Lamarck

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Lamarcks theory of evolution (1744-1829)

• 1. Every considerable or permanent change in the
  environment of any organism produces a change in
  the organisms needs.
• 2. New or enlarged structures appear because of
  the inner want of the organism to meet these
  needs.
• 3. Structures are acquired, enlarged, or reduced,
  or lost through use and disuse, and these changes
  are inherited by subsequent generations.

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Darwins theory of evolution (1809-1882)

• Published his masterpiece in 1859
• On the Origins of Species by Means of Natural
  Selection, or the Preservation of Favoured Races
  in the Struggle for Life
• Three main points
• 1.The recognition of evolution as a fact
• 2. The presentation of data demonstrating the
  fact
• 3. The development of a theory of how evolution
  occurred.

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Darwins theory of evolution (1809-1882)

• Observed facts
• All organisms exhibit variability.
• Observations from his travels to among other
  places the Galapagos Islands
• All organisms reproduce many more offspring than
  survive.
• A scientist Thomas Malthus had published an
  article in 1798 that argued that while the human
  population increases geometrically, the food
  supply only grows arithmetically.

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Darwins theory of evolution (1809-1882)

• Conclusions
• 1.The environment selects those individuals best
  fitted to survive, while individual variants less
  fitted fail to reproduce (natural selection).
• 2. The characteristics thus favored by selection
  are passed on to the next generation.
• This theory depends on variations in organisms
  and the effects of the surroundings on them.

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Alfred Russel Wallace(1823-1913)

• He wrote while ill in the Malay Archipelago
  around 1858
• Why do some die and some live?...from the
  effects of disease, the most healthy escape from
  enemies, the strongest, the swiftest, the most
  cunning from famine, the best hunters or those
  with the best digestion.
• Sent his ideas to Darwin.
• Darwin was stunned, their ideas were the same and
  he arranged for their presentation at the Linnean
  society in London. Thus the
• The Darwin - Wallace theory of evolution

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Natural selection

• Peppered moth Biston betularia
• Industrial melanism
• Manchester
• Up to 1848 most white, few black recorded.
• In 1895 98 of the peppered moth population was
  black.
• What
• happened?

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Natural selection

• Disruptive selection
• (divergent)
• Effect of environmental forces on the shape of
  clamshells.

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Selection

• Artificial selection

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Evidence for evolution

• Geographical distribution
• Mammals
• monotreme
• marsupials
• placental
• They have been separated for 100 million years
• Show convergent forms
• increase in similarity
• marsupial mole - placental mole
• jumping marsupial - jumping mouse
• flying phalanger - flying squirrel
• koala bear - Malayan bear

Australasia broke away and they became isolated
just after the arrival of primitive mammals
Developed elsewhere and later ousted the others,
except where geographical barriers prevented as
in Australasia
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Evidence for evolution

• Palaeontology
• The fossil record supports a theory of
  progressive increase in complexity of organisms
  and denies the fixity of species.
• Changes in climatic conditions and adaptation of
  organisms is evidenced in the fossil record f.ex.
  
• plants appeared on land before animals
• insects appeared before insect-pollinated flowers
• Organisms appear in early layers sometimes
  disappear at later levels
• species originated and became extinct
• But the fossil record is not continuous!

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Fossils

• Remains of organism, or direct evidence of its
  presence, preserved most often in rocks.
• Generally hard parts only are preserved.
• They are usually partly or wholly replaced, by
  mineral deposited by circulating water, as
  impressions or casts.

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Types of fossils

• Hard skeletal materials
• trapped in sand and clay
• shells, bones etc.
• Casts and moulds
• skeleton dissolves leaving impression that can be
  filled with fine material that harden to form
  cast.
• gastropods, mollusc shells
• Impressions
• Feathers of Archaeopteryx
• Petrifaction's
• gradual replacement by water-carried mineral
  deposits, such as silica etc.
• Tracks and traces
• Whole individuals in
• Permafrost, acid pits, amber

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Evidence for evolution

• The dating of rocks and fossils using radioactive
  isotopes
• Carbon 14 dating of fossils
• Ratio of C to C in the atmosphere is
  known
• The same ratio is absorbed into animals while
  they live
• After death the C decays into N
• No C is converted
• The ratio of C to C changes with time
• Every 5.700 year, 1/2 of C decays
• A radiation counter can also be used to compare
  the radioactivity of the fossil with a modern
  example of organic material.

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Evidence for evolution

• Potassium- Argon dating of rocks
• K decays into Ar
• When lava solidifies no Ar is present in the lava
  but K is.
• As the K starts to decay into Ar the argon is
  trapped in the rock.
• The half life of K is 1.25 b. y. that would
  mean that after that time the ratio is 11.
• The K to Ar ratio can be measured to
  estimate the age of the rock.
• Since the ratio of K/ Ar can if anything
  be too low (some Ar can escape from the rock) we
  can be sure that a fossil beneath a certain layer
  but be at least that old.

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Evidence for evolution

• The dating of rocks and fossils using
  
• radioactive isotopes
• Half life
• the length of time it takes for half of the
  isotope in a specimen to decay and become
  nonradioactive.

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Evidence for evolution

• Molecular record - The Biological Clock
• The longer the period since two species have
  diverged from a common ancestor, the greater the
  number of substitutions that are found in
  corresponding genes and proteins between the two
  species.
• Homologue anatomical structures
• Embryonic development of vertebrates
• Common ancestor
• As the various types of vertebrates evolved they
  each retained this basic vertebrate embryo as
  part of their life cycle.
• The pentadactyl limbs of vertebrates

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Human evolution

• Classification of humans

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Human evolution

• Classification of humans

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Evidence for evolution