1 Give one example of each of the following a a homologous m

1) Give one example of each of the following. a) a homologous molecular trait shared by all cellular organisms. b) a body part adapted to different functions in different species but showing clear homology of underlying structure. c) a non-homologous similarity between organisms adapted to similar habitats or niches (use an example NOT given in lecture). d) Amolecular vestigial trait shared by all primates, but not most other mammals. e) Amorphological vestigial trait shared by humans and great apes (chimpanzees, gorillas, etc.)but not vestigial in other primates (e.g. monkeys). 2) What is meant by the \"ambiguity\" of species boundaries, and why did Darwin use it as part of his argument for common descent? 3) The picture below shows three species as embryos (left) and as adults (right). What is the name of the phenomenon it illustrates? What evidence does the phenomenon give about evolution?

Solution

1.

a.Aminoacids : The 20 aminoacids are same in all cellular orgainsms.

b.Forelimbs

c.Stream lined body of sharks and whales, wings of birds and insects.

d.The gulono--lactone oxidase (GLO) pseudogene.

e.Coccyx is present in humans and great apes as fused bone but is not present in monkeys as they have tails.

2.Ambiguity of species boundaries means there is always a confusion as to which organisms can be grouped into species; wheather sexually reproducing organisms and asexually reproducing organisms.What boundaries should exist so as to group organisms into species has always been ambiguous.No such species boundaries were set earlier.Darwin used it as a part of his argument for common ancestor because according to him god had created the species and this was known as Creationism and he emphasized on the process of natural selection to be an active process that led to evolution from common ancestor.

3.The phenomenon that the diagram illustrates is homology.Homology in embryo is known as ontogenetic homology and means that two or more species share same embryological similarities and it gives an evidence that all the three embryos of species have a common ancestor but in process of time have undergone remodelling of body parts through natural selection.