EvolutionChange Over Time

EvolutionTheory proposed by

Charles Darwin

Latin word meaning unfolding or opening out

All living things on Earth are changed forms of living things that came before

Another DefinitionEvolution can be defined as a change

in species over time.

Species: a group of organisms that share similar characteristics and can interbreed to produce fertile offspring

MutationsAgents of change

A change in a gene will produce a change in the offspring

One major driving force behind evolution

Most mutations are negative, but sometimes they improve the organism

AdaptationA change that

increases an organism’s chances of survival is called an adaptation

Organisms that are better adapted live longer and reproduce

New species may evolve over long periods of time

Many small adaptations may occur over time…..new species evolves

New species may not resemble old

New species may result in the extinction of another

Populations Evolve……not individuals

Natural SelectionProcess that results in adaptation of an

organism to its environment by means of selectively reproducing changes in its genotype.

This is the driving force behind evolution.

Natural SelectionVariations that increase chances of survival

and reproduction are preserved and multiplied over generations

Less advantageous variations are overpowered by the better variations.

Natural SelectionMay arise from differences in survival,

fertility, rate of development, mating success, or any other aspect of the life cycle.

mutation, gene flow, and genetic drift, all of which are random processes, also alter gene abundance.

Natural SelectionUltimately over many generations the

number of organisms in a population with beneficial mutations (adaptations) increases and the harmful mutations are eliminated because those organisms that carry them die off.

Also known as “Survival of the Fittest”

Citation (MLA)  . Britannica Concise Encyclopedia.   Learn360. 11 March 2010  http://www.learn360.com/ShowArticle.aspx?ID=291902

Evidence to Support EvolutionFossil Record

Example: Whale-like skull found in 1983 from 50 million years ago…boney structure for hearing could not have worked under water….ancestors of modern whales must have spent time on land

Example of Fossil Evidence……armadillo and glyptodont

Anatomical EvidenceSimilarities in

physical structureExample: The shape

and arrangement of bones for a salamander, lizard, turtle, and opossum

This suggests evolution from a common ancestor

Anatomical Evidence Continued: Similar Vertebrate Limbs

Evolution of Horses (Anatomy Continued)

Evolution of Horses Graph

Embryological EvidenceEmbryos are organisms in early

stages of developmentGrowth and development are

controlled by genesSimilarities in embryos indicate

sharing a common ancestor

Embryological Evidence Continued

Chemical EvidenceDNA molecular

structure will be similar if two animals are closely relatedExample: Zebra-like

animal from 100 years ago is 95% similar in DNA to modern day zebra….they share common ancestry that dates back 3 million years

Molecular EvidenceProteins made by

genes can also be analyzed.

The closer the similarity in protein structure of different organisms, the more recently their common ancestor existed

Human Karyotype: Molecular Evidence

History of Life Timeline

Have we really evolved?