Transcript Natural selection - El Camino College

Evolution
Darwin (1809-82)
 English naturalist, wrote “On the Origin of
Species by Means of Natural Selection”
 explain why evolution and how, natural
selection
The voyage
Previous
1. Malthus (1798),
Essay on the
Principle of
Population
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human populations
increases
geometrically but
the food resources
grows
arithmetically
2. Lamarck:
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evolution occurred by the inheritance of acquired
characteristics, body and behavior
giraffes evolved long necks because ancestral
giraffes tended to stretch their necks and this
neck extension was passed on to subsequent
generations
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Darwin
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variation is not created by experience but
already exists when selection acts on it
populations of ancestral giraffes contained
variation in neck length individuals who
were able to feed higher up on the trees had
more food and so were able to survive and
reproduce better than their shorter-necked
relatives
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Darwin’s evidence to explain how
species evolve rather than remain fixed
1.
2.
3.
4.
fossils resemble living organisms
Organisms change gradually when move into
new habitats, islands have diverse animals and
plants related to the mainland sources
Comparative Embryology
Molecular Biology
Fossils
150 M
230 M
65 M
(Extinction)
Elephant Evolution
Modifications seen in
newer species
Older species replaced
Proof of Evolution - Biogeography
Four Galápagos finches
and what they eat:
1.
all the finches
shared a common
ancestor
2.
their beak sizes
had evolved to suit
their food
3.
genetic differences
account for the
physical differences
in the beaks
Proof of Evolution – Comparative Embryology
Comparing structures during embryo development
Ex: vertebrates and gills
Proof of Evolution –
Molecular Biology
All cells have
same/similar molecules
Suggest organisms share
similar ancestor
Concepts
1.
adaptive radiation: species
changes to occupy different
habitats: adapt
2. Macroevolution: grand scale
evolutionary changes that result in the
creation of new species
3. Microevolution: evolutionary change
within a species (population) that make
that species different from its immediate
ancestor
4. Homologous
structures:
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derive from the same body
part present in an ancestor
same bones used for different
functions in related species
5. Analagous structures
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similar-looking structures in
unrelated lineages
parallel evolution or
convergent evolution
Forelimbs of Animals – Homologous Structures
Same bones and similar
structures
Different functions
Insect
Bird
Examples of
Analogous
Structures
Organisms not
related!
Agents of Evolution
1.
2.
Mutation: change in DNA sequence
Migration: movement of individuals between
populations, effects based on two factors:
•
•
3.
4.
proportion of migrants in the population
difference in allele between migrants-original population
genetic drift: genetic changes in populations
isolated from one another
Selection: some individuals leave behind more
progeny than others
•
•
artificial selection, a breeder selects for the desired
characteristics
natural selection, conditions in nature determine
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Natural selection “survival of the
fittest”
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frequency of favorable characteristics
increasing in a population
favorable characteristics are specific to an
environment (not the biggest or the
strongest)
organisms whose characteristics are best
suited to their particular environment
survive more often and leave more offspring
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artificial
selection
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Evolution of
domesticated
animals through
selective breeding
the resulting
differences between
breeds of
domesticated
species are more
extreme than what
exists in nature
Who Are We?
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Humans are apes
Family: Hominidae
• Opposable thumbs
• 1% DNA difference
to chimps
2
Hominid Evolution
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First hominids appeared 5–7 mya
Characteristics of hominids
• Large brains
• Bipedal
• Toolmaking
• walked upright
© 2009 W.W. Norton & Company, Inc.
DISCOVER BIOLOGY 4/e
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Oldest Homo fossils are from 2.4
mya
© 2009 W.W. Norton & Company, Inc.
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8
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H. sapiens
showed
primitive
technology
• Toolmaking
• Building
shelters
• Control of fire
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10
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H. sapiens gave rise to Neandertals and modern humans
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Origin and Spread of Humans
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Out-of-Africa
hypothesis
Multiregional
hypothesis
© 2009 W.W. Norton & Company, Inc.
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Evolutionary Future of Humans
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Brain size
Agriculture
Genetic drift
Natural selection
Infectious disease
Anything else?
© 2009 W.W. Norton & Company, Inc.
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Lecture Practice questions
1. Changes in organisms over a long period of time, including the rise
of novel organisms and extinction, is known as
A)
natural selection.
B) microevolution.
c) macroevolution.
D) punctuated equilibrium.
2. One of the major sources of evidence for evolution is in the
comparative anatomy of organisms. Features that have a similar
look but different origin are called:
A)
homologous
B) analogous
c) vestigial structures.
D) equivalent
3. Chance events that cause a population to lose some individuals
(die), and hence a loss of alleles to the population, results in:
A) mutation. B) migration.
C) selection. D) genetic drift.