Question

1. Which bones in the human forelimb are present in the dog, whale, and bird forelimb? Why do you think these inclusions are significant?

2.what is the common ancestor for all four animals? Why is this important?

3.Define natural selection in your own words

Answer 1

Answer - 1 all the bones in forelimbs humerus ulna, radius , carpals and metacarpals are present in humans, dog,whale, and birds . The forelimbs appear to be different morphologicaly in these organisms but they all have the same basic structural plan of forelimb bones and arranged in same pattern and have same mode of development. The forelimbs in humans adapted for grasping, wings for flying, dog for running, and whale for reveals the homology in their structure. homology means similarity between structures in different species because of common origin and later on adapted to perform Different functions.

Ans-2) tiny shrew like creatures are considered to be the common ancestor of humans, birds, whales and dogs. They lived around 140 million years ago .Predicting common ancestor has many difficulties and controversies. From the common ancestor specied diverge more and more in morphology and acquire unique adaptation.

Ans-3 natural selection - it is a non random and predictable process in which some biological traits or characters become more or less common in the population because of differencial suvial of bearers .the frequency of genetic variants or characters which are best adapted/ suited in any environment increase while frequency of less adapted decreases over time. Natural selection can be directional, stabilizing or disruptive. An example is industrial melanism - it is the phenomenon by which light colore moths became dark colored moths due to natural selection during industrial revolution in london.