Evolution is the process in which modern organisms have descended from ancient organisms over time. Charles Darwin was known as the 'Father of Evolution", he developed the theory of evolution to explain the unity and diversity of life. Evolutionary biology is the study of how evolution occurs. The basic idea of evolution is that species change over time in order to adjust to their surroundings.
Darwin's Theory of Evolution
Charles Darwin's theory was based on natural selection, natural selection explains how different populations can evolve in a way where they can sustain themselves longer in a specific environment. From Darwin's theory grew another term, survival of the fittest, which means that the animals that were capable of adjusting were the only ones that lived and stayed long enough to reproduce. For example, the peppered moth became darker after the industrial revolution, this made it harder for the peppered moths to become prey, while some of the peppered moths didn't become darker, this caused them to fall prey to predatory animals. Some of the variations can help the peppered moths survive, and therefore maintain a stable population. These traits develop over years, and therefore more and more animals of the same species get these desirable adaptations, adaptations are favorable heritable features, for example how the antarctic fish have 'antifreeze' potions in their blood. These animals soon will become better suited for the environment so all of them can live longer. An example of Darwin's theory being applied was found in Galapagos Island. When the finches arrived on the island they all had the same beak shape, but as they explored the different islands and began inhabiting different islands, the finch's beak shape began to change. This was due to the fact that the birds had different types of foods that they had available. For example, the finches that ate seeds had different beaks than the birds that ate leaves. Therefore the finch population evolved and changed in order to survive.
Artificial selection is like natural selection, but this is where humans chose the "desirable traits" they want an animal or plant to have. For example, the dog called Labradoodle is a mix between a labrador retriever and a poodle. Breeders can take desirable traits from each breed and breed them together to get the desirable combo. However, artificial selection and natural selection are different, humans have no control over natural selection, hence the name NATURAL selection.
Different Types of Structural Evidence
Homologous structures are physical traits in a species that have been inherited by a common ancestor. An example of this would be the limbs of a whale, a human, and a bird. Although they are each meant to operate in a different environment, if you look at the bone structure they are quite similar. Vestigial structures are structures that have lost all al the dedicated function in a given species. The most common example of a vestigial structure is the human tail. The tailbone after year and year of evolution has reduced down just to the tailbone. An Analogous Structure evolved independently in different organisms because the organisms lived in similar environments or experienced similar selective pressure.