1. Section 4.1 Summary – pages 91-99
Principles of Population Growth
A population is a group of organisms, all of the same species, that live in a specific area.
A healthy population will grow and die at a steady rate unless it runs out of food or space, or is attacked in some way by disease or predators.
Scientists study changes in populations in a variety of ways.
One method involves introducing
organisms into an environment that
contains abundant resources and then
watching how the organisms react.
Section 4.1 Summary – pages 91-99

2. Section 4.1 Summary – pages 91-99
Limiting factors
A limiting factor is any biotic or abiotic factor that restricts the existence, numbers, reproduction, or distribution of organisms.
-- food, disease, predators, or lack of space, will cause population growth to slow.
Predation affects population size
The data in this graph reflect the number of hare and lynx pelts sold to the Hudson’s Bay Company in northern Canada from through 1935.
Lynx and Hare Pelts Sold to the Hudson’s Bay Company
Lynx
Hare
Number of organisms(in thousands)
Times (in years)
Section 4.1 Summary – pages 91-99

3. Section 4.1 Summary – pages 91-99
Carrying capacity
Deaths begin to exceed births and the population falls below carrying capacity.
Carrying capacity
Section 4.1 Summary – pages 91-99

4. Population Growth of Houseflies
Exponential growth means that as a population gets larger, it also grows at a faster rate.
A J-shaped growth curve illustrates exponential population growth.
Exponential growth results in unchecked growth.
1 million
Population size
500,000
100
One year

5. Characteristics of Population Growth
Limiting factors, such as availability of food, disease, predators, or lack of space, will cause population growth to slow.
Under these pressures, the population may stabilize in an S-shaped growth curve.
Logistic growth- S shape curve
Characteristics of Population Growth
PREDA- TORS
Exponential growth
DISEASE
SPACE
FOOD
Carrying capacity
J curve
S curve
Population
Time

6. Section 4.1 Summary – pages 91-99
Density-dependent factors include disease, competition, predators, parasites, and food.
Disease, for example, can spread more quickly in a population with members that live close together.
Density-independent factors can
affect all populations, regardless
of their density.
Most density-independent factors
are abiotic factors, such as
temperature, storms, floods,
drought, and major habitat disruption.
Section 4.1 Summary – pages 91-99

8. Question 1 A. grows at a slower rate B. grows at a faster rate
Exponential growth means that as a population gets larger, it also _____.
A. grows at a slower rate
B. grows at a faster rate
C. grows at a steady rate
D. stabilizes in an S-shaped growth curve
Section 1 Check

9. Population Growth of Houseflies
The answer is B. A J-shaped growth curve illustrates exponential growth.
Population Growth of Houseflies
1 million
Population size
500,000
100
One year
Section 1 Check

10. Question 2 A. population increases exponentially
Which of the following would you expect to observe after a population exceeds its carrying capacity?
A. population increases exponentially
B. births exceed deaths
C. deaths exceed births
D. population growth rate is unaffected by limiting factors
Section 1 Check

11. Characteristics of Population Growth
The answer is C. Limiting factors may come into effect after a population exceeds its carrying capacity. Deaths begin to exceed births and the population falls below carrying capacity.
Characteristics of Population Growth
Exponential growth
DISEASE
SPACE
PREDATORS
FOOD
Carrying capacity
J curve
S curve
Population
Time
Section 1 Check

12. Question 4 A. life-history pattern B. growth rate C. demographic
The number of organisms of one species that an environment can support indefinitely is its _____.
A. life-history pattern
B. growth rate
C. demographic
D. carrying capacity
Section 1 Check

13. The answer is D. If population size rises above the carrying capacity, more organisms die than are born and the population drops back below the carrying capacity.
Carrying capacity
Section 1 Check