evolution - bainbridge island school district · ocean creating an “organic soup” or ......
TRANSCRIPT
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
*Heraclitus:
543 – 477 BC
“Evolution might involve conflict and a struggle for survival.”
*Lamark: 1809
Inheritance of Acquired Characteristics
1. Organisms try to improve themselves and become more and more Advanced
2. The effort to improve causes the most used body structures to develop, while unused structures waste away (Principle of Use vs. Disuse)
3. Once a structure is modified, it is inherited by the organism’s offspring (Inheritance of Acquired Characteristics)
Weismann
Weismann performed an experiment that disproved Lamarck's hypothesis. Weismann cut off the tails of mice for hundreds of generations. No inherited change in tail length ever occurred.
*Phenotype changed
*Genotype did not change
Darwin 1831 1. There is Variation in populations
2. Some variations are favorable allowing you to live longer and reproduce more
3. Differential Reproduction: More offspring are produced each generation than can survive
4. Natural Selection: Those that survive and reproduce are those with favorable variations
5. Gradualism: Over enormous spans of time, small changes accumulate, and population change
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!
Darwin Supporters 1. Darwin Awards 2. Moth & Finch experiments 3. Fossil evidence 4. Gradualism: geological processes are slow 5. Malthus-too many humans, not enough
resources=competition * Malthus was Darwin's good friend who
was an economist and they discussed the idea of competition for resources and it's effect on species.
6. Wallace-same idea as Darwin’s: * Evolution by natural selection. Wallace was the first to publish this theory, but Darwin had 20 years of research to back it up.
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 the 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 they get too big.
• Are selectively permeable
Oldest Fossils
• Are composed 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
• Anaerobic, no O2 on early Earth
– Probably a bag of RNA and that’s it
• Similar to today’s prokaryotes (Ribose, Nucleic
Acid & Phosphate Group bound by Hydrogen)
Life on Earth
3.5 BYA: first anaerobic prokaryotes, (no O2 yet), heterotrphic
3.2 BYA: chemosynthetic prokaryotes, anaerobic, autotrophic
2.8 BYA: photosynthetic prokaryotes, anaerobic, autotrophic
2.5 BYA: aerobic prokarytoes (O2!), autotrophic, heterotrophic
1.5 BYA: eukaryotes, autotrophic, heterotrophic
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 ybp 4.6 billion
SO: # of critters = sex = energy = O2 = photosynthesis
Darwin's ideas underlying evolution
1. variation exists among individuals in a population (varying phenotypes due to varying genotypes, variations due to mutations)
2. in some environments resources may become limited and individuals must compete for the resources (survival of the fittest)
3. those individuals best adapted to their environment will survive and pass their genes on to the next generation
(this is the Theory on Natural Selection)
Adaptation: inherited trait or characteristics that increases an individual's survival in a particular environment
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 Evolution
Embryology
Empirical Evidence of Evolution
Genetic 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
Meiosis
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 Law And How often does this happen?
NEVER – all populations evolve because
eventually the environment changes
http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/li
fe4e_15-6-OSU.swf
Microevolution Example
Natural Selection of the Peppered Moth
Microevolution Example
Kinds of Selection: based on fitness
Stabilizing Directional Disruptive
Microevolution Example
Genetic 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 Example
Bottleneck: number of organisms is drastically
reduced for a few generation and the ones that
survive have a different gene frequency.
This population increases.
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
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 System Kingdom, 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
Fairies
X X Leprechauns
X X X Gnomes
X X Elves
NOT fly Find
Treasure
NOT
woods
Pointy
Ears
Classifying Organisms Fairies Gnomes Leprechauns Elves
Not Fly
Find Treasure
Pointy Ears Not live in
woods
Have Don’t Have
Evolution Nothing in Biology Makes Sense
Except in the Light of Evolution
Theodosius Dobzhansky (1900-1975)