Theory of Evolution Introduction to Vocabulary (Teacher Version)

Evolution Evolution: 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 evolutionary 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 Evidence Anatomical similarities suggest common descent Here all vertebrate forelimbs contain the same set of bones 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)

Copyright Pearson Prentice Hall Similarities in Embryology The 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 Pharyngeal pouches Post-anal tail

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 Other 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 Phenotypes  The Phenotype Gives The Survival Edge  Survivors 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 Concept Natural Selection On Single-Gene Traits Can Lead To Changes In Allele Frequencies And Thus To Evolution

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 Gene  Effects On Natural Selection Are More Complex

Copyright Pearson Prentice Hall Natural Selection on Polygenic Traits Natural selection can affect the distributions of phenotypes in any of three ways: directional selection stabilizing selection disruptive selection

Copyright Pearson Prentice Hall 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.

Copyright Pearson Prentice Hall 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.

Copyright Pearson Prentice Hall 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 Effect  The Bottlenose Effect

Genetic Drift  Founder Effect Colonization Of A New Habitat  Hawaiian Fruit Flies  Darwin’s Finches  Hawaiian Honey Creepers

Founder Effect

Genetic Drift The Bottleneck Effect Occurs When Man Made, or Natural Disasters Destroy Most Of A Population. The Remaining Members Usually Possess A Severely Diminished Gene Pool

Evolution vs. Genetic Equilibrium Under 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.