Question
Three new species (A, B, and C) of fossilized crocodile are discovered. The characteristics of these species are compared to those of the saltwater crocodile, Crocodylus porosus. The saltwater crocodile is found in Southeast Asia and Australia, and adults range in length from 5.5 to 5.8 meters and have 66 teeth. Data comparing the characteristics of the three fossilized crocodile species are shown in the table.
(a) Based on the data given, identify the fossil species that has the most in common with Crocodylus porosus.
(b) The number of teeth in a crocodile jaw correlates with increased predator efficiency. Identify the crocodile(s) that would be less efficient predators than C. porosus.
(c) Evaluate the claim that species B shares a more recent common ancestor with C. porosus than do species A or species C.
(d) Explain your reasoning for your response from part (c).
▶️Answer/Explanation
Ans:
(a) Species C has the most in common with Crocodylus porosus because they are both found in Asia, the number of teeth in species C is closest to the number of teeth in C. porosus, and the DNA sequence of species C has the highest percentage of homology with C. porosus.
(b) Species A and species B would be less efficient predators than C. porosus because they both have fewer teeth than C. porosus.
(c) The data do not support the claim that species B shares a more recent common ancestor with C. porosus than do species A or species C. In fact, species C has the most in common with C. porosus.
(d) The DNA from species B only has 90% homology with the DNA from C. porosus, while species C’s DNA has 98% homology with the DNA from C. porosus. Thus, species C likely has a more recent common ancestor with C. porosus than species B does.