Chapter 17, Problem 35A

Summary Introduction

To decide:

Whether two groups of frogs should or should not be placed in the same species based on species concept and speciation.

Introduction:

It is not easy to define a species. Organisms that are different species according to one definition might be same species according to different definition. Definitions change as knowledge increases. The concept of species today is much different from what it was 100 years ago.

Answer to Problem 35A

Since the two groups of frogs are identical and are able to interbreed in the lab conditions, they should be placed in the same species. In nature they are unable to interbreed due to some physical barriers so they are reproductively isolated. Hence it would not be wrong to consider them as different species.

Explanation of Solution

Biologicalspecies concept is based on the similar characteristics and the ability to interbreed and produce fertile offspring. It was proposed by Theodosius Dobzhansky and Ernst Mayr. So the organisms that are able to reproduce successfully are defined as species as per this concept.

The two groups of frogs are able to interbreed in the laboratory and produce fertile offspring. In nature they are unable to interbreed due to different reproductive calls and non- overlapping territories. If they have distinct appearance or some minor physical differences, they may be considered to be different varieties of same species.

For speciation to occur, a population must diverge and then be reproductively isolated. Since the frogs are unable to interbreed in nature, they may be considered different species.

The molecular data consisting of DNA and RNA analysis would solve the problem correctly. By comparing their DNA sequences one can correctly decide whether the two groups of frogs should be placed in same species or not.