hint: look at the notes when you are not in slide show review for important questions discussed in...

Hint: Look at the Notes when you are not in slide show review for important questions discussed in class!

A population is a group of individuals of the same species living in the same area.

A species is all individuals that are capable of interbreeding.

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Five key properties of any populationAbundanceBirth ratesDeath ratesGrowth ratesAge structure

Demographics is the statistical study of human populations.

The general study of population changes is called Population Dynamics.

How rapidly a pop changes depends on GR

Growth rate = (birth rate – death rate)

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The proportion of the population at each age.

Implication for current and future social and economic conditions - What if no one is having babies? What if 70% of the population is under age 30? (true in several countries)

Impact on the environment - do older people have as large an impact as young people?

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Four general typesPyramid- population w/ many young and

high death rate (short average lifetime) Inverted pyramid- top heavy (Japan?)Column- birth rate and death rate are low

and a high % of pop is elderlyColumn w/ a bulge- event in the past

caused a high birth or death rate for some age group

Pyramid example Column with bulge Column

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Exponential GrowthA pop increasing by a

constant percentage per unit time.

Human pop growth peaked at 2.1%

1965-1970 Human pop growth is now

appr. 1.2%

1. Early period of hunter and gathers - the total population was < a few million (>10,000 yrs ago)

2. Rise of agriculture- allowed for increase in population density and increased human population

3. Industrial revolution - improvements in health and food supply led to rapid inc in population

4. Today - the rate of growth is slow in industrialized nations but high in less developed nations

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Current world population >7 billionWith annual growth rate of 1.2%

At this rate 84 million people added to Earth in 1 year

Correlation between poverty and population growth

Positive feedback – Poverty Lacks education, healthcare, and family planning thus

= increase in birth rates and family sizes

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Current US growth rate 0.6%

Doubling time (time required for a pop to double in size) is very sensitive to growth rate (g.r)

It changes quickly as g.r. changesUS w/ a g.r. of 0.6% has a doubling time of 117 yrsNicaragua w/ a g.r. of 2.7%, d.t. = 26 yrsNorthern Europe w/ a g.r. of 0.2%, d.t. = 350 yrs

S shaped curve Increase exponentially only temporarilyThen growth rate would declineReach an upper pop limit @ logistic

carrying capacity (g.r. = 0)

Population evens out as it reaches carrying capacity

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Little evidence that animal populations actually follow this growth curve

Involves assumptionsConstant environmentConstant changing carrying capacityHomogeneous population

Unlikely if death rate continue to decrease

More births = increase in population

Three stage pattern of change in birth rates and death rates

Occurred during the process of industrial and economic development of Western nations

Leads to decline in pop growth rate

Stage 1Nonindustrial countryBirth rate and death rate high, growth

rate low Stage 2

Period of high growth rateW/ industrialization death rate declines

but birth rate stays high

Stage 3Birth rate drops toward death rateGrowth rate decreasesWill take place if parents come to believe

that having a small family is to their benefit.

Impact that all humans pose on the environment is a result of two factors

Number of people Impact of each person on the environment

Total impact (Ti) of the human population on environment = average individual impact x total # of individuals or …

Ti = P x I

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Modern technology increases the use of resources and enables us to effect the environment in new ways.

E.g. CFCs, automobiles

Therefore we see that although technology lowers birth rates and decreases death rates, it increases the the average environmental impact per person

How many people can live on Earth at the same time?

Answer depends on the quality of life people desire and are willing to accept.

Estimates vary based on assumptions made.

“distribution-problem” - largely it’s a matter of where people are and how many there are in that area

Second decline in death rateLeads to Stage IV

A second stable state would arise if birth rate then falls….. Leading to

Stage V Decision that might need to be made

Stop research on diseases of old age?Reduce birth rate?Wait for Malthus’ projections to come

true?Disallow “certain” people from having

babies?

If people of the world were to live at the same level as those in US

High resource useCarrying capacity would be low

If people of the world were to live at the same level as those in Bangladesh

Poverty and heavy drain on biodiversityCarrying capacity would be much higher

Acute or epidemic diseases - appear rapidly and affect a large numbers before declining.

Chronic disease- always present in a pop, typically occurring in small as result of long environmental exposure. (Smoking: lung cancer)

Emerging diseases could effect both industrial and less developed nations because of long range rapid transportation

SARS West Nile Virus Epidemic flu (or Pandemic - H1N1 - Swine flu)

Maximum lifetime- maximum possible age to which an individual of a species can live.

Life expectancy- the average # of years an individual can expect to live.

Higher in developed nation - due to availability of sanitation and technology

Japan highest, 82 yearsDeveloping nations - Botswana, Lesotho

and Swaziland lowest, 35 years; notice the dramatic differential!

Human populations will eventually be limited by some factor or combo of factors

Short-term - affect pop during the year in which they become limiting

Intermediate-term - effects are apparent after 1 yr but before 10yrs.

Long-term – effects are not apparent for 10yrs

Simplest and one of the most effective is to delay the age of 1st childbearing by women.

Birth ControlBreast-feeding can delay resumption of

ovulationFamily planning methods from abstinence

to induction of sterility w/ natural agentsONLY Zero population growth will allow for

a “sustainable” future.

The choice of population control methods is an issue that involves social, moral and religious beliefs

Wide range of approaches Information Accesses to birth control Rewards and penalties - Canadian system

example Limit household size – China’s one child

policy

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New York City Billings, Montana

The United Nations has a program focused on human population growth. Explore the website below to obtain more information on what experts believe is the state of the human population.

a) It is commonly assumed that those countries with the most cropland will have the greatest amount of food per capita and the fewest people who are undernourished. Is this assumption accurate? [Hint: look at the charts and graphs available on the website.] Southeastern and South-central Asia and Western Europe have the lowest amount of cropland per capita. What regions have the highest and lowest percentage of population who are undernourished? If the regions with the highest starvation rate are not the regions with the lowest amount of cropland per capita, what else could be causing people to be undernourished? If we are going to be able to reduce the number of people who are malnourished and/or starving, we need facts, not opinions. Explore the UN website for information that will help you arrive at a conclusion.

http://www.unfpa.org/swp/swpmain.htm

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The current human population represents something unprecedented in the history of the world. Never before has one species had such a great impact on the environment in such a short time and continued to increase so rapidly. These qualities make human population the underlying environmental issue. After reading this chapter, you should understand:

That ultimately, there can be no long-term solutions to environmental problems unless the human population stops increasing.That two major questions about the human population involve what controls its rate of growth and how many people the earth can sustain.That the rapid increase in the human population has occurred with little or no change in the maximum lifetime of an individual.That modern medical practices, as well as improvements in sanitation, control of disease-spreading organisms, and supplies of human necessities, have decreased death rates and accelerated the net rate of human population growth.That even under the best imaginable scenario that experts in human populations have put forward, the human population will double before it stops increasing.That countries with a high standard of living have moved more quickly to a lower birth rate than have countries with a low standard of living.That although we cannot predict with absolute certainty what the future human carrying capacity of Earth will be, understanding of human population can help us make useful forecasts.