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Historia Teoría sintética de la evolución
Transcript of Historia Teoría sintética de la evolución
The theory emphasizing
as a creative principle and source of discontinuity in
, particularly associated with the founders of modern genetics.
How does natural selection work?
based on a divine law, sometimes they disappear (great catastrophe).
do not show evolution (gradual changes), rather spp seemed to appear and disappear.
The evidence for NS wasn't there.
It makes the case for
It is logical, it is simple, but has Mr Darwin seen spp originate by NS? Can he prove that it really exists? No.
Can't be seen
It doesn't work
How spp transmit their features from one generation to another?
Darwin thought progeny was a mix between two parents (e.g. skin colour).
attacked Darwin's theory of evolution, suggesting that any new variation would be swamped by the greater numbers of the old version.
That was a question that Gregor
could have answered, but the monk's work was not known to Darwin.
The origin of variation
was a serious weakness in the explanation of evolution.
If variation blends it disappears. If there is not variation, there is not natural selection
Difficulties on theory - on the absence or rarity of transitional varieties
Darwin avoided a direct confrontation but confessed that some of Jenkin's arguments were troubling and in the last edition suggested, incorrectly, that perhaps
could be inherited.
Evolution is a fact... but natural selection?
Hugo Marie de Vries
One of the first geneticists.
The concept of
Introduced the term
1889, Intracellular Pangenesis
Modified version of Darwin's theory of Pangenesis of 1868
Different characters have different hereditary carriers: inheritance of
in organisms comes in particles.
He called these units
a term 20 years later to be shortened to genes by Wilhelm Johannsen.
Series of experiments
varieties of multiple plant species in the 1890s.
Unaware of Mendel's work, De Vries used the
laws of dominance
and recessiveness, segregation, and independent assortment to explain the 3:1 ratio of phenotypes in the second generation.
His observations also confirmed his hypothesis that inheritance of
specific traits in organisms comes in particles.
Oenothera lamarckiana = genetic freak!
Few spp mutate so spectacularly
1894, "Materials for the study of variation".
Interested in species
Experimental approach that should be used to study
with poultry and butterflies.
Bateson is credited with coining the terms
(later shortened to allele),
"zygote," "heterozygote" and "homozygote"
to describe the genetic interaction of two independent traits.
Mutation was the real creator force behind evolution, and natural selection wasn't needed.
50 years: scientific consensus shifted against Darwin
Germ plasm theory
, according to which (in a multicellular organism) inheritance only takes place by means of the
—the gametes such as egg cells and sperm cells. Other cells of the body—
—do not function as agents of heredity.
In Weismann's opinion the largely random process of
which must occur in the
(or stem cells that make them) is the only source of change for
to work on.
Some female morphs share a very
of colouration with various species of
butterfly (e.g. from the family Danaidae), while others have been found that mimic male appearance (andromorphs).
Evidence that Darwin was right:
Only natural selection working slow, in tiny steps, could possibly make 2 unrelated spp so very much alike.
spp create instantaneously by single spontaneous mutations
spp evolve gradually by the accumulation of great many tiny mutations
1919 - FISHER
Experiment on fertilisers
Invented new statistics (and maths)
NATURAL SELECTION = Evolution
Equation: Fundamental theorem
Peppered moth: the equation works!
It was more powerful
Evolution fast swifter
NEO DARWINIAN SYNTHESIS
'Modern synthesis' of Darwinian evolution through natural selection with
The transmission of characteristics from parent to child through the mechanism of
rather than the 'blending process' of pre-Mendelian evolutionary science.
Neo-Darwinism can also designate Darwin's ideas of natural selection separated from his hypothesis of Pangenesis as a Lamarckian source of variation involving
German evolutionary biologist
Ernst Mayr ranked him the second most notable evolutionary theorist of the 19th century, after Charles Darwin
Teoría sintética de la evolución