Question

While fishing you discover two types of mullet.  Some of the mullet jump out of the water frequently and some never jump.  You bring some mullet back to your special mullet lab and keep them for a generation.   The jumping trait appears to be under genetic control.  You monitor the wild population for several years and notice if one form becomes more common one year then it typically becomes less common the next year.  What is the most likely explanation for the evolution and persistence of these two forms (in other words why are there two forms rather than just one)?  Briefly describe how you would test your hypothesis.

Answer 1

Answer: Evolution is a continuous process, and is simply defined as descent with modification which comprises evolutionary changes of an organism at a various level such as genetic and population level. To understand the process of evolution, one has to understand evolutionary theories. This will give an idea about how life changes after its origin and how it is diversified. Charles Robert Darwin in 1859 proposed the theory evolution of an organism, that all the species are evolved from a common ancestor over the period of time, and is termed as the theory of natural selection. Darwin also provided evidence and explanation for their proposed theory in his book "The origin of species". He concluded that variation among the organisms already exists in a individuals of a species. None of the two individuals is similar, they display enormous variability at different levels. When the individuals of a species start growing, there will be the scarcity of resources which lead to the competition among themselves. Such competition will lead to the survival of only those organisms which are fittest. This is called survival of the fittest. The survival in the struggle for existence is a non-random phenomena and it depends on the heredity constitutions of an individual. Over a period of time, this process of natural selection leads to the gradual changes in the population and produce a new species. In the above-mentioned example, some of the mullet jump out of the water frequently and some never jump means variation in the population already exists. The trait was under genetic control, and after several years one form becomes more common and subsequently, it becomes less common in the next year. This suggests, only those individuals can survive which are having advantageous variation in the population (survival of the fittest). Some of the examples of natural selection are known, like industrial melanism in insect moth, Biston betularia in England. Before 1800, the moth was typically white coloured and the dark or black coloured moth population were rare but after the industrial revolution in England, the tree trunks become darker and allowed the white coloured species to become easy prey for the predators as compared to the dark coloured one. Another example is the evolution of drug resistance against HIV. The drug lamivudine (3TC) is a nucleoside inhibitor, it is an analogue of cytidine. During the reverse transcriptase, if there is the incorporation of 3TC instead of normal cytosine, it inhibits the process of DNA replications. The addition of 3TC leads to the additional driving force for the evolution of other forms of viruses, favouring the reproduction of resistance individuals and ultimately leads to the drug resistance.