Chapter 17, Problem 15A

Summary Introduction

Introduction:

Scientists believe that species sharing a common ancestor also share an evolutionary history. The evolutionary history of an organism is called its phylogeny. A system of classification that shows an evolutionary history of an organism is a phylogenetic classification and it reveals the evolutionary relationships of species. One biological system of classification that is based on phylogeny is cladistics.

Answer to Problem 15A

Correct answer:

The correct answer is option B. birds

Explanation of Solution

Explanation/justification for the correct answer:

Option B. birds − The given figure shows a cladogram according to which the birds diverged last as they are located at the end of the cladogram. Hence this is the correct option.

Explanation for incorrect answer:

Option A. alligators− The given figure shows a cladogram according to which the birds diverged last as they are located at the end of the cladogram. The alligators are not mentioned in the given cladogram.

Hence this is not the correct option.

Option C. crocodiles- The given figure shows a cladogram according to which the birds diverged last as they are located at the end of the cladogram. The crocodiles are the first ones to diverge from the main branch. Hence this is not the correct option.

Option D. dinosaurs − The given figure shows a cladogram according to which the birds diverged last as they are located at the end of the cladogram. The dinosaurs are second to diverge from the main branch. Hence this is not the correct option.