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Ch. 7 Notes Meiosis

Ch. 7 Notes Meiosis. By: Brianna Shields November 9, 2005. DO NOW. Listen to this pod cast 1. What benefit do we now believe bacteria can provide to humans? 2. Where in an animal’s body is this “beneficial activity” carried out?

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Ch. 7 Notes Meiosis

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  1. Ch. 7 NotesMeiosis By: Brianna Shields November 9, 2005

  2. DO NOW • Listen to this pod cast • 1. What benefit do we now believe bacteria can provide to humans? • 2. Where in an animal’s body is this “beneficial activity” carried out? • 3. What percentage of our energy uptake actually takes place within this structure in the body?

  3. Meiosis Crossing-over Independent assortment Spermatogenesis Sperm Oogenesis Ovum Asexual reproduction Clone Sexual reproduction Life cycle Fertilization Sporophyte Spore Gametophyte VOCAB NOTEBOOK-list the terms in your vocab notebook, leaving about 3-4 spaces between each term

  4. GOAL • Summarize the events that occur during meiosis • Relate crossing over, independent assortment and random fertilization to genetic variation • Compare spermatogenesis and oogenesis • Differentiate between sexual and asexual reproduction • Identify three types of asexual reproduction • Evaluate the relative genetic and evolutionary advantages and disadvantages of sexual and asexual reproduction • Differentiate between the three major sexual life cycles found in eukaryotes

  5. Meiosis Halves the number of chromosomes when forming gametes or spores Before beginning, DNA in the original cell is replicated Meiosis- Formation of Haploid Cells

  6. Meiosis PROPHASE I- Chromosomes condense Nuclear envelope disintegrates Homologues pair up Crossing over occurs (homologous chromosomes swap corresponding portions) Meiosis- Formation of Haploid Cells

  7. Meiosis METAPHASE I- Homologous chromosomes move together to equator of cell Meiosis- Formation of Haploid Cells

  8. Meiosis ANAPHASE I- Homologous chromosome pairs move to opposite poles with their new recombined genetic information Meiosis- Formation of Haploid Cells

  9. Meiosis TELOPHASE I- Individual chromosomes gather at poles, cytoplasm divides (each end contains one chromatid from each set of homologues) Meiosis- Formation of Haploid Cells

  10. Meiosis PROPHASE II New spindle forms Meiosis- Formation of Haploid Cells

  11. Meiosis METAPHASE II Chromosomes line up along equator, attached to spindle fibers by centromeres Meiosis- Formation of Haploid Cells

  12. Meiosis ANAPHASE II Chromatids split and move to opposite poles Meiosis- Formation of Haploid Cells

  13. Meiosis TELOPHASE II Nuclear envelope reforms, spindle breaks down, cytokinesis occurs Meiosis- Formation of Haploid Cells

  14. Meiosis Four haploid cells result Meiosis- Formation of Haploid Cells

  15. Genetic Variation Independent Assortment- random distribution of homologous chromosomes during meiosis Which of the 2 homologues each offspring receives is a matter of chance 8 million different gamete combinations can result Meiosis- Formation of Haploid Cells

  16. Genetic Variation Crossing Over- this DNA exchange during meiosis increases genetic variation Meiosis- Formation of Haploid Cells

  17. Genetic Variation Random Fertilization- two gametes are randomly joined to form a zygote 64 trillion possible outcomes Meiosis- Formation of Haploid Cells

  18. Importance of genetic variation 1. Meiosis and the joining of gametes are essential to evolution Meiosis- Formation of Haploid Cells

  19. Importance of genetic variation 2. Evolution appears to increase with increases in genetic variation Meiosis- Formation of Haploid Cells

  20. Importance of genetic variation 3. Breeding larger or faster animals can be limited until enough genetic variation is eventually generated to continue the breeding Meiosis- Formation of Haploid Cells

  21. Importance of genetic variation 4. Natural selection doesn’t always favor genetic change Existing conditions may be favorable, slowing evolution Meiosis- Formation of Haploid Cells

  22. Meiosis in females OOGENESIS- produces eggs in the ovary of female animals A. Diploid cell increases in size to a germ cell B. Undergoes meiosis I- cytoplasm splits unevenly into each egg cell C. Large cell develops, small cell (polar body) dies Meiosis- Formation of Haploid Cells

  23. Meiosis in females D. Undergoes meiosis II- more uneven cytoplasm distribution E. Larger “ovum” develops, small polar body dies F. One large egg cell results- rich in cytoplasm and nutrients Meiosis- Formation of Haploid Cells

  24. Meiosis in Males SPERMATOGENESIS- produce sperm in the testes of male animals A. Diploid cell increases in size to germ cell B. Undergoes meiosis I C. Undergoes meiosis II to form 4 haploid cells D. 4 cells develop tail (sperm) Meiosis- Formation of Haploid Cells

  25. Assessment One • Explain the significance of meiosis in sexual reproduction • Name the stage of meiosis during which chromatids are separated to opposite poles of the cell • Compare the process of crossing over and independent assortment • Differentiate gamete formation in male animals from gamete formation in female animals

  26. DO NOW • 1. How many functional egg cells are created through one round of oogenesis? • 2. How many functional sperm cells are created through one round of spermatogenesis? • 3. Name one factor related to meiosis that increases the amount of genetic variation in animals.

  27. Asexual Reproduction Single parent passes copies of all its genes to each offspring A. No fusion of gametes B. Offspring are clones (genetically identical to parent) Asexual vs. Sexual Reproduction

  28. Asexual Reproduction C. In prokaryotes and eukaryotes D. Fission- parent splits into two equal offspring Ex: Ameba Asexual vs. Sexual Reproduction

  29. Asexual Reproduction E. Fragmentation- body breaks into several pieces that grow into new individuals Asexual vs. Sexual Reproduction

  30. Asexual Reproduction F. Budding- new individuals grow as buds on parent and break off to develop Asexual vs. Sexual Reproduction

  31. Sexual Reproduction Two parents each form reproductive cells with half the number of chromosomes A. Haploid gametes join to form diploid offspring Asexual vs. Sexual Reproduction

  32. Sexual Reproduction B. Both parents contribute genetic material C. Offspring have traits of both parents (not exact copies) D. Occurs in eukaryotes Asexual vs. Sexual Reproduction

  33. Genetic Diversity in Asexual Simple, allows many offspring to be produced in a short amount of time No energy spent on gametes or finding mates DNA between individuals doesn’t vary much May be a disadvantage for adapting to a new environment Genetic Diversity

  34. Genetic Diversity in Sexual Quick and powerful way of making different combinations of genes Genetic Diversity

  35. Evolution of sexual reproduction Only diploid cells can repair their own chromosomal damage Early protists may have been diploid cells with this ability Now protists are haploid that only become diploid under environmental stress Evolution of Sexual Reproduction

  36. Life Cycle Entire span in the life of an organism from one generation to the next Sexual Life Cycles in Eukaryotes

  37. Sexual Haploid Life Cycle 1. Zygote is diploid but undergoes meiosis immediately to make new haploid cells (any DNA damage is repaired) Sexual Life Cycles in Eukaryotes

  38. Sexual Haploid Life Cycle 2. Haploid cells create haploid individuals 3. Gametes are produced by mitosis Sexual Life Cycles in Eukaryotes

  39. Sexual Haploid Life Cycle 4. Gametes fuse to produce diploid zygote, cycle continues Occurs in protists, fungi, algae, chlamydomonas Sexual Life Cycles in Eukaryotes

  40. Sexual Diploid Life Cycle 1. Adults are diploid, each inheriting characteristics from both parents 2. Diploid reproductive cells undergo meiosis to produce gametes Sexual Life Cycles in Eukaryotes

  41. Sexual Diploid Life Cycle 3. Fertilization- joining of gametes (sperm and egg) 4. Resulting zygote divides by mitosis Sexual Life Cycles in Eukaryotes

  42. Sexual Diploid Life Cycle 5. Cells of adult also end up diploid 6. All cells involved are diploid, except gametes which are haploid Ex: Humans/ Animals Sexual Life Cycles in Eukaryotes

  43. Alternation of generations 1. Often in plants, alternates between haploid and diploid phases Sexual Life Cycles in Eukaryotes

  44. Alternation of generations 2. Sporophyte- diploid phase in plant life cycle that produces spores Spore forming cells undergo meiosis to produce spores (haploid reproductive cell that become an adult without fusing with another cell) Sexual Life Cycles in Eukaryotes

  45. Alternation of generations 3. Gametophyte- haploid phase in plant life cycle that produces gametes through mitosis Gametes fuse and give rise to diploid phase Sexual Life Cycles in Eukaryotes

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