http://www.youtube.com/watch?v=6WS7naoEH5o

Characteristics of Populations

O Geographic distribution- the area inhabited by a population

O Population density- the number of individuals per unit area

O Ex: 73 persons per square mile in the U.S.

What factors affect population growth?

Number of births

Number of deaths

Emigration/Immigration

O Immigration- the movement of individuals moving into an area

O Emigration-the movement of individuals moving out of an area

OA decrease in birth rates and an increase in death rates may lead to a ______ in population growth.

OA decrease in birth rates and an increase in death rates may lead to a decrease in population growth.

Exponential GrowthO Occurs when the individuals in a

population reproduce at a constant rate.

O Ideal Conditions with unlimited resources

O Produces a J-Shaped Curve

Logistic GrowthO As resources become less available,

growth slows down or stopsO S-shaped curve

Phases of Logistic Growth

O Lag phaseO Exponential growth phaseO DecelerationO Stable equilibrium

Carrying CapacityO The maximum number of individuals

of a given species that the environment can support

O The closer a population is to carrying capacity:

the more likely resources become scarcebirth-rate expected to decline death-rate expected to increase

Limiting FactorsO Factors that cause population growth

to decreaseO Includes:O Density-dependentO Density-independent

Density-dependent factors

O Become limiting only when the population density reaches a certain level

O The percentage of the population affected increases as density of population increases

O Examples:O Predation, Competition, Parasites,

Disease

Density-independent factors

O Affect all populations in similar ways, regardless of population size

O Intensity of effect does not increase with increased population density

O Examples:O Droughts, freezes, hurricanes, floods,

forest fires

Activity O This activity will demonstrate

exponential growth of a virus while demonstrating a factor that limits population growth of humans

InstructionsO Each person will get a cup with a

liquidO 1st RoundO Find a partner and mix the contents

of your cup with partner. Make sure the contents are mixed thoroughly

O Evenly distribute the contents to cups of both partners

O 2nd RoundO Find a new partnerO Repeat Steps from 1st RoundO 3rd RoundO Find a new partner (different from 1st and

2nd rounds)O Repeat Steps from 1st RoundO 4th Round O Find new partnerO Repeat Steps from 1st Round

O http://www.youtube.com/watch?v=VcSX4ytEfcE

Human Population Growth

O The size of human population tends to increase with time.

O Demography is the scientific study of human populations.

O Human population growth started out very slowly

O What were some limiting factors that kept the human population low?

O Food scarcityO Diseases

O What advances helped lead to the increase in human population growth?

O AgriculturalO IndustrialO Improved SanitationO Improved medicine and healthcare

O Demographic transition- a dramatic change in birth and death rates

O Age-structure diagrams- population profile

Demographic Transition

O More-developed countries doubled population between 1850 and 1950

O Caused by decline in death rateO This was followed by decline in

birthrateO Only modest growth between 1950

and 1975O Stable Growth

Demographic Transition

O Yearly growth of less-developed countries peaked between 1960 and 1965 at 2.5 %

O Since then, death rate and birthrate have fallen

O Collective birthrate now 1.5%O But many LDCs have not participated

in this decline

United States Rwandan

Population

Percentage of Population Percentage of Population

More-developed vs. Less Developed Countries

O More-developed countries

O North America, Europe, Japan, Australia

O Low growthO Higher standard

of living

O Less-developed countries

O Some countries in Latin America, Africa, and Asia

O Population growth is expanding rapidly

O Many in poverty

Peppered MothO Melanistic moth

became increasingly common near areas of industry

O Pale or typical moth prevails in areas absent of heavy industry

Human Activities O What are some human activities that

have affected the environment?O Hunting and GatheringO AgricultureO Industrialization /Urbanization

Hunting and GatheringO Early hunters and gatherers caused

extinction of animals.O Examples: Woolly mammoths, giant

ground sloths, saber tooth cats

Hunting and GatheringO Early human populations in the

Mediterranean region ate large quantities of tortoises and shellfish

O Depleted these sourcesO Were then forced to eat hares,

partridges, and other small mammals and birds

AgricultureO Green Revolution

O Specialized Crops, pesticides, irrigation

O Industrialized agriculture

AgricultureO Clearing of large portions of land O Increased erosionO RunoffO Loss of biodiversityO Pest Resistance O Soil and water pollution