Population density is the number of individuals per unit area.
Three factors can affect population size: birthrate, deathrate, immigrants/emmigrants. Immigrant is the movement of individuals into an area, is another factor that can cause a population to grow. Emmigrant is the movement of individuals out of an area, can cause a population to decrease in size. Exponential growth occurs when the individuals in a population reproduce at a constant rate. Under ideal conditions with unlimited resources, a population will grow exponentially. Logistic growth occurs when a population's growth slows or stops following a period exponential growth. |
https://en.wikipedia.org/wiki/Population_density
http://zebu.uoregon.edu/2003/es202/lec07.html
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http://scienceaid.co.uk/biology/ecology/predation.html
https://denalibiomeproject.wikispaces.com/Predator-Prey+Relationships
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Limiting factors is a factor that causes populations growth to decrease.
Density-dependent limiting factor is a limiting factor that depends on population size. It include competition, predation, paratism, and disease. Predator-prey relationship is one of the best-known mechanisms of population control. Density-independent limiting factors affect all populations in similar ways, regardless of the population size. (unusual weather, natural disasters, seasonal cycles, and certain human activities.) |
Like the populations of many other living organisms, the size of the human population tends to increase with time.
Demography is the scientific study of human populations Birthrates, deathrates, and the age structure of a population help predict why some countries have high growth rates while other countries grow more slowly. Demographic transition is a dramatic change in birth and death rates. Age-structure diagrams or population profiles is the models predicted future growth. |
http://madagascardemographics.wikispaces.com/age+structure+diagrams
https://en.wikipedia.org/wiki/Demographic_transition
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