Chapter 17, Problem 20A

Summary Introduction

To summarize:

The ways in which biochemical characters can be used to determine phylogeny.

Introduction:

Biologists use a system of classification to organize information about the diversity of living things. Classification provides a framework in which to study the relationships among living and extinct species. To classify a species scientists often use characters to construct patterns of descent or phylogenies. The characters can be morphological or biochemical.

Answer to Problem 20A

There are many ways in which biochemical characters can be used to determine phylogeny

• Aminoacids and nucleotides can be used to determine evolutionary relationships among species.
• Chromosome structure and number can give clues for similarities between species.
• DNA and RNA analyses are powerful tools for constructing phylogenies.
• DNA sequences can be compared to determine phylogenies.

Explanation of Solution

• Biochemical characters like amino acids and nucleotides can be used to determine evolutionary relationships among species. Organisms with common ancestry have same nucleotide sequences and amino acids.
• Chromosome structure and number can give clues for similarities between species. Members of mustard family have almost identical chromosome structures. This is strong evidence that they share common ancestor. Similar appearance of chromosomes among chimpanzees, gorillas, and orangutans suggests a shared ancestry.
• DNA and RNA analyses are powerful tools for constructing phylogenies. The nucleotide sequences in DNA define the genes that direct RNA to make proteins. The greater the number of shared DNA sequences between species, the greater the number of shared genes. This suggests that the species shared a common ancestor.
• DNA sequences can be compared to determine phylogenies. Variety of techniques is used to compare DNA sequences. Whole genome of different organisms can be compared or genome maps can be compared. DNA- DNA hybridization technique can also be used to establish phylogenies. The success of hybridization depends on the similarity of sequences.