Homology can be defined as the presence of common structures because of shared ancestry. Homology can involve genes, proteins, or anatomical structures. As a result of "descent with modification," many homologous structures have adapted different purposes. (a) List three anatomical structures in vertebrates that are homologous but have different functions. (b) Is it likely that homologous proteins from different species have the same or similar functions? Explain. (c) Under what circumstances might one expect proteins of similar function to not share homology? Would you expect such proteins to be homologous at the level of DNA sequences?
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(a) Three anatomical structures in vertebrates that are homologous but have different functions are: Show more…
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Analogy and homology are important concepts used in comparing species. Traits are homologous if they are derived, evolutionarily and developmentally, from the same source structure. Traits are analogous if they have similar functions but are derived, evolutionarily and developmentally, from different source structures. A classic example of analogous structures is insect wings and bat wings. Which of the following pairs of structures are analogous and which are homologous? a. The dorsal fins of a porpoise and a salmon b. The flippers of a porpoise and the pectoral fins (front fins) of a salmon c. The jointed leg of a ladybird beetle and a robin d. A rhesus monkey's tail and a human's coccyx e. The bright red bracts (modified leaves) of a poinsettia and the green leaves of a rose f. $\operatorname{Red}$ bracts on a poinsettia and red petals on a rose
Scientists use the concept of homology in identifying evolutionary relationships among organisms. Features shared by two groups of organisms are said to be homologous if the similarities reflect shared ancestry. Homology is found in comparisons of structural, molecular, biochemical, developmental, physiological, and behavioral characteristics of organisms. For each hypothesis below, give an in-depth explanation of 2 examples of homology that support it. 1. Chloroplasts are related to photosynthetic prokaryotes. 2. Spiders and insects are closely related. 3. Echinoderms are closely related to the chordates. 4. Reptiles and birds are closely related. 5. Humans and chimpanzees are closely related primates.
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