Theory of Evolution

Introduction to Vocabulary(Teacher Version)

EvolutionEvolution: change in the traits of

a species over time (Loooong time)

Species: a group of organisms who can produce fertile offspring

Charles Darwin: developed the theory of evolution called Natural Selection

Phylogeny Phylogeny: the evolutionary history of an

organism; this is used to classify organisms into kingdoms, phyla, classes, etc.; a phylogenetic tree or cladogram shows how organisms are related to one another and how they evolved

examples of phylogenetic trees

Prove it….

Evidence to support Evolution

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Fossils These are

imprints or remains of living things.

In undisturbed layers of sedimentary rock, the deeper it is, the older it is.

Give us information about extinct species.

Fossil Evidence: allows reconstruction of Fossil Evidence: allows reconstruction of evolutionary treesevolutionary trees

Based on: Mader, S., Inquiry Into Life, McGraw-Hill

Anatomical (body shape) Evidence

homologous structure: same structure with different functions found in different species and thought to be inherited from common ancestors

ex: humans, whales, and bats all have the same # and type of bones in the forelimbs but their functions are different

Anatomical EvidenceAnatomical EvidenceAnatomical Anatomical similarities similarities suggest suggest common common descentdescent

Here all Here all vertebrate vertebrate forelimbs forelimbs contain the contain the same set of same set of bonesbones

Based on: Mader, S., Inquiry Into Life, McGraw-Hill

Biogeographic Evidence

Geographical Distribution

Similar, But Unrelated Species

Embryology Similarity in embryo development shows a close

relationship (vertebrate embryos all have tail & gill slits)

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Similarities in EmbryologyThe early stages, or embryos, of many animals with

backbones are very similar.

The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates.

Chick embryo (LM) Human embryo

Pharyngealpouches

Post-analtail

Molecular Data DNA: by comparing the DNA sequences of two organisms or the amino acid

sequences made from the DNA, scientists can learn which organisms are related; the more DNA two organisms have in common, the closer related they are

•Using the table, compare the amino acid sequence of the chimp and the human.

•Notice that for this protein the chimp and human have the exact same sequence.

•Now compare the baboon and the human.

•Notice that there are 5 differences in the sequence.

•This tells you that the human is more closely related to the chimp than the baboon.

Fig. 27.6

Other Molecular EvidenceOther Molecular Evidence

Based on: Mader, S., Inquiry Into Life, McGraw-Hill

So how does it happen….

Methods of Evolution

Evolution (Natural or Man-made) Artificial Selection

Natural provides a great variety of living things. In artificial selection humans pick the varieties or characteristics that are the most useful and selectively breed for those traits.

Natural Selection states that: there is variation (differences) within populations some variations are favorable (favorable variations

improve an organism’s ability to function and reproduce in its own environment)

not all young produced in each generation can survive individuals that survive and reproduce are those with

favorable variations; these individuals can then pass on the favorable traits to their offspring

Example of Artificial Selection

Natural Selection

Does NOT Act Directly On Genes

Does Act On PhenotypesThe Phenotype Gives The Survival EdgeSurvivors Must Reproduce

Alters Relative Frequency of Alleles Over Time

Evolution

Acts On Populations

Does NOT Act On Individuals

Natural Selection on Single Gene Traits

Key ConceptNatural Selection On Single-Gene

Traits Can Lead To Changes In Allele Frequencies And Thus To Evolution

Camouflage

Camouflage

Camouflage

Natural Selection on Single Gene Traits

BUT:What If Black Allowed The

Lizard To Warm Up Faster & Move Quicker??????

Natural Selection on Polygenic Traits

Traits Controlled By More Than One GeneEffects On Natural Selection Are

More Complex

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Natural Selection onPolygenic Traits

Natural selection can affect the distributions of phenotypes in any of three ways:

directional selectionstabilizing selectiondisruptive selection

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Directional Selection When individuals at one end of the curve have

higher fitness than individuals in the middle or at the other end, directional selection takes place.

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Stabilizing Selection When individuals

near the center of the curve have higher fitness than individuals at either end of the curve, stabilizing selection takes place.

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Disruptive Selection When individuals at the upper and lower ends of the

curve have higher fitness than individuals near the middle, disruptive selection takes place.

If Severe Enough, May Cause The Development Of TWO Phenotypes

Genetic Drift

Natural Selection Is Not The Only Source of Evolutionary Change

In Small Populations, An Allele Can Become More Or Less Common By Chance

Genetic Drift

Key Concept:In Small Populations, Individuals That Carry

A Particular Allele May Leave More Descendents Than Other Individuals, Just By Chance. Over Time, A Series Of Chance Occurrences Of This Type Can Cause An Allele To Become Common In A Population

Circumstances That May Result In Genetic Drift:

The Founder’s EffectThe Bottlenose Effect

Genetic Drift

Founder EffectColonization Of A New Habitat

Hawaiian Fruit FliesDarwin’s FinchesHawaiian Honey Creepers

Founder Effect

Genetic Drift

The Bottleneck EffectOccurs When Man Made, or Natural

Disasters Destroy Most Of A Population. The Remaining Members Usually Possess A Severely Diminished Gene Pool

Evolution vs. Genetic EquilibriumUnder What Conditions Will Evolution

NOT Occur:1. Random Mating

2. Population Must Be Very Large

3. No Movement In or Out of Pop.

4. No Mutations

5. No Natural Selection

This is called the Hardy-Weinberg Principle (1908) Key Concept:

Genetic Equilibrium will be maintained from Generation To Generation if the 5 conditions are met.

Random Mating

All Members Of The Population Must have An Equal Opportunity To

Produce Offspring

Large Population

Genetic Drift Has Less Effect On Large Populations

No Movement Into or Out Of The Population

New Alleles Must Not Enter

Rare Alleles Must Not Be Allowed To Leave

No Mutations

Mutations Introduce New Alleles Causing A Change In Allele

Frequencies

No Natural Selection

All Genotypes Must Have Equal Opportunity To Survive & Reproduce

No Phenotype Can Have An Advantage Over Another

Extinction

A population is extinct when the last of that species is dead.

Example: There are no more dinosaurs. What happened? Their habitat was destroyed. When

they no longer have what they need to live, they die.