How Populations GrowSection 5-1

1. e. Explain how the amount of life any environment can support is limited by the available matter and energy and by

the ability of ecosystems to recycle the residue of dead organic materials.

i. Explain the concept of carrying capacity

j. Describe the growth of populations, including exponential and logistic growth .

What do ALL tables and graphs need?

1. Title

2. Labeled axes

3. Evenly spaced intervals on axes

• On which axis do you plot the independent variable?

Inquiry Activity: How Do Populations Grow?

• Textbook: p.118 (20 minutes)

• Math Hint:

Year # of Rabbits # of “Couples”

# of Offspring

1 2 1 6

2 6

3

4

5

When setting up your graph, pay attention to the fact that you will have to extrapolate data through 20 years (so leave that room!)

The Sea Otters and the Giant Kelp• http://www.youtube.com/watch?v=v_aSl3iL7rM

• Kelp forest→ sea urchins → sea otters

• What is this “relationship” called?

• What do the arrows indicate?

• A century-old tale of population growth and decline (p.119)

• These population changes are studied in “population biology”.

Characteristics of Populations

• Three important characteristics:1. Geographic distribution (where? range?)

2. Population density: the number of individuals per unit area (grass blades vs. pine trees)

3. Growth rate (how fast?)

Population Growth• Three factors that affect population size:

1. # of births

2. # of deaths

3. # of individuals that enter or leave the population

• What is migration?– Immigration: the movement of individuals into an

area

– Emigration: the movement of individuals out of an area (individuals exiting an area)

Two Types of Growth Patterns1. Exponential growth:

– Occurs under ideal conditions: ample food and space, protection from predators and disease

– Individuals reproduce at a constant rate– Graph is a J-shaped curve

2. Logistic growth:– Population growth slows as resources become

less available– Produces an S-shaped graph

Carrying Capacity• Definition: the maximum number of

individuals that a given environment can support

The Sea Otters and the Giant Kelp1. What type of growth would you expect to

have seen a. in the sea urchins when the otters were hunted?

b. in the sea urchins as the kelp disappeared?

c. in the kelp when the sea otters were protected?

d. in the sea otters when they were first protected?

2. Where on a population graph would you expect the populations of sea otters, sea urchins, and giant kelp to be found now?

Assignment

• Analyzing Data: Population Trends (p.123)