Answer:
Homologous structures are similar body parts in different species that indicate the species are related by evolution. The similarity of bat wings and human arms indicate that these
two types of organisms share a common ancestor. The forelimbs of vertebrates contain the same
sets of bones organized in similar ways, even though these forelimbs may function in different
ways today.
Organisms that seem very different in their adult forms may have similarities duringem bryological development. Such similarities indicate an evolutionary relationship between
species. For example, all vertebrates have a notochord and pharyngeal pouches early in
development. In fishes and amphibians, these pouches become gills. In humans, two pairs of
pouches differentiate into several structures, including the middle ear cavity, tonsils, and certain
glands. This similarity is explained if fish were an earlier and less developed vertebrate than
humans.The fact that almost all known living organisms use similar set of biological molecules also suggests that these organisms descended from a single common ancestor.
Organisms use the same 20 amino acids to make their proteins. Organisms store their genetic
information in DNA and use ATP as the main energy carrier. Also, very different organisms have
many similar enzymes.