Norway rats (Rattus norvegicus) and roof rats (Rattus rattus) are different species. Occasionally, mating occurs if the two species are kept together in captivity. The resulting pregnancies are not successful and the embryos die. This is an example of
A. mechanical isolation.
B. lack of F2 fitness.
C. hybrid sterility.
D. hybrid inviability.
Answer: D
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An adult axolotl salamander (Ambystoma mexicanum) retains the juvenile characteristics of external gills and a tail fin
This is an example of what mechanism? a. allometry b. hybridization c. preadaptation d. paedomorphosis e. adaptive radiation
Forests are generally regarded as CO2 ________.
A. both a source and a sink B. sinks C. sources D. None of the choices are correct.
What are the two molecular components of ribosomes?
a. water and cholesterol b. fatty acids and phosphate groups c. protein and cholesterol d. RNA and protein
The exact path that led to the evolution of modern cells and the organic molecules contained in these cells to support life is not known
The best guess is that some sort of self-replicating organic molecule formed along mudflats and most likely resembled A) single-stranded DNA. B) single-stranded RNA. C) small amino acids such as lysine and glycine. D) double-stranded DNA. E) ATP.