Cell Structure

Learning Objectives Cell theory states that the cell is the fundamental unit of life. However, cells vary significantly in size, shape, structure, and function. At the simplest level of construction, all cells possess a few fundamental components. These include cytosol (a gel-like substance…

Prokaryotes

Scientists have studied prokaryotes for centuries, but it wasn’t until 1977 that Carl Woese discovered two distinct lineages within the prokaryotes: Bacteria and Archaea. Prokaryotes have an important role in changing, shaping, and sustaining the entire biosphere. They can produce proteins and…

Chapter Summary

All organisms on Earth are related at some point in evolutionary history. In western science, a taxonomic classification system is used to nest organisms into related groups of increasing specificity. Domain is the least specific (most inclusive) level of classification,…

Perspectives on the Phylogenetic Tree

Learning Objectives The concepts of phylogenetic modeling are constantly changing. It is one of the most dynamic fields of study in all of biology. Over the last several decades, new research has challenged scientists’ ideas about how organisms are related.…

Determining Evolutionary Relationships

Learning Objectives Scientists must collect accurate information that allows them to make evolutionary connections among organisms. Similar to detective work, scientists must use evidence to uncover the facts. In the case of phylogenies, evolutionary investigations focus on two types of…

Organizing Life on Earth

Learning Objectives The evolutionary history of a group of species is referred to as a phylogeny. Phylogeny describes the relationships of the group within the context of related organisms. Though phylogenetic relationships provide information on shared ancestry, they don’t necessarily address how organisms…

Introduction

The history of life on earth goes back more than 3.5 billion years, with all life evolving from a common ancestor and diversifying to what we currently see on earth today. The evolutionary history of a group of species is…