Biology Project
Published on Nov 18, 2015
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PRESENTATION OUTLINE
Population
A population is a group of organisms of the same species that live in a certain area. Ecologists regularly monitor the number of organisms in many populations.
Photo by Hammonton Photography
Populations that are growing and shrinking can be indicators of potential problems occurring in the organisms' environment, and gives ecologists a 'heads up' if something is going wrong.
Photo by IITA Image Library
Any population will grow if more organisms are being created, or born, than are dying. If a population has more organisms dying than are being born, then the population will shrink.
Photo by lloydi
The number of births in a population is called a birth rate.
The number of deaths in a population is called the death rate.
Photo by jstanier
Therefore, if the birth rate is higher than the death rate, a population will grow. Conversely, if the death rate is higher than the birth rate, the population will shrink.
Photo by VinothChandar
If a population is growing exponentially, then the birth rate is higher than the death rate.
If a population is endangered, then the death rate is higher than the birth rate.
Limiting Factors
A population's growth is limited by two general factors: density- dependent factors and density- independent factors.
Photo by dsevilla
If the population's density does not influence whether or not the factor stops the population's growth, then it is called a density- independent factor.
Photo by kevin dooley
Natural disasters are an example of a density- independent factor
Photo by ecstaticist
A factor that stops a population's growth that is influenced by the population's density is a density- dependent factor.
Photo by Darwin Bell
Resources are an example of a density- dependent factor.
Photo by Don J Schulte
A population stops growing when it reaches maximum number of organisms that can be supported by the environment.
Photo by swisscan
The number of organisms that a population can carry is known as the population's carrying capacity.
Photo by Korona4Reel
A logistic population growth graph represents what actually occurs as a population's numbers get too large for the environment to support it.
Photo by blmiers2
LOGISTIC POPULATION GROWTH
In the previous logistic growth graph, the rabbits' carrying capacity is around 65. The population between mid- May and mid- June is growing very fast. There is a steep incline in the graph.
Photo by blmiers2
The period of growth before a population reaches it's carrying capacity is called exponential growth.
In logistic population growth, the population eventually levels off.
In exponential population growth, there is only an increase in population.
Photo by cuellar
The human population is currently growing exponentially. Diseases or competition for resources could arise when the population reaches it's carrying capacity.
Photo by Werner Kunz
As the number of lynx increases, the number of snowshoe hare decrease.
This is an example of predation, a density-dependent factor. The lynx depends on the hares for their energy for survival. Once the snowshoe hare population is low the lynx population will decrease as well because of lack of energy. This is the same for people's pets. The pets depend on their owner for food. If the owner runs out of food the pet will die. In this case, the pet is the lynx and the snow hare is the owner.
Photo by Pilottage
Emigration occurs when a population reaches it's carrying capacity. Organisms leave and go to a new place for resources.
Emigration causes a
decrease in population.
Photo by Pink Sherbet Photography
