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.
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:
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.