Speciation Evolution explained
Mutation • The DNA in genes in all living things acts as a blue print for the production of various proteins. • Proteins made from the DNA in cells include enzymes that affect growth and the production of pigments in hair, skin, flowers and photosynthetic pigments, digestive enzymes, cell structures and the immune system. • A change in DNA sequence is called a mutation. • Due to the frequency of cell replication mutation naturally at a low rate.
Mutation cont’d • However, UV radiation and certain chemicals in the environment can increase the rate of mutation. • Mutations as a whole are generally detrimental to an organism as the proteins required for survival are no longer produced. • Many mutations are neutral and cause no effect. • But on the odd occasion a mutation arises that gives the individual the heads up where survival is concerned, and therefore will be favoured by natural selection. • Variation arising from mutation and thereby natural selection is the basis by which evolution acts.
In the case of disease in humans, such people with genetic mutations decreases their chance of survival and therefore ability to reproduce. This in turn means that the mutated genes have less chance of surviving in the population of future generations. However, in recent times medical technology has increased the life span of such people and therefore their likely hood of reproducing. What does this mean for unfavourable genes in the future poplulation?
Mutation • In some cases mutation causes the duplication of a particular gene. • Since one copy of the original gene can keep functioning as normal, the other may evolve a different role. • Eg. • The DoucLangur eats leaves which is made possible by the second but different copy of enzyme RNASE IB
Speciation • Speciation, the formation of new species, can occur by two means: • 1. Reproductive Isolation • 2. Geographical Isoloation • In both cases a population is forced to split due to environmental conditions (weather such as ice age) or barriers (such as river or mountains) • Years will pass and genetic differences will accumulate leading to both populations being unable to interbreed. • In some instances reproductive isolation can occur by a single large-scale genetic change, producing a separate species in one generation.
Examples of sceciation Reproductive Isolation Darwin’s Finches