HPS211H1 Lecture Notes - Lecture 7: Ronald Fisher, Reductionism, Thomas Robert MalthusPremium

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3 pages58 viewsWinter 2016

Department
History and Philosophy of Science and Technology
Course Code
HPS211H1
Professor
noahstemeroff
Lecture
7

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HPS211 – 03/09/2016
The Genetic Revolution
Nature is a machine (mechanical philosophy)
-The mechanisms of the living world possesses such a complex structure and purpose that
it could only have been produced by a benevolent creator.
-For example, the human eye: It is perfectly suited for our environment—so it must have
been created specifically for that purpose.
-What about diversity? By compiling a detailed taxonomy, John Ray set out to detail ‘gods
handiwork’, gods rational pattern.
1. Fit: “… the exquisite adaptation of one part to the whole, and to their conditions of
existence…”
2. Diversity: the sheer number and variety of different biological forms.
-Same gaol, different mechanism
Darwin & Natural Selection
-Evolution occurs via the change in heritable traits of a population over time.
-In competition, individuals with certain variants of a trait may survive and reproduce
more than individuals with other less successful traits.
-Three tasks Darwin had to answer:
1. To prove that evolution was a fact—the route that all existing creatures had assumed
their present form.
2. To provide a plausible mechanism to explain how change over time led to adaptation
(Natural Selection).
3. To provide an explanation of heredity: how “like begets like”—the similarity between
parent and offspring—while accounting for variation upon which selection acted.
Pangenesis
-The Variation of Animals and Plants under Domestication (1868).
-The idea is that different parts of the body released “gemmules” (small copies of
themselves) that are passed on to reproductive organs and transmitted to the offspring.
-Each individual therefore a unique mix of parents, grandparents.
-This was a form of ‘blending inheritance’.
Fleeming Jenkins
-Darwin’s theory of evolution could not be valid if blending inheritance occurred.
-Mathematically proved that advantageous traits would eventually be ‘swamped’ or
diluted.
-The “MS” is characterized as having fixed this by conciliating genetics and evolutionary
theory
Francis Galton
-Rabbit Experiments; blood transfusion to see if the exchanging the blood effected their
offspring, refuted Pangenisis
-Pangenesis seen in nature
August Weismann
-Sequestration of the Germline
-Hereditary info only flows germline to some, not vice versa
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