The Theory of Evolution by Natural Selection Charles Darwin The Origin of Species

1. Overproduction & Struggle for Existence Individuals produce more offspring than the environment can support. Individuals must compete …the struggle for existence.

2. Variation and Adaptation Individuals in a population have variations. Some variations make an organism better adapted….adaptation.

3. Survival of the Fittest Individuals with the best adaptations are better suited to their environment (have greater fitness), as a result they can survive and reproduce.

4. Natural Selection Organisms with variations most suited to their environment survive and leave more offspring. The environment (nature) “selects” which organisms will survive.

EVIDENCE OF EVOLUTION

THE AGE OF THE EARTH FOSSILS ANATOMY Evolution takes a long time. Earth is about 4.5 billion years old. FOSSILS Fossils offer the most direct evidence of evolution. ANATOMY similar arrangement of bones… evidence of common ancestor.

Some organisms have structures that are no longer useful buthad important function in the organism’s ancestor.

EMBRYOLOGY Very different animals have similar structures during development. The similar features of embryos in very different organisms suggest evolution from a common ancestor.

Biological Molecules Many proteins in bacteria are similar in structure and function to proteins in animals. DNA Sequences: The more similar the nucleotide sequence in a gene the more closely related the organisms.

GENETIC CODE All living things use the same genetic code. This genetic code is nearly identical in almost all organisms, from bacteria to animals.

Evolutionary Trees

An evolutionary tree represents the evolutionary relationships among a group of organisms.   Evolutionary relationships among organisms are based on physical features and the DNA sequences of their genes.

Which is more closely related? A & B or B & C

Which is more closely related? B & D or C & E

Which is more closely related? B & D or D & E

Which is more closely related? Amphibian & Reptiles Reptiles & Mammals

Human Evolution Homo sapien - “wise man”

Upright bipedal walking - allowed the hands to be freed for other things such as tool/weapon use.

Smaller, blunt canines - suggests a change in diet.

Increase in brain size

Opposable thumbs help: monkeys and apes climb trees. grasp objects such as tools and weapons.