13.4 Flashcards
Note 1 —-»
Evolution is a process of descent with modification—characteristics present in an ancestral organism are altered over time by natural selection as its descendants face different environmental conditions. In other words, evolution is a remodeling process. As a result, related species can have characteristics that have an underlying similarity yet function differently. Similarity resulting from common ancestry is known as homology.
Homology
The similarity in characteristics resulting from shared ancestry.
Homologous Structures
Structures in different species that are similar because of common ancestry.
Molecular Biology
The study of biological structures, functions, and heredity at the molecular level.
Note 4 —-»
If two species have homologous genes with sequences that match closely, biologists conclude that these sequences must have been inherited from a relatively recent common ancestor. Conversely, the greater the number of sequence differences between species, the more distant is their last common ancestor. Molecular comparisons between diverse organisms have allowed biologists to develop hypotheses about the evolutionary divergence of major branches on the tree of life, as you learned in the previous module on the origin of whales.
Note 3 —-»
If two species have homologous genes with sequences that match closely, biologists conclude that these sequences must have been inherited from a relatively recent common ancestor. Conversely, the greater the number of sequence differences between species, the more distant is their last common ancestor. Molecular comparisons between diverse organisms have allowed biologists to develop hypotheses about the evolutionary divergence of major branches on the tree of life, as you learned in the previous module on the origin of whales.
Note 4 —-»
Darwin’s boldest hypothesis was that all life forms are related. Molecular biology provides strong evidence for this claim: All forms of life use the same genetic language of DNA and RNA, and the genetic code—how RNA triplets are translated into amino acids—is essentially universal. Thus, it is likely that all species descended from common ancestors that used this code. Because of these homologies, bacteria engineered with human genes can produce human proteins such as insulin and human growth hormone
Note 5 —-»
Some of the most interesting homologies are “leftover” structures that are of marginal or perhaps no importance to the organism.
Vestigial Structures
A feature of an organism that is a historical remnant of a structure that served a function in the organism’s ancestors.
What is homology? How does the concept of homology relate to molecular biology?
Homology is the similarity in different species due to evolution from a common ancestor. Similarities in DNA sequences or proteins reflect the evolutionary relationship that is the basis of homology.
