Evolution

Following our nature walk before easter i began thinking about the process of evolution. Evolution was proposed almost simultaneously by two men, Charles Darwin as we all know, and Alfred Wallace (1). Evolution is driven by the struggle of living things to survive long enough to reproduce.Darwin and Wallace both noticed that animals often have many more offspring than are able to survive.

Geese have many goslings, a large number will not survive.

 They also saw that traits present in the parents were also present in the offspring. Now this was before the discovery of DNA so Darwin and Wallace did not know what caused this, but they knew it must be important. Today we know that these changes within a population are caused by a slight mutation of the genetic code, if this mutated genotype leads to a helpful phenotype then it may be passed on to future generations.

This is where the process known as 'Natural Selection' begins. Some animals inherited traits that gave them a higher likelyhood of surviving to reproduce. These animals will then pass successful traits to their offspring. Over time these traits may become more and more pronounced. (2) Now these changes can be anything from a different shaped beak that allows them to feed on something that their competetors can't, to a slightly different hip shape that allows an ancient primate to stand on its back legs for longer (2), you can see where the term 'survival of the fittest' come from.

The varied beaks of these finches allow them to avoid competition by feeding on different things.

 After many generations have passed, these differences will build up until the decendents of the original mutation will appear radicaly different (4). This will eventualy lead to the creation of a new species. After  Evolution is not limited to animals, though its effects may be more obvious, exactly the same processes happen in plants, bacteria and fungi, traits that allow for succesful competition will always florish in a population.

Not all changes however are based on survival to breed, others are know as 'Sexual Selection' (3). In this situation, traits that are desirable are chosen, usually by the female, are selcted for. In Birds of Paradise, males are often brightly coloured and put on complex dispays in order to attract a much less colourful mate.

The male dances to attract a mate, a bit like clubbing really.

A successful male will pass on his genes to his offspring, passing on traits that increase their chances of mating themselves.

The evidence for evolution is overwelming, fossil evidence combined with observations of nature show us that organisms change over time and produce the wonderous variety that we see everyday.

By
Rob Jones



(1) http://www.nhm.ac.uk/nature-online/evolution/what-is-evolution/the-theory/index.html
(2) http://www.nhm.ac.uk/nature-online/evolution/what-is-evolution/how-does-evol-work/index.html
(3) http://www.nhm.ac.uk/nature-online/evolution/sexual-reproduction/index.html
(4) http://www.newscientist.com/article/dn9953-instant-expert-evolution.html