For any species - -For any species population sizes would increase exponentially if all individuals that are born reproduced

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-For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully -Nonetheless, populations tend to remain stable in size, except for seasonal fluctuations. -Resources are limited since production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving each generation. -Members of a population vary extensively in their characteristics; no two individuals are exactly alike -Much of this variation is heritable. Survival depends in part on inherited traits. Individuals whose inherited traits give them a high probability of surviving and reproducing in a given environment have a higher fitness and are likely to leave more offspring than less fit individuals -Unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over generations. SUMMARY OF NATURAL SELECTION -Natural selection is the differential success in reproduction among individuals that vary in their heritable traits. These differences emerge as each individual interacts with its environment. Over time, natural selection can increase the adaptation of organisms to their environment. If an environment changes over time, or if individuals of a particular species move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species in the process. Individuals do not evolve; populations are the smallest units that can evolve. Evolution can be measured only as changes in relative proportions of heritable variations in a population over a succession of generations. Natural selection can amplify or diminish only heritable traits; traits that come from an organism and its own interactions with the environment cannot be passed onto offspring.
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This note was uploaded on 04/09/2008 for the course BIO 311D taught by Professor Reichler during the Spring '08 term at University of Texas at Austin.

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For any species - -For any species population sizes would increase exponentially if all individuals that are born reproduced

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