descent with modification: a darwinian view of life
TRANSCRIPT
CAMPBELL & REECE:CHAPTER 22
Descent with Modification: A Darwinian View of Life
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
EVOLUTIONDESCENT WITH
MODIFICATION
EVOLUTION A CHANGE in the GENETIC COMPOSITION of a POPULATION from GENERATION to GENERATION
EVOLUTION
CAN BE VIEWED IN 2 WAYS1. A PATTERN
OBSERVATIONS FROM NATURAL WORLD
2. A PROCESS MECHANISMS THAT PRODUCED
THE OBSERVED PATTERNS
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
CAROLUS LINNAEUS(1701 – 1778)
DEVELOPED BINOMIAL NOMENCLATURE
WITH A “NESTED” CLASSIFICATION SYSTEM
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
GEORGES CUVIER
CATASTOPHISM: EVENTS IN THE PAST OCCURRED SUDDENLY & WERE CAUSED BY DIFFERENT MECHANISMS THAN SEEN NOW
JAMES HUTTON(1726 – 1797)
Scottish Geologist Explain geologic features by
gradual mechanisms still going on now
CHARLES LYELL(1797 – 1875)
Principle of UniformitarianismMechanisms of
change are constant over time
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
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
LAMARCK(1744 – 1829)
EVOLUTION HAPPENS BECAUSE ORGANISMS INATELY WANT TO BECOME MORE COMPLEX
VOYAGE of the BEAGLE1831 - 1836
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
Darwin’s Observations: Descent with Modification Took note of
many adaptations saw adaptations & the origin of a new species as closely related processes
Darwin’s Finches 14 different
species each clearly adapted to a specific niche
all similar to finches on mainland SA (common ancestor)
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
Natural Selection: a process in which individuals with certain inherited traits tend to survive & reproduce at higher rates than other individuals without those traits
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
NATURALSELECTION
ARTIFICIALSELECTION
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
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
Over time natural selection increases the
match between organisms & their environment
When the environment changes natural selection may result in adaptations that give
rise to a new species
Natural Selection in response to invasive species
BALLOONVINE
GOLDENRAIN TREE
SOAPBERRY BUGS
SEEDS BURIED DEEPER IN PODS OF NATIVE PLANT, BALLOON VINE
BUGS THAT FEED ON INVASIVE GOLDENRAIN PODS NOW HAVE SHORTER BEAKS
CONCLUSION CHANGING THE
ENVIRONMENT CAN RESULT IN EVOLUTION BY NATURAL SELECTION FOR MATCHING BEAK SIZE
DRUG-RESISTANTBACTERIA
Normal for 1 out of 3 people to have Staph aureus on skin
MRSA (methicillin-resistant staph
aureus)Can be fatal
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
HOMOLOGY
SIMILARITY RESULTING FROM COMMON ANCESTORS
Homologous Structures: Embryology
Similarities in early stages of development suggest common ancestryAt some point in development
all vertebrates have a tail
VESTIGIAL STRUCTURES
REMNANTS OF FEATURES THAT WERE IMPORTANT IN EVOLUTIONARY ANCESTOR
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”
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
Evolutionary Trees
are hypotheses that summarize our current understanding of patterns of descent
Convergent Evolution
The independent evolution of similar features in different lineages
Analogous Features
are seen in species that share similar structures but not common ancestry
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
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
Continental Drift
Understanding continental drift scientists look for fossil evidence explained by the movement of land masses
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