http://www.pbs.org/wgbh/evolution/index.html Public Broadcasting Service – www section about 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 ha ve been dated at 3,5 thousands million years.
Ediacara Hills - Australia Tribrachidium Charniodiscus Mawsonites Dickinsonia Fossils of precambrian soft-bodied organisms
Ediacaran (Vendian) organisms – possible reconstruction
Riddle of Ediacara
Cambrian – beginning of Paleozoic
Pikaia – a fossil of the first chordate
Pikaia – reconstruction
Cambrian explosion (cambrian radiation)
At the end of Paleozoic first land vertebrates appeared reptile Dimetrodon
Mass extinction at the end of Permian 90% of species extinct
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 year s ? 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)
(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.
The fate of the Darwin's theory
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
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
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.
Theodosius Dobzhansky (1900 – 1975) "Nothing in biology makes sense except in the light of evolution."