Chapter 17, Problem 11A

Summary Introduction

To explain:

Difference between cladogram and molecular clock.

Introduction:

Classification systems have changed over times as information has increased, so the different species concept were given and different models were proposed to compare the similarities and differences such as molecular clocks and cladogram.

Explanation of Solution

A molecular clock is a model that is used to compare DNA sequences from two difference species to estimate how long species have been evolving since they diverged from common ancestor.

Molecular clocks are used to compare the DNA sequences or amino-acid sequences of genes that are shared by different species. The differences between the genes indicates the presence of mutations, the more mutations that have accumulated, the more time have been passed since divergence.

A cladogram is a branching diagram that represents a proposed phylogeny or evolutionary history of a species or group. A cladogram can be simple, relating only two or three groups of organisms, or it can be massively complex and comprise all the known forms of life.

Cladogram design is worldwide, although simple. A cladogram comprises the organisms being studied, lines, and nodes where those lines cross. The lines denote evolutionary time, or a series of organisms that lead to the population it connects to. Nodes denote common ancestors between species. At some point in the past a population of common ancestor organisms was divided, giving rise to the different organisms being studied. Some cladograms show evolutionary time over the scale of the lines, longer lines meaning more time. Some cladograms chose to show extinct species, while others neglect them. Any specific cladogram is framed specifically for the use it is needed.