According to current theories of evolution of organic world, total diversity of biological species evolved from universal single-celled progenitor organism of extremely primitive constitution.
These progenitors were heterotrophic and received nutrients from the primal ocean, enriched by simple organic compounds. Subsequent differentiation of these first organisms resulted in formation of eucariotic cells, autotrophic cells capable of photosynthesis and first multicellular colonies.
As a result of intensive photosynthesis large amounts of free oxygen appeared in the atmosphere. Thus more effective aerobic ways of metabolism became possible.
Having mastered photosynthesis and breathing, living organisms started to acclimate to the different zones and locations. These organisms were subjected to different sets of environmental factors. While adapting to these different conditions, organisms obtained different sets of adaptive features that were secured by the natural selection. The deeper was specialization of the group of organisms, the more unique set of features it developed. Thus the biological diversity had formed.
2. I am agree with the theory of evolution, because it explains in a logical and consistent way how the life had emerged and developed to its current diversity of species. Also theory of evolution explains the processes that are implemented widely by the human race since stone age to cultivate species of plants and animals in a fashion most fit to satisfy the needs and requirements of certain climatic zone.
Application of principles of natural and artificial selection allows to predict approximately what effects will have influence of certain factors during production of new breed or species and how should directional selection be performed to cultivate breeds or sorts with desired qualities.
Theory of evolution also makes sense of paleontologic discoveries and allows to analyze and predict relation between more or less distant groups of organisms based upon constitution of their predicted common progenitors.
3. Artificial selection and genetic engineering are widely applied in contemporary scientific research works, industrial processes and in production of agricultural goods. Logically arises question if these artificial, human-governed factors could influence natural processes of evolution.
Artificial selection is, in fact, natural selection that is directed and controlled to obtain certain desired features in a breed of an existent species. Artificial selection can result in formation of new species only if applied continuously over very extended periods of time. Such activity may contribute certain scientific interest but hardly could be economically profitable and, hence, hardly can be expected to happen.
Genetic engineering, though, is a tool that is potentially capable of much more swift and radical changes than natural or artificial selection could ever provide. So in theory it is possible to expect certain impact of products of genetic engineering upon natural evolution. That is why experiments based on genetic engineering should be designed carefully and well-thought before application.
1. BCB705 Biodiversity: Chapter2 – Evolution of Biodiversity. 3 Jun. 2008. The Department of Biodiversity & Conservation Biology and The University of the Western Cape. 3 January 2009 <http://planet.uwc.ac.za/nisl/biodiversity/Chapter2/index.html>