Topic 1Introduction to the Study of Life

1.2 Diversity and Evolution

Biology 1001September 12, 2005

Diversity – THe Hallmark of Life

1.8 million species identified & named• 5200 prokaryotes

• 100,000 fungi

• 290,000 plants

• 52,000 vertebrates

• 1,000,000 insects

10 million 200 million species in total

Unity in Diversity

Examples of Unity

Cells & DNA

Feedback Regulation

Correlation between structure and function

Cell ultrastructure

EvolutionEvolution Accounts for BOTH THE Accounts for BOTH THE UNITYUNITY AND AND THE THE DIVERSITYDIVERSITY OF OF LIFELIFE

The unifying principle of biology:

The evolutionary view of life came into sharp focus in 1859 when Charles Darwin published On the Origin of Species by Natural Selection

The history of life is a saga of a changing Earth billions of years old

Darwin’s First Main Point

• Contemporary species arose from a succession of ancestors – Descent With Modification

• DWM captures unity in kinship of species and diversity in modifications that evolve as species branch from their common ancestor

Darwin’s Second Main Point

Darwin’s Observations

1. Individual Variation

2. Overproduction & Competition

His Inferences

1. Unequal Reproductive Success

2. Evolutionary Adaptation

The Evolutionary Mechanism Responsible For Descent With Modification is Natural Selection

NATURAL SELECTION

Evolutionary Adaptations

• The products of natural selection

– Are exquisite adaptations of organisms to the special circumstances of their way of life and their environment

Trees of Life

• Natural selection enables an ancestral species to “split” into two or more descendant species, resulting in a “tree of life”

• Trees of life encapsulate unity due to common ancestry and diversity due to modifications caused by natural selection as species evolve

• Each species is one twig of a branching tree of life extending back in time through ancestral species more and more remote

• All of life is connected through its long evolutionary history

Darwin’s Finches