Nous utilisons des cookies pour comprendre comment vous utilisez notre site et pour améliorer votre expérience. Cela inclut la personnalisation du contenu et de la publicité. En continuant à utiliser notre site, vous acceptez l'utilisation de cookies, la politique de confidentialité et les conditions d'utilisation. Cookies, Privacy Policy Term of use.
Video Player is loading.
Current Time 0:00
Duration 0:00
Loaded: 0%
Stream Type LIVE
Remaining Time 0:00
 
1x
34 views • August 18, 2016

How Evolution Works | What Is Evolution?

Natural World Facts
Welcome to another episode of Natural World Facts! This fact file is all about What Is Evolution. How evolution works: Okay, so first of all, what is Evolution? The theory of evolution by natural selection is the process through which organisms change over time as a result of changes in physical or behavioural traits. These changes will allow an organism to adapt better to its environment and thus help it survive and have more offspring.  Natural selection can change a species in very small ways, causing a population to change colour or size over the course of several generations. This is called “microevolution." But natural selection is also capable of a lot more. Given enough time and enough accumulated changes, natural selection can create entirely new species, known as "macroevolution." It was able to turn dinosaurs into birds, amphibious mammals into whales and the ancestors of apes into humans. For example, In "The Origin of Species,” Charles Darwin came up with a theory about how natural selection could cause a land mammal to turn into a whale. Darwin used North American black bears as an example, which were known to catch fish by swimming in the water with their mouths open. The transition of early whales from land to water happened in a series of predictable steps. The evolution of the blowhole, for example, might have happened through random genetic changes that resulted in at least one whale having its nostrils placed farther back on its head. Those animals with this adaptation would have been more suited to a marine lifestyle, as they would not have had to completely surface to breathe. Such individuals would have been more successful and produced more offspring. Other body parts of early whales also changed. Front legs became flippers. Back legs disappeared as they were no longer needed, Their bodies became more streamlined and they developed large tails to propel themselves through water. Darwin also theorised a form of natural selection that depends on an organism's success at attracting a mate, a process known as sexual selection. The brightly coloured plumage of peacocks and the antlers of male deer are both examples of traits that evolved to better their chances of reproducing. The physical and behavioural changes that make natural selection possible happen because of mutations of an animals DNA and genes. Mutations can be caused by random errors in the DNA, or by chemical damage. Mutations are usually harmful or neutral, but sometimes a mutation can be beneficial to the organism and allow it to become better suited to its lifestyle. If so, it will become more successful in the next generation and spread throughout the population. In this way, natural selection is guiding the process of evolution by keeping and preserving the beneficial mutations and rejecting the bad ones through the animals success. But where is the evidence for all this? Although scientists could predict what early whales should look like, they hadn’t found the fossil evidence to back them up. Creationists took this as proof that evolution didn't occur and mocked the idea that there could ever have been a walking whale. But in 1994, palaeontologists found the fossilised remains of ‘Ambulocetus natans', an animal whose name translates as "swimming-walking whale." Its forelimbs had fingers and small hooves but its hind feet were enormous for its size. It was distinctly adapted for swimming, but it was also capable of moving clumsily on land, much like a seal. When it swam, it moved much like an otter, pushing back with its hind feet and rolling its spine and tail side to side. Modern whales move through the water using powerful beats of their horizontal tails, but Ambulocetus had a whip-like tail and used its legs for propulsion through water. Natural World Facts is a channel dedicated to bringing you fascinating facts about our natural world, and the wonderful animals that we share it with. Subscribe for more videos! Leave a suggestion in the comments for what animal you would like to learn about next. OUR WEBSITE: ht
Show All
Comment 0