Natural Selection Paper Essay Example

continent he observed that the fossils were different from the modern species and yet there was still a resemblance between the fossils and the modern organisms. In his book The Origin of Species Darwin stated that as descendants of the earliest life forms spread into various habitats, over time, they accumulated different adaptations to diverse ways of life.

In his view, evolution is like a tree with the various branches representing the evolution of different traits from a common trunk. this needs to be cited) How Natural Selection results in Biodiversity Natural selection is based upon a couple of important facts that result in unequal reproductive success. First, overpopulation and competition will affect the population of any species and individual variation will make some individuals more likely to survive and pass on these variations to their offspring (Campbell, et al, 2007). Second, adaptation is a mechanism for evolution due to generations of natural selection weeding out individuals that do not have the trait that is dominant at survival.

Biodiversity is short for biological diversity which consists of three main concepts: Ecosystem variety, species variety, and genetic variation within the species. These three biodiversity variables connect closely with the concepts of natural selection. Natural selection results in biodiversity in the following ways; overpopulation and competition are the primary considerations in the operation and success of an ecosystem. If there is no diversity in the species that exist in the ecosystems, there will be overpopulation and competition for the same foods and habitat. By the adaptation of the variety of species to non-competing food and habitat, an ecosystem can support itself. The species that successfully adapt to the non-competition

will be more successful at survival and natural selection occurs.

An example of adaptation and sharing an ecosystem is the savannah of Africa. Each of the species interacts with its environment in a cycle of giving nutrients and taking nutrients. The diverse species co-exist and actually contribute in some degree to the welfare of the other species. When biodiversity and adaptation do not occur, the species compete with each other until the populations are all at risk. Why Biodiversity is Important to Continued Evolution The three levels of biodiversity are as follows: diversity of the ecosystems, diversity of species within the communities, and diversity within species. The loss of species within the ecosystems and within the community can cause a catastrophic result, as species live and feed on other species.

Species close to extinction are endangered species, therefore protecting them from predators and offering the chance to reproduce and repopulate. Unfortunately, with little support within the environment, a species can become extinct due to population density. Proper monitoring of an endangered species is required in order to keep species actively reproducing and changing with the environment around them. There is another side to the biodiversity of the evolutionary field, as the population weakens the species start the inbreeding of smaller populations, thus playing a role in the extinction of a species. Inbreeding is reproduction among members of a species that are genetically similar.

The genetic inbreeding is designed to bolster populations of species whose numbers are in decline. However, when only a few species or varieties of a species are cultivated or survive, the genetic diversity of the organism declines, and population is more vulnerable to being wiped

out by new diseases or climate changes because of the inbreeding (Alters, 2000). Conservation biologists recognize that biodiversity can be sustained only if the evolutionary mechanisms that have given rise to species and communities of organisms continue to operate. The goal is to preserve individual species and sustain ecosystems where natural selection can continue to function (Campbell, 2004). The goal of preserving individual species can only be obtained when a successful habitat fragmentation and subdivided population is achieved.

The determination of a high-quality patch of land, free from predators and with abundant food sources, allows the reproductive cycle to start and maintain a constant reproduction of offspring, allowing the area to sustain the species. A habitat where a subpopulation’s reproductive success exceeds its death rate will allow individuals to disperse to other areas, often in search for food or places to reproduce. The migration of individuals allows the biodiversity of a species to be maintained and allows for continued evolution, resulting in ecosystem balance. Sources of Genetic Variation Genetic variation is the process by which basic mechanism of evolutionary change takes place.

Like the Mendellian patterns, there are recessive and dominant genes, but along side these inheritance studies are contributing factors such as structure of DNA, transcription of DNA to mRNA, translation of the mRNA to protein. Basically three areas are responsible for genetic ariation: mutation, gene flow, and sex. (cite Mendellain patterns) Mutation—This is a change in DNA or the hereditary components of life. Mutations are random, (Lederberg, 1967), and can be beneficial, neutral, or harmful to F1 as a result of germ line mutations or changes in reproductive cells during meiosis.

Some bacteria are antibiotic-resistant, some

are not, and some viruses have genetic coding that allows science to produce immunizing agents for them, whereas some like Human Immunodeficiency Virus, HIV, do not. In fact, recent research now shows the Duffy Antigen Receptor for Chemokines, (DARC), which evolved to protect Africans against malaria, actually makes them more susceptible to HIV. (Is this from Lederberg, 1967? ) Gene Flow— is also referred to as migration or movement of genes from one population to another such as cross-pollination with plants, or movement of genes from city to city with people. Gene flow can either be low rates such as plant pollination with limited distance, or high rate as in viruses carried by insects for several miles. Gene flow can introduce or reintroduce genes increasing the variation. In addition genes can move across populations reducing any likelihood of speciation.

Sex—Another descriptive word for this is shuffling or the congregating of genetic material which differentiates outcomes even within similar families. As haploid cells change to diploid cells resulting in 23 pairs of chromosomes, the meiotic process then configures the codons in three-letter combinations. As this sequencing takes place the variations of the sequences create numerous changes in the outcome or genetic variation. An example of this would be trisomy 21 which is the addition of a chromosome causing Down syndrome in humans.

Conclusion Ignoring the concept of natural selection would be unwise. The planet is constantly evolving and with biological diversity the descendants of survivors are able to adapt whether through mutation or variation and filling the gaps left those who are now extinct. The history of natural selection provides numerous examples that validate this process and there

are those being discovered even now. The theory of natural selection is one of the most important biological findings and should receive the acceptance it deserves.