population change chapter 8

Population Change

Chapter 8

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Do Now

1. What is Population Ecology?

2. What are some Principles of Population Ecology?

Principles of Population Ecology

Deals with the Deals with the number of individuals of a number of individuals of a particular speciesparticular species that are found in an area that are found in an area & how & & how & why those numberswhy those numbers change over change over time.time.

Used in Used in Forestry, agriculture, animal Forestry, agriculture, animal husbandry, and wildlife managementhusbandry, and wildlife management..


Population ecologists ask:

1) How many are in the population?

2) Are its numbers increasing / decreasing?

3) What is its pattern of reproduction?

4) What is its pattern of mortality?


Population Density:

• Not enough to know just how many.

• Need to know per unit area.

20 / 100 m220 / 25 m2

Do Now: Principles of Population Ecology

How have immigration and emigration affected your local population?

HINT: consider impacts on education (K-HINT: consider impacts on education (K-postsecondary), housing, transportation, the postsecondary), housing, transportation, the workforce, social services, the local economy, workforce, social services, the local economy, and the local political climate,and the local political climate,


How Do Populations Change in Size?

On a global scale (closed system):



On a local scale (open system):



Global scale:

r = b – d

Growth rate

Birth rate

Death rate



Local scale:

r = (b – d) + (i – e)

Growth rate

Birth rate

Death rate

Immigration rate

Emigration rate

Hypothesize: : Your employer makes you this offer,

Would you rather make: 0.01¢ a day that grows exponentially for 30 days

$75 an hour working 30 days 8 hours a day?

Hypothesize: Your employer makes you this offer,

Would you rather make: 0.01¢ a day that grows exponentially for 30 days

$75 an hour working 30 days 8 hours a day?

$75/hour x 8 hours= $600/day x 30days = $18,000/30days

Hypothesize: Your employer makes you this offer,

Would you rather make: 0.01¢ a day that grows exponentially for 30

days

Day $ 1. 0.012. 0.023. 0.044. 0.085. 0.166. 0.327. 0.648. 1.289. 2.5610. 5.1211. 10.2412. 20.4813. 40.96. 14. 81.9215. 163.84

Day $ 27 671,088.6428 1,342,177.2829 2,684,35430 $5,368,709.12


Maximum Population Growth-

under ideal conditions = intrinsic rate of increase (aka biotic potential)

J-shaped curve (exponential growth)


Explain why cockroach populations will not

expand indefinitely and take over the entire

world.

Include in your discussion appropriate

definitions of population growth terminology

such as: exponential growth, logistic

growth, carrying capacity, and resistant

factors.

Do Now: ANSWERSPrinciples of Population Ecology

Cockroaches populations exhibit exponential growth, that is accelerating population growth that occurs when optimal conditions allow a constant reproductive rate over a period of time.

When the cockroach population grows exponentially, the larger the population gets, the faster it grows (J curve).

However, environment resistance factors limit growth of the population. These factors include such unfavorable environmental conditions as the

limited availability of food, water, shelter, and other essential resources (resulting in increased competition) as well as limits imposed by disease and predation.

As the number of individuals in a population increases, so does environmental resistance, which acts to limit population growth. Because the environment sets limits, cockroach population growth is transformed from exponential growth into logistic growth.

In the logistic growth pattern, the population of roaches would level at the carrying capacity appropriate for the local environment. The carrying capacity is the maximum number of individual of a given species that a particular environment can support for an indefinite period, assuming thee are no changes in the environment.

Principles of Population EcologyEnvironmental Resistance-

• Exponential growth cannot occur forever.– The larger the population the faster it ____ ?

• What factors prevent it from doing so?

S-shaped curve (logistic growth)

Grows


Overshooting the carrying capacity can lead to a population crash.

Do Now: Reproductive Strategies

Please provide the 2 Life History Strategies.

List the their characteristics.

Do Now: Answers Reproductive Strategies

Life History Strategies

r-selected K-selectedvs.

high growth rate slow growth rate

small body size large body size

early maturity late maturity

short life span long life span

large broods small broods

little / no parental care high parental care

Reproductive Strategies

Survivorship

Do Now: Reproductive Strategies

Identify the two most extreme types of reproductive strategies and make a distinction between the traits that would characterize these extremes.

Give an example of an organism that illustrates each strategy.

Do Now: Answers Reproductive Strategies

•Populations described by r selection have traits that contribute to a high population growth rate. •Weeds, such as dandelions, and insects, such as mosquitoes, are examples of “r” strategists. •Distinguishing traits typical of r strategists include: small body size, early maturity, short life spans, large broods and little or no parental care of offspring. •These organisms live in unpredictable environments where the probability of long-term survival is low.

•In populations described by K selection, traits maximize the chance of surviving in an environment where the number of individuals is near the carrying capacity of the environment. •Characteristics of K strategists include: long life spans with slow development, delayed reproduction, large body size, and a low reproductive rate with high parental obligations to offspring. •Tawny Owls, humans, elephants, and redwood trees are all examples of the “K” strategists.


Describe an example of a density- dependent and independent population factor.

Do Now: ANSWERPrinciples of Population Ecology

Describe an example of a density- dependent and independent population factor.

density-independent factors impact populations uniformly no matter the population density

•these are usually abiotic, “natural disaster” phenomena such as freezes, heat waves, droughts, floods, severe fires or hurricanes

density dependent factors are those that influence low density populations differently from high density populations

•d-d factors influence population growth by decreasing birth rates and / or increasing death rates

•d-d factors include such things as disease, predation and / or competition for any resource necessary for that population

•the impact of d-d factors is difficult to assess in a wild population because of the many variables that affect population growth

Factors that Affect Population Size

Density-Dependent Factors-

• Factors that influence population growth when its density is high.

• Predation, competition, disease.


Density-Independent Factors-

• Regardless of population density, influences population growth.

• Weather, fire.


Density-Dependence and Boom-or-Bust Population Cycles

Do Now: ANSWERS

Who was Thomas Malthus and what were his Who was Thomas Malthus and what were his ideas about human population growth? ideas about human population growth? Was he correct or not? Justify your Was he correct or not? Justify your answer.answer.

Do Now: ANSWERS

Thomas Malthus was a 19th century British economist who was one of the first people to recognize that the human population cannot increase indefinitely.

He correctly pointed out human population growth is not always desirable because it can exceed the food supply resulting in famine, disease and war. Since Mathus’s time, the human population has increased from 1 to 6 billion.

Scientific advances have allowed food production to keep pace with population growth. Malthus may ultimately be correct in his ideas because we do not know if our increase in food production is sustainable.


Case-in-Point: Predatory Prey Dynamics on Case-in-Point: Predatory Prey Dynamics on Isle RoyaleIsle Royale

Do Now: Factors that Affect Population SizeDiscuss the factors that have regulated the Discuss the factors that have regulated the

moose population on Isle Royale. Your moose population on Isle Royale. Your discussion should include the following discussion should include the following terms: Predator-prey dynamics, density terms: Predator-prey dynamics, density dependence, density independent factors.dependence, density independent factors.

Do Now: ANSWERDo Now: ANSWERFactors that Affect Population SizeFactors that Affect Population SizeOn the island of Isle Royale, the moose population

is preyed on by wolves. Prior to the introduction of predators on Isle Royale, the moose population was controlled by the supply of vegetation and viral diseases, which are both density dependent factors.

In addition, the density independent factor of severe winters killed the old and the young moose alike. When wolves were introduced, the predator – prey dynamics between the wolf and moose populations became the primary regulating factor of the moose population.


Case-in-Point: Predatory Prey Dynamics on Case-in-Point: Predatory Prey Dynamics on Isle RoyaleIsle Royale


Case-in-Point: Predatory Prey Dynamics on Isle Royale


East end of island

West end of island

example of large annual growth

example of small annual growth


The Human Population

Human population size


Current Population Numbers

In 2004 = ~6.4 billion

Check out:

http://www.census.gov/main/www/popclock.html



Question about Human Population

The world population increased by 82 million from 2003-2004. Why has this occurred if the birth rate has declined during the past 200 years?

Question: ANSWER about Human Population

Due to advances in modern medical technologies; Vaccines, antibiotics, advances in medical facilities has led to a dramatic decrease in death rates.


Current Population Numbers

Rapid growth primarily due to drop in death rates

The Human PopulationProjecting Future Population Numbers

When will zero population growth occur?

Do Now: Demographics of Countries

Describe at least three factors that determine whether a nation is classified as a developed or developing country?

Do Now: Answers Demographics of Countries

Describe at least three factors that determine whether a nation is classified as a developed or developing country?

•degree of industrialization•standard of living•literacy rate•birth rate•death rate, esp. infant mortality rate•per capita GDP•degree of urbanization

•life expectancy•health care system•educational system, esp. opportunities for women•amount of infrastructure•global vs local market economy•use of technology

Demographics of Countries

Most Populous Countries Insert Table 8.1


Developed vs. Developing Countries Demographics Insert Table 8.2 (note

reconstruction)

Question: Demographic Stages???

To date, all highly developed and moderately developed countries with more advanced economies have gone through a progress or demographic transition.

Describe the four steps in this process in terms of the impact birth and death rates have on population growth.

Question: ANSWERDemographic Stages???

As countries become industrialized and urbanized, they go from having relative high birth and death rates to having relatively low birth and death rates.

There are four stages in this process: 1. the pre-industrial stage in which birth and death rates are high and

the population grows at a modest rate. Famine plagues2. Then as a result of improved heath care, better food and water

supplies, the population enters the transitional stage characterized by a lower death rate. The population grows rapidly because the birth rate is still high. Increased water quality and reliable food production

3.The third demographic stage is the industrial stage characterized by a decline in birth rate, which slows the population growth despite a relative low death rate.

4.Finally, low birth and death rates characterized the last stage. This is the post industrial stage when people are better educated and more affluent and the population grows slowly or not at all in this stage. increased focus on education and smaller families


Demographic Stages


Age Structure of Countries

Generalized Age Structure


Examples:

Do Now: Demographics of the US

How does the population growth of the United States compare to that of other countries, both highly developed and developing?

What factor(s) may account for the unique aspects of population growth seen in the U.S.?

Do Now:ANSWERS Demographics of the US

The U.S. has the largest population of all highly developed countries and one of the highest rates of population increase.

U.S. citizens have a high level of material well being compared to the global population.

Highly developed countries, such as the U.S. have the lowest birth rates in the world as well as low infant mortality rates. However, the unique aspect of population growth seen in the U.S. stems from immigration (authorized and unauthorized).

Immigration has a greater effect on population size in the U.S. than in other nations as more people from developing countries immigrate to the U.S. for a better life.


Examples:


Population Under Age 15:

Do Now: Demographics of the US

What is the environmental issue regarding current immigration policy in the U.S. and why is this issue controversial?

Do Now: AnswersDemographics of the US

Adding immigrants (authorized and unauthorized) to the population of the U.S., given our current rate of consumption of resources has a global environmental impact.

The issue centers on allowing large number of immigrants to enter the U.S. without consideration for the altered forces placed on resource consumption.

The U.S. has space and room for more people, but the U.S. lifestyle is such that we are using between 6-50 times the resources of other countries per person.

The larger U.S. population contributes to pollution and resource depletion.

Demographics of the US

Case-in-Point: US Immigration

Demographics of the US

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population change chapter 8

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