1. Populations

2. Review What is a population?
A population consists of multiple individuals belonging to the same species, living in the same area at the same time
Three important characteristics of a population are its:

3. 1. Geographic Distribution
This is the geographic range that the population inhabits
In other words, this is where in the world that species is found

4. 2. Density
Which side has a higher density?
Population density is the number of individuals per unit area
This describes how closely packed together the individuals of a population are A B

5. 3. Growth rate
The growth rate is the increase or decrease of the number of individuals in a population over time

6. 3 factors that affect population growth
Number of births
Number of deaths
Number of individuals that enter or leave the population
Immigration: entering
Emigration: leaving
Births
Deaths
Immigration
Emigration

7. Therefore… A population grows when: A population shrinks when:
Birth rate > death rate
Immigration > emigration
A population shrinks when:
Birth rate < death rate
Immigration < emigration

8. Two Types of Growth rates
Exponential Growth: occurs when individuals of a population reproduce at a constant rate
Logistic Growth: occurs when a population’s growth slows or stops following a period of exponential growth

9. Exponential Growth
Under ideal conditions with unlimited resources, a population will grow exponentially
Do you think this type of growth is common in nature? Why or why not?

10. Logistic Growth
As resources become less available, the growth of a population slows or stops
Carrying capacity is the largest number of individuals of a population that a given environment can support