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http://www.pbs.org/wgbh/evolution/index.html
Public Broadcasting Service
– www section about evolution
EVOLUTION• gradual unfolding of new varieties of life from
previous forms over long periods of time (Darwin)
• from the genetic perspective : a change in allele frequency from one generation to the next
• TWO KINDS OF EVOLUTION– microevolution – short term effects occuring over
just a few generations– macroevolution – long-term effects through fossil
history, large changes produced only after many generations
EARLY EVOLUTIONARY HISTORY
• The origin of Earth – 4,5 – 4,6 thousands million years ago
• The oldest fossils were found in 3,8 thousands million years old sedimentary rocks from Greenland (the oldest terrestrial rocks).
• Earliest known structurally preserved organisms are stromatolites found near the North Pole, Australia. They has been dated at 3,5 thousands million years.
EARLY EVOLUTIONARY HISTORY II.
• Earliest known structurally preserved organisms are stromatolites found near the North Pole, Australia.
• They have been dated at 3,5 thousands million years.
Ediacara Hills - Australia
Tribrachidium
CharniodiscusMawsonites
Dickinsonia
Fossils of precambrian soft-bodied organisms
http://www.pbs.org/wgbh/evolution/change/deeptime/index.html
Evolution of life
http://www.pbs.org/wgbh/evolution/extinction/dinosaurs/index.html
What happened before 65 millions
of years?K/T border (= cretaceous / tertiary) – extinction
of dinosaurs and a lot of other species (approximately 75 % of species)
JEAN BAPTISTE LAMARCK (1744 – 1829)
• Popularised the idea of evolution
• First scientific evolution theory
• Basic concepts of the Lamarck’s theory:– emphasis on the dynamic interaction of organic
forms with the environment
– environment affects and induce change in organic forms
– acquired characteristic is passed through heredity to the next generations
GEORGES CUVIER(1769 – 1832)
• the „father“ of zoology, palaeontology, and comparative anatomy
• criticised Lamarck’s views on evolution• proposed theory of catastrophism:
– series of violent and sudden catastrophes– all of creatures were destroyed during the
catastrophe– after things settled down, areas were restocked
with new organisms different from those previously living there)
CHARLES DARWIN(1809 – 1882)
• 1828 – 1831 theology studies (Christ’s College, Cambridge)
• (Reverend John Stevens Henslow – lectures in botany)
• 1831 – 1836 naturalist on a scientific expedition around the globe (H.M.S. Beagle) – recommended by Professor Henslow
• 1842 – short summary of Darwin’s views on natural selection
• 1859 – Darwin completed and published his work “On the Origin of Species by means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life”
Charles Darwin
stopover at the Galápagos Islands – Darwin described 13 species of finches resembled one another in the structure of their beaks, body
forms, and plumage
DARWIN’S CONCEPT OF EVOLUTION
• All species are capable of producing offspring faster than the food supply increases.
• All living things show variation; no two individuals of a species are exactly alike.
• Because there are more individuals than can possibly survive, there is a fierce struggle for existence and those with a favourable variation in characteristics are necessary for survival will possess an advantage over others.
• These favourable variations are inherited and passed on to the next variation.
• Over long periods of geologic time, these successful variations produce great differences that result in new species.
• The background of the process is natural selection.
Alfred Russel Wallace
(1823 – 1913)
• 1855 –published an article concerning the succession of species and their mutability
NEODARWINISM - THE MODERN SYNTHESIS
• Evolution is defined as a two stage
process:
– Production and redistribution of variation
(inherited differences between individuals)
– Natural selection acts on this variation
(inherited differences, or variation, among
individuals differentially affect their ability
to reproduce successfully
RECENT CHALLENGES TO THE MODERN SYNTHESIS
• neutral mutations– Much of variation in natural population is due to neutral
mutations and chance factors (i.e. genetic drift).
– Neutral mutations are not controlled by natural selection.
– “Natural selection is the editor, rather than composer of genetic message” (King and Jukes 1969)
• gradualism X punctuationalism– gradualism – evolution changes accumulate gradually in
evolving lineages
– punctuationalism (punctuated equilibrium) – evolution is nongradual process, evolutionary rates are not constant, the evolution is a process of long stasis and sudden quick spurts
MECHANISMS OF EVOLUTION
• Factors that produce and redistribute variation– mutation– migration– genetic drift– recombination
• Natural selection– differential net reproductive success– Some of genetic variations among
individual within a population may influence reproductive success. Therefore some individuals contribute more offspring to succeeding generations.
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