Question

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. Dorsal fins of porpoise and a salmon
b. Flippers of porpoise and pectoral fins (front fins) of salmon
c. Joined leg of ladybird beetle and a robin
d. Rhesus monkey's tail and human's coccyx
e. Bright red bracts of poinsettia and green leaves of rose
f. Red bracts on a poinsettia and red petals on rose

Answer 1

a. analogous

b. homologous

c. analogous

d. homologous

e. homologous

f. homologous

Step-by-step explanation:

a. Analogous. Porpoises are mammals while salmon are fish. In this case, fins are analogous structures that evolved separately in both groups.

b. Homologous. Pectoral fins evolved from the forearms of tetrapods, and early tetrapods evolved from fish.

c. Analogous. These structures evolved independently through convergent evolution in both groups.

d. Homologous. They are homologous structures that were inherited from a common ancestor (primates).

e. Homologous. Bright red bracts (modified leaves) of poinsettia and green leaves of rose share a common ancestor (i.e., angiosperms).

f. Homologous. They are homologous structures that were inherited from a common ancestor (i.e., angiosperms).