Chapter 17, Problem 37A

Summary Introduction

To compare and contrast:

The two given cladograms and indicate how molecular evidence change the relationship between centipede and spiders

Introduction:

Scientists believe that species sharing a common ancestor also share an evolutionary history. The evolutionary history of an organism is called its phylogeny. One biological system of classification that is based on phylogeny is cladistics. A cladogram is a branching diagram that represents that proposed phylogeny or evolutionary history of a species or group. A clade is one branch of the cladogram. Shared derived characters are used to construct a cladogram.

Answer to Problem 37A

Similarity:

Both the cladograms consider the insects to be the most evolved group of species and sea spiders as the most ancestral group.

Dissimilarity: Hwang et al considered insects and crustaceans to have a common ancestor and spiders and centipedes to have a common ancestor.

Explanation of Solution

The cladograms begin with sea spiders and end with insects. So insects are the most evolved group of species and sea spiders are the most ancestral group.

According to the cladogram given by Hwang et al on the right, insects and crustaceans have a common ancestor and spiders and centipedes have a common ancestor. According to the cladogram given by Giribet et al on the left, spiders, centipedes and crustaceans have evolved in series.

The diversification of centipedes and crustaceans is early in cladogram given by Hwang et al than in cladogram given by Giribet et al. This is due to molecular evidence.