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A habitat is where an organism lives.
· A ecosystem is how organisms within a community interact with each other
and there environments.
· A population is a group of interbreeding organisms of one species within a
habitat at one time.
· A niche describes how an organism fits into an environment.
· Ecology is the study of the inter ­ relationship between organisms and their
· A community is a collection of populations living in a habitat.
· Biotic factors are the living components within an ecosystem.
· Abiotic factors are the physical and chemical components with an ecosystem.
· A species is a group of organisms that are able to breed to produce fertile
· Demography is the statistical study of human populations…read more

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Estimating Populations
·To estimate a plant population we use quadrat.
·We then decide what size quadrat to use, the number of quadrats and the position of
the quadrats.
· We can either randomly sample or systematically sample in a belt or line transect.
· To estimate animal populations we use mark-release-recapture.
·Organisms are captured, marked, released and recaptured.
· The following assumptions are made:
· The mark is not rubbed off, kill the organism or makes them more prone to predation
·The population doesn't change between the release and recapture.
·The marked individuals evenly redistribute themselves
·The proportion of marked to unmarked individuals in the 2nd sample is equal to the
proportion of marked to unmarked individuals in the total population.
· The equation to estimate the population is:
Total no. of individuals in 1st sample X Total no. of individuals in 2nd sample
No. of marked recaptured…read more

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Abiotic and Biotic Factors
· Abiotic Factor are:
CO2 levels pH Light Intensity
O2 levels Temperature Wind
Humidity Mineral ion concentration
· Biotic Factor are:
There are two types of competition:
Intra-specific competition ­ This is between 2 members of the same species
Inter-specific competition ­ This is between 2 different species.
When 2 species are competing for limited resources the one that uses the
resources most efficiently will eliminate the other.…read more

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Human Populations
· Factors affecting birth rates:
· Economic Conditions ­ Low income countries have higher birth rates
· Birth Control ­ contraception and abortion decrease birth rate
· Cultural and Religious Background ­ some religions band contraception
· Governmental Influence ­ taxation and education
· Social Pressure.
BIRTH RATE = No. of births per year X 1000
Total population in the same year
· Factors affecting death rates:
· Natural disaster
· Wars
· Medical care and sanitation
· Food supply and water
DEATH RATE = No. of deaths per year X 1000
Total population in the same year…read more

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Human Populations
Population Growth = (birth + immigration) ­ (death + emigration)
% population grate rate = Population change X 100
Population at the start of the year
Population structure:
The life expectancy in different countries is different. These changes are
This is a pyramid for a stable
country This is a
This is a
pyramid for
pyramid for a
country…read more

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