How Populations Grow
Section 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
1
2
3
4
5
# of Rabbits # of
# of
“Couples” Offspring
2
1
6
6
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_aSl3iL7r
M
• 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 Patterns
1. 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 Kelp
1. What type of growth would you expect to
have seen
a.
b.
c.
d.
in the sea urchins when the otters were hunted?
in the sea urchins as the kelp disappeared?
in the kelp when the sea otters were protected?
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)