"This preservation of favourable individual differences and variations, and the destruction of those that are injurious, I have called Natural Selection, or Survival of the Fittest. Variations neither useful nor injurious would not be affected by natural selection . . ."
Charles Darwin, The Origin of Species by Means of Natural Selection, 1872

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Evolution

Change through time.
Theory of Evolution states that all living organisms are evolutionary descendants of life-forms that existed during the past.

Charles Darwin

Origin of Species
Evolution based on natural selection.
Individuals within a species with favorable adaptations will have the best chance of survival and for transmitting those traits to the next generation.
“Survival of the Fittest”
Reproductive success

Genetics

Flaw in Darwin’s theory: unable to explain how favorable traits were retained or passed on to offspring.
Genetics can explain
All cells contain chromosomes
- complex double strands of DNA
- deoxyribonucleic acid
- information about organism
Chromosomes divide when cell divides (replicates itself)
Resulting cells contain same DNA information as original (clone)

Mutation

Changes in DNA can occur, altering the information – Mutation.
Mutations which occur in reproductive cells will be passed on to next generation.
Result from:

Mutations - Speciation

Mutations are random with respect to fitness.
Mutations may be:
New species evolve from old species if enough mutation occurs within a population – Speciation.

Types of Speciation

Allopatric Speciation: due to isolation (physical barriers) of a population.
Peripatric Speciation: small groups of individuals break off from the larger group and form a new species
Parapatric Speciation: species is spread out over a large geographic area; isolation by distance
Sympatric Speciation: new species evolve from a single ancestral species while inhabiting the same geographic region

Phyletic Gradualism vs. Punctuated Equilibrium

Speciation due to gradual changes.
- One species gradually evolves into and is replace by another species.
Species remain stable for long periods of time then change very rapidly over a very short period of time.

Styles of Evolution

Divergent Evolution: diversification of a species into two or more species
Parallel Evolution: development of similarities in two or more closely related descendants.
Convergent Evolution: development of similarities in two or more distantly related groups.

Evidence of Evolution

Comparative Anatomy: comparison of anatomical structures.
Embryology: study of features and phenomena exhibited in the formation and development of embryos.
Fossils: remains or traces of ancient life.

Taxonomy

Science of arrangement or classification
System for naming organisms
Classification scheme based on Species: group of organisms having structural, functional and developmental similarities; able to interbreed, produce fertile offspring.
Evolutionary relationships

The End of Evolution

Extinction: total disappearance of a species
Extinctions occur because of:
Pseudoextinction: Evolution of one species into a new species
Mass Extinction: when large numbers of species all die out at the same time.
An estimated 99.9% of all species that ever lived are now extinct.

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