1. Environmental Science Chapter 8
Populations
Environmental Science
Chapter 8

2. Understanding Populations
Section 8.1

3. What is a Population?
A population is all the members of a species living in the same place at the same time.
The three main properties of a population are size, density, and dispersion.

4. Density vs. dispersion
Density is the number of individuals per unit area or volume.
Dispersion is the relative distribution or arrangement of its individuals within a given amount of space.
Population Density

5. Even
Dispersion
Even
Clumped
Random
Clumped
Random

6. How does a population grow?
Births and immigration increase a population
Deaths and emigration decrease a population
Growth rate is the birth rate minus the death rate.

7. Growth Rates Positive: more births than deaths
Negative: more deaths than births
Zero: the average number of births equals the average number of deaths

8. How fast can populations grow?
Biotic potential is the fastest rate at which its population can grow.
Reproductive potential is the maximum number of offspring that each member of the population can produce.

9. Reproductive potential increases when:
Individuals produce more offspring at a time
Reproduce more often
Reproduce earlier in life

10. Exponential Growth
When a population grows exponentially because there are plenty of resources available and little or no predators.

11. What limits population growth?
Carrying capacity: the maximum population that the ecosystem can support indefinitely.
Resource limits: consuming natural resources at the same rate they are being produced.
Competition: members of the population fighting over available resources.

12. Two types of population regulation
Density dependent means it depends on population size
Examples: competition and predator-prey
Density independent means it does not depend on the size of the population
Examples: severe weather and natural disasters

13. That’s all for 8.1
Time for a reading quiz

14. How species interact with each other
Section 8.2

15. Habitat vs. niche Habitat is an organism’s location.
Think of it as your address.
Niche is the role of a species within its habitat.
Physical home, environmental factors, and interactions.
Habitat
Niche

16. Competition is when different individuals or populations use the same limited resources
Niche overlap
Insects feeding on same plant or same feeder but at different times of day.
Niche division or restriction
Birds feeding on different parts of the tree.
Niche overlap
Niche division

17. predation Is when an organism feeds on another organism
Predator is the one feeding.
Prey is the one being fed upon.

18. parasitism Is when one organism lives in or on another organism.
The one that benefits is the parasite.
The host is harmed.

19. mutualism
Is when both species benefit from the relationship.

20. commensalism
Is when one organism benefits and the other organism is not affected at all.

21. Symbiosis and coevolution
A relationship in which two different species live in close association with each other.
Three types: mutualism, commensalism, and parasitism
When two species evolve adaptations that reduce the harm or improve the benefit of the relationship.
symbiosis
coevolution

22. That’s all for 8.2
Time for reading quiz