● `color{Violet}"Comparative anatomy"` `color{Violet}"and morphology"` shows similarities and differences among organisms of today and those that existed years ago.

● Such similarities can be interpreted to understand whether `color{Violet}"common ancestors were shared"` or not.

● For example `color{Violet}"whales, bats"`, `color{Violet}"Cheetah and human"` (all mammals) share similarities in the pattern of `color{Violet}"bones of forelimbs"`.

● Though these forelimbs perform `color{Violet}"different functions"` in these animals, they have similar `color{Violet}"anatomical structure"` – all of them have humerus, radius, ulna, carpals, metacarpals and phalanges in their forelimbs.

● Hence, in these animals, the `color{Violet}"same structure"` developed along `color{Violet}"different directions"` due to adaptions to `color{Violet}"different needs"`.

● This is `color{Brown}"divergent evolution"` and these structures are `color{Brown}"homologous"`.

● Homology indicates `color{Violet}"common ancestry"`.

● Other examples are `color{Violet}"vertebrate hearts"` or `color{Violet}"brains"`.

● In plants also, the `color{Violet}"thorn and tendrils"` of `color{Violet}"Bougainvillea and Cucurbita:"` represent homology .

● `color{Violet}"Homology"` is based on divergent evolution whereas `color{Violet}"analog"`y refers to a situation exactly opposite.

● `color{Violet}"Wings"` of `color{Violet}"butterfly"` and of `color{Violet}"birds"` look alike.

● They are `color{Violet}"not anatomically similar"` structures though they perform `color{Violet}"similar functions"`.

● Hence,`color{Brown}"analogous structures"` are a result of `color{Brown}"convergent evolution"` - different structures evolving for the same function and hence having similarity.

● Other examples of analogy are the `color{Violet}"eye of the octopus"` and of `color{Violet}"mammals"` or the `color{Violet}"flippers of Penguins"` and `color{Violet}"Dolphins"`.



One can say that it is the `color{Violet}"similar habitat"` that has resulted in selection of `color{Violet}"similar adaptive features"` in different groups of organisms but toward the same function:

● `color{Violet}"Sweet potato"` (root modification) and `color{Violet}"potato"` (stem modification) is another example for analogy.

● Similarities in `color{Violet}"proteins and genes"` performing a given function among diverse organisms give clues to `color{Violet}"common ancestry"`.

● These `color{Violet}"biochemical similarities"` point to the `color{Violet}"same shared ancestry"` as structural similarities among diverse organisms.



● Man has bred `color{Violet}"selected plants and animals"` for agriculture, horticulture, sport or security.

● Man has `color{Violet}"domesticated"` many wild animals and crops.

● This `color{Violet}"intensive breeding programme"` has created breeds that differ from other breeds (e.g., dogs) but still are of the same group.

● It is argued that if `color{Violet}"within hundred of years"`, man could create `color{Violet}"new breeds"`, could not nature have done the same over millions of years?

● Another `color{Violet}"interesting observation"` supporting evolution by natural selection comes from `color{Violet}"England"`.

● In a `color{Violet}"collection of moths"` made in `color{Brown}"1850s"`, i.e., `color{Violet}"before industrialisation"` set in, it was observed that there were more `color{Violet}"white-winged moths"` on trees than dark-winged or melanised moths.

● However, in the collection carried out from the same area, but `color{Violet}"after industrialisation"`, i.e., in `color{Brown}"1920"`, there were more `color{Violet}"dark-winged moths"` in the same area, i.e., the proportion was reversed.

● The explanation put forth for this observation was that `color{Brown}"predators will spot"` `color{Brown}"a moth against"` `color{Brown}"a contrasting background"`

● During `color{Violet}"post industrialisation period"`, the tree trunks became dark due to `color{Violet}"industrial smoke"` and `color{Violet}"soots"`.

● Under this condition the `color{Violet}"white-winged moth"` did not survive due to `color{Violet}"predators"`, dark-winged or melanised moth survived.

● `color{Violet}"Before industrialisation"` set in, thick growth of almost `color{Violet}"white-coloured lichen"` covered the trees - in that background the white winged moth survived but the dark-coloured moth were picked out by predators.

● `color{Brown}"NOTE"`: `color{Violet}"Lichens"` can be used as `color{Violet}"industrial pollution indicators"`. They will `color{Violet}"not grow"` in areas that are polluted.

● Hence, moths that were able to `color{Violet}"camouflage themselves"`, i.e., hide in the background, survived.

● This understanding is supported by the fact that in areas where `color{Violet}"industrialisation did not occur"` e.g., in rural areas, the count of `color{Violet}"melanic moths was low"`.

● This showed that in a `color{Violet}"mixed population"`, those that can `color{Violet}"better-adapt"`, survive and `color{Violet}"increase in population"` size.

● Remember that no variant is `color{Violet}"completely wiped out"`.

● Similarly, `color{Violet}"excess use"` of herbicides, pesticides, etc., has only resulted in `color{Violet}"selection of resistant varieties"` in a much lesser time scale.



● This is also true for `color{Violet}"microbes"` against which we employ `color{Violet}"antibiotics"` or drugs against `color{Violet}"eukaryotic organisms/cell"`.

● Hence, `color{Violet}"resistant organisms"`/cells are appearing in a time scale of `color{Violet}"months or years"` and not centuries.

● These are examples of `color{Brown}"evolution by"` `color{Brown}"anthropogenic action"`.

● This also tells us that evolution is `color{Violet}"not a direct process"` in the `color{Violet}"sense of determinism"`.

● It is a `color{Violet}"stochastic process"` based on `color{Violet}"chance events"` in nature and chance mutation in the organisms