population growth notes module 2 ecology. growing rapidly tripled in size in about 70 years est....
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POPULATION GROWTH NOTES
Module 2 Ecology
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Growing rapidlyTripled in size in about 70 yearsEst. size to day 6 billion+ (approx. 2 billion in 1930)
Human Population
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Problems cause by humans
Thinning ozone layer – ozone layer protects living things from ultraviolet radiation form the sun
Climatic changes Greenhouse effect: insulates earth from the deep
freeze of space; keep Earth warm Caused extinction of other species – extinction rate
higher today than at any other time Increased pop. requires increasing amts. of food,
energy, space – greater share of Earth’s resources will be required
Burning Fossil Fuels for energy – releases carbon dioxide; excess CO2 traps too much heat in Earth’s atmosphere
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Human Population Growth
Improved by agricultural development, hygiene, diet, and economic conditions improved
Today, population growth is faster in less-developed countries and slower in more developed countries
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Population Dynamics
Changes in size and composition over time
Measure include: birth rate - number of births over time (in US
it is 4 million per year) death or mortality rate – number of deaths
in a period of time (in US it is 2.4 million per year)
life expectancy – how long an individual is expected to live (1996: in US it was 72 yrs. for a man and 79 for a woman)
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Population Growth Rates
Amount of change within a population’s size in a given time
Four factors that affect growth rates: Birth Death Emigration – movement out of a population Immigrations – movement into a population
Demographers – scientists who study populations dynamics
Birth rate – death rate = growth rate
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Carrying capacity of a population is the number if individuals the environment can support for an indefinite period of time.
Populations fluctuate over time do to environmental changes.
Small populations are less able to rebound from environmental changes. They are more likely to experience inbreeding and their genetic diversity is low.
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Population Growth Curves
Linear – growth occurs along a straight lineNOT what we see w/ populations of organisms
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Population Growth Curves
Exponential – as population gets larger, it grows faster (population explosion)“J shaped”
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Predator-Prey
Predator-Prey – (predation is density dependent limiting factor)
When population grows beyond carrying capacity of environment, density-dependent Limiting Factors reduce population population grows/shrinks cycles
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Carrying Capacity
What is seen in most populations of organisms. Population growth is limited by factors in the environment such as food supply or habitat.