Download Populations

Populations
• A population - a group of
organisms of the same species
in the same area.
Population Topics
A. What affects population size
B. Population growth patterns
C. Limits to population growth
• “Analyzing Data”
• Make a graph showing fruit fly population growth
• Make a graph showing rabbit population growth
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A. Population Size
• Factors that increase population size:
• Natality (births)
• Immigration
• Factors that reduce population size:
• Mortality
• Emigration
• Calculate the Population Size of Akron, CO:
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In 2010, there were 1400 residents.
92 babies born
47 new people moved there
88 people died
41 people moved away
• IN 2011: 1410 residents!
B. Population Growth
Exponential Growth
• Under ideal conditions with
unlimited resources, a population
will grow exponentially.
• Exponential growth occurs when
the individuals in a population
reproduce at a constant rate.
• The population becomes larger
and larger until it approaches an
infinitely large size.
Logistic Growth
• As resources become less
available, the growth of a
population slows or stops.
• Logistic growth occurs when a
population's growth slows or
stops following a period of
exponential growth
Logistic Growth – 3 phases
Logistic Growth – 3 phases
1. Exponential Growth Phase – there is unlimited growth of
the population due to absence of limiting factors.
• Examples:
• germinating annual plants in a new season.
• a bacterial population during the initial phases of an
infection.
• The population of any species occupying a previously
unoccupied habitat
Logistic Growth – 3 phases
2. Transitional Phase – limiting factors start influencing the
rate of increase of the population. Population is still
increasing, but not as rapidly.
Examples:
• Organisms start competing with each other for available
resources
• Survival of the fittest
• predators move in
Logistic Growth – 3 phases
3. Plateau Phase – Population stops increasing, due to
limiting factors. The population has reached its carrying
capacity.
Natality + Immigration = Mortality + Emigration
Carrying Capacity – the maximum number of individuals
of a species that can be supported by the environment.
• What are some things that would limit:
• Plant population growth?
• Animal population growth?
Think with a partner
C. Limiting Factors
1. Animals
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Amount of food available
Presence of diseases or parasites
Amount of predation
Available nesting sites
2. Plants
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Amount of light available
Temperature
Amount of water available
Space