Download 8.2: More Evidence for Evolution: Anatomy, Embryology, and DNA

8.2: More Evidence for Evolution: Anatomy, Embryology, and DNA
As vertebrates evolved, the same bones were sometimes put to different uses. The structure of bones
gives away their evolutionary past.
Homologous Structures: structures that have similar structural elements and origin but may have a
different function.
Analogous Structures: structure of organisms that do not have a common evolutionary origin but
perform similar function.
Environmental factors pressure for the selection of structures to perform the same functions in different
species.
Embryology: the study of early pre-birth stages of an organism’s development.
At some time during development, all vertebrates have a supporting dorsal rod, called a notochord, and
paired pouches of the throat. In fish and some amphibians these pouches develop into gills. In humans
the first pouches will form the middle ear and auditory tube. The similarity of embryos provides
evidence of their common ancestry.
Genetic and biochemical research has provided evidence that supports evolution. Almost all living
organisms use the same basic biochemical molecules, including DNA, ATP, and many identical or nearly
identical enzymes.
The degree of similarity of DNA base sequences and amino acids sequences between two organisms is
thought to indicate their degree of relatedness.
Learning Check
1. Are the paired throat pouches in vertebrate embryos homologous or analogous structures? Justify
your choice.
2. Are a bird wing and an insect wing homologous or analogous structures? Explain.
3. All vertebrates have a protein hemoglobin. Like all proteins, hemoglobin is composed of a series of
amino acids. Which vertebrate would you expect to have hemoglobin most similar to human
hemoglobin; macaques (monkeys) or frogs? Explain Why.