Chapter

5

Populations

5 – 1 How Populations Grow

Characteristics of Populations

Three important characteristics of a population are:1. geographic distribution - _________________________________________________

2. density - ______________________________________________________________

3. growth rate - ___________________________________________________________

Population Growth

Three factors can affect population size:

1.

2.

3.

Exponential Growth

Under ideal conditions with unlimited resources, a population will grow exponentially

Exponential growth - ______________________________________________________

________________________________________________________________________

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Logistic Growth

Obviously, the conditions for logistic growth are rarely ever met As resources become less available, the growth of a population slows or stops

Logistic Growth - _________________________________________________________

________________________________________________________________________

________________________________________________________________________

Q: Why does this happen?

A:

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Carrying Capacity - _______________________________________________________

_______________________________________________________________________

Q: What is the growth rate when a population is at carrying capacity?

A:

Name ___________________________________ Date ___________________ Per ____

5 – 1 Section Review

1. List three characteristics that are used to describe a population.

2. What factors can change a population’s size?

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3. What is the difference between exponential growth and logistic growth?

4. What is meant by population density?

5. Define carrying capacity.

6. What factors might cause the carrying capacity of a population to change?

5 – 2 Limits to Growth

Limiting Factor – ________________________________________________________

_______________________________________________________________________

Ex.)

A resource base that is limited can also affect the long term survival of a species

Density – dependent Factors

Limiting factors that depend on _______________________________________ Density dependent factors become limiting only when the population density reaches

a certain level These factors operate most strongly when a population is large and dense

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Density dependent factors include: ________________________________________

________________________________________________________________________

Density – Independent Factors

Affect all populations in similar ways regardless of the populationEx.) In response to such factors, many species show a characteristic crash in population

size Environments are always changing, and most populations can adapt to a certain

amount of change Populations often grow and shrink in response to such changes Major upsets in an ecosystem can lead to long term declines in certain populations

Name ___________________________________ Date ___________________ Per ____

5 – 2 Section Review

1. List three density-dependent factors and three density-independent factors that can limit the growth of a population.

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2. What is the relationship between competition and population size?

3. If an entire lynx population disappears, what is likely to happen to the hare population on which it preys?

4. Give an example of a density-independent limiting factor that has affected a human population. Describe how this factor changed the human population.

5 – 3 Human Population Growth

Historical Overview

Like the populations of many other living organisms, the size of the human population tends to increase with time

In the U.S. and other developed countries, the current growth is _________________ In some developing countries, the human population is growing at a rate of

________________________________________ The human population is well on its way to reaching __________________________

in your lifetime

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Exponential Human Growth

The following factors have caused a rapid increase in population growth

Patterns of Population Growth

Q: Why can’t the human population keep growing exponentially forever?

A:

Demography - ___________________________________________________________

Birthrates, death rates, and age structure of a population help to protect why some countries have a high growth rate while others grow more slowly

The Demographic Transition

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Age Structure

Population growth depends, in part on how many people of different ages make up a given population

age-structure diagrams - ____________________________________________________

________________________________________________________________________

________________________________________________________________________

Future Population Growth

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World Population: 1950 - 2050Year Average Annual

Growth Rate (%)Population

19501.47 2,555,360,972

19601.33 3,039,669,330

19622.19 3,136,556,092

19632.19 3,206,072,286

19702.07

3,708,067,105

19801.69

4,454,607,332

19901.58 5,275,407,789

20001.23

6,078,684,329

20101.06

6,812,009,338

2020.87

7,515,218,898

2030.68

8,127,227,506

2040.54 8,646,671,023

2050.43 9,078,850,714

Name ___________________________________ Date ___________________ Per ____

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5 – 3 Section Review

1. Describe the general trend of human population growth that has occurred over time.

2. What factors explain why populations in different countries grow at different rates?

3. What is demography?

4. Describe the demographic transition and explain how it might affect a country’s population growth rate.

5. Why do you think age-structure diagrams can help predict future population trends?

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