Download shumate 22ppt descent with modification

Descent with Modification:
A Darwinian View of Life
Part A: Darwin & Natural
Selection
Theme:
 Evolutionary change is based on the interactions
between populations & their environment which
results in adaptations (inherited characteristics)
to increase fitness
Evolution = change over time in the genetic
composition of a population; descent with
modification
Carolus Linnaeus
1707-1778
Linnaeus: founder of taxonomy;
binomial nomenclature
 Domain – Kingdom –
Phylum – Class – Order –
Family - Genus – Species
 (Dear King Philip Came
Over For Good Spaghetti)
 Domains = Eubacteria,
Archaea, Eukarya
 Classification based on
anatomy & morphology
Cuvier:
 Paleontologist – studied fossils
 Deeper strata (layers) - very different fossils
from current life
 Opposed idea of evolution
 Catastrophism – catastrophe destroyed many
living species, then repopulated by
immigrant species
George Cuvier
(1769-1832)
Hutton :
Gradualism = geologic change results from slow &
gradual, continuous process
 Slow & subtle changes in organisms
James Hutton
1726-1797
 Lyell:
Uniformitarianism = Earth’s processes same
rate in past & present (are constant)
therefore Earth is very old
Charles Lyell
1797-1875
Lamarck:


Published theory of evolution (1809- Darwin birth year)
Compared living species with fossil forms, found several lines of
descent

Use and Disuse: parts of body used  bigger, stronger
(eg. giraffe’s neck)

Inheritance of Acquired Characteristics: modifications
can be passed on

Believed organisms have innate drive to become more
complex

Importance: Recognized that species evolve, although
explanation was flawed
Jean-Baptiste Lamarck
1744-1829
Thomas Malthus
(1766-1834)
Malthus: English cleric and scholar,
influential in the fields of political
economy and demography
 More babies born than deaths
 Consequences of overproducing
within environment = war, famine,
disease (limits of human pop.)
 Struggle for existence
Charles Darwin (1809-1882)
 English naturalist
 1831 to 1836: joined the HMS
Beagle for a 5-year research
voyage around the world
 Collected and studied plant
and animal specimens,
bones, fossils
 Notable stop: Galapagos
Islands
Darwin’s Finch Collection/Tortoise Shell
The birds were all
about the same size,
but the shape and
size of the beaks of
each species were
different.
Many islands also show
distinct local variations in
tortoise morphology…
…perhaps these are
the first steps in the
splitting of one species
into several?
 Darwin waited 30 years before he published his
ideas on evolution
 Alfred Russell Wallace – published paper on
natural selection first (1858)
 Charles Darwin (1859): On the Origin of Species by
Means of Natural Selection
 Mechanism for evolution is Natural Selection
 Darwin didn’t use “evolution”, but rather “descent
with modification”
12
Darwin’s Theory of Natural Selection:
1.
2.
3.
4.
5.
Overproduction-Populations produce more offspring
than can possibly survive. Overproduction leads to
competition.
Natural Variation-Individuals in a population vary
extensively from each other, mostly due to inheritance.
Fitness : struggle to survive, individuals whose inherited
characteristics best fit to environment leave more offspring
than less fit.
Adaptation: enhance an organism’s ability to survive and
reproduce
Descent with modification- Unequal ability of
individuals to survive and reproduce leads to gradual
change in population, with favorable characteristics
accumulating over generations.
 Adaptations enhance an organism’s ability to survive
and reproduce
 Eg. Desert fox - large ears, arctic fox - small ears
 Overproduction of offspring leads to competition
for resources
Key Ideas:
 Populations evolve, not individuals.
 Fitness is determined by the environment.
In summary:
Natural Selection = Differential success in reproduction
Product of natural selection = Adaptations of populations to
environment
 Camouflage
(Cryptic coloration)
Mullerian Mimicry –
Unpalatable mimics
unpalatable
The Peppered Moth –
An Example of Natural
Selection
 Batesian Mimicry – Palatable mimics
unpalatable
Warning Coloration (Aposematic coloration)
 Disruptive Coloration
Eye spots
Counter Shading
Natural selection in action
 Insecticide &
drug resistance
 insecticide didn’t
kill all individuals
 resistant survivors
reproduce
 resistance is inherited
 insecticide becomes less &
less effective
Evidence of Evolution
2007-2008
Evidence supporting evolution
 Fossil record
 transition species
 Anatomical record
 homologous & vestigial structures
 embryology & development
 Molecular record
 protein & DNA sequence
 Artificial selection
 human-caused evolution
Fossil record
 Layers of sedimentary rock contain fossils
 new layers cover older ones, creating a record
over time
 fossils within layers show that a succession of
organisms have populated Earth throughout a
long period of time
Fossil record
 A record showing us that today’s organisms
descended from ancestral species
Evolutionary change in horses
550
500
Body size (kg)
450
Equus
400
350
300
250
Merychippus
200
150
Mesohippus
Hyracotherium
100
50
Nannippus
60 55 50 45 40 35 30 25 20 15 10 5 0
Millions of years ago
Evolution of birds
 Archaeopteryx
 lived about 150 mya
 links reptiles & birds
Smithsonian Museum,
Washington, DC
Land Mammal
?
?
?
?
Homologous structures
 Similar structure
 Similar development
 Different functions
 similarities in characteristics resulting from
common ancestry
Analogous structures
 Separate evolution of structures
similar functions
 similar external form
 different internal structure &
development
 different origin
 no evolutionary relationship

Don’t be fooled
by their looks!
Solving a similar problem with a similar solution
Convergent evolution
 Flight evolved in 3 separate animal groups
 evolved similar “solution” to similar “problems”
 filling similar ecological roles in similar
environments, so similar adaptations were selected
(similar niches)
 analogous structures, not closely related
Convergent evolution
 Fish: aquatic vertebrates
 Dolphins: aquatic mammals
similar adaptations to
life in the sea
 not closely related

Those fins & tails
& sleek bodies are
analogous structures!
Vestigial organs
 Modern animals may have structures that serve little or no function
 remnants of structures that were functional in ancestral species
 deleterious mutations accumulate in genes for non-critical structures
without reducing fitness
 snakes & whales — remains of pelvis & leg bones of walking ancestors
 eyes on blind cave fish
 human tail bone and
Comparative embryology
 Similar embryological development in closely related
species
 all vertebrate embryos have similar structures at different
stages of development

gill pouch in fish, frog, snake, birds, human, etc.
Evidence for Evolution
Comparative Embryology- The complete picture
Molecular record
 Comparing DNA & protein structure
 universal genetic code!

DNA & RNA
 compare common genes
 cytochrome C (respiration)
 hemoglobin (gas exchange)
Human/kangaroo
Closely related species have
sequences that are more similar
than distantly related species
 DNA & proteins are a molecular
record of evolutionary relationships
Nucleotide substitutions
100
Dog/
cow
75
Human/
cow
Rabbit/
rodent
50 Horse/
donkey
Llama/
cow
Horse/cow
Sheep/
goat
25
Human/rodent
Pig/
cow
Goat/cow
0
0
25
50
75
100
Millions of years ago
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Artificial selection
 Artificial breeding can use variations in
populations to create vastly different “breeds” &
“varieties”
“descendants” of wild mustard
“descendants” of the wolf
Natural Selection
Artificial Selection
•Nature decides
•“Man” decides
•Works on individual
•Selective breeding
•Inbreeding occurs
•eg. Finch beaks
•eg. Breeds of dogs
Evidence for Evolution
 Direct Evidence
 Rapid Evolution
 Strains of bacteria becoming resistant to
antibiotics
 Weeds and herbicides
 Insects and insecticides
Life has changed over time
& in turn has changed the Earth
Living creatures have
changed Earth’s enviro
making other life poss
Essence of Darwin’s ideas
(1) Variation exists in natural populations
(2) Many more offspring are born each season
than can possibly survive to maturity
(3) As a result, there is a struggle for existence
- competition
(4) Characteristics beneficial in the struggle
for existence will tend to become more
common in the population, changing the
average characteristics of the population
- adaptations
(5) Over long periods of time, and given a steady input of
new variation into a population, these processes lead to
the emergence of new species