Transcript Evolution intro _12

Evolution
- constancy & change
Modern Evidence for
Natural Selection
1.
2.
3.
4.
5.
6.
fossil records – organisms change over time
biogeography – related organisms in same area
comparative anatomy – homologous structures
comparative embryology – similar embryos
molecular biology – similarities in DNA, proteins
artificial selection – selective breeding
Phylogeny &
Molecular Systematics
• Phylogeny – study of evolutionary
relationships
• Molecular Systematics – study of
molecular structures (DNA, protein) to
determine evolutionary relationships
*animals, including humans, and fungi,
are more closely related to each other
than either are to plants
Occam’s Razor &
Parsimony
• Occam’s Razor (law of parsimony) - "All
other things being equal, the simplest
solution is the best."
• Used to justify a phylogenetic tree that
represents the smallest number of
evolutionary changes
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Cladogram (phylogeny)
- shows ancestral relationships
Comparison of
hemoglobin
Cladogram
- primate DNA
comparisons
Molecular Systematics
Molecular Clocks
• DNA or protein comparisons to
estimate the length of time that two
species have been evolving
independently
Primate evolution
• Humans have 99.99% similarity
• Humans and chimps have 98%
similarity
“Ontogeny recapitulates
Phylogeny"
The embryonic development of a
species (ontogeny) is a replay of
its evolutionary history
(phylogeny).
- 1866 Ernst Haeckel
Comparative Embryology (faked)
Drawings vs. photographs
Comparative
Anatomy
Animal developmental
characteristics
p.371
•body plan
•symmetry
•body cavity
•digestive tract
•segmentation
mono-, para-, or polyphyletic
monophyletic –
all descendants
paraphyletic not all descendants
polyphyletic - last common ancestor
is NOT within group
Monophyletic includes the most recent common ancestor of a group of
organisms and all of its descendants
Polyphyletic does not include the common ancestor
Paraphyletic includes most recent common ancestor, but not all of its
descendants
Restriction Maps
4
3
10
13
17
17
1. Gibbon is least similar; chimp is
most similar.
Skull Morphology
deer
cat
dog
bear
gorilla
human
brain size
teeth types
herbivore
brain to face ratio
meat-eaters
mammals
Skull Morphology
deer
cat
dog
bear
gorilla
human
brain size
teeth types
herbivore
brain to face ratio
meat-eaters
mammals
Restriction Maps
2. Changes will go back and forth as
environment changes.
3. Neutral changes will accumulate.
4. Advantageous changes will
accumulate more often.
5. Two closely related organisms will
have fewer genetic differences.
Animal Development
& Phylogeny
Animal developmental
characteristics
p.371
•body plan
•symmetry
•body cavity
•digestive tract
•segmentation
Tissue
Organization
1. no tissue
- no specialized fxn
2. tissue
- specialization
Body Symmetry
1. radial
- looks same cut
from any side at top
2. bilateral
- looks same cut
from 1 side at top
Body Cavity
1. acoelomate
- no body cavity,
digestive tube
connected to
muscle
2.
pseudocoelomate
- partial cavity
3. coelomate
- digestive tube
separated from
muscles
Digestive Tract
1. protostome
- spiral cleavage
- blastopore-->mouth
2. deuterostome
- radial cleavage
- blastopore-->anus
http://www.mun.ca/biology/scarr/141993_Protostome_vs_Deuterostome.jpg..jpg
Comparative Embryology
• closely related organisms go through
similar stages in their embryonic
development
*all vertebrate embryos have gill slits:
– gill slits in fish form gills
– human gill slits form the Eustachian tubes
connecting the middle ear with the throat
Comparative
Anatomy
Vestigial Structures
– pelvic bones in whale
- eye sockets in blind salamanders
Convergent Evolution
-similar solutions to similar “problems”
Analogous structures
• similar functions, no evolutionary relationship;
different internal structure & development
*flight - bird vs bat vs insect
*reproduction - marsupials vs placentals
*aquatic vertebrates - dolphins vs fish
Artificial selection
• breeding
Artificial selection
• pesticide resistance
• antibiotic resistance
Natural Selection
“survival of the fittest”?
Charles Darwin
• (1809-1882) British naturalist
• 1831-1836 Voyage on HMS
Beagle
• collected specimens of fossils as
well as living; observed the
various adaptations of plants and
animals
• breeding experiments
• 1859 “On the Origin of Species
by Means of Natural Selection”
“Origin of Species”
Key Points
1. descent with modification
•
all species evolved from ancestral species
and were not specially created; diverse
modifications accumulated over millions of
years
2. natural selection
•
mechanism of evolution; a consequence of
interactions between individual organisms
and their environment
Natural Selection Requires…
1. Variation - individuals within a population
show variation in their characteristics
2. Overproduction / competition environmental resources are limited
3. Survival / reproduction – only those best
suited to environment will survive to
reproduce and pass on favorable variations
Historical Views of Origin of Life
Creationism (Judeo–Christian):
Earth is ~6000 years old and was populated
by unchanging life forms made by the
Creator during a single week
Greek philosophy (Aristotle ~350 BC):
scala naturae (scale of increasing complexity)
– species were fixed in form, did not evolve
Carolus Linnaeus
• (1707 – 1778) Swedish
physician, botanist
• father of taxonomy —
developed the binomial
nomenclature system
• organized organisms into
categories based on similar
physical features
James Hutton
• (1726-1797) Scottish geologist
• proposed geological
gradualism – change is the
cumulative product of slow,
continuous processes
*canyons are formed by
erosion from rivers
Georges Cuvier
• (1769-1832) French anatomist
• founder of paleontology –
study of fossils
• proposed catastrophism –
periodic catastrophes result in
mass extinctions; migrating
species repopulate the area
Charles Lyell
• (1797-1875) geologist
• “Principles of Geology”
proposed uniformitarianism –
geological processes are
uniform and balanced
throughout Earth
*processes that build
mountains are eventually
balanced by the erosion of
mountains by wind and water
Jean Baptiste Lamarck
• (1744-1829) naturalist
• evolution is driven towards
complexity and perfection
(organisms became better adapted
to their environments)
• 1809 proposed inheritance of
acquired characteristics:
– use and disuse
*giraffes
Reverend Thomas Malthus
•(1766-1834) studied human overpopulation:
1. all species over-produce
2. competition for resources
3. only a fraction survive to
reproduce
4. eventually populations reach
carrying capacity
Stephen Gould
• 1972 proposed theory of
punctuated equilibrium
- based on fossil record: little
change occurs, then rapid
localized speciation occurs
• exaptation – shifts in function
of a trait during evolution
*mammalian limb
Michael Behe
• 1992 irreducible complexity
(argument for intelligent design)
– biological systems are too complex
to have evolved through natural
selection
– evolutionary pathways may contain
one or more unselected steps
The Subtleties of Natural
Selection
•
•
•
individuals do not
evolve; populations do
only heritable
variations can be
changed
an adaptation to a set of
conditions may be
useful or detrimental,
under different
circumstances
Modern Examples of Natural
Selection
• Kettlewell - observed peppered moths
• Grants on the island of Daphne Major observed shifts in the frequency of beak sizes
over short periods of time
• Antibiotic resistance in bacteria
• How do genetic variations arise in nature?
Industrial Melanism
– Peppered Moths
•1848 Kettlewell’s
observations –
moths are darker in
polluted areas
1973 Grant
- change in finch
beak size