They argued that the embryos of 'higher' animals went through or recapitulated a series of stages, each of which resembled an animal lower down the great chain of being. For example, the brain of a human embryo looked first like that of a fishthen in turn like that of a reptilebirdand mammal before becoming clearly human.
What is Darwin's Theory of Evolution? Changes that allow an organism to better adapt to its environment will help it survive and have more offspring. Evolution by natural selection is one of the best substantiated theories in the history of science, supported by evidence from a wide variety of scientific disciplines, including paleontology, geology, genetics and developmental biology.
More simply put, the theory can be described as "descent with modification," said Briana Pobiner, an anthropologist and educator at the Smithsonian Institution National Museum of Natural History in Washington, D.
The theory is sometimes described as " survival of the fittest ," but that can be misleading, Pobiner said. Here, "fitness" refers not to an organism's strength or athletic ability, but rather the ability to survive and reproduce.
For example, a study on human evolution on 1, students, published online in the journal Personality and Individual Differences in Octoberfound that many people may have trouble finding a mate because of rapidly changing social technological advances that are evolving faster than humans.
As a hypothetical example, Darwin used North American black bears, which were known to catch insects by swimming in the water with their mouths open: The idea didn't go over very well with the public. Darwin was so embarrassed by the ridicule he received that the swimming-bear passage was removed from later editions of the book.
Scientists now know that Darwin had the right idea but the wrong animal. Instead of looking at bears, he should have instead been looking at cows and hippopotamuses. The story of the origin of whales is one of evolution's most fascinating tales and one of the best examples scientists have of natural selection.
The last shore-dwelling ancestor of modern whales was Sinonyx, top left, a hyena-like animal. Over 60 million years, several transitional forms evolved: NOAA Natural selection To understand the origin of whales, it's necessary to have a basic understanding of how natural selection works.
Natural selection can change a species in small ways, causing a population to change color or size over the course of several generations. This is called "microevolution. Given enough time and enough accumulated changes, natural selection can create entirely new species, known as "macroevolution.
Take the example of whales — using evolution as their guide and knowing how natural selection works, biologists knew that the transition of early whales from land to water occurred in a series of predictable steps. The evolution of the blowhole, for example, might have happened in the following way: Random genetic changes resulted in at least one whale having its nostrils placed farther back on its head.
Those animals with this adaptation would have been better suited to a marine lifestyle, since they would not have had to completely surface to breathe.
Such animals would have been more successful and had more offspring. In later generations, more genetic changes occurred, moving the nose farther back on the head. Other body parts of early whales also changed. Front legs became flippers. Their bodies became more streamlined and they developed tail flukes to better propel themselves through water.
Darwin also described a form of natural selection that depends on an organism's success at attracting a mate, a process known as sexual selection. The colorful plumage of peacocks and the antlers of male deer are both examples of traits that evolved under this type of selection.Brief biographical information about Charles Darwin and Alfred Russel Wallace intended to convey how their respective backgrounds and characters gave them potential towards the development of the .
In , Charles Darwin received a letter from Wallace, in which Darwin's as-yet-unpublished theory of evolution and adaptation was precisely detailed.
Darwin and his colleagues arranged for Wallace's paper to be read at the July 1, meeting of the Linnean Society, along with . The evolutionary embryologist Gavin de Beer anticipated evolutionary developmental biology in his book Embryos and Ancestors, by showing that evolution could occur by heterochrony, such as in the retention of juvenile features in the adult.
Ecological evolutionary developmental biology (eco-evo-devo) integrates research from developmental biology and ecology to examine their relationship with evolutionary theory. Researchers study concepts and mechanisms such as developmental plasticity, epigenetic inheritance, genetic assimilation, niche construction and symbiosis.
The Concept of Evolution to First published Tue May 17, ; substantive revision Tue Jun 3, [ Editor's Note: The following revised entry has a new title. The scientific theory of evolution by natural selection was proposed by Charles Darwin and Alfred Russel Wallace in the midth century and was set out in detail in Darwin's book On the Origin of Species ().
Evolution by natural selection was first demonstrated by the observation that more offspring are often produced than can possibly survive.