Paleontologists (evolutionary biologists who study fossil organisms) have discov
ID: 273138 • Letter: P
Question
Paleontologists (evolutionary biologists who study fossil organisms) have discovered and described an extinct pygmy mammoth" (like a shaggy elephant) on the Channel Islands of California. Pygmy mam?moths were only about 6 ft. in height. Pygmy mammoth fossils have not been found on the mainland. Mainland mammoths living at the same time were much larger, about 14 ft. in height. Using the Components of Darwin's Theory of Evolution by Natural Selection explain the conditions that must have existed in the original population of large mammoths that became established on the Channel Islands for Natural Selection to affect body size and how these conditions interacted to produce a population with much smaller average size over many generations (ie. by a slow gradual process). Include and underline all of the following (given in no meaning of each: struggle for existence, reproductive fitness, Va. rep particular order) in your answer and explain the roductive excess, Vp. Also l terms how the genetic composition of the population must have changed over time. vari anceExplanation / Answer
Answer:
Pygmy mammoth found on Channel Island of California were short in their height as compared to the other mainland mammoths. It is believed that a small population from the mainland embarked on the journey to the new island that lead to the formation of a new species. These mainland mammoths or Columbian mammoths are believed to have swam to the new island location. In the ice age, sea level was comparable lower as it is today, so, this facilitated their migration to a new location. They were good swimmers as they possessed snorkel-like trunk. This marked their migration to the island on the other side.
Once a small population have reached to a new location, their number relatively increased there. However, their evolution pattern is based on the Darwin's evolutionary components which are of 4 types- (i) Variation, (ii) Inheritance, (iii) Population growth and (iv) Reproduction and differential survival.Since they were then separatd from the mainland mammoth population, the Vg value (genetic variance value) decreased. This happened due to null interaction among two population due to geographical isolation. Once their number increased, they competed for the available food or other required resources for their survival. At this stage, any those population existed which had an ability to compete for the available resources better than other (by applying the concept of survival of the fittest / struggle for existance). Therefore, only those mammoths survived which had short strature which favoured them for less food and water intake. They acquired their short strature over the glacial period of evolution, aound 150,000-250,000 years ago.
When the short stratured population interbred, more short population emerged. And, based upon lower resource consumption, nature selected these short stratured population only (by applyting the concept of reproductive fitness). New population is thus believed to have inherited the short strature from their ancesstors for their selection and differential survival. Thus, the number of naturally selected individuals increased by reproduction among the selected individuals (by applyting the concept of reproductve excess) which inhabited the island.
Genetic composition in a popuation changes over time by processes such as- genetic drift, mutations and migration.
Genetic Drift is basically a process of sudden change in the allele frequency in a given population. It may either increase or decrease the variability withoin a population. Migration is synonymous to gene flow, whose general effect is to bring about the similarity within the population by restoring the allele frequency lost in genetic drift. Mutation is the process that occurs at the DNA level which changes the nucleotides of the DNA sequence which can have consequnces at the molecular lever. Mutation may be caused by either deletion, or insertion, or by substitution.
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