Explain taking one example of vertebrate anatomy that evolution of life has occurred on earth.
'Nature selects for fitness'. Explain with suitable example.
Answers
Answer:
The forelimbs of cheetah, whales, bats and human have a similar anatomical structure but have been modified differently to perform different functions.
* All of them have the bones humerus, radius, carpals, metacarpals and phalanges.
* It indicates divergent evolution where the same structure has developed along different directions as adaptations to different needs.
* Such structures are called homologous organs and homology indicates common ancestry and divergent evolution.
Natural Selection :
In the modern or synthetic theory of evolution, natural selection is considered as a population related genetic phenomenon. It leads to change in allele frequencies and favours or promotes adaptation as a product of evolution.
When the population size of animals or plants in a specific locality increases, certain environmental factors such as availability of food may become limiting factors. Those organisms exhibiting characteristics which give them a competitive advantage may survive. Thus population size and environmental limiting factors operate together to produce selective pressure.
The selective pressure may increase or decrease the spreading of an allele in a gene pool depending on its adaptive value which in turn will lead to evolutionary changes.
Interesting observation supporting evolution comes from England. In a collection of moths in 1850 before the advent of industrialization, it was observed that there were more white winged moths on trees than dark winged one or melanised moths. However, in 1920, the population of dark winged ones increased and white winged ones reduced.
The explanation put forth for this observation was that predators could spot a moth against a contrasting background. During post industrialization period, the tree trunks became dark due to industrial smoke and soot. Under this condition, white moths did not survive due to predators but dark winged or melanised moths survived.
Before industrialization, white coloured lichens grew thickly and covered the trees. In that background, the white winged moths survived but dark ones were picked up by the predators. Hence, moths that were able to camouflage in both the backgrounds were able to survive. No variant was wiped out completely.
Answer:
The forelimbs of cheetah, whales, bats and human have a similar anatomical structure but have been modified differently to perform different functions.
* All of them have the bones humerus, radius, carpals, metacarpals and phalanges.
* It indicates divergent evolution where the same structure has developed along different directions as adaptations to different needs.
* Such structures are called homologous organs and homology indicates common ancestry and divergent evolution.
Natural Selection :
In the modern or synthetic theory of evolution, natural selection is considered as a population related genetic phenomenon. It leads to change in allele frequencies and favours or promotes adaptation as a product of evolution.
When the population size of animals or plants in a specific locality increases, certain environmental factors such as availability of food may become limiting factors. Those organisms exhibiting characteristics which give them a competitive advantage may survive. Thus population size and environmental limiting factors operate together to produce selective pressure.
The selective pressure may increase or decrease the spreading of an allele in a gene pool depending on its adaptive value which in turn will lead to evolutionary changes.
Interesting observation supporting evolution comes from England. In a collection of moths in 1850 before the advent of industrialization, it was observed that there were more white winged moths on trees than dark winged one or melanised moths. However, in 1920, the population of dark winged ones increased and white winged ones reduced.
The explanation put forth for this observation was that predators could spot a moth against a contrasting background. During post industrialization period, the tree trunks became dark due to industrial smoke and soot. Under this condition, white moths did not survive due to predators but dark winged or melanised moths survived.
Before industrialization, white coloured lichens grew thickly and covered the trees. In that background, the white winged moths survived but dark ones were picked up by the predators. Hence, moths that were able to camouflage in both the backgrounds were able to survive. No variant was wiped out completely.