Since Darwin developed his ideas on descent with modification and the pressures of natural selection, a variety of evidence has been gathered supporting the theory of evolution.
Fossil evidence shows the changes in lineages over millions of years, such as in hominids and horses. Studying anatomy allows scientists to identify homologous structures across diverse groups of related organisms, such as leg bones. Vestigial structures also offer clues to common ancestors. Using embryology, scientists can identify common ancestors through structures present only during development and not in the adult form.
Biogeography offers further clues about evolutionary relationships. The presence of related organisms across continents indicates when these organisms may have evolved. For example, some flora and fauna of the northern continents are similar across these landmasses but distinct from that of the southern continents.
Islands such as Australia and the Galapagos chain often have unique species that evolved after these landmasses separated from the mainland. Finally, molecular biology provides data supporting the theory of evolution. In particular, the universality of DNA and near universality of the genetic code for proteins shows that all life once shared a common ancestor.
DNA also provides clues into how evolution may have happened. Gene duplications allow one copy to undergo mutational events without harming an organism, as one copy continues to produce functional protein. Many misconceptions exist about the theory of evolution—including some perpetuated by critics of the theory.
First, evolution as a scientific theory means that it has years of observation and accumulated data supporting it. Another misconception is that individuals evolve, though in fact it is populations that evolve over time. Individuals simply carry mutations. Furthermore, these mutations neither arise on purpose nor do they arise in response to an environmental pressure.
Instead, mutations in DNA happen spontaneously and are already present in individuals of a population when a selective pressure occurs.
Once the environment begins to favor a particular trait, then those individuals already carrying that mutation will have a selective advantage and are likely to survive better and outproduce others without the adaptation. Finally, the theory of evolution does not in fact address the origins of life on this planet.
Scientists believe that we cannot, in fact, repeat the circumstances that led to life on Earth because at this time life already exists. The presence of life has so dramatically changed the environment that the origins cannot be totally produced for study. Answer the question s below to see how well you understand the topics covered in the previous section.
This short quiz does not count toward your grade in the class, and you can retake it an unlimited number of times. Use this quiz to check your understanding and decide whether to 1 study the previous section further or 2 move on to the next section. Skip to main content. Module Theory of Evolution. Search for:. Evidence for Evolution Describe how the theory of evolution by natural selection is supported by evidence The evidence for evolution is compelling and extensive.
Learning Objectives Outline physical evidence that supports the theory of evolution Outline biological evidence that supports the theory of evolution Refute common misconceptions about evolution. Visit this interactive site to guess which bones structures are homologous and which are analogous, and see examples of evolutionary adaptations to illustrate these concepts. This site addresses some of the main misconceptions associated with the theory of evolution.
In Summary: Evidence for Evolution Since Darwin developed his ideas on descent with modification and the pressures of natural selection, a variety of evidence has been gathered supporting the theory of evolution. Licenses and Attributions. CC licensed content, Original. This is the process by which a single species evolves into many new species to fill available ecological niches. They spent more than 30 years on the project, but their efforts paid off. They were able to observe evolution by natural selection actually taking place.
Birds with smaller beaks could crack open and eat only the smaller seeds. Birds with bigger beaks could crack open and eat seeds of all sizes. As a result, many of the smaller-beaked birds died in the drought, whereas birds with bigger beaks survived and reproduced. In other words, evolution by natural selection had occurred. The Galapagos finches remain one of our world's greatest examples of adaptive radiation. Watch as these evolutionary biologists detail their year project to document the evolution of these famous finches:.
A Horse Is a Horse, of Course, of Course This drawing was created in , but it's likely that you recognize the animal it depicts as a horse. The fossil record reveals how horses evolved. The lineage that led to modern horses Equus grew taller over time from the 0. This lineage also developed longer molar teeth and the degeneration of the outer phalanges on the feet. They became taller, which would help them see predators while they fed in tall grasses. Eventually, they reached a height of about 1.
They evolved a single large toe that eventually became a hoof. This would help them run swiftly and escape predators. Their molars back teeth became longer and covered with hard cement.
This would allow them to grind tough grasses and grass seeds without wearing out their teeth. Evidence from Living Species Scientists can learn a great deal about evolution by studying living species. Insects such as praying mantis and water boatman also have homologous limbs. Cat legs and praying mantis legs are analogous - looking similar but from different evolutionary lineages. Comparative Embryology Comparative embryology is the study of the similarities and differences in the embryos of different species.
Rows I, II, and III illustrate the development of the embryos of fish on the far left, salamander, tortoise, chick, hog, calf, rabbit, and human on the far right, from the earliest to the latest stages.
Vestigial Structures Structures like the human tail bone are called vestigial structures. Comparing DNA Darwin could compare only the anatomy and embryos of living things. This cladogram is based on DNA comparisons. It shows how humans are related to apes by descent from common ancestors. Humans are most closely related to chimpanzees and Bonobo our common ancestor existed most recently.
We are less closely related to gorillas, and even less closely related to Orangutan. Evidence from Biogeography Biogeography is the study of how and why organisms live where they do. Camel Migrations and Present-Day Variation. Members of the camel family now live in different parts of the world. They differ from one another in a number of traits. However, they share basic similarities.
This is because they all evolved from a common ancestor. What differences and similarities do you see? Island Biogeography The biogeography of islands yields some of the best evidence for evolution. Those eating buds and fruits have the largest beaks. Insect and grub eaters have narrower beaks. The left graph shows the beak sizes of the entire finch population studied by the Grants in The right graph shows the beak sizes of the survivors in A clear example of homologous structures is the forelimb of mammals.
When examined closely, the forelimbs of humans, whales, dogs, and bats all are very similar in structure. Each possesses the same number of bones, arranged in almost the same way. While they have different external features and they function in different ways, the embryological development and anatomical similarities in form are striking.
By comparing the anatomy of these organisms, scientists have determined that they share a common evolutionary ancestor and in an evolutionary sense, they are relatively closely related. Other organisms have anatomical structures that function in very similar ways, however, morphologically and developmentally these structures are very different.
These are called analogous structures. Since these structures are so different, even though they have the same function, they do not indicate an evolutionary relationship nor that two species share a common ancestor. For example, the wings of a bird and dragonfly both serve the same function; they help the organism to fly. However, when comparing the anatomy of these wings, they are very different.
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