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Bio 163 evolution lmk 2013 for moodle

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Unit 8 Evolution
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Page 1: Bio 163 evolution lmk 2013 for moodle

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 StructuresAs similar organisms adapted to different environments,

the function of their appendages changed. Result of descent with modification from a common ancestor.

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, although structurally different.

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 (Molecular Biology)

Comparison of the amino acid 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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Lamark’s Giraffes

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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?

Species vary globallySpecies vary locallySpecies vary over

time

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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 Assumptions Variations

Differences among members of the same speciesOverproduction

More offspring are produced than will surviveStruggle for Existence

Predation and competitionSurvival 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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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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Patterns and Processes of Evolution

Macroevolutionary Patterns Large-scale (more than a single species) Occurs over long periods of time

Microevolution Small-scale (within a single species) Forms variations in populations

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Speciation – Isolating MechanismSpecies – group of organisms that interbreed to

produce fertile offspring under normal conditions –

share a common gene poolSpeciation – formation of a new species

Requires reproductive isolation – organisms do not interbreed; gene pools become separateBehavioralGeographicTemporal

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Patterns of Extinction

Background Extinction – “business as usual” extinction – slow and steady

Mass Extinction – many species become extinct over a short period of timeCauses:AsteroidVolcanic eruptionsMoving continentsChanging sea levels

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Rates of Evolution

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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Patterns of Macroevolution:

Adaptive RadiationA single species evolves into many speciesOften occurs when a niche opens up

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Organisms come to resemble one another but evolved differently

Source of analogous structures!

Examples: Dolphins and sharks Marsupials and

mammals

Patterns of Macroevolution:

Convergent Evolution

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Coevolution

Organisms with close ecological relationships evolve togetherPollinators and flowers

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The Role of Genes in Evolution

In terms of genetics, evolution is the change in the frequency of alleles in a population’s gene pool

Natural selection leads to that change

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Genetic DriftRandom change in allele frequency –

changes in the gene pool of a small population due to chance

Types of Genetic Drift: Bottleneck Effect – change in allele

frequency following dramatic reduction in population size

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Genetic Drift Founder Effect – small group colonizes a

new habitat

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Molecular Evolution

Molecular Clocks – use mutation rates in DNA to estimate time two species have been evolving independently

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Molecular Evolution: Hox Genes

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Genes which control an organism’s basic body plan Anterior/posterior ends Limbs, wings

small sequence changes during embryological development can cause large changes in adults

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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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