Lamarcks theory of evolution 1744 1829 1 Every

Lamarck´s theory of evolution (1744 -1829) • 1. Every considerable or permanent change in the environment of any organism produces a change in the organism´s 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.

Darwin´s 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.

Darwin´s 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.

Darwin´s 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.

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

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?

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

Selection • Artificial selection

Evidence for evolution • Geographical distribution Mammals Australasia broke away • monotreme • marsupials • placental 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 – 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

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!

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.

Types of fossils • Hard skeletal materials – trapped in sand 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

Evidence for evolution The dating of rocks and fossils using radioactive isotopes • Carbon 14 dating of fossils – Ratio of 14 C to 12 C in the atmosphere is known – The same ratio is absorbed into animals while they live – After death the 14 C decays into 14 N – No 12 C is converted – The ratio of 14 C to 12 C changes with time – Every 5. 700 year, 1/2 of 14 C decays – A radiation counter can also be used to compare the radioactivity of the fossil with a modern example of organic material.

Evidence for evolution • Potassium- Argon dating of rocks – 40 K decays into 40 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 40 K is 1. 25 b. y. that would mean that after that time the ratio is 1: 1. – The 40 K to 40 Ar ratio can be measured to estimate the age of the rock. 40 40 – 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.

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.

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

Human evolution • Classification of humans

Human evolution • Classification of humans

Evidence for evolution