Why Are Living Organism So Diverse ?

Why are Living Organism so Diverse ?

Regardless of world's life diversity, we all, from the ant to the whale and us humans have DNA linkage, which gives us the evidence for one common ancestor. The question that comes up now is how from this very primitive common ancestor did we all end up so diverse. Biologist have dedicated they life to answer this question,

Through this essay I shall show how through different aspects life has become so diverse.

Timescale

Life as not evolve suddenly from its primitive form to complex organism like it is observed today, changes have operated over large timescales. For example Homo sapiens is the result of 4 million years of evolution from the Australopithecus afarensis. Homo sapiens as seen on diagram 1.1 as evolved through many evolutionary stages before becoming what he is today. This scale of time shows us how life has evolved gradually over great amount of time and through different stages. From this fact of gradual evolution, each organism today has evolved, each one over great timescales. This has given them the chances to be exposed to possible changes in environment and population. These changes than have given life the possibility to have substantial changes in its biodiversity. Therefore it can be seen that life diversity before and today is influence by gradual changes over large timescales. This principle is called gradualism, it was used by Darwin to explain biological evolution and the principle was influence by Charles Lyell (1797-1875) uniformitarianism and James Hutton (1721-1797).

Diagram 1.1 human evolutionary tree over 4 million years timescale

Environmental changes and differences

The change and difference in environment leads to adaptation between individuals, a good example would be the Galapagos finches. As seen on picture 1.1 three species of finch have evolved on different islands and environment, which than have lead to the diversity of three finches over each island. Each finches through environmental changes have evolved differently and have today physical adaptation to these environments, the cactus eater finch as a long and sharp beak to be able to eat cactus flowers and the pulp, the finch seed eater has a large beak which enable him to crack seeds and the finch insect eater has a narrow beak that gives him the ability to seize insects. The example of mantids camouflage show how diversity in the same species have evolved through environmental adaptation, in picture 1.2 we can observe the variety of physical adaptation among mantids. Through an environmental change, or an environment difference among specie it is possible to observe over time, the creation of new species by the result of adaptation to new conditions and natural selection. It is possible to identify different environmental evolutions, such as allopatric speciation and sympatric speciation. Allopatric speciation consist of the fact of the separation of two population by geographic factors which than leads to the formation of a new specie from its parent population, an example of this is the as seen in picture 1.3 is, antelope squirrels which have evolved from each different side of the Grand Canyon. Sympatric speciation consist of the fact that a population evolves to a new specie with out any geographical or any separation of the population.

The bottleneck effect can also explain how species can evolve at certain area to different species, for example if a great fire, flood, change in temperature occurs, than a great number of the population could be radically reduce to a small number and so would be the gene pool of that population. This would result that only certain genes alleles would be retain in the population and eventually the population of survivors might not resemble to the first population.

Therefore it is possible to argue that the diversity of living organism are due in part to the diversity of they environment which than by the drilling force of natural selection and adaptation have separated them into millions of different adapt organisms.

Picture 1.1 to show the diversity of finches and physical differences due to adaptation

Picture 1.2 To show the diversity of mantids (www.geocities.com/brisbane_hoppers/Mantids.htm)

Picture 1.3 To show the allopatric speciation of antelope squirrels in the Grand Canyon

Natural selection

The natural selection is one of the factor that leads to diversity of species, natural selection leads to changes in the gene pool by influencing the population sizes, therefore only certain genes and specific alleles are selected among individuals and this leads to the population adaptation to they environment.

A good up to date example of natural selection is the virus HIV (human immunodeficiency virus). The virus has rapid rates of reproduction and therefore a lot of variation exists among a large number of the individuals in the HIV population. While using drugs to treat this virus, researchers actually use natural selection among the HIV population. As few virus will always be resistant to the drug it is treated with, they will than pass on the genes that are resistant to this drug to the next generation of HIV, than by the mean of fast reproduction the HIV population becomes resistant to that drug. Artificial selection today has been widely used to create new species, in agriculture for example (picture 1.4) the wild mustard plant as been used to produce broccoli, cauliflower, cabbage, Brussels sprouts, kale and kohlrabi by selecting desired features in each part of the plant breeders have than reproduce and selected individuals to obtain a diversity of new species of plants.

We can than observe that through natural selection and artificial selection a wide range of species have arise.