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  2. 2. EVOLUTION• Evolution is the change in the inherited characteristics of biologica l populations over..successive generatio ns.• Evolutionary processes give rise to diversity at every level of biological organisation,including species, individua l organisms and molecules such as DNA and proteins.
  3. 3. Evolution Descent with Modification Evolution means change over timeEvolution can also be defined more narrowly as a change in the geneticcomposition of a population from generation to generation.
  4. 4. Evolution on earth• Formation of Amino Acids – Millers Experiment Process of Evolution
  5. 5. Genes and Chromosomes• Complex, double-stranded helical molecules – of deoxyribonucleic acid (DNA) • called chromosomes – are found in cells of organisms• Specific segments of DNA – are the basic units of heredity (genes)• The number of chromosomes – varies from one species to another – fruit flies 8; humans 46; horses 64
  6. 6. Theories of Organic Evolution Historically three theories1. Lamarck’s Theory of Evolution, 2. Darwin’s Theory of Evolution, 3. De Vries Mutation Theory of Evolution. The views of most modern biologists combine the second and third No evidence of the first theory, that of Lamarck’s Use and disuse theory.
  7. 7. Jean Baptiste Lamarck, 1744-1829 • French geologist and naturalist • published Philosophie Zoologique in 1809 • Speculated about mechanisms of biological evolution, offered no evidence
  8. 8. In 1809 Jean-Baptiste Lamarke hypothesized that “simple”organisms emerge spontaneously and evolve to greater“complexity”. Principles to his theory 1. Organisms constantly strive to improve themselves. 2. Most used body structures develop and unused waste away. (Use and Disuse) 3. A structure is modified by use or disuse, the modification is inherited to the offspring. (Inheritance of acquired characteristics).
  9. 9. • Structural variations are due to functional needs – “to use or disuse”• Use of a structure increases its size.• Failure to use it decreases its size• These variations (now referred to as “acquired characteristics” are inherited.• There is no supporting evidence in modern biology to support Lamarck’s idea
  10. 10. Lamarck’s Giraffes• According to Lamarck’s theory of inheritance of acquired characteristics – ancestral short-necked giraffes – stretched their necks – to reach leaves high on trees. – Their offspring were born – with longer necks
  11. 11. Charles Darwin: The Theory of Natural Selection• His theory was effectively presented to the world in 1859 when his book “The Origin of Species” was published.• Darwin’s Theory rests on 5 principles:
  12. 12. 5 principles of Darwin’s Theory1. Overproduction - All species have a tendency and the potential to increase at a geometric rate.All organisms produce more organisms but only a few survive.2. Competition - Due to environmental pressures, the organisms within a population must compete with each other to survive.
  13. 13. 3. Variation - Individuals in a population vary greatly in their characteristics.4. Adaptation - individuals who best adapt to the environment are the ones who will most likely survive5. Natural Selection - Individuals having favorable traits will produce more offspring, and those with unfavorable traits will produce fewer offspring.• Speciation -The process in which new genetically distinct species evolve usually as a result of genetic isolation from the main population.
  14. 14. DE VRIES MUTATION THEORY• His experiment was on evening primose.• Mutation form raw material for evolution.• It suddenly appears.• Single mutation may produce new species.
  15. 15. Modern Synthesis Theory Important points of Modern Evolutionary Theory All evolutionary phenomena can be explained in a wayconsistent with known genetic mechanisms.Evolution is gradual: small genetic changes regulated by naturalselection accumulate over long periods. Discontinuities amongstspecies are explained as originating gradually throughgeographical separation and extinction.Natural selection is by far the main mechanism of change.Thinking in terms of populations rather than individuals, isprimary: the genetic diversity existing in natural populations is akey factor in evolution
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  17. 17. • THANK YOY