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Origins of Diversity

Origins of Diversity. 11.4. The Diversity of Species. Result of the formation of different species How? A possible explanation: evolution through NATURAL SELECTION Proposed by Charles Darwin in 1859 in his book “The Origin of Species by means of Natural Selection’. Genetic Variation.

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Origins of Diversity

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  1. Origins of Diversity 11.4

  2. The Diversity of Species • Result of the formation of different species • How? • A possible explanation: evolution through NATURAL SELECTION • Proposed by Charles Darwin in 1859 in his book “The Origin of Species by means of Natural Selection’

  3. Genetic Variation • The basis of natural selection • Changes in the characteristics of a species are produced by a combination of • Random genetic mutations • Selection for a particular characteristic which increases survival and breeding success. Sexual Reproduction: provides genetic variation within a population  reassortment of genes Selection is then made amongst this variation.

  4. Natural Selection • Environment selects individuals with the characteristics that allow them to survive over other individuals with characteristics that are not suited for the environmental conditions.

  5. Shell Activity • Demonstration.

  6. Selection occurs within the variation of the population • Selected organisms produce more offspring • More may survive to reproductive age • May be more attractive to opposite sex

  7. Determining Relatedness • One goal of taxonomy: to determine the evolutionary history of groups of organisms. • Use different types of evidence to study evolutionary relationships. • Anatomy • Development • Biochemistry • DNA Read pages 400-403 on these topics. Briefly summarize how each type of evidence is used to study evolutionary relationships.

  8. Phylogeny • The evolutionary history of organisms. • The ‘root’ represents the oldest ancestral species • Forks represent points in past at which ancestral species split into two new species. • Primitive characteristics: general characteristics that are shared by all species evolved from it • Determine the Order • Ex// Artiodactyla all have even number of hooved toes on each hindfoot and have specialized teeth and digestive systems adapted to eat plants. • 150 members: goats, deer, cattle, camels, pigs, etc. • Derived characteristics: new additional features giving rise to new species. • With continuing evolution, further new derived characteristics are added.

  9. Cladistics • Classification scheme based on phylogeny. • Each group of related species has one common ancestor, and organisms retain some ancestral characteristics and gain some unique derived characteristics as they evolve and diverge from the common ancestor. • Cladogram • Branching diagram that resembles a phylogenetic tree • Can be used to test alternate hypotheses.

  10. Example: • Three species share a primitive characteristic from a common ancestor. • Which species diverged first? • Which are more closely related?

  11. Seatwork/Homework • Page 408, • #1,2,3, 4, 5, 6, 7 • Page 409 • 1, 2, 4, 6, 7, 8, 9, 11, 12, 13, 15, 20, 21, 22, 24, 26.

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