2.07 Evidence of Evolution 1

According to evolution, an organism's characteristics arose from similar characteristics that existed in the organism's ancestors.

Comparative anatomy presents scientists with evidence that all vertebrate animals - birds, reptiles, mammals, and amphibians- arose from a common ancestor millions of years ago. Evidence from fossils indicates that the ancestors of vertebrates had many of the same structures of animals that live today.

Several lines of evidence from anatomy and development support the theory of evolution.

Comparative embryology, comparative anatomy, and the study of vestigial structures all show evolutionary relationships over time. Those comparisons reveal evolutionary relationships among species by revealing the shared ancestry of their structures.

Similarity in homologous structures implies that the underlying structure arose in a common ancestor and became modified as different populations adapted to different environments.

Continued modification of bones resulted in somewhat different shapes as populations of different species were adapted to different environments.

Vertebrate embryos develop in similar ways, suggesting that vertebrates share genes derived from a common ancestor.

Development and differentiation are processes under the control of genes. Similar patterns of early embryonic development suggest that vertebrates shares the genetic heritage of a common ancestor. Comparative embryology is the scientific comparison of different types of embryos.

Similar structures in different species that are modified from those of a common ancestor are known as homologous structures.

Homologous structures have different functions, but they are made of bones derived from a common ancestors. Structural similarity between organisms, suggests shared evolutionary history.

Many different lines of scientific evidence support the theory of evolution by natural selection.

Three main lines of evidence support this aspect of the theory of evolution: Anatomical similarities: Many organisms have similar anatomical features such as limbs. Embryonic development: Some features become apparent as an embryo develops. Vestigial structures: Some features that has a function in an organism's ancestors no longer have that function.

The existence of vestigial structures supports the idea of descent with modification.

Vestigial structures are features that appear to be necessary adaptations in the ancestors of modern-day organisms, but when the environment changes, the structures lost their function.