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Post on 04-Jan-2016
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Essential knowledge 1.A.2:
Natural selection acts on phenotypic variations in
populations.
Environments change and act as selective mechanism on populations.
http://concord.org/stem-resources/natural-selection
Example 1: Flowering time in relation to global climate change
Ecology. 2008 Feb;89(2):332-41. Global warming and flowering times in Thoreau's Concord: a community perspective. Miller-Rushing AJ, Primack RB. As a result of climate change, many plants are now flowering
measurably earlier than they did in the past. Concord, Massachusetts - Records began with six years of
observations by the famous naturalist Henry David Thoreau from 1852 to 1858, continued with 16 years of observations by the botanist Alfred Hosmer in 1878 and 1888-1902, and concluded with our own observations in 2004, 2005, and 2006.
From 1852 through 2006, Concord warmed by 2.4 degrees C due to global climate change and urbanization.
Using a subset of 43 common species, we determined that plants are now flowering seven days earlier on average than they did in Thoreau's times.
Misconceptions
Changes in phenotype are directed by changes in the environment.
False Phenotypic variations are not directed
by the environment but occur through random changes in the DNA and through new gene combinations.
Some phenotypic variations significantly increase or decrease fitness of the organism and the population.
Example 1: Sickle cell anemia
Example 2: DDT resistance in insects
Humans impact variation in other species.
Example 1: Artificial Selection
Example 2: Loss of genetic diversity within a crop species
Monoculture – Planting only one crop How is this affecting the gene pool?
Example 3: Overuse of antibiotics
Essential knowledge 1.A.2:
Natural selection acts on phenotypic variations in
populations.
Genetic Drift
Genetic drift is a nonselective process that can lead to large changes occurring in small populations.
Random drift is caused by recurring small population sizes, severe reductions in population size called "bottlenecks" and founder effect where a new population starts from a small number of individuals.
Bottleneck Effect
Reducing Genes can increasing differences
Reduction of genetic variation within a given population
can increase the differences between populations of the same species.
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