Chapter 5, Problem 23A

Summary Introduction

Introduction:

Extinction refers to the complete elimination of species form the Earth. Extinction of species is the major cause of biodiversity. Natural extinction or background extinction is a slow process through which the existing species are replaced by the better-adapted species due to alternate evolution, environmental changes, predation, diseases, etc. A smaller population is more likely to become extinct than the larger population due to inbreeding depression and normal population fluctuations during unfavorable conditions.

Answer to Problem 23A

Correct answer:

Option (C) 1000 times.

Explanation of Solution

Explanation/justification for the correct answer:

Option (C) 1000 times. Earth has experienced five mass extinctions due to environmental catastrophes. It seems that the Earth is heading 6^th extinction but it would be anthropogenic. It is due to human activities like settlements, hunting, overexploitation, and habitat destruction. The colonization of tropical islands by humans has resulted in the extinction of more than 2000 species of native birds. Presently, some 15,500 species worldwide are threatened. The current rate of extinction is 100-1000 times faster than pre-human times.

Explanation for incorrect answer:

Option (A) 1 time. According to this option, the current background extinction rate is similar to that of the normal rate. In reality, it is faster than the normal rate. Thus, it is an incorrect answer.

Option (B) 10 times. Based on the data collected by scientists, the current rate of background extinction exceeds the normal rate by more than 10-times. Thus, it is an incorrect answer.

Option (D) 10,000 times. The future rate of extinction is likely to be 10,000 times faster if the anthropogenic activities continued to destruct the habitat of other species at the same pace. Hence, it is an incorrect answer.