Evolution Evidence

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Evolution Evidence

Evidence of Evolution

Similarities in Genes and ChromosomesOrganisms with similar genes and chromosomes show a common ancestor. This shows evolution because genes had to have been passed down from generation to generation to share similar characteristics. Cladistics is a classification in which organisms are grouped together based on whether or not they have one or more shared unique characteristics that come from the last common ancestor. Scientists believe that the higher number of characteristics two or more organisms share, the more recently they developed from a common ancestor. these groups are called clades.

Geographic DistributionGeographic distribution is the natural arrangement of animals and plants in particular regions. Darwin explored the islands of the Galapagos and discovered that all the birds were finches but each had different characteristics suited to their environment. He decided that the birds descended with modification from a common ancestor, Darwin also concluded that although animals that had similar anatomies and behaviors lived in different regions, they all were exposed to similar situations of natural selection and ecologic conditions and ended up evolving with similar features.

Natural and Artificial SelectionNatural selection is also referred to as surival of the fittest. Individuals that are better suited to their environment survive and reproduce most sucessfully. Organisms with characteristics that are not well suited to their environment either die or have few offspring. In both natural and artificial selection, only certain traits are selected and individuals with these specific traits are selected to produce new individuals.

Chemical and Anatomical SimilaritiesBy Darwin's time, scientist noticed that many living vertebrates had similar body parts, but varied in form and functions. Limbs such as a bird's wings or a dolphin's flipper vary in function but are constructed in similar ways. Structures that have different forms but develop from the same embryonic tissues are homologous. Not all homologous structures serve important purposes; these structures are called vestigial organs. These organs resemble homologous organs in other species but do not serve a key purpose in the species with the vestigial organs. Analogous structures are another example of evolutional evidence. These include different species with similar structues, but do not share a common ancestor.

Fossil RecordIn Darwin's time, it was already known that different layers of rock were formed at different periods of Earth's history and that fossils were the remains and evidence of ancient times. Darwin observed that numerous species walked the Earth and then vanished. Noticing the changes in size, shapes and varities of fossils, Darwin concluded that life on Earth changed over time.

Fossil Record

Natural Selection

Geologic Distribution

Chemical and Anatomical Similarities


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