Unit 8 evolution for moodle
Transcript of Unit 8 evolution for moodle
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Unit 8 Evolution
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What is Evolution?
A well-supported scientific theory stating that organisms change over time
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Evidence in stone
Preserved remains of a once living organism is called a FOSSIL
Fossil evidence supported that organisms changed gradually
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Anatomical Evidence
Comparative Anatomy: study of similarities and differences between organismsHomologous StructuresAnalogous StructuresVestigial Organs
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Homologous Structures
As similar organisms adapt to different environments, the function of their appendages changed
A bird’s arms became wings to flap
A human’s arm is used to pick-up, carry, grasp, etc…
A horse’s arm became a fore-leg to run on
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Analogous Structures
Different organisms began living in similar environments, their appendages evolved to perform the same function
A butterfly has wings to fly that are made from an exoskeleton
A sparrow has wings to fly that have an endoskeleton
BirdButterfly
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Vestigial Structures
Structures which remain in organisms but have no obvious function Leg bones in snakes and whales Appendix in humans ** Ear muscles in humans
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Comparative Embryology
Examining the embryos of organisms
Organisms with similar embryos are thought to be more closely related
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Biochemical Evidence (aka Molecular Biology)
Comparison of the amino acid and DNA sequencesChimp and human hemoglobin are VERY similar
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Genetic Evidence
DNA passes on traits When mutations occur the genes and
chromosomes can changeHumans have imposed change
through selective breedingThe higher the percentage of
similarities the closer the relationship between two organisms
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Jean Baptiste de Lamark
First to recognize that organisms change
Published his hypotheses in 1809
Theory was disproved!
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3 Key Assumptions:Desire to Change: organisms have an
inborn urge to better themselvesLaw of Use and Disuse: body parts
that are used will develop; those not used will become smaller/disappear
Inheritance of Acquired Characteristics: organisms pass on traits acquired during their lifetime
Jean Baptiste de Lamark
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Charles Darwin
Credited for the theory of evolutionHMS Beagle sailed in 1831 – Galapagos
IslandsPublished Origin of Species in 1858
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Darwin’s Observations
Observed tortoises, iguanas, and finches
The islands had different climates and vegetation
The animals were similar… but had noticeable differences
WHY?
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Darwin’s Assumptions Variations
Differences among members of the same speciesStruggle for Existence
Predation and competitionOverproduction
More offspring are produced than will surviveSurvival of the Fittest (Natural
Selection) Individuals best suited for the environment will
survive, reproduce, and pass on traits to their offspring
Descent with ModificationPrinciple that species change but descend from
common ancestors
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Lamark’s Giraffes
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Darwin’s Theory of Natural Selection
Variations help members of a species to survive in a given environment
The environment selects the beneficial adaptation and over time this trait will become more prevelant
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Darwin’s Finches
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Fossil Formation
Dead organisms are buried by layers of sediment, which forms new rock
The preserved remains may later be discovered and studied.
Water carries small rock particles to lakes and seas
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Fossil Record
Preserved remains of a once living organism is called a FOSSIL IE: amber, sedimentary rock, tar, and ice
Fossil record is incomplete
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Relative Dating
Used to ESTIMATE the age of fossils
Older fossils are in deeper layers of rock
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Genes and Evolution In terms of genetics, evolution is the change in
frequency of alleles in a population’s gene poolNatural selection leads to change in gene frequencyMolecular clocks use mutation rates to estimate
how recent a common ancestor was
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Hox Genes
Genes which control an organism’s basic body plan Anterior/posterior ends Limbs, wings
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Genetic Drift
Changes in the gene pool of a small population due to random chance ex: small group
colonizes a new habitat – founder effect
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Speciation
Gradualism – change in species is slow and steady
Punctuated Equilibrium – long periods of stability followed by short periods of rapid change
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Punctuated Equilibrium vs. Gradualism
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Speciation – Isolating Mechanisms
For new species to form, reproductive isolation needs to occur
Organisms don’t interbreed- gene pools become separate
- Behavioral, Geographic, Temporal
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Adaptive RadiationA single species evolves into many speciesOften occurs when a niche opens up
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Convergent Evolution
Organisms come to resemble one another but evolved differently
Analogous structures!
Examples: Dolphins and sharks Marsupials and
mammals
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Coevolution
Organisms with close ecological relationships evolve together Pollinators and flowers
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Ancient Earth
Atmosphere was composed of gases:
CO2, N2, water vapor, CH4, H2S
No O2
Earth formed ~4.6 billion years ago
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First Organic Molecules
1950’s Miller & Urey reproduced conditions of ancient Earth
Electric sparks simulated lightning
Amino acids began to form
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First Cell
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Oxygen Accumulation in Atmosphere
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What is a Primate?Binocular VisionDeveloped brainLong fingers & toesRotating shoulders
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What makes us Human?
Characteristics of the Hominine Family Bipedal Opposable
Thumbs Larger Brains
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Did we evolve from chimps?
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Hominine Evolution
Ardipithecus ramedus “Ardi”, 4.4 myaAustralopithecus afarensis “Lucy”, 3.2 myaHomo habilis “handy man”, ≈ 2 mya
Used tools, first of the genus Homo
Homo erectus, “Java Man”, ≈ 1.6 mya 1st to use fire
Homo neanderthalensis ≈ 200,000 years ago
Homo sapien Modern Human ≈ 100,000 years ago
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Family Tree or Bush?
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