theory of evolution introduction to vocabulary (teacher version)
TRANSCRIPT
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
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
Embryology Similarity in embryo development shows a close
relationship (vertebrate embryos all have tail & gill slits)
Copyright Pearson Prentice Hall
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
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
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
Natural Selection on Single Gene Traits
Key ConceptNatural Selection On Single-Gene
Traits Can Lead To Changes In Allele Frequencies And Thus To Evolution
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
Genetic Drift
Founder EffectColonization Of A New Habitat
Hawaiian Fruit FliesDarwin’s FinchesHawaiian Honey Creepers
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.
No Movement Into or Out Of The Population
New Alleles Must Not Enter
Rare Alleles Must Not Be Allowed To Leave
No Natural Selection
All Genotypes Must Have Equal Opportunity To Survive & Reproduce
No Phenotype Can Have An Advantage Over Another