Darwin's big idea and how it changed biology Flashcards
Paley’s Argument
Contrasted rock with a watch - it’s just sitting there, it didn’t have some special creator
- The plant in the background is much more like a plant then a rock because it has adaptations that serves a function as well as purposes and a creator
Jean-Baptiste de Lamarck
- first to use the term evolution
first to provide a casual mechanism - inheritance of acquired characters
Lamarck’s theory
Lamarck did not have the idea that all organisms were related…
Darwin and Wallace
Came with chief mechanisms of evolution (natural selection )
- And overwhelming evidence that we came from a common ancestor
The Origin of Species
All organisms have descended with
modification from common ancestors
* The process leading to adaptation is
natural selection operating on variation
among individuals
Development of Darwin
’s ideas
on evolution - exploration
Darwin influenced by the botanist John S.
Henslow at Cambridge
* Voyage on H.M.S. Beagle around the
world (1831-1836) as ship’s naturalist
* Made numerous observations and
collections of plants, animals & fossils
* Returned to England and spent the rest
of his life in seclusion at Down House
developing his ideas, conducting
experiments and writing books (25 in all)
Development of Darwin
’s ideas
on evolution – gradualism
Darwin reads Lyell’s book
“Principles of Geology” (1830)
* Lyell argued that present day
geological processes can explain the
history of the earth – gradualism
* The notion of a dynamic rather than
a static world emerged in Darwin’s
thinking
Development of Darwin
’s ideas
on evolution – species vary
Variation patterns of
Galápagos mockingbirds
* Darwin doubts fixity of species
(March, 1837)
* There are 4 similar species
endemic to the islands
descended from a South
American mainland ancestor
Development of Darwin’s Ideas
on Evolution
Darwin reads Malthus’ (1798)
Essay on the Principle of Population (Sept., 1838)
Events Leading up to the Publication
of The Origin of Species
20 years taken up with accumulation of
evidence for the theory of evolution
* 1844: Wrote but did not publish an
essay on natural selection
* 1856: Began work on natural selection
book
June 1858 - Received “on the tendency of varieties to depart indefinitely from the og type by A.R Wallace
July 1858: Linnean Society
presentation of Darwin–Wallace paper
* 1859: Publication of “The origin of
species by means of natural selection or
the preservation of favoured races in the
struggle for life”
Darwin’s Mechanism of
Natural Selection
Variation: Individual variation in a
population
* Heredity: Progeny resemble their
parents more than unrelated individuals
* Selection: Some forms are more
successful at surviving and breeding
than others in a given environment
Why was Lamarck wrong?
nheritance only by germ cells
(gametes); somatic cells
(soma/body) do not function as
agents of heredity
1) Thus genetic information cannot
pass from soma to gametes and
onto next generation
1) Modern interpretation stated in
molecular terms genetic
information flows in one direction
only from DNA to protein but never
in reverse
Important Elements of Darwin’s Theory
1) Evolution occurs primarily at the population
level (individuals don’t evolve)
2) Variation is not determined by
environment/is not directed (individuals
don’t induce adaptive variation when
needed)
3) Most fit type depends on the environment
4) ‘Survival of the fitter’: Evolution works with
available variation, will not achieve
perfection
Implications of Darwin’s
Theory of Evolution
Concept of a changing universe
replaced view of a static world.
* A phenomenon with no purpose
Natural selection revealed how
complex adaptations with
important ‘functions’ can appear
through a blind, unplanned
process
What was missing from darwins theory?
heritability
