evolution - constancy & change. modern evidence for natural selection 1.fossil records –...
TRANSCRIPT
Evolution- constancy & change
Modern Evidence for Natural Selection
1. fossil records – organisms change over time
2. biogeography – related organisms in same area
3. comparative anatomy – homologous structures
4. comparative embryology – similar embryos
5. molecular biology – similarities in DNA, proteins
6. 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 (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
Occam’s Razor & Parsimony
Comparison of hemoglobin
Cladogram (phylogeny)- shows ancestral relationships
Cladogram
- primate DNA comparisons
Molecular Clocks• DNA or protein comparisons to
estimate the length of time that two species have been evolving independently
Molecular Systematics
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
1717
1310
43
1. Gibbon is least similar; chimp is most similar.
Skull Morphology
humandeer cat dog bear gorilla
brain size
teeth types
brain to face ratio
meat-eaters
mammals
herbivore
Skull Morphology
humandeer cat dog bear gorilla
brain size
teeth types
brain to face ratio
meat-eaters
mammals
herbivore
Restriction Maps2. 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 Organizatio
n
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 Cavity1. 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 LifeCreationism (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
1. all species over-produce
2. competition for resources
3. only a fraction survive to reproduce
4. eventually populations reach carrying capacity
•(1766-1834) studied human overpopulation:
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