1. Understanding Populations

2. How Populations Change in Size
Objectives
1. Describe the three main properties of a population.
2. Describe exponential population growth.
3. Describe how the reproductive behavior of individuals can affect the growth rate of their population.
4. Explain how population sizes in nature are regulated.

3. What is a population?
All members of a species living in the same place at the same time
Properties of Populations
Density – the number of individuals per unit area or volume

4. Dispersion – the relative distribution or arrangement of its individuals within a given amount of space
Size – actual number of individuals

5. How does a population grow
More births than deaths
Growth rate – change in pop. Over time
Change in pop. Size = births - deaths

6. How fast can a population grow
Reproductive potential – the max number of offspring that each member of a population can produce

7. Most organisms have a high reproductive potential because few offspring actually survive

8. Potential increases when individuals produce more offspring at a time, more often, and reproduction early (shortens generation time – ave. time it takes to reach reproductive age)

9. Small animals usually have a shorter generation time than larger animals

10. Exponential Growth
As a population grows, it grows faster
Occurs in nature when populations have plenty of food and space and no competition

11. What limits population growth
Carrying capacity - max pop. That the ecosystem can support indefinitely
Amount of resources – limited resources determines carrying capacity

12. Competition within a population
Territory
Food
mates

13. Types of population regulation
Density dependent – density, of individuals affects growth’ all individuals are affected
diseases

14. Density independent – certain portions of the pop
Density independent – certain portions of the pop. May die regardless of the pop. Density
Severe weather, natural disasters

15. How Species Interact Objectives
1. Explain the difference between niche and habitat.
2. Give examples of parts of a niche.
3. Describe the five major types of interactions between species.
4. Explain the difference between parasitism and predation.
5. Explain how symbiotic relationships may evolve.

16. Organism’s niche
Unique role of a species within an ecosystem or a pattern of use of its habitat or it’s “job”
Includes physical home, environmental factors necessary for survival, and all interactions

17. Ways species interact
Competition – both harmful
Relationship in which different individuals or population attempt to use the same limited resource

18. Within and between species
Between different species it’s called overlap

19. Competition is reduced by
Indirect competition – when species do not come into contact with each other
Competition is reduced by
Evolution – better adaptations
Divide niche in time and space

20. Predation – 1 benefits and the other is harmed
Populations of predators depend on populations of prey

21. Adaptations to avoid predators
Camouflage used to lie and wait or hide
Warning coloration
Mimicry
Protective covering

22. Parasitism – 1 benefits, other is harmed or killed
Parasite (flees, ticks, tape and heartworms, leaches, mistletoe
Host

23. Mutualism – both benefit
Bees and flowers
Commensalism – 1 benefits, the other is unaffected
“hitchhikers”, birds and trees

24. Symbiosis – close relationship
coevolution