The theory of evolution is based on the idea that all species are related and gradually change over time. All animals undergo changes as each new generation succeeds the one before them. The changes are very minor and very hard to recognize but over thousands of years, They completely change the lifestyle of the species. This process allows animals to discover new opportunities in the environment and deal with changes occurring in the surrounding. in short, It is modifying the previous characteristics of a species by very small cell mutations.
Evolution is made possible by the variation that exists within the animals, It occurs mainly because animals have to compete with each other over a limited source of food and space. In this competition, Some characteristics have proven to be better than other characteristics. This means the animals who own better properties are going to reproduce better and quickly. In contrast to those, Who have poor properties will have difficulty to survive and reproduce. The ones with the winning properties will widespread, And the one with the poor properties will eventually decrease in number and then extinct. This is called natures selection.
species and speciation
A specie is any group of animals that have the potential to interbreed and that, under normal circumstance, does not breed with any other group. speciation is one of the evolutionary processes that bring about new species. It usually occurs when an existing species become split up into 2 or more isolated groups, which are kept apart due to physical barriers, such as seas and mountains or by the change in behavior. speciation is difficult to observe as it occurs very slowly, but evidence of it is not that hard to find.
Extinction is a part of evolution. As for some species to succeed some should lose. The process of extinction occurs to those who are unable to adapt accordingly to the surrounding changes leading to reproduce less and lead to extinction. Dinosaurs are a great example of mass extinction. They could not survive the changes occurring in the environment and were swept away 65 million years ago. Today the major cause of animal extinction is human interference in the ecosystem like deforestation and rapid industrialization which are destroying animal habitats.
Unrelated animals often develop very noticeable similarities. for example, sharks and dolphins are fundamentally very different, but both have streamlined bodies with upright dorsal fin, a shape of the fin that gives them speed and stability underwater. While moles and marsupial moles share a range of adaptations for life underground, Amphisbaenians and caecillians also look very similar, although the former are reptiles and the latter are highly unusual amphibians. such similarities are the result of convergent evolution, a process in which natural selection comes up with the same adaptation a particular way of life.
Animals partnership is a natural way of promoting mutualism. There are different kinds of animal partnerships. A partnership in which both the animals are equally benefited like oxpeckers and large mammals such as hippos this partnership is called mutualism. There are partnerships like insects helping in pollination in which they can not survive without each other. Remoras and their host fish are also a type of animal partnership in which one is being benefitted but the other has no such benefit in this partnership known as the commensal partnership.
The animal partnership may seem obliging but all the members are driven by their own interest and benefits. If one partner leads the balance in its favor the natural selection will help it such as parasites that live on the expense of the host’s body.
The present-day distribution of animals is the combined result of many factors. Among them are continental drift and volcanic activity, which constantly reshape the surface of the earth. By splitting up groups of animals, and creating completely new habitats, these geological processes have had a profound impact on animal life. One of the most important effects can be seen on remote islands, such as Australia and Madagascar, which have been isolated from the rest of the world for millions of years. Until humans arrived, their land-based animals lived in total seclusion, unaffected by competitors from outside.
The result is a whole range of indigenous species, such as kangaroos and lemurs, which are found nowhere outside their native homes. Animals are separated when continents drift apart, and they are brought together when they collide. The distribution of animals is evidence of such events long after they occur. For example, Australasia and Southeast Asia became close neighbors long ago, but their wildlife remains entirely different: it is divided by “Wallace’s line”, an invisible boundary that indicates where the continents came together.