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