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Adaptations

Adaptations

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Adaptations

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  1. Adaptations Night Mesophyll cell CO2 CO2 4-C compound 4-C compound CO2 CO2 CALVIN CYCLE CALVIN CYCLE Bundle- sheath cell 3-C sugar 3-C sugar Day CAM plant C4 plant

  2. Evolution Ch 13

  3. Charles Darwin 1874 1859

  4. Voyage of the HMS Beagle

  5. On the Origin of Species… • Descent With Modification • By means of Natural Selection

  6. How Did Darwin Come Up With His Ideas? • Scientific Method • Key observations • Traits vary in a population • Most traits are inherited from parent to offspring • More offspring are produced than the environment can support (Thomas Malthus)

  7. Recap • Limited resources • Overproduction of offspring • Heritable individual variation • Therefore, survival depends partly on inherited features

  8. Darwin’s Theory of Evolution • In a varied population, individuals whose inherited characters best adapt them to the environment are more likely to survive and reproduce. • Therefore, more fit individuals tend to leave more offspring than less fit individuals. • Natural Selection is the mechanism • Reproduction (differential) is Key

  9. Darwin’s Theory of Evolution Natural Selection is the mechanism Reproduction (differential) is Key Fitness- degree of adaptation to a specific environment Adaptive if it enhances individual’s fitness

  10. Natural Selection

  11. Artificial Selection

  12. A flower mantidin Malaysia A leaf mantid in Costa Rica Figure 13.5A 0 Observing natural selection • Camouflage adaptations that evolved in different environments

  13. Chromosome with geneconferring resistanceto pesticide Pesticide application Survivor Additionalapplications of thesame pesticide willbe less effective, andthe frequency ofresistant insects inthe populationwill grow Figure 13.5B 0 Pestacide Resistance

  14. Support for Descent with Modification Biogeography Fossil Record Molecular Biology, Biochemistry, Cell Biology Comparative Anatomy

  15. Biogeography 0 • Geographic distribution of species • Galápagos animals resembled species of the South American mainland more than animals on similar but distant islands • Organisms may have common ancestor

  16. Fossil Evidence 0 A Skull of Homoerectus D Dinosaur tracks B Petrified tree C Ammonite casts E Fossilized organicmatter of a leaf G “Ice Man” • Organisms evolved in a historical sequence F Insect in amber Figure 13.3A–G

  17. Fossil Evidence Figure 13.3I 0 Many fossils link early extinct species with species living today

  18. Comparative Anatomy Cat Whale Bat Human Figure 13.4A 0 • Comparison of body structures in different species • Homology- similar characteristics resulting from common ancestry • Homologous structures- features with different functions but structurally similar due to common ancestry

  19. Comparative Embryology 0 Pharyngealpouches Post-analtail Human embryo Chick embryo Figure 13.4B 0 Comparison of early stages of development among different organisms

  20. Molecular Biology Table 13.4 0 Comparisons of DNA and amino acid sequences between different organisms to reveal evolutionary relationships

  21. 0 Unit of Evolution • Evolution acts on individuals, affects whole populations • Populations are the unit of evolution • Group of individuals of the same species living in the same place at the same time

  22. Unit of Evolution • Evolution is change in prevalence of heritable traits in population through time • A gene pool • Is the total collection of genes in a population at any one time • Microevolution • Is a change in the relative frequencies of alleles in a gene pool

  23. Hardy-Weinberg Equilibrium • Frequency of alleles in a stable population will not change over time • Very large population • Population is isolated • Mutations don’t alter gene pool • Random mating • All individuals are equal in reproductive success • In reality, this never happens

  24. Agents of Change • Genetic Drift • Bottle neck affect • Founder affect • Gene Flow • Mutation • Non Random Mating • Natural Selection

  25. Figure 13.11 0 Variation • Extensive in most populations • Mutation and sexual recombination generate variation and can create new alleles.

  26. 0 Endangered species often have reduced variation • Low genetic variability • May reduce the capacity of endangered species to survive as humans continue to alter the environment Figure 13.10

  27. Selection Models

  28. Sexual Selection • Sexual Dimorphism • Sexual Selection- where individuals with certain characteristics are more likely to obtain mates than others. • Intrasexual selection • Intersexual selection

  29. Selection • Heterozygote advantage • Balancing selection • Ex: Sickle cell anemia • Frequency-dependent selection • Fitness of genotype depends on frequency it occurs • Ex: mimicry • Neutral Variation • Little to no impact on phenotype or fitness • Natural Selection cannot distinguish alleles

  30. Natural Selection is Limited • Only act on existing variation • Historical constraints • Compromise • Chance, selection and the environment