Chapter 17, Problem 39A

Summary Introduction

To identify:

The group that appears to be most ancestral

Introduction:

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 39A

Sea spiders

Explanation of Solution

The branch of a cladogram indicates phylogeny. The closeness of clades in the cladogram indicates the number of characters shared. The group that is farthest away from the recent group of species is the most ancestral group.

According to the cladogram given by Hwang et al on the right and Giribet et al on the left, sea spiders is the most ancestral group as they are the farthest from insects.