evolution
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Evolution. Why not invoke the supernatural (god or gods) to explain how we got here?. The task of science is to make use of nature’s redundancy to describe the world simply. We can use only empirical data. Everything else is outside the realm of science. - PowerPoint PPT PresentationTRANSCRIPT
Evolution
Why not invoke the supernatural (god or gods) to explain how we
got here?• The task of science is to make use of nature’s
redundancy to describe the world simply.
• We can use only empirical data.
• Everything else is outside the realm of science.
• We can’t use the methods of science to confirm or reject the supernatural. (Science is falsifiable; the supernatural is not.)
The National Association of Biology Teachers affirms that teaching biology must be in a standards-based instructional framework, upholding scientific integrity and the right to teach accurate and current science without penalty of political or religious influences on content. Experimentation, logical analysis, and evidence-based revision, based on detectable and measurable data, are procedures that clearly differentiate and separate science from other ways of knowing. Explanations or ways of knowing that invoke metaphysical, non-naturalistic or supernatural events are outside the scope of science and not part of a valid science curriculum.
Submitted by the NABT Board of Directors April 8, 2008.
Theories of Evolution• Darwin Wasn’t the
First:– Heraclitus (543 –
477 BC)“Evolution might involve conflict and a struggle for survival.”
– LeMark: Inheritance of Aquired Characteristics
Theories of Evolution• Hutton:
"...if an organised body is not in the situation and circumstances best adapted to its sustenance and propagation, then, in conceiving an indefinite variety among the individuals of that species, we must be assured, that, on the one hand, those which depart most from the best adapted constitution, will be the most liable to perish, while, on the other hand, those organised bodies, which most approach to the best constitution for the present circumstances, will be best adapted to continue, in preserving themselves and multiplying the individuals of their race."
Darwin
• Was different because he came up with a MECHANISM that was TESTABLE:
The theory of evolution BY MEANS OF NATURAL SELECTION
• Unlike many theories, his has not yet been disproven. Amazing!
Early Earth
4.6 billion years old
Originally chaotic:Volcanoes
• Produced gases– N2, CO2, H2O, CO, CH4
– No O2; O in CO2, H2O, CO, CH4
» Know because rocks aren’t oxidized
• Extreme temperature variations
Lightening & UV Light• Energy sources
How did the first organic chemicals form?
• Oparin and Haldane hypothesized that organic chemicals were made from the gases of the early atmosphere and the energy from lightening, UV light, and radioactivity from the Earth’s core.
• These organic molecules accumulated in the ocean creating an “organic soup” or “primordial soup.”
Miller - Urey Experiment
Stanley Miller
Results of more recent, refined Miller – Urey experiments
• 13 of 20 amino acids• All bases of DNA and RNA• Ribose
ALSO: found amino acids in meteorites and formaldehyde in tail of Haley’s comet.
Life may have originated in undersea vents
Biological Evolution
• Organic compounds had to come together to form complex molecules.– Clay could have attracted, held, and catalyzed
the reactions between them.
• Molecules have to self-replicate– Some RNA can, AND they work as enzymes
• May have been original molecule of life.
Biological Evolution, cont’
• Membranes have to form:– Put amino acids and fat
in water, fat will surround amino acids in spheres similar to cells.
• Split when get too big.• Are selectively
permeable
Oldest Fossils
• Are of microorganisms
• 3.485 billion years old
• Found in stromatolites (mats of bacteria)
Earliest Life
• Bacteria (prokaryotes)– Heterotrophs
• Didn’t have the machinery to photosynthesize
• Absorbed organic nutrients from the primordial soup
– Probably a bag of RNA and that’s its• Similar to today’s prokaryotes
Earliest Eukaryotes
• Developed by endosymbiosis:– Theory by Lynn Margulis– Large bacteria incorporated smaller, energy
producing bacteria– Mutualistic, symbiotic relationship formed
eukaryotes from prokaryotes• Large bacteria get nutrients
• Small bacteria get protection
Earliest Eukaryotes
Evidence for endosymbiosis:
• Mitochondria and Chloroplasts have– Own DNA – like today’s bacteria– Own ribosomes – like today’s bacteria– Double membranes (outer may have been from
vacuoles that engulfed the bacteria)
Biodiversity Increased With the Accumulation of Oxygen
Presently Earth has about 3 million different kinds of organisms.
For variation you need sexual reproduction.
For sexual reproduction you need a lot of energy.
To get a lot of energy (ATP) you need aerobic respiration.
Biodiversity Increased With the Accumulation of Oxygen
For aerobic respiration you need oxygen.
For oxygen you need photosynthesis.
For photosynthesis you need plants.
Variation did not come about until plants had produced significant quantities of oxygen so that aerobic respiration could take place.
Biodiversity and Oxygen
Level of Oxygen Gas (O2)
Number of different kinds of organisms
600 million ybp4.6 billion
SO: # of critters = sex = energy = O2 = photosynthesis
Empirical Evidence of Evolution
Fossil Evidence
• Study of fossils = paleontology
• Record is incomplete– Most organisms decay– Not all found
• NOTE: Older fossils found in deeper rock
– Not many people who hunt for them
Empirical Evidence of Evolution
Fossil Evidence• Best finds:
Intermediate forms (species to species)– E.g., Archaeopteryx
& China fossils• Feathers and wings of
birds, but teeth and tails of reptiles.
Empirical Evidence of Evolution
Homologous Structures
Empirical Evidence of EvolutionEmbryology
Empirical Evidence of EvolutionGenetic Information
Origin of Species
• Individuals do not evolve, populations do.
• Evolution– change in a population through time– Source of changes in genes
• Mutations
• Recombination at fertilization
• Crossing over
• Independent assortment
Origin of Species
– Outside Influences led to study of Epigenetics• Chemicals in the environment
• Diet
• Family History
• ????
Origin of Species
• Microevolution– Change in gene frequency within an individual
population.• Studies can help us tell what is going on in the
environment.
• Have to look at the gene pool
Hardy-Weinberg Law(useful for studying large, sexually
reproducing populations)
A population will NOT change IF
1. There is no mutation
2. Mating is completely random
3. There is no migration in or out
4. Natural selection does not occur (one individual is not favored over another)
Hardy-Weinberg LawAnd How often does this happen?
A population will NOT change IF
1. There is no mutation
2. Mating is completely random
3. There is no migration in or out
4. Natural selection does not occur (one individual is not favored over another)
NEVER – all populations evolve because eventually the environment changes
http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/life4e_15-6-OSU.swf
The Hardy Weinberg Equilibrium
F = “The frequency of”
So:FA x FA + 2(FA X Fa) + Fa X Fa= FA2 + 2 (FAFa) + Fa2 = 100%
Microevolution Example
Natural Selection of the Peppered Moth
Microevolution Example
Kinds of Selection
Stabilizing Directional Disruptive
Microevolution ExampleGenetic Drift in Beetles: Occurs in small populations
because the chances of coming up with the expected results is low compared to a large population.
Microevolution Example
Founder Effect
Migrate out and found a new population with different gene frequency.
Microevolution ExampleBottleneck: number of organisms is drastically
reduced for a few generation and the ones that survive have a different gene frequency.
Origin of Species
• Macroevolution– Change in species– Source of change in species = MUTATIONS– Inherited variations give some individuals an
improved chance to survive and reproduce as the environment changes.
• NOTE: ENVIRONMENT = LIVING THINGS TOO!– Viruses and Bacteria– Competitors
Origin of Species
• Organisms do not intentionally change. They cannot “will” a mutation because they “need” it. Those with mutations that help them survive do. Those without, die.
Origin of Species
• For new species to evolve– Two populations become so different in their
genetic makeup that they can no longer interbreed.
– Most common mechanism that separates populations: geographic isolation.
Geographic Isolation
Prezygotic Isolation
Other Forms of Isolation
Gamete Isolation – sperm not chemically attracted to egg or not gain entry to egg
Prezygotic Isolation
Other Forms of Isolation
Seasonal Isolation – Trees may give off pollen at different times of year
Prezygotic Isolation
Other Forms of Isolation
Zygote doesn’t develop normally, or produces a sterile offspring.
Postzygotic Isolation
Back to Geographic Isolation
New environments with few competitors allow populations to easily separate and go their own ways. Speciation will result– Called adaptive radiation
Evolution - Rate• Darwin:
– gradualism
• Niles Eldridge and Stephan J. Gould:– Punctuated Equilibrium
• Fossil evidence shows long periods of stasis followed by rapid change (an asteroid falls on your head)
Gradualism
Punctuated Equilibrium
Extinctions - Many
So What Do We Have Today?
3,000,000 different types
of organisms.
“Types” means “species”
Species Concept
Two organisms are of the same species IF they• Breed naturally• Produce fertile offspring
“Species” is a man-made term to help us organize our thinking
Classification of Organisms = Taxonomy
Now based on evolutionary relationships (DNA) rather than just physical characteristics.
Physical characteristics are important still– About the only thing we
can see in fossils!
Classification SystemKingdom, Phylum (Division for plants), Class,
Order, Family, Genus, Species
Why not common names?
Which one of these is a gopher?
Florida Washington
Classification System
Binomial nomenclature = Two-name naming system
• Invented by Carolus Linnaeus– Uses Latin (dead language doesn’t change)
Classification System• Species name = genus + specific epithet
– E.g., • Homo sapiens (humans)• Amphiprion percula
(clown fish)
Classifying Organisms
• Cladistics - based on evolutionary relationships and homologous structures– Compare shared derived characteristics
Classifying Organisms
• Elves, Gnomes, Leprechauns, and Fairies are thought to form an evolutionary group of little people with magic powers. However, the exact relationships are unknown. Infer the phylogenetic pattern based on the following information.
Classifying Organisms
• Pointy ears evolved from ears that were not pointy.
• Inhabiting woods is more primitive than inhabiting other places
• Ability to find hidden treasure evolved from the lack of such ability
• Ability to fly is primitive
Classifying Organisms
• Elves: pointy ears; haunt woods; can't find treasure; can't fly
• Fairies:ears not pointy: live in woods; can't find treasure; can fly
• Gnomes: ears not pointy; live in mines and quarries; find treasure; can't fly
• Leprechauns:ears not pointy; live in woods; find treasure; can't fly
Classifying Organisms
Pointy Ears
NOT woods
Find Treasure
NOT fly
Elves X X
Gnomes X X X
Leprechauns X X
Fairies
Classifying Organisms
Fairies
GnomesLeprechaunsElves
Not Fly
Find Treasure
Pointy EarsNot live in woods
EvolutionNothing in Biology Makes Sense Except in the Light of Evolution
Theodosius Dobzhansky (1900-1975)