Chapter 29, Problem 8A

Summary Introduction

Introduction:

Reptiles are fully adapted to life on earth. Characteristics that enable reptiles to survive on land include shelled egg, scaly skin, and more effective circulatory and respiratory systems. The dry skin of the reptiles prevents them from losing internal fluids to the air. A layer of scales on the outside of many reptiles also prevents them from drying out.

Answer to Problem 8A

Correct answer:

The correct answer is option (B) Birds and crocodiles are the closest relatives of dinosaurs.

Explanation of Solution

Explanation/justification for the correct answer:

Option (B) Birds and crocodiles are the closest relatives of dinosaurs. Like birds and crocodiles, some dinosaurs built nests and looked after the eggs and the young. Some dinosaurs may have been able to regulate their body temperatures. Fossil evidence shows that one group of dinosaurs had feathers and evolved into birds of today. So, the correct answer is option (B).

Explanation for incorrect answer:

Option (A) Dinosaurs evolved into modern-day reptiles such as lizards, snakes, and turtles. Fossils evidence shows that one group of dinosaurs had feathers and evolved into today's birds. So, this is an incorrect option.

Option (C) The earliest reptiles did not have amniotic eggs. All reptiles have amniotic eggs that have an amnion and other membranes that surround the embryo as it develops. So, this is an incorrect answer.

Option (D) Dinosaurs become extinct because they were too big. According to some scientists, a meteorite crashed to Earth and caused the extinction of many species including dinosaurs. So, this is an incorrect answer.