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Essay:Understanding evolution

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Essay.svg This essay is an original work by Javascap. It is based on the lectures he has had in class.
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Lecture 1, intro to Understanding Evolution[edit]

Basics of science[edit]

discuss term scientist, what is is based off, what biology is, note taxonomy

Scientific reasoning[edit]

  • Observation, scietific method, explain phenomena
  • why things happen, allude to puzzle
  • explanations in science are hypotheses
  • Tentative, only natural causes explain natural phenomena
  • Science uses inductive reasoning
  • A hypothesis must be testable
  • Tested by conducting experiments of observations
  • works specifically to generally.
  • Deductive reasoning, if hypothesis is correct then we can expect a specific outcome.

Scientific method[edit]

Observation - question - hypothesis - experiment - conclusion

  • (Insert scientific method chart)
  • key points of method
  • a theory is a set of related hypothesis supported by evidance tat explains some aspect of natural world
  1. Scientific claims are subject to revision in light of new evidance
  2. Results must be reproducable
  3. Sciencetific claims must be falsifiable (white swan example)
  • Hypothesis with several experimental tests are "well supported and highly corroborated.

Lecture 2, Variation in Population[edit]

  • Living things are organised hierachically


  • Basic heriditry unit
  • Every inherited trait has one gene
  • Most traits have more than one gene


  • complete set of genes in given spcie
  • Each individual has two copies of every gene

-One from mom, one from dad, mention alleles

  • These may be same or different
  • Somge genes have only one allele, most have two +
  • Human ABO blood, 4 alleles

Deformed frogs[edit]

Mississippi, 1958

  • bullfrogs with many legs
  • Only appeared one year

Minnesota and other states, 19995

  • Deformed in many species
  • Appeared in later years
  • Many populations affected
  • Some went extinct

How is this explained?[edit]

May have been caused by a teratogen (agent in environment that causes birth disorders) Many teratogens have been identified

  • chemicals, radiation, parasites, temperature extremes, diet problems, lack of oxygen


  • Sleeping pill/tranqualizer banned in US and other countries.
1961 - Proven to cause "seal limbs"
1962 - Banned worldwide
1997 - Legalised for leprosy treatment


Test environmental modification
Mention that genetic makeup is not altered, not inhereted
  • Another hypothesis
allele: One variant of gene
dominant ones are always expressed
None-dominant ones (recessive) are repressed with a dominant allele
Carrier, normal apperance, one dominant, one recessive

Ellis Van Creveld syndrome[edit]

Six fingers, short limbs, malformed hearts

  • suprisingly common in Amish (mention founder effect)

Lecture 3, Darwinian scheme of evolution[edit]

Erasmus Darwin, 1731 - 1802[edit]

  • English physicial, natural philosopher, "psychologist, inventer and poet
  • CD's grandfather
  • Wrote "Zoonomia, or the laws of organic life"
  • Presented evolutionary ideas in poetry
  • Did NOT propose a method, but discussed how life could have "evolved" from one filament

James Usher[edit]

  • Annals of the torah from beginnning of world
  • Calcuated date "23 Oct BCE"
  • Sept 21, 2004 BCE in gregorian calender

Catastrophism vs. Uniformitarinism[edit]

Conflicting geological theories


  • Geological features were shaped during dramatic upheavals, not gradual changes
  • George Curvier
  • Early explanation for fossil record
  • Curvier's hypothesis is mixed with biblical catrasphies like flood


  • Charles Lyell
  • Gradual changes over a long period of time
  • Argued that forces we see today worked at the same time
  • Printed "principles of geology"

Darwin's voyage[edit]


  • 22 year old Darwin left on a 5 year boyage on HMS beagle
  • Unpaid naturalist and companion to Robert Fritzgerald (explain class division)
  • Took Lyell's book "Principles of Geology with him

Darwin's observations[edit]

Extinct species[edit]

Darwin obsered ancient forms had same basic body forms.
Saw relationships as evidance organisms changed over time
  • Living species had ancestors now extinct

Galapagos tortises[edit]

  • galapagos islands, 600 miles west of Ecuador
Each of 13 large islands had another subspecie
Each tortise specie was unique to its environment
Subspecies closely related to others and tortises on mainland

Darwin's finches[edit]

  1. A dozen species live on Galapagos, some only on one island
  2. Beaks adapted to specific diets
  3. Darwin observed finches on many islands and other finches on mainland
  4. Initially proposed that species changed over geological distance
  5. Apparently, one specie gave rise to many others

Mechanisms of evolution[edit]

Darwin returned in 1836, convinced observations could only be explained by "descent with modification". Did not know mechanism quite yet.

Artificial selection[edit]

Late 1830's, darwin studied animal and plant breeding
domestic breeds revealed great variability hidden in single specie (link to lecture 8)
Breeders with artificial selection bred only types they found interesting.
Darwin pondered how traits were inhereted, initially accepted Lamarkian scheme of evolution.

Thomas Malthus[edit]

1766 - 1834

  • Essay, "Principle of population"
reproductive capacity of humans exceedes food supply
Humans compete for "necesseties of life"
Competition causes vice, misery, famine, and war
Called malthusianism

Natural selection and struggle for evolution[edit]

  • Darwin read malthus's work, and came to conclusion that struggle for survival resulted in natural selection
  • THERE IS NO PLAN for evolution

Alferd Russel Wallace[edit]

  • British biologist, explored geography and anthropology
  • collected extensivly
  • Developed theory of natural selection independently, almost same as Darwins
  • developed idea while stricken by malaria
  • Kept belief, later became whats known as "Thiestic evolutionist"


  1. 1844 - Darwin goes to Lyell for advice. Lyell urges him to publish. He doesn't.
  2. 1858 - Gets letter from wallace. Darwin and Wallace recieve credit together, and present before Linnaen essay
  3. 1859 - finially publishes "Origin of Species

Observations of evolution[edit]

  1. Exponental population growth - Organisms have such great fertility that they exponentally increase in population if all individuals reproduce sucessfully.
  2. Populations tend to remain mostly stable
  3. Resources are limited.
  4. Individuals tend to vary slightly
  5. Variation is inevitiable.

Conclusions drawn[edit]

  1. From 1, 2, and 3, we can conclude that there is a struggle among organisms to survive.
  2. From 4 and 5, we can conclude that individuals vary.
  3. From all the above, we can observe that unequal survival and reproduction eads to adaptation, and unequal adaptation leads to gradual change. Favorable characteristics tend to accumulate in a population.

Important points[edit]

  • Natural selection has no plan or purpose
  • Individuals do not evolve. Populations do.
  • Natural selection is an analogy to artifical slection
  • Breeders aim at specific results, natural selection aims for survival

Lecture 4, Gregor Mendell[edit]

1856 - Studied inheritance in peas.

Believed paretn's traits "blended" into offspring
Nobody knew anything about genes, chromosomes, or meiosis
  • All mendell worked with were visible characteristics, colour, shape, size.

Mendel's discoveries[edit]

  1. Traits are inhereted as units or "factors". Factors are now known as genes.
  2. Teses factors come in pairs (now called alleles)
  3. Factors segregate before reproduction (gametes)
  4. Factors do not blend.

He was mostly correct, examples of where he was wrong later.


  • 1859 - Origin published
  • 1866 - Mendell publishes work in Latin in an obscure journal... and is forgotten.
  • 1882 - Chromosomes discovered
  • 1887 - august weismann suggests process that halves chromosome number
  • 1990 - Meiosis is discovered, and Mendel's work is rediscovered
  • 1903 - Walter Sutton proposed that the physical location of Mendel's factors must be the chromosome

From there, the modern theory of evolution kicks off.