Transcript Evolution & Natural Selection

Theory of Evolution &
Microevolution
Chapter 13
Evolution
• Darwin and his theory
• Evolution Evidence
Charles Darwin
Natural Theology
• Based on a literal view of the Genesis
Story
• Earth 6,000 yrs old
• No new species
• No physical changes (valleys, mountains)
Putting Darwin in the context
of his time
Important people
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Linnaeus
Lamarck
Malthus
Lyell
Linnaeus
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Studying biology to reveal a divine plan
Developed modern taxonomy
Made Binomials: Homo sapiens
Based groupings on morphology
Did not believe in evolution,
Taxonomy data would later provide some
of best evidence
Lamarck
• Got the genetics wrong
• Stressed acquired traits-(wrong)
– Giraffes stretched their necks
– Babies had longer necks
• But- said species evolved to be better
suited to environment – right!
Malthus
• British economist studied Paris after the
revolution
• Limited resources
• Excess population growth
• Struggle to survive,
• competion among individuals
• Survival of the richest
Malthus
• Darwin was influenced
by Thomas Malthus’s
Essay on the Principle
of Population (1798)
– Populations
increase
geometrically, while
food supply
increases only
arithmetically
Fig. 2.6
Lyell
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British geologist.
Following Hutton’s work
Earth is old
Valleys formed by erosion
Mountains by uplifting
Slow processes over LONG periods of
time
Fig. 2.13
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5 year voyage of the Beagle
British Isles
North America
Europe
Western
Isles
North Atlantic
Ocean
Asia
Canary
Islands
Cape Verde
Islands
Marquesas
Society
Islands
Africa
Indian
Ocean Keeling
South
America
Galápagos
Islands
Valparaiso
Straits of Magellan
Cape Horn
Bahia
North Pacific
Ocean
Philippine
Islands
Islands
Madagascar
Ascension
St Helena
Rio de Janeiro
Montevideo
Buenos Aires
Mauritius
Bourbon Island
Equator
Australia
Friendly
Islands
Sydney
Cape of
Good Hope
Port Desire
South Atlantic
Falkland
Islands
Ocean
Tierra del Fuego
King George’s
Sound
Hobart
New
Zealand
Evidence that Made Darwin think..
• The variation among organisms in a population
• Biogeography – where species are found around
the globe
• Fossil record
• Comparative morphology – Linnaeus's
classification
• Artificial Selection
• Geology and the age of the earth
• Malthus and economic theory
• Lamarck’s theory and adaptations
Evolution- Just a Theory?
• Theory vs. Law vs. Dogma
Terms:
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Theory – explain a process
Law- describes a phenomenon, a formula
Dogma is not testable – beliefs
Science is limited to things we can
measure, test.
• Hypothesis – is an “educated” guess to
explain a problem,
Scientific Method
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Problem, observation
Background information, literature search
Hypothesis based on previous work
Experiment to test hypothesis
Analyze results
If hypothesis supported – publish a paper.
Darwin’s Theory
• Populations have inherent variation among
individuals.
• These traits are heritable
• Resources in the environment are limited
• Populations have a greater fertility than
their environment can sustain.
• Populations would grow exponentially, but
most remain stable in size.
A population of Liguus fascitus
Variation in shell coloration patterns
Darwin’s Theory continued:
• There is a struggle to survive among the
offspring called Natural Selection.
• The survivors are better fit
• Fitness is the ability to have more offspring
(frequency of genes in the genepool).
Natural Selection
• “struggle “ or competition does not have to
be a fight to death
• May just be as simple as a seed germinating
earlier and getting established first. It
produces 120 seeds. A later germinating
plant makes only 50 seeds.
• “Fitness” is the success rate of the offspring
in future generations.
Fig. 2.7
Some Evidence for Evolution
• Microevolution- antibiotic, pesticide resistance
– Artificial selection
• Fossil record
• Biochemical comparisons
– Protein sequences
– DNA, gene comparisons
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Morphological comparisons
Embryology
Biogeography
Genetically modified organisms
Fig. 2.9
Fig. 2.5
Fig. CO 2
Fig. 2.10
Evolution in progress
around us:
• Antibiotic resistance
• Herbicide, Pesticide resistances
• New disease threats (AIDS, SARS, Ebola,
West Nile Virus)
• Climate change
• Introduced species
• Biotechnology ???
Fig. 2.8
Darwin and
Human Evolution
• Published “Descent
of Man” in 1871
• Wasn’t first to
hypothesis our
relation to apes
• caused more
popular criticism of
his general theory
All made by Artificial
Selection from wild mustard
Artificial Selection: human designed breeding of plants and animals for desired
traits by selecting which individuals get to reproduce.
backbone
pelvic girdle
coccyx (bones
where many
other mammals
have a tail)
thighbone
attached to
pelvic girdle
small bone
attached to
pelvic girdle
Missing Links
Galapagos Finches
• Specialization to different feeding sources
may have diversified the species.
Sexual Selection
Directional Selection
modifies Beak depth during
drought periods
Fig. 2.16
Fig. 2.15
Homologous features
• Derived from a common ancestor
• Often do not have similar functions
• Changes in the timing of genes forming
body parts can alter their over-all shape.
adult
proportions in infant
chimpanzee
adult
proportions in infant
human
4
3
early reptile
21
5
21
3
4
pterosaur
1
chicken
2
3
1
2
bat
3 4
1
5
porpoise
2
4
3
5
penguin
2
1
2
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4
5
3
human
Analogous Features
• Have same functions ( by convergence)
• Do not have a common ancestry
• Are not derived from the same ancestral feature
Butterfly and Bird
• No bones in butterfly, not
from common ancestor
• Structures not related
Ecotypes
• Populations that adapted to local
environmental conditions.
• Still one species – inter-fertile
• Can form clines – serial ecotypes along a
gradient
– Common garden experiment (e.g. elevation
and yarrow)
• Need to preserve local adaptations in
plants
– In Botanical garden they always list source of
plant
Ecotypes forming a cline Fig.
23.8
Convergent Evolution
• Sometimes unrelated species may
superficially look alike
• Both species have adapted to similar
habitats.
• Evolution comes up with similar
adaptations to the conditions
• Does not mean they are closely related
Convergent Evolution
Ocotillo
North America
Allauidia
Madagascar
Fig. 13.9b