Natural Selection Type Chart
Theories about height as a trait, the height of individuals in a population will vary, and most individuals have an average height and fewer are very short or very high.
Further Explanation
The effect of stochastic variations on demographic levels (reproduction and death) is much higher for small populations than for large ones. Stochastic variations in demographic levels cause small populations to fluctuate in random sizes.
The environment can directly affect the survival of small populations. Some adverse effects include stochastic variations in the environment, (year-to-year variations in rainfall, temperature) that can produce temporarily correlated birth and death rates (ie 'good' years when birth rates are high and mortality rates are low and 'bad' years when low birth rate and high mortality rate) which causes fluctuations in population size.
Island populations often also have small populations due to geographical isolation, limited habitat and high levels of endemism. Because their environment is very isolated, gene flow is poor in island populations. Without recognition of genetic diversity from gene flow, the alleles are quickly repaired or lost. This reduces the ability of island populations to adapt to new conditions and can lead to higher extinction rates.
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Natural Selection Type Chart
Variation/Population
Details
Class: Middle School
Subject: Health
Keyword: genetic, chart, variation/population