1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 14.3 Populations group of organisms that belong to the same species and live in a particular place at the same time measured in terms of size, density, dispersion, growth rate, age structure, and survivorship

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Population Size –the number of individuals that the population contains

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Population Density –Density is a measure of how crowded the population is –The measure of the number of individuals divided by the area they live in

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Population Dispersion –describes the distribution of individuals within the population –Three types Random Uniform Clumped

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Three Patterns of Population Dispersion

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Population Dynamics Age Structure –indicates the percentage of individuals at each age

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Patterns of Mortality –Populations show three patterns of mortality or survivorship curves: Type I (low mortality until late in life) Type II (constant mortality throughout life) Type III (high mortality early in life followed by low mortality for the remaining life span).

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Survivorship Curves

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 14.4 Population Growth Rate Demographers, scientists who study population dynamics, define the growth rate of a population as the amount by which a population’s size changes in a given time Population Size –Birth rate - death rate = growth rate

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Exponential Model describes perpetual growth at a steady rate in a population assumes constant birth and death rates and no immigration or emigration

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Logistic Model birth rates fall and death rates climb as the population grows When the carrying capacity is reached, the number of individuals the environment can support is reached and population growth becomes stable

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Two Population Growth Models

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Population Regulation Population-limiting factors, such as competition, are density-dependent because the effect on each individual depends on the number of other individuals present in the same area.

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Population Regulation Population-limiting factors, such as bad weather and fires, are density-independent because the effect on each individual does not depend on the number of other individuals present in the same area.

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Perils of Small Populations –Small populations have low genetic diversity and are subject to inbreeding, so they are less likely to adapt to environmental changes

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 14.5 Community Stability –Disturbances can alter a community by eliminating or removing organisms or altering resource availability –Species richness may improve a community’s stability –Areas of low species richness may be less stable in the event of an ecological disturbance

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Ecological Succession is a change in the species composition of a community over time Primary Succession –is the assembly of a community on newly created habitat –occurs in areas that have been recently exposed to the elements and lack soil

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Ecological Succession Secondary Succession –is the change in an existing community following a disturbance –occurs in areas where the original ecosystem has been cleared by a disturbance

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Complexity of Succession The traditional description of succession is that the community proceeds through a predictable series of stages until it reaches a stable end point, called the climax community. Primary succession typically proceeds from lichens and mosses to a climax community. Secondary succession typically proceeds from weeds to a climax community.

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Ecological Succession at Glacier Bay