explain examples of homologous and analogous organs.

Define saltation and speciation with examples?

Homologous organs are those organs which are similar in origin but different in function. It represents a case of divergent evolution. The presence of a structure or physiological process in an ancestral organism, which has become greatly modified in more specialized, apparently related organisms , may be interpreted as indicating a process of descent by modification. In this case the function of organs diversified and became different from the common ancestor. Example the thorn and tendrils of Bougainvillea and Cucurbita

Analogous structures are those which are different in origin but similar in function. The existence of analogous structures suggest the occurrence of convergent evolution. It may be explained in terms of the environment, acting through the agency of natural selection, favouring those variations which confer increased survival and reproductive potential on those organisms which possess them. In this case different organs with different origins start performing similar functions and differ from their ancestral trait. Example is Wings of butterfly and of birds

Speciation is the process in which one or more species arise from previously existing species. A single species may give rise to a new species or two different species may give rise to a new species. For example humans have evolved from dryopithecus.

Saltation is single step large mutation in an organism which results in abrupt change in its phenotype.

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HOMOLOGOUS ORGANS

  these organs have similar structural plan  but different functions.eg  is fore limbs of man , cheetta , frog ,bat,whale &  birds.all these have  similar pattern of arrangement of bones. they  arise in a general structural plan & r  similar  embryologically. they  possess  approx,  same no: of bones(tumerous ,  radius , ulna , carpels , meta carpels & falanges) their  muscles , blood vessels &   nerves r  arranged in a similar way.  in plants  thornes of bougain villa & tendrils of cucumber r egs:

ANALOGOUS  ORGANS.

these have  different  structural plan but have same functions.egs r 1 .  wings of birds , butterflies, & bats .2. eyes of octopus & mammals . 3. flippers of penguin & dolphin . 4.potato  (stem  modification )& sweet potato.( root modification ) . 5.leaves of plants & cladode of ruscus. these organs bear superficial similarity  in function  &  r seen in  same habbitat .

single step large mutations  are called saltation.

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