Evolution - Evolution - practicalspracticals

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

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 years?K/T border (= cretaceous / tertiary) – extinction

of dinosaurs and a lot of other species (approximately 75 % of species)

Evolutional theories

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.

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

• 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.

Theodosius Dobzhansky (1900 – 1975)

"Nothing in

biology makes

sense except in

the light of

evolution."