descent with modification: a darwinian view of life
TRANSCRIPT
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CAMPBELL & REECE:CHAPTER 22
Descent with Modification: A Darwinian View of Life
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3 key observations about life1. Striking ways
organisms are suited to their environment
2. Unity of living things(so many common features)
3. Rich diversity of life
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EVOLUTIONDESCENT WITH
MODIFICATION
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EVOLUTION A CHANGE in the GENETIC COMPOSITION of a POPULATION from GENERATION to GENERATION
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EVOLUTION
CAN BE VIEWED IN 2 WAYS1. A PATTERN
OBSERVATIONS FROM NATURAL WORLD
2. A PROCESS MECHANISMS THAT PRODUCED
THE OBSERVED PATTERNS
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ARISTOTLE(384 – 322 BCE)
DID NOT BELIEVE ORGANISMS CHANGED OVER TIME (some Greeks did)
Viewed organisms as fixed: could be arranged on ladder from least complex most complex
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CAROLUS LINNAEUS(1701 – 1778)
DEVELOPED BINOMIAL NOMENCLATURE
WITH A “NESTED” CLASSIFICATION SYSTEM
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PALEONTOLOGY
STUDY OF FOSSILS GEORGES CUVIER (1769 –
1832)OLDER THE STRATUM OF
SEDEMENTARY ROCK THE OLDER & MORE DISSIMILAR THE FOSSILS WERE TO CURRENT LIFE
NEW SPECIES APPEARED, SOME DISAPPEARED
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GEORGES CUVIER
CATASTOPHISM: EVENTS IN THE PAST OCCURRED SUDDENLY & WERE CAUSED BY DIFFERENT MECHANISMS THAN SEEN NOW
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JAMES HUTTON(1726 – 1797)
Scottish Geologist Explain geologic features by
gradual mechanisms still going on now
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CHARLES LYELL(1797 – 1875)
Principle of UniformitarianismMechanisms of
change are constant over time
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Hutton & Lyell’s ideas influenced Darwin
Both indicated Earth had to be much older than previously believed
Darwin reasoned: slow & subtle processes could produce biological changes
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Lamarck’s Hypothesis of Evolution
1st to propose mechanism of evolutionParts of body used the most become larger, stronger; parts not used deteriorate
Inheritance of Acquired Traits
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LAMARCK(1744 – 1829)
EVOLUTION HAPPENS BECAUSE ORGANISMS INATELY WANT TO BECOME MORE COMPLEX
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VOYAGE of the BEAGLE1831 - 1836
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Darwin’s Observations
Plants & animals in temperate zones of SA closely resembled plants & animals of temperate regions of Europe
Fossils in SA resembled living organisms in SA
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Darwin’s Observations: Descent with Modification Took note of
many adaptations saw adaptations & the origin of a new species as closely related processes
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Darwin’s Finches 14 different
species each clearly adapted to a specific niche
all similar to finches on mainland SA (common ancestor)
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Darwin’s Theory
Proposed that natural selection over long periods of time could cause an ancestral species to give rise to 2 or more descendant species
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Natural Selection: a process in which individuals with certain inherited traits tend to survive & reproduce at higher rates than other individuals without those traits
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The Origin of the Species by Means of Natural
Selection Darwin provided massive amounts
of evidence that descent with modification by natural selection explains :
Unity of LifeDiversity of LifeMatch between Organisms & their Environment
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NATURALSELECTION
ARTIFICIALSELECTION
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Darwin’s Reasoning
OBSERVATIONS INFERENCES
1. There are variations of traits in populations
1. Individual with variations that are favorable will leave more offspring than one without those traits
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Darwin’s Reasoning
OBSERVATION INFERENCE
2. Species produce more offspring than can survive
2. overpopulation leads to competition, those with traits that will help them survive reproduce more passing along favorable traits
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Over time natural selection increases the
match between organisms & their environment
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When the environment changes natural selection may result in adaptations that give
rise to a new species
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Natural Selection in response to invasive species
BALLOONVINE
GOLDENRAIN TREE
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SOAPBERRY BUGS
SEEDS BURIED DEEPER IN PODS OF NATIVE PLANT, BALLOON VINE
BUGS THAT FEED ON INVASIVE GOLDENRAIN PODS NOW HAVE SHORTER BEAKS
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CONCLUSION CHANGING THE
ENVIRONMENT CAN RESULT IN EVOLUTION BY NATURAL SELECTION FOR MATCHING BEAK SIZE
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DRUG-RESISTANTBACTERIA
Normal for 1 out of 3 people to have Staph aureus on skin
MRSA (methicillin-resistant staph
aureus)Can be fatal
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Soapberry bug & MRSA both examples of
1. natural selection does not “create” it “selects” for variants already present in population
2. natural selection depends on time & place
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HOMOLOGY
SIMILARITY RESULTING FROM COMMON ANCESTORS
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Homologous Structures: Embryology
Similarities in early stages of development suggest common ancestryAt some point in development
all vertebrates have a tail
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VESTIGIAL STRUCTURES
REMNANTS OF FEATURES THAT WERE IMPORTANT IN EVOLUTIONARY ANCESTOR
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Molecular Homologies
All life forms use DNA & RNA Genetic code is universal Some human genes code for
exact same protein as bacterial gene +/- have same function
Some organisms carry “vestigial genes”
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Evolutionary Tree
Can organize organisms with shared characteristics in nested groups Deepest layer all living things
share Each successive smaller group
have their own unique homologies
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Evolutionary Trees
are hypotheses that summarize our current understanding of patterns of descent
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Convergent Evolution
The independent evolution of similar features in different lineages
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Analogous Features
are seen in species that share similar structures but not common ancestry
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The Fossil Record Shows:
1. past organisms differ from current ones
2. many species have become extinct
3. the evolutionary changes that have occurred in various groups of organisms
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BIOGEOGRAPHY
The GEOGRAPHIC DISTRIBUTION of ORGANISMS
Influenced by:Continental Drift
250 million yrs ago all land masses joined Pangea
200 million yrs ago split began 20 million yrs ago looked close to what we have today
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Continental Drift
Understanding continental drift scientists look for fossil evidence explained by the movement of land masses
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Summary: 4 Types of Evidences for Evolution
1. Direct Observations1. Effect of invasive species2. Drug-resistance in bacteria
2. Anatomical Similarities1. Homologous & Vestigial Structures2. Universal Genetic Code
3. Fossils4. Biogeography