below carrying capacity, it will grow rapidly
When it nears or exceeds carrying capacity, death rates rise quickly.

9. Population Pyramids Age Structure Graphs
Population of a Growing Country
Population of a Stable Country
Age Structure Graphs