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Lecture 6

NATS 1760 Lecture Notes - Lecture 6: Carl Linnaeus, Georges Cuvier, Binomial Nomenclature


Department
Natural Science
Course Code
NATS 1760
Professor
Vera Pavri
Lecture
6

Page:
of 4
NATS 1760- Darwin and Evolution
Darwin came up with a mechanism to understand the evolutionary process, the idea that
things evolve through time is a debating topic that came about and does not belong to Darwin
I. Intellectual and Scientific Background Prior to Darwin
a. Great Chain of Being
-Great Chain of Being: dominated religious thinking; fixity of species
-God created all species according to certain order
-Single hierarchy stretching from man to simplest form of life
-Highest place on chain: God, angels, man
-Hierarchy stable and harmonious but there is a problem: difficult to explain idea of extinction; if
something is fixed how can it not exist, goes against notion of stability
-To reconcile idea, had to image chain not as a stable representation (fixed) but as a sequence
that would gradually change over long period of time
-Dimension of time introduced
b. Debates in Natural History and Classification * study each natural philosopher according
to the questions
-Debates center around following: how should things be classified (i.e. single or multiple
characteristics); how much weight should be given to these characteristics; how much
emphasis should be placed on how a living thing behaves, how it is constructed, or its natural
environment; is behaviour important or is it the anatomy
Carolus Linnaeus (1707-1778): publishes Systema Naturae in 1735
-Classified huge number of animals and plants: binomial nomenclature – How to classify living
things?
-Classified them according to seven groups (kingdom, class, order, genus, species, variety)
-Belief that both plants and animals had been created in limited supply (fixed) by God; he
focused on differentiating species based on their sexual/reproductive systems
-Claimed there were essential characteristics of all living things but that they were difficult to
identify
Charles Buffon (1707-88):
-Disagreed with Linnaeus and attacked hierarchal classification (emphasis of hierarchy) and too
abstract systems
-Wanted more “practical” method to organize species: look for patterns by observation,
obtaining facts (application of Baconian ideals)
-Bacons influence can be seen in Buffon, Inductive method
-Believer in uniformitarianism (earth older than what was believed); publishes his book Natural
History in 1749
-Up until this time age of earth was thought to be 6000 years, a sufficient amount of time for
geological processes to take place
-Claims age of earth much older
-Wants to use present natural laws to explain past phenomena
Jean Lamarck (1744-1829): early 19th century French naturalist
-Advocated an evolutionary theory prior to Darwin
-Believes in uniformitarianism (age is very old); fossils can aid in determining earth’s age
-He had this idea that Simplest form of life (species) evolved from matter to more complex:
spontaneous generation
-Higher degree of organization equals higher degree of perfection
-Species progress from lower to higher part of chain
-Problem: how did evolution take place
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-Had to be mechanism from which species adapt to changing environment
-I.e. giraffe: neck originally small, but stretched it to get food from tree and eventually develops
long neck
-Used organs will evolve; disused or unused organs will degenerate
-His theory is based on the idea of Inheritance of Acquired Characteristics: different from
Darwin’s later theory
-He was focused on species adapting to their environment
-Environment shapes any given species, species not used become extinct (LOOK AT
RECORDING)
-Many of Lamarck’s ideas ignored; too vague
-One individual that was especially against him was Cuvier who mobilized French biologists not
to respond to Lamarck’s ideas
E.g. Giraffe: First short necked creatures and eventually adapted to environment to look to for new
resources, which required them to stretch their neck; reproduction of giraffes become long necked
creatures
Georges Cuvier (1769-1832)
-French Philosopher, opposed Lamarck’s ideas
-Interested in internal anatomy of invertebrates
-His view looks for similarities in internal structure: comparative anatomy
-Very interested in classifying species by function (i.e. flying, swimming)
-Principle of correlation of parts: you should be able to tell properties of creature by just
seeing one of its parts
-Can thus rebuild and reconstruct animals
-No belief in mingling of species, breeds do not mix together to create new species
c. Geological Debates over Fossils
-Discovery of fossils creates interest for naturalists
-Problem of extinction: fossils of creatures like mammoths caused people to initially believe that
these mammals were still living somewhere [how can this extinction occur if things are
supposed to be “fixed”]
-As fossils accumulate, fossils record points to fact that many mammals now extinct; problem is
why mammals become extinct
-Two explanations: uniformitarianism versus catastrophism
Uniformitarianism
-Long time span for formative process; geological mechanisms can help explain past events
-Extinction takes place in a uniform way through an extensive period of time, gradually & slowly
-God is a rational being, therefore likely to create a rational order world, and when accounting
for change these kinds of changes would be done in a uniform and methodological way
-Deists: Christians who believe God is rational; nature is ordered, rational
-As such, should not have to invoke natural catastrophes to explain nature
-Age of earth must be very old for these slow, gradual changes to occur
-Evidence for older age of earth: lava found underneath volcano grounds
-Depth and thickness of sedentary deposits in earth also suggest earth old
-Australia: animals exist here that do not exist anywhere else
-Differences found between existing animals were not as significant as differences between
fossil animals
Catastrophism:
-Periodic disasters have occurred throughout history; idea accounts for change through natural
disasters
-Allows for a much shorter time span for geological process, like extinction
-Age of the earth is very young
-Catastrophes are natural disasters (i.e. floods, earthquakes, etc…)
-Believers had a traditional view of Bible
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-Allows for divine involvement: fits with Biblical ideas about earth not being very old;
catastrophes provide explanation for major changes
-Cuvier believes in this theory and strongly opposes evolution: earth underwent revolutionary
changes from sudden and abrupt catastrophes;
-Cuvier was anti uniformitarianism
-Species that were once living were now completely destroyed
-Belief that species immutable; never change, they were fixed
-God may extinguish species and then recreate them, can do this to those species which are
extinct
-Explanation has problems: if at one point all species living together, why don’t we find fossils of
all living creatures
II. Charles Darwin (1809-1882)
-Born into wealthy and well-known family; son of physician
-Erasmus Darwin: Darwin’s grandfather was evolutionist: suggests that God designed species to
be self-improving over time; life gets more complex over time
-Development new organs to meet with environmental needs
-Believes in spontaneous generation
-Prepares for clergy; studies zoological theory, botanical taxonomy
III. Darwin and Evolution
-Darwin’s major achievement not just evolutionary theory; it was the fact that he proposed a
specific mechanism for evolution
-Revolutionary mechanism was NATURAL SELECTION
-Voyage on Beagle (1831-36); on Galapagos Islands, Darwin discovers many different types of
species and records findings in diary
-Takes Charles Lyell’s Principles of Geology with him
-Lyell believes in uniformitarianism, that long, slow gradual processes are predicators of change;
sees relationship between environment and organism; best organism wins
-Found that different islands had different species even though environmental conditions were
similar
-How to explain these different species? Not satisfied with explanation that God created them
-There initially had existed same species on island but they evolved in different ways: why?
-Not able to answer these kinds of questions during his trip and returns home; here, he observes
actions of animal breeders who create artificial adaptations by artificial selection
-While in artificial environment breeder is the selector of beneficial/useful traits, what happens
in the natural world
-What was selector in natural selection? What mechanism provides for having the most fit
species?
-As breeder selects individuals, starts to get idea that nature might select certain organisms for
survival
-Greatly influenced by Thomas Malthus, who publishes work Essay on Population in 1798
-Malthus’ work is based on people: population versus food supply
-Begins of industrialization leads to urbanization, migration
-Threat of disease: typhoid, tuberculosis, yellow fever
-Struggle/competition for food causes changes in population
-Malthus: Population grows geometrically while food grows arithmetically
-Darwin takes this idea and applies it to this theory on evolution
-Natural selection occurs because of this struggle for existence over limited resources as
species adapt to their environments
-Some species better suited to their environment than others; more likely to live and produce
offspring who will then pass traits to future generations
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