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EOC – BIOLOGY REVIEW

EOC – BIOLOGY REVIEW. Evolution. There is a great variety of life on Earth. Our Diverse World. How? Much debate, some still continues Generally agreed that all life originated from one common ancestor. Image by Nick Hobgood [Own work, CC3].

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EOC – BIOLOGY REVIEW

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  1. EOC – BIOLOGY REVIEW Evolution

  2. There is a great variety of life on Earth. • Our Diverse World • How? • Much debate, some still continues • Generally agreed that all life originated from one common ancestor Image by Nick Hobgood[Own work, CC3]

  3. Common descentscientific theory that all living organisms on Earth descended from a common ancestor Common ancestryscientific theory that groups of related organisms share a common ancestor All – common descent Part – common ancestry • Common Ancestry & Descent

  4. Know the Evidences for Evolution

  5. Progressive change visible when fossil records are almost complete • Limbs elongated • Digits reduced • Longer and wider teeth • Fossil Evidence for Common Ancestry Image by M. C. Jerry[Own work, GNU]

  6. Homologies – similar features between different organisms resulting from common ancestry Scientists study different types • Anatomical • Molecular • Developmental • What are Homologies?

  7. Starting points can change • Homologous structures – similar structures that share an ancestral form • Anatomical Homologies – Evidence for Common Ancestry

  8. Anatomical Homologies – Evidence for Common Ancestry Starting points can change • Vestigial structures – degenerated and/or nonfunctional structures Image by Konversionlexikon[Own work, Public Domain]

  9. Limitations of anatomical homologies • Must differentiate between homologous and analogous structures • homologous – from a common ancestor • analogous – evolved independently • Anatomical Homologies – Evidence for Common Ancestry Bird Bat Image by John Romanes[Own work, Public Domain]

  10. Conserved DNA sequences • Similar genomes indicates related species • Molecular Homologies – Evidence for Common Ancestry

  11. Developmental homologies – similar features in embryos of different species • What are Developmental Homologies?

  12. Biogeography – Evidence for Common Ancestry Similar environments are found across the world • Sometimes similar but unique organisms. How? • Geological event separated populations, diverged

  13. Natural selection – process by which individuals with favorable variations of a trait survive and reproduce at a higher rate than individuals with less favorable variations • Originally proposed by Charles Darwin • Causes change in populations • Key mechanism of evolution • Natural Selection

  14. Adaptation – trait that helps an organism to survive and/or reproduce in its unique environment • Natural selection favors variations of traits that increase organism’s ability to survive and reproduce • Adaptations Images by L. Shyamal (Own work) [CC-BY-SA-2.5]

  15. Example: • Speed in cheetahs • Development of Adaptations Image by Vitaliy Gutnichenko [Own Work, GFDL]

  16. Genetic diversity – differences in genetic characteristics among organisms within the same species or among different species • Natural selection can increase or decrease genetic diversity • Genetic Diversity Image by Graphodatsky et al. [CC-BY-2.0]

  17. Three major types of natural selection can affect the diversity within a species • Directional • Disruptive • Stabilizing • Genetic Diversity Within a Species Frequency Phenotypes Frequency Frequency Frequency Phenotypes Phenotypes Phenotypes Diversifying Directional Stabilizing

  18. Directional selection – a single variation of a trait that was not previously favored is now favored in a species • Result of migration or environmental changes • Directional Selection Frequency Phenotypes Frequency Phenotypes

  19. Disruptive selection – multiple variations of a trait are favored in a single species • Disruptive Selection Frequency Phenotypes Frequency Phenotypes

  20. Stabilizing selection – a single variation of a trait is favored in a species • Stabilizing Selection Frequency Phenotypes Frequency Phenotypes

  21. Natural selection may increase genetic diversity among different species • Different traits are favored in different species • Example: • Variety of bird beak shapes • Genetic Diversity Among Species Images by L. Shyamal (Own work) [CC-BY-SA-2.5]

  22. Population – group of organisms of the same species living together in a given region Natural Selection – process whereby organisms with favorable traits survive and produce more offspring than less well-adapted organisms • Proposed by Darwin • Key mechanism of evolution • Natural Selection in Populations

  23. Differential reproductive success – one group has more offspring than another • Caused by natural selection • Natural Selection in Populations

  24. No two individuals in a population are exactly alike • Organisms vary in size, coloration, structural characteristics, and behavior • Variations important in populations • Individuals with mostadaptive variations survive and pass on traits • Differential reproductive rates • Inherited Variation Image by Loba Wolf (Own work) [CC-BY-SA-3.0]

  25. Resources are limited • Food • Fresh water • Space Carrying capacity – number of individuals of a given population that the environment can support Limits create competition • Winners survive and reproduce • Finite Resources

  26. Lamarck’s theory of evolution • Inheritance of acquired characteristics – the characteristics an organism develops over time can be passed on to offspring • Mouse gets its tail cut off, offspring should have no tails • Giraffe stretches its neck out to reach tall leaves, offspring should have longer necks • Incorrect, not supported by scientific evidence • Stimulated thought about evolution • Lamarck’s Theory

  27. No individual is capable of evolving • Natural selection produces changes in populations, not individual organisms • Organism may be born with a favorable mutation • Acquired traits are not passed on to offspring • Natural Selection in Populations

  28. How does natural selection produce changes in populations? • No two individuals in a population are exactly alike • Organisms vary in size, coloration, structural characteristics, and behavior • Variations important in populations • Individuals with mostadaptive variations survive and pass on traits • Over time, population shifts towards adaptive variations • Natural Selection in Populations Image by Loba Wolf (Own work) [CC-BY-SA-3.0]

  29. Random mutations - color variations in moth population • Enables the moths to blend into tree trunks • Harder for birds to locate “camouflaged” moths • Natural selection occurs • Moths with mutation survive and reproduce • Favorable coloring is passed on to offspring • Natural Selection in Moth Population Image by Gilles San Martin (Own work) [CC-BY-SA-3.0]

  30. Genetic Equilibrium – the genetic makeup of a population will remain relatively stable unless something happens to make it change • Populations in genetic equilibrium do not change or evolve • Natural selection upsets genetic equilibrium and causes changes in populations • Natural Selection in Populations

  31. Gene pool – all of the genes in a population Allelic frequency – the frequency of a specific allele Evolution – change in frequencies of alleles in a population over time • Gene Pools

  32. Genetic drift – changes in allele frequencies because of random events • Generally affects smaller populations • Related to probability • Genetic Drift

  33. Gene Flow – Immigration or Emigration

  34. How does gene flow affect gene pools? • New allele in gene pool • Gene Flow

  35. Mutation – a change in the nucleotide sequence of DNA • Happen naturally • Environment can trigger more mutations • Sometimes alter proteins produced • Mutations

  36. Types of mutations • Insertion – a nucleotide is added A G C T T A C G T  A G C T GT A C G T • Deletion – a nucleotide is removed A G C T T A C G T  A G T T A C G T • Substitution – a different nucleotide is used A G C T T A C G T  A G C AT A C G T • Mutations Frame shift mutations

  37. How do mutations affect gene pools? • New allele in gene pool • Can be beneficial or harmful • Mutations

  38. Recombination – exchange of DNA between two chromosomes • Happens during meiosis • Recombination

  39. How does recombination affect gene pools? • Alleles moved, but no net change • Recombination

  40. What kinds of organic molecules spontaneously formed in Earth’s early atmosphere? Theories: • Miller-Urey Experiment  amino acids, adenine • RNA World  RNA then protein • Formation of Organic Molecules

  41. Set up of Miller-Urey Experiment: • Miller-Urey Experiment Image by Yassine Mrabet [GFDL]

  42. RNA World – without hereditary molecule, other molecules would not have formed consistently • Organic molecules produced: • RNA • RNA  protein formation • RNA World

  43. Prokaryote – “before nucleus,” simple cell lacking nucleus • Example: bacteria Eukaryote – “true nucleus,” more complex cell containing nucleus • Example: plant cell Which cell type evolved first? • Theory: Prokaryotes • Cell Complexity

  44. First Eukaryotes Support for endosymbiotic theory • Presence of numerous symbiotic relationships • Present-day mitochondria, chloroplasts, and centrioles contain their own DNA • Similar to DNA of bacteria in size and character

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