Understanding Evolution: your one-stop source for information on evolution
Resource library Teaching materials Evolution 101
 
EVOLUTION 101

Introduction

Patterns

Mechanisms

Microevolution

Speciation

Macroevolution

The big issues

en Espanol en Español     print print

The family tree

The process of evolution produces a pattern of relationships between species. As lineages evolve and split and modifications are inherited, their evolutionary paths diverge. This produces a branching pattern of evolutionary relationships.

By studying inherited species' characteristics and other historical evidence, we can reconstruct evolutionary relationships and represent them on a "family tree," called a phylogeny. The phylogeny you see below represents the basic relationships that tie all life on Earth together.

Three domains

Download this graphic from the Image library.
 

The three domains
This tree, like all phylogenetic trees, is a hypothesis about the relationships among organisms. It illustrates the idea that all of life is related and can be divided into three major clades, often referred to as the three domains: Archaea, Bacteria, and Eukaryota. We can zoom in on particular branches of the tree to explore the phylogeny of particular lineages, such as Animalia (outlined in red). And then we can zoom in even further to examine some of the major lineages within Vertebrata. Just click the button below.

Zoom in on Animalia

The tree is supported by many lines of evidence, but it is probably not flawless. Scientists constantly reevaluate hypotheses and compare them to new evidence. As scientists gather even more data, they may revise these particular hypotheses, rearranging some of the branches on the tree. For example, evidence discovered in the last 50 years suggests that birds are dinosaurs, which required adjustment to several "vertebrate twigs."



previous
The history of life: looking at the patterns

  next
Understanding phylogenies


Photo credits for life, animals, and vertebrates trees

Patterns
page 2 of 11
previous | next  >


Teach this
Teach your students about evolutionary relationships and phylogenetics:

Find additional lessons, activities, videos, and articles that focus on phylogenetics.