Chapter 17.2, Problem 3MI

Summary Introduction

To define:

The given terms using a book or a dictionary

Introduction:

Scientists believe that species sharing a common ancestor also share an evolutionary history. A system of classification that shows an evolutionary history of an organism is a phylogenetic classification and it reveals the evolutionary relationships of species.

Answer to Problem 3MI

Phylogeny- The evolutionary history of an organism is called its phylogeny.

Character- Characters are inherited features that vary among species. They can be morphological or biochemical.

Molecular clock- A molecular clock is a model that is used by systematics to compare DNA sequences from two different species to estimate how long the species have been evolving since they diverged from a common ancestor.

Cladistics- It is a biological system of classification that is based on phylogeny.

Cladogram- A cladogram is a branching diagram that represents that proposed phylogeny or evolutionary history of a species or group.

Explanation of Solution

Phylogeny- The word phylogeny comes from the Greek words phylon , meaning “related group,” and geny , meaning “origin”. The evolutionary history of an organism is called its phylogeny. Early classification systems did not reveal the phylogenetic relationships among the organisms.

Character − Characters are inherited features that vary among species. They can be morphological or biochemical. Based on shared characters, scientists construct patterns of descent or phylogenies. Shared morphological characters suggest that the species are closely related and evolved from common ancestor. However analogous characters do not indicate close phylogeny.

Molecular clock- A molecular clock is a model that is used by systematics to compare DNA sequences from two different species to estimate how long the species have been evolving since they diverged from a common ancestor. Biologists use molecular clocks to compare DNA sequences or amino acid sequences of genes that are shared by different species. The differences between the genes indicate the presence of mutations. The more mutations that have accumulated, the more time has passed since divergence. Researchers try to compare genes that accumulate mutations at a relatively constant rate in a wide variety of organisms.

Cladistics- One biological system of classification that is based on phylogeny is cladistics. Scientists who use cladistics assume that as groups of organisms diverge and evolve from a common ancestor, they retain some unique inherited characteristics that are called traits by taxonomists.

Cladogram − A cladogram is a model of the phylogeny of a species or group. It is similar to pedigree or family trees but different it does not show direct ancestry like a pedigree. It only shows a phylogeny. A clade is one branch of the cladogram. Shared derived characters are used to construct a cladogram. In a cladogram two groups on diverging branches share a more recent ancestor than those farther away.