limiting factors, density, distribution, age structure

1. Objectives
yesterday
 You have to identify what
components make up the
climate of an area and
thus biome distribution
AND
List as many biomes as you
could
today
 You need to distinguish
between density
dependent and density
independent limiting
factors
AND
Give several examples of
each type

2. POPULATIONS

3. Characteristics of Populations
• Density
• Distribution
• Age Structure
• Carrying Capacity
• Mortality rate

4. Population Distribution
• Clumped
• Uniform
• Random
•Microenvironments
suitable to a populations
needs leads to clumped
distribution
•Some plants secrete
chemicals to keep other
plants away, territoriality
•Wind blown seeds, not
as common as clumped
Most common
Least
common,
mostly plants
Occurs when
there are no
strong reasons
to be the other
two

5. Patterns of Growth
Dependent on:
• Births
• Immigration
• Deaths
• Emigration

6. Limiting Factors
• Major factor in
defining an
organisms niche
• e.g tall trees
cannot grow in
desert
• Water is limiting

7. Other Limiting Factors?
•
•
•
•
•
•
•
???

8. Density-Dependent Controls
• Competition for resources
• Predation
• Parasitism
• Disease
• Pollution

9. Density-Independent Controls
• Natural
disasters
• Climate change
• Habitat Loss

10. Density Controls

11. J-curve
Exponential Pattern of Growth

12. Logistic Pattern of Growth
S-curve

13. Comparing Curves

14. Population Explosions
r-selected species (r stands for growth rate)
K-selected species (K stands for carrying capacity)
Can you think
of some
examples of
each type?

15. Intrinsic Pattern of Growth

16. LE 52-18
1960
Year
Moosepopulationsize
2,500
Steady decline probably
caused largely by wolf
predation
2,000
1,500
1,000
500
0
1970 1980 1990 2000
Dramatic collapse caused by severe
winter weather and food shortage,
leading to starvation of more than
75% of the population

17. Extreme fluctuations in
population size are
typically more common in
invertebrates than in large
mammals

18. LE 52-19
1960
Year
Commercialcatch(kg)of
malecrabs(logscale)
730,000
100,000
10,000
1970 1980 19901950

19. Human Population Growth
• 10,700 babies/hour

20. Rapid Growth

21. Slow Growth/ Stable
Young and older more equal
Overall shape?
WHY??

22. Declining
 Smaller at the bottom than in the middle?
 Overall shape?
 WHY??

23. The United States

25. Nearly ½ of the human
population lives within this circle

26. Influences on Growth
• Expansion
• Agriculture
• Better Medicine
• Improved
Sanitation

27. Controlling Population Growth
• Economic Family Planning

28. Controlling Population Growth
• Warfare Disease,
Starvation

29. Ultimate Carrying Capacity?

30. Zero Population Growth

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
1. A few members of a population have reached a favorable
habitat with few predators and unlimited resources, but their
population growth rate is slower than that of the parent
population. What is a possible explanation for this situation? *
a) The genetic makeup of these founders may be less favorable
than that of the parent population.
b) The parent population may still be in the exponential part of its
growth curve and not yet limited by density-dependent factors.
c) There are not enough population members present for
successful reproduction.
d) a, b, and c may apply.
e) This scenario would not happen.

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
2. As N approaches K for a certain population,
which of the following is predicted by the
logistic growth equation?
a) The growth rate will not change.
b) The growth rate will approach zero.
c) The population will not have enough
members to reproduce successfully.
d) The population will increase exponentially.
e) The carrying capacity of the environment will
increase.

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
3. In which of the following habitats would you
expect to find the largest number of K-
selected individuals?
a) an abandoned field in Ohio
b) the sand dunes south of Lake Michigan
c) the rain forests of Brazil
d) south Florida after a hurricane
e) a newly emergent volcanic island

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The following question refers to the figure below,
which depicts the age structure of three
populations

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
4. Assuming these age structure diagrams describe human
populations, in which population is unemployment likely
to be most severe in the future?
A. I
B. II
C. III
D. No differences in the magnitude of future unemployment
would be expected among these populations.
E. It is not possible to infer anything about future social
conditions from age structure diagrams.

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
5. Which of the following variables is (are)
important in contributing to the rapid growth of
human populations?
A. the high percentage of young people
B. the average age to first give birth
C. carrying capacity of the environment
D. only A and B
E. A, B, and C