All organisms share common ancestors- Species are populations of interbreeding organisms. Species differ from geographic regions, from ancestors that lived in the recent past, and in form and behavior.
- Populations divide over time, evolving to fit new environments. Fossil evidence supports this claim.
- Shared ancestry explains common traits between species, such as embryonic development, anatomy, and biochemical processes.
- Similarities in Embryonic Development
Embryos also provide evidence for common ancestry. Embryonic development is similar among various species. The embryos of man, pig, reptile, and bird shown to the right. In addition, all embryos have a tail and pharyngeal pouches at early stages of development.
- Similarities in Anatomical Structures
Many organisms share structural similarities, such as the skeletal organization pictured on the left. These structures are homologous structures, or features that are similar in arrangement or function that origination from a common evolutionary origin.
However, not all homologous structures are similar in function. Some structures that are present in organisms are no longer used for their original purposes. Such structures are known as vestigial structures, and are strong evidence of descent from common ancestry.
- Similarities in Biochemical Processes
Biochemical evidence also supports the theory of common ancestry. Nucleic acids, DNA and RNA, are present in nearly all organisms. These nucleic acids are necessary to create proteins and enzymes. One such enzyme is adenosine triphosphate, or ATP. ATP is used in nearly all life to power cellular processes.
