Download Origin of Diversity Notes

Origin of Diversity notes
KEY WORDS/
QUESTIONS
Diversity
Of
Life:
NOTES
There is a tremendous diversity of life on Earth
today. Look at virtually any environment and you
will discover an incredible variety of plants,
animals and other living things of all shapes, sizes
and lifestyles. This leads to a causal question,
CQ = How did all this diversity arise?
Theories on the
origin of
diversity:
Theories about the origin of diversity fall into three
main categories:
1- Spontaneous Generation, 2-Special Creation,
3-Transmutation of Species = Evolution
Abiogenesis
Abiogenesis is also known as Spontaneous
Generation. It means life emerging from non-living
materials in a spontaneous manner. This was the
ruling theory in Europe for over 1000 years.
Evidence
For:
Against:
Some observations seemed consistent
1. Maggots forming out of dead meat
2. Tadpoles forming from pond scum.
3. Microorganisms (or something) forming in
broth solutions, stagnant water  worms and algae
Other observations supported the opposite:
biogenesis (life from life)
1. Chickens come from eggs, eggs come from
Origin of Diversity notes
chickens
2. Calves come from cows, cows come from calves
Note:
Our observations and ability to observe limit our
Ability to understand nature.
Besides…
Aristotle said that frogs and insects were generated
by moist soil. Science like society was authority
driven.
Experiments
Redi
Redi (1600's) asked and attempted to answer the
following causal question:
Where did these maggots in my meat come from?
Possible explanations:
a. Spontaneous generation =abiogenesis
b. Biogenesis = life comes from preexisting life
(1) We know the maggots turn into flies
(2) Where must maggots have come from: flies
Experiment to tell the difference between the two:
Put piece of meat into two sets of jars, Draw
covered 1 with cloth but not the other
Predictions
- under spontaneous generation: maggots in both
- under biogenesis: no maggots in covered jar
Results: maggots only in the uncovered
Conclusions: Support biogenesis
Reject: abiogenesis
Origin of Diversity notes
Similar experiments showed that many animals and
plants come only from living ancestors
Advent of
Microscope
Leads to
Discovery of
New world
Late 1600s Anton van Leewenhook - ground lenses,
made microscope, found microbes in water, pond
scum, even own body... hypothesized that these too
came from preexisting life.
Argument
revisited:
1700s Needham vs Spallanzani
Argument wouldn't die, spontaneous generation
still felt to be true in some places.
Role of Hidden
Agendae:
Needham:
Many have too much invested (prestige and
professional standing) in old paradigm to give it up.
Needham: 1748 (English clergyman)
Observation: broth spoils or "goes bad"
Possible explanations: “vitalism”
(life force) vs biogenesis
Experiment: put mutton gravy in a corked
container & boiled briefly. Draw
Predictions: Vitalism: microbes and spoiling,
Biogenesis: no microbes or spoiling
Results: microbes and spoiling
Conclusion: supports vitalism, rejects biogenesis
Origin of Diversity notes
Spallanzani:
Said, “Wait a minute, you have problems”:
You used a crudy old cork and you probably didn't
boil it long enough. So he offers his own test:
Same observation: thing go bad
Possible explanation: same as above
vitalism vs biogenesis
Experiment: (Draw):
prepared flasks of gravy, boiled for an hour then
melted top to seal
Predicitions: Vitalism: still spoil
Biogenesis: not spoil
Results: no microbes or spoiling unless opened
Conclusion: rejects vitalism, supports biogenesis
Needham's
reaction:
Did he roll over and play dead? No, remember
hidden agenda. Instead he said that, “the life force
in the air" was destroyed by sealing bottles. That
life force needs “elastic air” to operate.
Needham and Spallanzani argued about methods
and the "elasticity of air" for years.
Final resolution: Louis Pasteur 1862 – created "S" shaped open
flasks (Draw) and partially filled with broth then
boiled. The flasks did not spoil. In fact some were
displayed for 80 years before finally being sealed.
When flasks were tipped allowing some of the fluid
into the trap and back: they quickly became
infected became infected. This provided convincing
Origin of Diversity notes
Some
concluding
points:
.
evidence to reject abiogenesis once and for all.
1. Scientists don't always agree on everything.
2. When they disagree, they often resort to arguing
methods
3. The role of biases
a. We usually have them
b. In my work, I thought I saw one hypothesis
which seemed more logical /explaining more
c. What happens when special interests fund
research (i.e. Tobacco Research Institute
claimed for thirty years that “cigarettes don’t
cause cancer”
4. Scientific fraud, is always a possibility unless
proper procedures are followed (peer review)
So where does
this leave us?
Back to the
other two:
Abiogenisis is a rejected theory,
but is still a theory since it attempts to explain the
origins of diversity.
Religion caveate - there is a difference between
scientific and religious hypotheses and theories.
Religious theories rely on faith for acceptance.
Scientific theories rely on scientific testing and
falsifiability for acceptance.
If a religious theory is not testable & falsifiable, it is
not scientific. That does not necessarily mean it is
wrong…..
Origin of Diversity notes
Teaching religious theories in public school is a
violation of the establishment clause of the U.S.
Constitution… We will not be discussing Special
creation, at least not directly.
Observation:
Causal Question: There is diversity…. Why?
Explantion:
Transmutation / Evolution
Experiment:
Evidence from
Taxonomy:
Conclusion:
Note:
Evidence from
Embryology:
Experiment? Hmm. Maybe we can infer using
study of relationships between species
1. Not all individuals within a species look the same
(there is variance)
2. Between species, we often find intermediates
a. Rattlesnakes, Elapids, rear fanged colubrids
Draw on back
b. lizards- legless lizards/boas-snake
c. peripatus - annelids / arthropods
d. Archaeopteryx – reptile to birds
Doesn't necessarily reject all alternatives, BUT
It is consistant with evolution.
Variation within a species says something about
transmutability or the ability to evolve.
Embryology = the study of the development of
organisms from zygote to adult.
“Ontogeny recapitulates phylogeny” claim was that
organisms went through all the body forms of their
ancestors as they developed.
Not true, actually organisms go through similar
larval stages as their close (evolutionary) relatives.
Origin of Diversity notes
The more closely related two organisms are, the
longer they resemble each other.
Origin of Diversity notes
Evidence from
Anatomy:
Homologies – homologous organs in two different
species are derived a common ancestor.
Homologies and Many times these organs are no longer useful and
said to be vestigial. Examples include the hip and
Vestigial organs thigh bones in snakes and whales and the tail bone
and appendix in man.
How are these useful to other organisms?
Appendix of man = blind end pouch full of bacteria
which can become infected. Appendix of Gorilla
used to help digest leafy vegetarian diet.
Analogies
– analogous organs have similar form and function
but were derived from different ancestors.
These organs serve a useful purpose. Examples
include the fluke of a whale and the tail of a fish,
penguin “wings” and fish fins, wing of a bat / wing
of a bird vs insect wing.
Convergent
evolution:
Conclusion:
Evidence from
biochemistry:
In each case, we find different organs adapted to
similar jobs. This results in convergent evolution –
similar answers to similar problems.
Doesn't necessarily reject all alternatives, BUT
It is clearly consistent with evolution
The closer related taxonomically (phylogenetically)
two organisms are, the closer their chemistry &
DNA are.
Origin of Diversity notes
Evidence from
genetics and
agriculture:
We've been transmutating species for at least
10,000 yrs.
1. Prehistoric dairy farmer
a. Can maintain five cows
b. If they all have calves, how many will he have?
c. Only some should be permitted to reproduce
d. Alternatively, you eat some and keep others
Which calves do they keep?
Note:
2. Darwin called this "Artificial" selection. I like
"Human directed" better
3. Darwin cited many examples with pigeons.
4. Man has done this repeatedly with dogs, cats,
cattle, horses etc.
5. Cabbage, cauliflower, brussel sprouts all started
out as same plant.
Again demonstrates transmutability.
Doesn't necessarily reject all alternatives, BUT
clearly supports evolution
Conclusion:
Fossil evidence:
Fossil record: Draw how fossils are formed etc
NOTE, there are no gaps that we wouldn't expect
to find due to need for specimens to be rapidly
buried in sediment plus soft tissues are poorly
preserved
Origin of Diversity notes
Grand Canyon
fossil record:
Natural laboratory to test evolution.
Draw on board.
Predictions
for Evolution:
We should find a slow gradual increase in
complexity and diversity.
for Abiogenesis:
There should be no real pattern in complexity and
diversity. Species should appear and disappear at
random.
Conclusion:
KEY WORDS/
QUESTIONS
Darwin’s
conceptual
framework:
Most convincing support for evolution yet. Clearly
rejects leading alternatives.
NOTES
1. Malthus essay on population – gave Darwin idea
of Biotic Potential = ability of organisms to
produce more offspring than environment can
support. This leads to a struggle for survival
2. Geology – Theory of Gradualism (Hutton 1795),
Form of Earth due to slow gradual change, not
through a few catastrophies.
Origin of Diversity notes
3. Uniformitarianism
(Lyell 1830) same processes that work today
worked in past
4. Lamark 1809, theory of inheritance of acquired
characteristics (i.e giraffe’s neck)
5. Voyage of Beagle (1831-1836)
Darwin was the ships “naturalist”
6. Darwin writes of transmutation 1837
Informal notes to friends
7. Wallace writes to Darwin (1858) and publishes
essay on natural selection.
8. Darwin publishes On the Origin of Species, 1859
Summary of
Natural
selection:
9. 1866, Mendel publishes his Theory of Particulate
Inheritance
1. Organisms alive today are the result of evolution
not special creation
2. More organisms are produced than can survive =
Biotic potential. Resources are limited, leads to
a struggle for survival “survival of the fittest”
3. Characteristics vary and can be inherited.
4. Some traits are better adapted and leave
more offspring.
5. Over long periods of time natural selection can
both change existing species and create new ones.
Biological
Species:
A natural population or group of interbreeding
individuals which produce fertile offspring and are
reproductively isolated.
Origin of Diversity notes
Biological
Significance:
Since evolution from a shared ancestors has shaped
organs and physiology from worms to humans we
can learn about ourselves by studying bacteria,
dogs, rats..... also.... since ecological assembleges
of plants and animals have evolved together over
time, many features of their physiology are
intimately interconnected in ways that we do not
yet understand and ignore at our own peril!!
Important terms Convergent evolution (analogous structures) =
similar answers to similar problems
and concepts…
Evolutionary arms race ie. parasitism, predation,
herbivory drive evolution
Evolutionary fitness determined by the size of an
organisms reproductive output
Evolutionary adaptation = a form of a trait
increases fitness, can be physical, chemical or
behavioral
Types of
Selection:
Stabilizing selection - keeps phenotypic values
steady, usually around median
Directional selection - shoves average value towards
one extreme or other.
Disruptive selection - shoves values away from
mean towards extremes, can lead to speciation
Origin of Diversity notes
Adaptive
radiation:
Adaptive radiation = the evolution of a number of
diverse species specialized for survival in diverse
environments (niches)
Hardy
Weinberg:
Evolution won't occur if:
1. chance events do not effect gene frequency in a
population
2. mutations don't occur or balance each other out
3. all genotypes have equal reproductive success;
ie. no natural selection is operating on population
4. no net flow of alleles (genes) in or out of pop
(no migration or imigration)
5. all mating in population is at random
Genetic drift:
Speciation:
a chance events that effect genetic frequencies
(founder effect or log falls in the forest)
macroevolution due to reproductive isolating
Mechanisms.
May be prezygotic (mechanical, temporal,
ecological isolation, behavioral, chemical) also
known as allopatry, or postzygotic (hybrid
inviability = liger or mule).
Chemosynthesis Inorganic molecules reacted with energy input
from lightning etc. forming simple organic
theory
compounds (sugar, amino acids, nitrogenous bases,
fatty acids). These then combined to form complex
Origin of Diversity notes
carbohydrates, proteins, lipids and nucleic acids.
When these complex molecules were concentrated
in pools they combined to form simple cells.
Note
Gradualism
Vs
Punctated
Equilibrium
Bottleneck
Founder effect
Chemosynthesis theory is not part of evolution.
Evolution starts with life which is then shaped and
diversified by natural selection.
Darwin said it took millions of years for one
organism to evolve into another. The Cambrian
fossil record shows that evolution may have long
periods of relatively no change followed by periods
of rapid speciation triggered by drastic climatic
change
Occurs when a population is drastically reduced
and continues on from a few ancestors
Occurs when a few individuals (not very diverse)
give rise to a population …..Amish etc.