Evo

LIFE IN THE PAST - EVOLUTION Darshil Shah Evolution is the process of development of complex living things from earlier simpler forms. Evolution has been thought of for years in ancient and in more modern times. Everyone knows Charles Darwin and Alfred Wallace as the fathers of evolution, who raised issues both scientifically and religiously which still continue to be debated today. Jean Lamarck first proposed a mechanism for evolution. Lamarck suggested that evolution occurs when the environment acts on an organism and causes it to change, whereas Charles Darwin suggested that only the fittest (them most suited to the environment) survive. For example, Lamarck would say that giraffes’ necks became long to reach the leaves on the trees. Darwin would say that only giraffes with long necks survive and pass the characteristics on to their offspring. The most sensible theory or idea is expressed by Lamarck because there is no question of how the animals can have greatly different characteristics in the same place at very short periods of times. Even though both theories are questionable (such as what drives the force of evolution) Lamarck portrays it simply as something that changes because it has to instead of the gene pool spreading and enlarging over such a short period of time in a very unrealistic change. The diagram shows the popular island flinches. Darwin noted how each bird had different characteristics on different islands. This is how divergent evolution works. The ‘new’ isolated population evolves to ‘fit’ in their new environment. Convergent evolution works when two unrelated species share similar environment and gradually develop the same characteristics. Examples are Sharks, Dolphins and Whales who all have similar body shapes. The fossil record also provides evidence for evolution. Darwin noted how modern armadillos in South America show how they developed from a common ancestor. Comparative anatomy also provides evidence for evolution. Modern horses can be traced to 60-million old ancestors. The forelimbs of unrelated vertebrates show how they developed from a common ancestor. Comparative embryology has shows that embryos of some animals of some vertebrates have structures that may lead to a common ancestor or the evolutionary past. For example, human embryos have a yolk sac, gill slits and a tail in their early stage (so do fishes, lizards, chickens and many more). Biogeographical evidence can also suggest common ancestors for evolution. For example, there are two distinct species worldwide of whip bird on the east and west coast of Australia. They were once found everywhere in Australia, but now they are separate and have their own characteristics. There is increasing genetic and biochemical evidence providing links with common ancestors. DNA testing has shows links with humans and other primates.