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1.2 Studying Populations
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Gravity
-describe methods for determining population size -explain causes of changes in population size -identify factors that limit population growth
Terms in this set (14)
Methods to determine population size include
direct and indirect observations, sampling, and mark-and-recapture studies.
Direct Observation
Counting all the members of a population (e.g., crabs in a tide pool).
Indirect Observation
Observing signs of an organism (e.g., counting nest entrance holes (if 4 per nest and 120 nests, 480 individuals).
Sampling
Estimating population by counting the number of organisms in a small representative area (sample) and multiplying
Estimate
an approximation of a number, based on reasonable assumptions.
Mark-and-recapture studies
Catching, counting, and marking organisms, then recapturing to count again, to make a mathematical estimate of total organisms in the population.
Populations can change in size when
new members join or when members leave.
Birth rate
the number of births in a population in a given time.
Population statement
If birth rate is greater than death rate, the population size increases; if birth rate is less than death rate, the population decreases.
Immigration
moving INTO a population
Emigration
moving OUT of a population (exit)
Population density formula
PD = Number of individuals/Unit area (e.g., 2 monarch butterflies/square meter)
Limiting factors
environmental factors, such as food, water, space, and weather, that causes a population to decrease.
Carrying capacity
the largest population an area can support.
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