1. CHAPTER 5
How Populations Grow

2. Food Chain -sea otters, giant kelp, smaller kelp, sea urchins
At one time sea otters were almost eliminated by hunting; sea urchin populations increased and kelp forests nearly disappeared. Why?

3. The kelp was eaten by hordes of sea urchins!
Sea otters were declared an endangered species and were protected from hunting.

4. Sea otters were declared an endangered species and were protected from hunting.
The sea otters population _________.
Sea urchin populations____________.
Kelp populations______________.

5. CHARACTERISTICS OF POPULAITONS
4 important characteristics of a population are i.
ii.
iii.
iv.

6. CHARACTERISTICS OF POPULAITONS
3 important characteristics of a population are
i. Geographic distribution
ii. Density
iii. Growth Rate
iv. Density independent/dependent factors

7. 1. Georgraphic distribution is a term that describes the area inhabited by a population.
The range can vary in size from a few cubic centrimeters occupied by bacteria in a rotting apple to the millions of square kilometers occupied by migrating whales in the Pacific Ocean.

8. Population Density is the number of individuals per unit area.
-this number can vary depending on the species and its ecosystem.
Growth Rate: 3 factors can affect population size:
I. # of births
ii. # of deaths
iii. # of individuals that leave or enter
the population

9. Immigration is the movement of individuals into an area.
Emigration is the movement of individuals out of a population.

10. Under ideal conditions and unlimited resources, a population will continue to grow in a pattern called exponential growth.
As resources are used up and population growth slows or stops, the population exhibits logistic growth.

13. GROWTH OF A POPULATION WILL EVENTUALLY SLOW DOWN. WHY?
Resources become less available.
Ex. Food, space, water
Birth rate decreases.
Death rate increases.
Increased emigration
5. Decreased immigration

14. The carrying capacity of an environment for a particular species is the largest number of individuals that the environment can support.
Refer to the logistic growth curve.

15. FACTORS THAT LIMIT THE GROWTH OF A POPULATION
A limiting factor is a factor that causes population to decrease.
Density-Dependent Factors
Density- Independent Factors

16. Density-Dependent Factors
Competition
Predation
Parasitism
iv. Disease

17. Density-Dependent Factors
Competition
-when populations become crowded, organisms compete for food, water, space, sunlight, and other essentials.
Ex. Birds compete for limited nesting sites.

18. Density-Dependent Factors
Competition
-when populations become crowded, organisms compete for food, water, space, sunlight, and other essentials.
Ex. Birds compete for limited nesting sites.
-the more individuals living in an area, the sooner they use up the available resources.

19. Density-Dependent Factors
Competition
-when populations become crowded, organisms compete for food, water, space, sunlight, and other essentials.
Ex. Birds compete for limited nesting sites.
-the more individuals living in an area, the sooner they use up the available resources.
competition can occur btw members of the same species or btw members of different species.

20. Density-Dependent Factors
Competition
-when populations become crowded, organisms compete for food, water, space, sunlight, and other essentials.
Ex. Birds compete for limited nesting sites.
-the more individuals living in an area, the sooner they use up the available resources.
competition can occur btw members of the same species or btw members of different species.
-when 2 species compete for the same resources both species are under pressure to change in ways that decrease their competition - the species over time may evolve to occupy separare niches.

21. Density-Dependent Factors
Predation
Populations in nature are often controlled by predation, within a predator-prey relationship.
Ex. The relationship btw a sea otters and sea urchins and btw sea otters and killer whales are examples of predator-prey relationships that affect population growth.
Ex. Wolves and Moose - refer to fig 5-7 p126.

22. Density-Dependent Factors
iii. Parasitism and iv. Disease
Like predators, parasites take nourishment at the expense of their hosts, often weakening them and causing disease or death.
Ex. Wasp cacoons can weaken or kill many caterpillars. Fig 5-8 p126.
-the wasp inserts its eggs beneath the moth’s skin. After hatching, the wasp larvae feed on their host internally until they appear as white cacoons on its back.

23. Density- Independent Factors
Affects all populations in a similar way, regardless of the population size.
For example
i. Weather
Natural Disasters
Seasonal Cycles
Certain human activities such as clear cutting forests.

24. Practice Questions
P 135 Ch 5 Assessment
Q 1-8; 11-19, 23
P137 Prep Test - do all questions.