Problem 3 For each of the scenarios below: a. state why evolution is occurring b

Question

Problem 3 For each of the scenarios below: a. state why evolution is occurring b. state whether mutation, natural selection, genetic drift or gene flow appears to be the mechanism of evolution and describe why you picked a particular mechanism of evolution c. Researchers have been studying an isolated, small population of wolves (fewer than 30 individuals) on Isle Royale in Lake Superior for the past 30 years. This year they find that there are only 16 individuals left in the population and only 1 of these individuals is a female. .A large population of colonially nesting (large groups of individuals nest together in a colony) shorebirds varies in plumage color from very white to dark gray. During the breeding season, a train derailment causes a toxic substance to flow into a lake where the colony is located. Approximately 75% of the mating individuals in the colony die. During the following breeding season, researchers notice that almost all of the individuals in the population have medium to dark gray plumage.

Explanation / Answer

Evolution is the change in the inherited characteres of a species from generation to generation.These characters are the expression of genes which are copied and passed to next generation during reproduction. Evolution takes place due to several reasons they are i) Mutation ii) Genetic drift, iii) natural selection iv) Gene flow.

Mutations in the genes can produce new or altered traits, giving rise to heritable differences ( that is genetic variation) among organisms.

New traits can also come by transfer of genes between populations, due to migration, or between species, in horizontal gene transfer.

Evolution takes palce when these heritable differences become more common or rare in a population, either non-randomly by natural selection or randomly by genetic drift.

In Natural selection heritable traits which are helpful for survival and reproduction become more common, and harmful traits become rare.

In case -A -

a) Evolution - Evolution is the change in the inherited characteristics of a species from generation to generation.

In case of the researchers studying an isolated small population of wolves (less than 30 ) in Isle Royale lake superior for past 30 years suddenly it is found that only 16 individuals left in the population and 1 is female.

b) This occured due to Genetic drift mechanism of evolution.

c) Genetic drift is defined as variation in the relative frequency of different genotypes in a small population, leading to the chance disappearance of certain genes when individuals die or do not reproduce.

As in this case the wolves were in Isle Royale lake superior, which is a cold terrain and the population was small and isolated so inbreeding occured here , inbreeding reduces the heterozygosity and increases homozygosity , due to heterozygosity fitness decreases, also sudden decreases in population size might have occured due to Bottle neck effect, as the fitness decreased due to homozygosity there might be a outbreak of disease. so the population size decreased.

Case- B-

a)  Evolution - Evolution is the change in the inherited characteristics of a species from generation to generation.

b) The Mechanism of evolution taking place in case- B is Mutation.

c) Mutation is a change in DNA, the hereditary material of an organism. An organism's DNA affects it 's look, it's behaviour , and its physiology .So a change in an organism's DNA can cause changes in all aspects of its life. In this case due to a train derailment the spill of the toxic substance caused death of 75% birds, here the oil spill spread toxic materials in the ecosystem , which went inside the organisms by food chain in consecutive generations as the toxic materials do not easily goes out of the ecosystem, so in next generation that affected the birds leading to the production of medium to dark grey plumage.

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