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BIOL 3200 Study Guide - Midterm Guide: Erasmus Darwin, Blending Inheritance, Divergent Evolution

Course Code
BIOL 3200
Jan Sapp
Study Guide

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BIOL 3200 Notes
Natural theology belief of God and divine creation
17th-19th centuries
Natural theologists believed in intelligent design/divine creation
o Somebody is in charge of life and nature
They believed the Earth to be only a few thousand years old
World was static (not changing)
God had formed all species exactly the way they are
Organisms were separate entities and had no relationship to each other whatsoever
Extinct species seen in the fossil record were the results of catastrophes such as floods
Belief in the Great chain of being
o Species were ordered from most simple to most complex and perfect
o This resembled a ladder
No way nature resulted in the complexity of organisms
Their presence can only be explained by purpose and design known as teleology
Evolutionary theory natural world is steadily changing and organisms have diverged from common
aestors, ad that the’e ee trasfored i geologial tie
Thus, all organisms are related and their relationships resemble a branching tree rather than a
There is no preconceived design/plan in nature; organisms evolve in relation to changing
ecological conditions and their evolution is not directed in any other way (i.e. by a God)
Evolutionary thinking
Part of a new approach to investigating and understanding natural history that developed in late
18th century
Was a naturalistic, or mechanistic way to explain and understand nature
o The forces underlying the diversity of life and the relationships between species could
be explained without magical forces or a creator
The dynamics of nature could be investigated and explained through observation and
Darwin, Lyell, Cuvier, etc. offered a different opinion and calculated/believed the Earth to be millions-
billions of years old
Today scientists estimate:
Universe 10-20 byo
Earth 4.5 byo
Life 3.5 byo
Hominids 4 myo
Homo sapiens 130 000 yo
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Fossil Record showing a progressivity from simple to complex interpreted as:
Progressive evolution (as species evolved they became more complex)
Progressive perfection was driven by a spirit imposing its will and purpose on nature
Geothermal theory as earth changed, God created species that suited the new conditions of
Eolutioists do’t eessaril ot eliee i a God
Some are agonists (need proof)/on the fence
Others believe a God caused the origin of life, and nature took it from there
Darwinism used to explain the world
“truggle for eistee as used to eplai people’s a of life
It was used in politics to justify wars by saying there are superior, more fit races
Ma people uderstood the ter struggle for eistee as a eas to justif ad eourage
conflict and competition
Used to validate building of empires by saying, inferior and uncivilized races were being
While Darwin and his champions emphasized conflict, others emphasized mutualism and altruism as
evolutionary progress
Struggles Darwin had of convincing people of Natural selection
People refused to be that natural selection could be the mechanism of evolution because it was
so haphazard, passive, undirected, acting on chance
o It ould’t possil diret eolutio
People believed earth to be young
o Natural selection was said to be gradual (occur very slowly over a long period of time)
o If earth was only a few thousand years old, at. sel. Would’t hae had eough tie to
explain evolution
People believed in the idea of blending inheritance (progeny are a blend of their parents)
o A good trait would diminish from generation to generation as it kept blending with poor
Dari did’t eliee speies ere real; the ere just lassifiatio
o He said individuals and the differences between them are real
o If speies did’t eist, ho ould the eole?
If natural selection was mechanism for evolution, then every character an individual has must be
advantageous (an adaptation) in the struggle for existence
o Darwin even recognized this not to be the case and explained some traits to be for
attracting mates etc.
o Problems stemming from this arose
o How could complex organs such as the eye arise from natural selection?
Why would nat. seln favour an undeveloped eye until the point it became
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Holes in fossil record
o Darwin attempted to explain these based on the fact that not all areas were suitable for
o Discovery of transitionary animals such as Archaeopteyx were important in showing
transition from one class to another
3 alternatives to evolution by Natural selection
1. Neo-lamarckism inheritance of acquired characteristics
a. Allowed nature to be more progressive and direct than natural selection alone
b. Also offered a less gri ie o life; it as’t just a ostat struggle for eistee
c. Animals generated their own evolution because they could consciously choose how to
respond to their environment
i. Generated a sense that life controls its own destiny
d. Also could explain morality and mutualistic and altruistic behaviours
2. Orthogenesis directed evolution of a characteristic along a straight line or certain path
a. Closely associated with neo-larmarckism
b. Could be used to explain extinction e.g. irish elk
c. Variations were not random, but followed a directed path
3. Saltationism evolution by leaps
a. Sudden appearance of species without the aid of selection
b. Explains leaps in fossil record
c. Would have gotten around the idea of blending inheritance
d. Could have occurred quickly and more rapidly (meaning earth could have been young)
e. Resolved how complex organs could have developed
f. All geneticists were saltationists
Convergent vs. Divergent evolution
o Leads to analogous structures (same function, different morphology) diff. ancestor
o Same environmental conditions and niches lead to similar adaptations
o Explains why evolution seems to repeat itself why creatures today resemble those
that went extinct mya
o Leads to homologous structures (similar morphology, different function) Common
Aristotle & Plato
Belieed i the Great hai of eig or scala naturae
o Organisms were organised in a single-file manner, from least complex (and perfect) to
most complex and perfect
o This resembled a ladder
o The most perfect organisms were most closely associated with God
Each species was a perfect essence
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