Evolution: A change in a kind of organism over time. The process of

modern organisms coming from ancient organisms

Evolution and Natural Selection

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Change over time

EvolutionEvolution is a

scientific theory. There is much

evidence to support evolution

Lamarck (1809)First suggested

changes overtime Stated that changes

are adaptations acquired in one’s lifetime due to selective use or disuse of certain traits

These traits would then be passed on to their offspring, but not through genes; forces

Desire to do something led to adaptations

Example: Giraffes kept stretching their necks over generations until they could reach the leaves.

DarwinJoined the crew of

the HMS Beagle for a 5 year survey adventure. (1831-1836)

Naturalist; wanted to study and observe different species.

http://www.youtube.com/watch?v=E2y1DJ1rhck

During his travels , Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes

Galapagos Island TortoiseDarwin noted that the

island were very small and varied greatly

Some hot, dry and nearly barren

Other islands had greater rainfall and had more diverse vegetation

He noted the tortoises’ shape of their shell corresponded to their different habitat

FinchesStudied finches on

each island Noticed similar

types of finches had small beak adaptations depending on available food sources

1859- “The Origin of Species by Means of Natural Selection”

Stated that organisms evolved Mechanism for evolution called Natural

SelectionPresented evidence that evolution has been

taking place for millions of years – and continues in all living things

Darwin

1-Variation: Each organism has it’s own variations in it’s struggle for existence

2-Competition-Organisms compete for natural resources

3- Pop. Growth-Organisms produce more offspring than can survive

4- Differential reproduction- Those organisms best suited to the environment will survive and pass along their genes to their offspring

Darwin’s 4 main points of Natural Selection

Results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment

Natural selection is one of the basic mechanisms of evolution, along with mutation, migration, and genetic drift.

Natural Selection

Natural Selection ObservedPeppered moths -

England1850’s - light color (few

were dark)Early 1900’s - pollution

darkened tree trunksLight moths eatenDark moths camouflaged

- increasedRecently - pollution

controls - trees lightenLight moths increase in

number again

In artificial selection, nature provided the variation, and humans selected those variations that they found useful

Ex. Dogs, Vegetables, Cows

Artificial Selection

Common descent- principle that all living things were derived from common ancestors

Fossil recordFossils show the links between species Radioactive dating can tell how old the

fossils are Scientists calculate the half-life of certain

isotopes, like Carbon-14, in the fossil to determine the age in years.

Evidence of Evolution

Evidence From StructureSimilar structures are evidence of a common

ancestor.

Selection causes modifications for different environments.

Homologous structures - different functions but common ancestry.

Vestigial organs - small or incomplete organs with no apparent function.

Comparative Anatomy

Vestigial OrgansImplication: the vestigial organ

served a function in the ancestor of the organism, but not its present holder

Examples

Evidence from EmbryologyEmbryo - developing

organismEarly stages of

development are similar

More closely related organisms have more similar embryological patterns

Evidence From BiochemistryUniversal genetic code

- evidence of evolution.All living things are

made up of the same 4 nucleotides: A,G, C, T

Many of the same DNA sequences, or genes, are exact or similar depending on how closely related we are

The evolutionary process by which new species arise.

Arise for different reasons, but reproductive isolation and geographic isolation are the most common

Reproductive isolation is when no mating occurs between species for so long that sexual selection changes or having offspring

Geographic occurs when species are separated by a barrier, such as a mountain range or a river

Speciation

Geographic IsolationAbert squirrel and Kaibab squirrel - used to

be same population.About 1 million years ago - Colorado river

changed course and split population.Kaibab is a subspecies of the Abert squirrel.

Reproductive Isolation Washington- two populations of

sockeye salmon became established

One spawning in a river and one along a lake beach.

Sockeye salmon bury their eggs and spawn in different kinds of locations, and in a variety of environments, even in a small system such as this.

When new populations become established at different sites, you'd expect them to evolve different adaptations, and that's in fact what happened. Body depth in males Size of breeding females

Convergent EvolutionDefinition: when the

environment puts similar selective pressure on different species.

Results in similar adaptations for organisms that are not closely related.Example: fish do not

have same immediate ancestor as whales.

Bird wing vs. insect wing