Background: What does it mean when we observe two organisms that are different?
ID: 201613 • Letter: B
Question
Background: What does it mean when we observe two organisms that are different? How did this difference come about? Is it genetically based or not? Is it adaptive or not? In class, we have introduced the fundamental framework of thinking about this. The difference could be due to either 1) PHENOTYPIC PLASTICITY or 2) EVOLUTION, and if it is genetically based, it could be 2A) Evolution by GENETIC DRIFT or 2B) Evolution by (natural) SELECTION Question prompt: In all 3 cases, 1). 2A), and 2B), the environment plays a role. Compare and contrast the role of the environment in these 3 cases and formulate an answer that clearly and convincingly explains this to someone else. Use examples as they may help you.
Explanation / Answer
1) PHENOTYPIC PLASTICITY is the phenotypic variation of an organism having same genotype.One of the example is of - Himalayan rabbits . These kind of rabbit breeds are extremely vulnerable to environment and climate and shows phenotypic variations.Normaly Himalayan rabbits have white color with black marks but when the climate is too worm it changes it's color to complete white and when the climate is too cold it completely changes to black.
2A) GENETIC DRIFT is the change or loss of freequency of an allele due to death or infertility of any population.If in a population the recessive allele has a freequency of 0.25 and the dominant allele has the rest 0.75.But somehow a natural calamity takes place and a large number of population has died.Now among the living population the recessive allele freequency became 0.6 and the dominant allele has rest 0.4.So one incident causes change to the freequency of alleles and traits expressed by those due to genetic drift.
2B) NATURAL SELECTION is the old theory of Darwin of survival of fittest.The best example of the giraffes - There were both high neck giraffes and short neck giraffes but when all the leaves of short plants have been ended ,the high neck giraffes had reached for leaves of large trees but short neck giraffes could not and thus all the short neck giraffes got extinct due to starvation and now we can only see high neck giraffes as per natural selection.
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