Archive for the ‘Biology’ Category

Speciation or formation of new species is of a great concern to evolutionary biologists. At all times, scientists wondered how it happened that so many new species appeared on the planet. Yet before people could have a clue about genetics and heredity, Darwin presented his book On the Origin of Species (1859). According to Darwin, evolution was the result of natural selection. It was thought to be very long and durable process so that researchers looked for more evidence. In the era of genetics, the theory of Modern Synthesis introduced mutation and recombination as means of species formation (the 1930s). A decade later, the study of barriers to reproduction became popular. It said, there must be hurdles for mating for new species to emerge. In the 1990s, the mechanisms of speciation were reconsidered and it acquired ideas such as ecological speciation, sexual selection, genetic drift, and mutation-order speciation.

Processes of microevolution make the basis for us to understand these complex ideas that biologists and genetics developed over the 20th century. New species form as old species change their genes in some ways. Mutation, gene flow, genetic drift, and natural selection are considered to ensure species change their genes. Some genes randomly mutate and then can be passed to offspring. The interchange of genes is especially fast when carriers of these genes migrate. Genetic drift explains why offspring have more diversified genetic makeup than their parents. And natural selection is the old Darwin’s idea that only the species that best suit for survival can survive and reproduce.

Evolution of species has a lot to do with natural selection. Organisms with different phenotypes have different chances for survival in a particular environment. Some species are better suited to survive in hot conditions, other species are better suited to the cold environment. Naturally, they cannot exist side by side, because the natural selection has smartly chosen which genes are preferable on a particular territory.

Selective pressure is an inevitable part of natural selection. To be precise, there are dozens of pressures that make species die out, mutate, develop new traits essential to survive. Native African people, for example, never have a fair skin, and desert plants are always meant to store a lot of water in their cells. Obviously, only dark-skinned people are well-equipped to survive in the equatorial area. In course of evolution, water-rich succulents have outlived many plants that were not meant to survive with little water under the blazing sun.

Interestingly, the immune system is a strong selective pressure to pathogenic organisms. Some of them have phenotypes that make them highly resistant to the host’s immune reaction, which makes bacteria and viruses mutate. This way some pathogens can disguise themselves within the host, which makes them difficult to find or fight.

Climate, food, predators, diseases, and human influence are typical selective pressures. They urge organisms to move, transform, or die out – the fierce law of wild nature. When humans are better prepared to resist absolutely any trouble from within, animals are defenseless, and that makes natural selection work.