Natural Selection Theory Essay

• Explanation of the concept of natural selection and how it takes place The theory of natural selection was developed by Charles Darwin and Alfred Russel Wallace. They suggested that the mechanism of natural selection was that some organisms have characteristics that are better suited to the environment they live in then others that don’t have these characteristics. These organisms are then more expected to survive to reproduce offspring with these characteristics, over generations new organisms would be better adapted to the environment would evolve.

Natural selection occurs in a specific process that results in the formation of new species. This process includes: 1. A species produce more offspring than what can survive 2. In each species all the individuals have different variations. 3. The organisms with the variations better suited to their environment will survive and reproduce 4. Over generations more variations will evolve within the species making it better suited to its environment throughout the whole population. Natural Selection was the differential survival and reproduction of genotypes that were consistent to particular phenotypes.

Natural selection will only happen on an existing variation within a population. These variations can come about from mutation, which is the change in genetic code for a particular trait which leads to a change in the variations produced in a species. • Outline the evidence of natural selection There are a series of different studies that show evidence of natural selection these studies include: Palaeontology is the study of prehistoric life through fossils, footprints, and past climatic events.

As an organisms dies they sometimes leave behind pieces of bones which over time become fixed into rock and preserved. Over time as fossils are found information is gathered to form fossil records, this shows a timeline of the historical changes of an organism, where it can visually be seen the evolution of an organisms over a long period of time. For example a fossil that demonstrates the transition states between one form of a species and its offspring, this is known as transitional fossils. Comparative anatomy is the comparison of structures belonging to living things.

From studies of the structures of living things it was concluded that all living things have a common ancestor. All organisms that have a very similar structure and organisation of bones in the forelimb but have completely different movements are known as homologous structures, some of these organisms include: humans, bats, cats, alligators and whales, all these organisms have been concluded to have a common ancestor. Whereas any organisms that have completely different bone structures but have similar functions, do not have a common ancestor and only have similar functions because of the environment.

Comparative embryology is closely related species that have a similar embryological development. It was found that if various vertebrate animals are compared that those that are similar as embryos but later form completely different animals. When a species has similar embryos it also shows the chances of the species having a common ancestor. Biogeography is the study of organisms living all over the earth. It is used as evidence to support natural selection because by comparing similar species that have little adaptions so the species are best suited to their environment.

For example when Charles Darwin was studying finches on Galapagos Island, he noticed that they were similar to finches in South America but had differently shaped bills due to the food they would eat. Biochemical analysis: Biochemistry is the study of the process occurring inside living organisms. Many of the chemical reactions occurring in a human’s cell, a fungus and a bacterial cell are all different from each other however many are actually the same showing that all organisms share a common ancestry.

For example biochemical analysis can be used for respiration in mitochondria this process includes the testing for common mutations in mitochondrial DNA in blood and urine as well as POLG mutations and measurements of thymidine. Then if this shows a negative result they will begin to take tissue samples from skeletal muscle, the heart or liver where biochemical analysis is then used to measure the respiratory chain activities and the amount of coenzyme Q10, this then allows them to pinpoint the mitochondrial DNA arrangements and rearrangements.

Describe the historical development of evolution and assess social and political influences on these. At the beginning of the 19th century there was evidence available for evolution but no mechanism. At this point people preferred to believe that organisms were created by themselves. It wasn’t until Jean-Baptiste Lamarck proposed that environmental change began the start of changes in an organism =. Characteristics were now thought to be able to inherit. Inheritance was now believed to be the possible mechanism. This went on to be believed by everyone from 1801 up until 1831.

In 1831 Charles Darwin became a naturalist aboard the Beagle, where he visited Galapagos Islands and Australia, there he studied fauna and flora and also took notice of the geographical isolation of Australia In 1859 Charles Darwin published the book “origins of species”. After releasing it he was attacked by the church for saying that humans evolved from animals and not “made in gods image”. Cartoons were soon published in the media mocking Darwin’s theory of evolution. In the fall of 1924, John Scopes started teaching algebra, chemistry and physics.

At this same point in time there was an ongoing national debate about whether evolution should be taught in schools. This was due to Darwin’s theory that directly crossed over with the bible on the beginning of life. By 1925 Tennessee where he was working made it against the law. The American Civil Liberties Union wanted to challenge the new law in court. Scopes volunteered to be trialled under the new law after admitting he used a textbook involving evolution one time while being a substitute biology teacher. He saw this as his chance to stand up for academic freedom.

On July10, 1925 he appeared in a Dayton courtroom for trial. The trial topped headlines, Dayton was a religious community led many to believe that a guilty verdict was what had to happen. John Scopes was found guilty but was later overturned. How did this change to modern understanding of evolution • Explain how one advance in technology has changed scientific thinking about evolutionary relationships DNA Hybridisation is the process of by which DNA of different species can be compared. The process of DNA Hybridisation uses heat to separate the 2 strands of the double helix ladder from different species.

Once the heating strands of DNA reach 86°C the hydrogen bonds break at the complementary base pairs, resulting in single strand segments of DNA. These strands of DNA are then mixed together and left to cool. Single strands of DNA from either species will then start to chemically join together. If the two species are closely related the base pairs will come together and have a close temperature of separation normally at 86°C although if the separation temperatures are further apart usually less than 86°C and not many base pairs join together they are believed to not be closely related.

Before DNA hybridisation was introduced scientists at first classified the relations of species on analysis of visible traits, protein structures. They figured that two organisms that have similar protein structures are closely related by evolution. From DNA hybridisation scientists have now been able to determine how similar a species is through their genetic similarity this has allowed them to present evolutionary relationships more accurately. DNA hybridisation shows that humans are more closely related to chimpanzees than what a gorilla is. Describe a case study to explain a modern example of how environmental change can lead to a change in species Case Study: DDT and Mosquitoes Mosquitoes have a slender body, long legs, and one pair of scaled wings and are mostly smaller than 15 mm in length and weigh less than 2. 5mg. Mosquitos are very resilient insects, where the female population draw blood from a varying range of animals.

They were known to carry a number of various infectious diseases which include: Malaria, Chikungunya, Dog heartworm, Dengue, Yellow Fever, Lacrosse encephalitis, Eastern equine encephalitis, Western equine encephalitis, St. Louis encephalitis, West Nile Virus and Zika Virus. DDT was one of the first pesticide’s to be used all over the world. At first DDT was highly effective on the population of mosquitoes. However over time mosquitoes developed a resistance towards DDT. In the 1950s it was uncommon for a mosquito to be resistant however by the 1980s and 1990s most insects were resistant to the chemicals. DDT not only affected the mosquito population but also killed or harmed birds, fish and invertebrate species, like stoneflies and crayfish.

DDT did not break down in the environment or bodies of species, it is insoluble in water meaning it can’t just be washed away. Instead it dissolves in body fats of animals eventually as each species is eaten the prey of that animal will develop a higher concentration of DDT and so it will eventually reach the top of the food chain. DDT also slowed down the growth and photosynthesis in green algae, however in aquatic vertebrates it can cause nervous system disorders or reproductive disabilities which could potentially mean the species could die out.

Mosquitoes were sprayed with DDT in order to kill them off so it would cause a decrease the chances of a species getting any of the harmful diseases that they can carry. When a mosquito were sprayed with DDT it opens sodium ion channels in the neuron meaning they fire spontaneously and eventually leads to spasms and death. However when an insect becomes resistant to DDT they develop particular mutations in the sodium channel gene.

As the chemicals were sprayed all over the environments of where mosquitoes were they got over what they eat and would be ingested and eventually getting into the bloodstream and killing the mosquito. Although as the environment was sprayed more and more they began to develop variations and become resistant to the sprayed chemicals. This is an example of a micro evolution because as a species becomes resistant to the chemicals, they are able to reproduce offspring and pass on the resistance to DDT through many generations of the species.