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Impact of Natural Selection .pptx

  2. IMPACT OF NATURAL SELECTION Convergence Regression Radiation Extinction Natural Selection
  3. CONVERGENCE Convergence evolution occurs when species occupy similar ecological niches and adapt similar ways in response to similar selective pressure. Traits that arise to convergent evolution are referred as analogous structure.
  4. 1 • Species often look extremely similar, however they are not closely related to free of life. 2 • Individual environment are offensively similar and they need indistinguishable variations to achieve success and reproduce. 3 • Organisms with favorable distinctions can survive, while other go away from the environment. 4 • Most cases occur in different geographical areas of world, similar climate.
  5. Convergent evolution between Placental Mammals & Marsupials.  Marsupial and placental mammals have evolved separately to occupy equivalent niches on different continents; they are ecological equivalents.
  6. RADIATION In fact, many classical examples of adaptive radiation involves Island or lakes, notable examples include Darwin finches of Galapagos, honeycreeper birds and silvers word plants of Hawaii, and cichlid fish of lakes Malawai and Victoria in Africa. An adaptive radiation occurs when single or large group of ancestral species rapidly diversifies into large number of descendant species. Number of descendants with great variety of adaptions to different niches.
  7. Most common example of adaptive radiation is Darwin's Finches, discovered during Darwin's Voyage to the Galapagos archipelago. Speciation is the development of one of multiple new species in the evolutionary process, where the original species produces mutated forms which successfully survive in other environments due to these mutations. EXAMPLE These 14 species belong to 4 genera: Geospiza Camarhynchus Certhidea Pinaroloxias
  8. EXAMPLE In case of Darwin finches adaptation occurred relatively rapidly. Blown over to various islands with various flora and fauna, beak morphology might ensure either the survival or death of the bird. For example, Wabler finches and ground finches have evolved from common ancestor. Wabler finches have long, thin beak perfectly for eating insects. Ground finches have thick, blunt beaks ideal for breaking over the husks of nuts and seeds.
  9. REGRESSION Regression evolution refers to the loss of useless characters over time. It is critical evolutionary process in all organisms. For example, human would be as hairy and tailed as other primates if regressive evolution did not prune unused ancestral traits. Natural selection may favor regression.
  10. EXAMPLE It is a process of partial or complete reduction of organs that have lost their adaptive significance. For example, replacement of the notochord by a cartilaginous skeleton and later by a bony skeleton in the process of vertebrate evolution, replacement of gills by lungs when vertebrate emerged onto dry land.
  11. EXTINCTION Natural selection is a process through which the traits that are helpful in the survival of an organism are passed on to the next generation while those that can hinder survival are eliminated. The extinction of species ( and larger groups) is closes tied to the process of natural selection and is thus major component of progressive evolution. In some passages of the Origin, Darwin seems to have seen extinction as part of natural selection, in other, as an inevitable outcome.
  12. CONT…. oDinosaurs become extinct sixty five million yeas ago. oThe end of species or group of species oNatural selection causes extinction Most common cause for extinction: 1. Species compete for limited resources 2. Environment resources ... individual can't survive