“Nothing in biology makes sense except in the light of evolution.” – Theodosius Dobzhansky • “Most species do their own evolving, making it up as they go along, which is the way Nature intended. And this is all very natural and organic and in tune with the mysterious cycles of the cosmos…which believes that there’s nothing like millions of years of really frustrating trial and error to give a species moral fiber and…in some cases…a backbone.” - Terry Pratchett
Write-Away: 4-2 • What do you think when you hear the word evolution? • Pg 1 in packet (Rate Yourself & PBS Video #1) • Rat Lab Practical • Do pg 2-3 in packet (On-line History of the Earth)
Write-Away: 4-3 • What is evolution? • Finish On-Line History of the Earth (pg 2-3) • Talk about Human Systems Tests
Evolution • The gradual change in organisms over time.
Write-Away: 4-4 • What is a theory? • Timeline Activity (pg 4)
A theory (in science) is… • …created when a hypothesis or group of hypotheses has been supported with repeated testing. • If enough evidence accumulates to support a hypothesis, it moves to the next step—known as a theory—in the scientific method and becomes accepted as a valid explanation of a phenomenon.
Write-Away: 4-7 • How old is the earth and how long have humans been a species? Compare this to a clock. • What surprised you about the activity yesterday? • Darwin Award! • Finish Timeline Activity (pg 4) • PBS Video #2 • Pg 5 (Stitch in Time) • HWK: Finish pg 1-5 in packet
Write-Away: 4-8 • Who is the father of evolution? • Darwin Award! • Darwin & His Adventures (Slides 10-15 & pg 8) • PBS Videos #3 & #4
16.1 Developing a Theory
Charles Darwin • The Father of Evolution • Life/Journey • Doctor? No, ecologist & naturalist • Sailed the world on a ship: The H.M.S. Beagle • Age 24-29 • Took samples of species and detailed observations… • Visited Galapagos Islands • Found unique organisms • Studied many species, ex. finches, tortoises, iguanas • Noticed adaptations for food, mates, habitats…to survive
Charles Darwin, cont… • Raised and bred exotic pigeons • Artificial selection – breeders select parents with desirable traits so those traits are passed on • Ex today – Dogs, horses, cows, crops, etc. • Wrote books • On the Origin of Species • The Descent of Man • Selection in Relation to Sex • The Expression of the Emotions in Man and Animals
Quick Quiz #1 • What is evolution? • A gradual change in species over time • Who is the ‘father of evolution’? • Charles Darwin • What is artificial selection? • Breeders selecting for desirable traits • What is natural selection? • Species evolve to fit their changing environment.
Write-Away: 4-9 • What is speciation? • What’s the difference between micro and macro evolution? • Darwin Award! • Slides 16-22 & Take Notes (pg 8) • PBS Videos #4 & #5 • Play Survival of the Fittest Game (pg 7)
16.2 Applying Darwin’s Ideas
Natural Selection • The process where individuals with advantageous traits (for their environment) survive and reproduce • Those traits seen more frequently in future generations • Eg. Speed, ability to fly further distances, ability to adapt, resistance to insecticide, etc. • Requirements for natural selection: 1. Overpopulation 2. Variation of traits 3. Selection of mates 4. Adaptation
Natural Selection on Traits… • Stabilizing • Pressure from two directions makes average trait most fit (outliers least fit) • Disruptive • Pressure on the average trait results in divergence (outliers most fit) • Directional • Pressure from one direction alters frequency of trait
Question…? • Does natural selection act on the phenotype or genotype of a species?
An adaptation is… • …a change in behavior, physiology, and/or structure of an organism or species to become more suited to an environment…gradual • Eg. Dolphin behavior video
Quick Quiz #2 • What is natural selection? • When individuals with advantageous traits survive and reproduce. • What are the three ways natural selection affects traits? • Directional, stabilizing, & disruptive • What is an adaptation? • A change in behavior, physiology, or structure that makes a species more suited to an environment
Write-Away: 4-10 • What is survival of the fittest/natural selection? • What is an adaptation? • Darwin Award! • Do pg 9-10 in packet
Write-Away: 4-11 • What is adaptive radiation? • Darwin Award! • Natural Selection Activity
Write-Away: 4-14 • What did the activity Friday have to do with evolution? • Finish Natural Selection Activity • Rate Yourself: Mid-Unit Pg 1 • Homologous vs Analogous Computer Activity (finish as HWK)
Write-Away: 4-15 • What are homologous structures? • What are analogous structures? • Slides 27-41 & Take Notes (pg 8) • Questions about quiz Tomorrow…?
Write-Away Cont. • Which organisms do you think are most closely related? Why?
16.2 Evidence for Evolution
Biogeography… • World distribution of organisms • Shows similarities among species living on different continents
Convergence… • Trait adapted to similar function but with a different origin
Early Development… • Embryos of many vertebrates are very similar • Similar stages of development
Homologous Structures… • Limbs come from the same embryonic tissue and at same basic location • Why use the same skeletal plan for these very different appendages?
Fossils… • Record shows biodiversity • Shows changes in species over time…stages of development • Law of Superposition…
Darwin’s Finches… • 14 species of finches • Different niches • Different food sources • What does this show?
Similar DNA… • Biochemistry • Commonality of genetic code, similar amino acids
Similar DNA, cont… • Why should different organisms have so many similar genes? • Called a cladogram
Can we see evolution…? • We can see the effects of evolution, artificial selection • Tuberculosis video…
Darwin was not alone… Charles Lyell – uniformatarianism 1797-1875 Georges Cuvier – species extinction 1769-1832
Darwin was not alone… Thomas Malthus – struggle for existence 1766-1834 Jean Baptiste de Lamarck – evolution by acquired characteristics 1744-1829
And the less well known… • Alfred Russel Wallace • Drew same conclusions as Darwin • Not an easy journey… • 11 years up in smoke (Amazon River Basin) • 8 more years of work (Malay Archipelago) • Later worked jointly with Darwin
Darwin’s Theory…a summary • Uncontrolled populations grow exponentially • Limited resources = survival of the fittest • No two individuals are exactly the same • If the inherited traits allow one to be “better” they will survive and pass on those traits • As the fittest survive, the population’s traits change over time
Quick Quiz #3 • List five reasons evolution is a supported theory. • Biogeography • Convergence • Early development • Homologous structures • Fossils • Darwin’s finches (adaptive radiation) • Similar DNA (biochemistry) • Other scientists came up with similar hypotheses as Darwin…he wasn’t alone
Write-Away: 4-16 • What evidence is there for evolution? List at least three things. • Question basket. • Evolution Quiz • Cladogram Activity
Write-Away: 4-17 • What’s the Law of Superposition? • According to this law, which layer is the oldest on the diagram below? • Fossil Activity
Write-Away: 4-21 • What’s the difference between genetic drift, gene flow, and a gene pool? • Quizzes and Review • Finish Fossil Activity • Slides 45-55 & Notes (pg 8) • HWK: Review sheet for test
16.3 Beyond Darwinian Theory
Microevolution is… • Changes in the genes of populations • Small scale (generation to generation)
How does Microevo. Happen? • Natural Selection • Mate Choice • Mutations in DNA • Gene Shuffling • Random mixing of genes during sexual reproduction • Gene Flow (not completely random) • Immigration • Emigration • Migration • Genetic Drift (random)
Genetic Drift is… • Individuals with a particular trait have more descendants just by random chance • Random changes of allele (trait) frequency in a population • Eg. Wildfire, disease, earthquake, etc. • Can lead to a ‘bottleneck effect’
Biodiversity… • Variation within a species helps insure that some will survive major changes in the environment and continue the species • Variation of species is vital for the continuation of life. • For life to continue we need ___________________.