1. Define Population
Copyright Pearson Prentice Hall

2. 5-1 How Populations Grow
Photo Credit: © Frans Lanting/Minden Pictures, Inc.
Copyright Pearson Prentice Hall

3. Sea otters play key role in the kelp forest community.
Need lots of energy for warmth so they eat a lot of sea urchins, which feed on kelp.
If sea urchin populations get too big, they destroy the kelp.
Copyright Pearson Prentice Hall

4. What was the role of sea otters in the kelp forest community?
Copyright Pearson Prentice Hall

5. Characteristics of Populations
Important characteristics of a population are its:
geographic distribution
population density
growth rate
Age structure
Copyright Pearson Prentice Hall

6. Population density: the number of individuals per unit area.
Can vary greatly depending on species and ecosystem
Population density = number of individuals/unit area
Copyright Pearson Prentice Hall

7. Example: Suppose there are 150 bullfrogs living in a pond that covers an area of 3 sq km. What is the population density of the bullfrog?
50 bullfrogs per sq km
Copyright Pearson Prentice Hall

8. Factors can affect population size: the number of births
the number of deaths
the number of individuals that enter or leave the population
Immigration
Emigration
Copyright Pearson Prentice Hall

9. Populations grown when birth rate exceeds death rate.
Populations shrink when death rate is greater than birth rate.
Populations remain the same when birth rate and death rate are equal.
Copyright Pearson Prentice Hall

10. Population Growth
Immigration: the movement of individuals into an area. Emigration: the movement of individuals out of an area.
Copyright Pearson Prentice Hall

11. Example: Emigration can occur when young animals leave the area where they were born, find mates, and establish new territories. A shortage of food in one area may lead to emigration.
Copyright Pearson Prentice Hall

12. Under ideal conditions with unlimited resources, a population will grow exponentially. Exponential growth occurs when the individuals in a population reproduce at a constant rate. The population becomes larger and larger until it approaches an infinitely large size.
Copyright Pearson Prentice Hall

13. Bacteria reproduce by splitting in half every 20 minutes.
In one day, one colony of bacteria can produce 4,720,000,000,000,000,000,000
Copyright Pearson Prentice Hall

14. Exponential Growth Exponential Growth
In the presence of unlimited resources and in the absence of predation and disease, a population will grow exponentially. Both hypothetical graphs show the characteristic J-shape of exponential population growth.
Copyright Pearson Prentice Hall

15. Logistic Growth
Logistic Growth As resources become less available, the growth of a population slows or stops. Logistic growth occurs when a population's growth slows or stops following a period of exponential growth.
Copyright Pearson Prentice Hall

16. Carrying capacity: the number of individuals that a given environment can support
Copyright Pearson Prentice Hall

17. Logistic growth is characterized by an S-shaped curve.
This graph shows the S-shaped curve of logistic growth. As resources become less available, the population growth rate slows or stops. The growth of this population has leveled off at its carrying capacity.
Copyright Pearson Prentice Hall

18. What factors limit population growth?
Limiting Factors
What factors limit population growth?
Copyright Pearson Prentice Hall

19. Density-Dependent Factors
Wolf and Moose Populations on Isle Royale
The relationship between moose and wolves on Isle Royale illustrates how predation can affect population growth. In this example, the moose population was also affected by changes in food supply, and the wolf population was also affected by disease.
Moose Wolves
Density-Dependent Activity
Copyright Pearson Prentice Hall

20. 5-1 Population density is the number of individuals
that are born each year.
per unit area.
that immigrate.
that emigrate.
Copyright Pearson Prentice Hall

21. 5-1
When the birthrate of a population exceeds its death rate, the population
decreases.
increases.
stays the same.
increases then decreases.
Copyright Pearson Prentice Hall

22. 5-1
An S-shaped curve on a graph of population growth is characteristic of
exponential growth.
logistic growth.
carrying capacity.
delayed growth.
Copyright Pearson Prentice Hall

23. 5-1 Exponential growth in a population slows down or stops as
resources become limited.
rate of immigration increases.
rate of emigration decreases.
birth rate increases.
Copyright Pearson Prentice Hall

24. 5-1
Exponential growth rate means that each new generation of a population
adds the same number of new individuals as the previous generation did.
increases at the same rate as the previous generation.
is the same size as the generation before.
increases by a varying amount.
Copyright Pearson Prentice Hall