Hand in W'S' Meiosis before the bell rings - PowerPoint PPT Presentation

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Hand in W'S' Meiosis before the bell rings

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'They (fathers) give it (the Y chromosome) to their sons because ... Hydra, sea stars, sponges, plants. Fission, budding, fragmentation, vegatative propagation ... – PowerPoint PPT presentation

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Title: Hand in W'S' Meiosis before the bell rings


1
Class Topics
Title Biology 1/30/08
Objectives
  • To review learning about meiosis and begin
    learning about gametogenesis (formation of
    gametes)
  • Hand in W.S. Meiosis before the bell rings
  • Notes
  • Gametogenesis
  • Genetic Variability
  • They (fathers) give it (the Y chromosome) to
    their sons because if they give it to their
    daughter, theyre not a daughter.
  • Nathan Hoofie Steele

Sunday, November 15, 2009 1101 AM
2
Class Assignments
By When
What
  • Packet W.S. Meiosis 1/30/08
  • Chapter 8 (Meiosis) Test 2/1/08
  • Due this class period
  • Due next class period
  • Due in the future

3
Genetic variation
  • Allows for new genetic combinations
  • Unlike mitosis
  • 1. Independent assortment
  • Random distribution of homologous chromosomes
  • Each of the 23 pairs segregates independently
  • 223 combinations (8,388,608) from one cell
  • 2. Crossing-over
  • Crossing-over adds more recombination

4
Genetic variation
  • 3. Random fertilization
  • Random fertilization means each gamete was
    independently assorted
  • (223 223) 70,368,744,177,664 combinations

5
Importance of genetic variation
  • Very important for evolution
  • change in characteristics of a population from
    one generation to the next
  • The pace of evolution can be sped up by increased
    genetic variation
  • Depends on natural selection

6
Meiosis and Gamete Formation
  • Spermatogenesis
  • Formation of sperm in the testes
  • Primary spermatocytes (2n)
  • Secondary spermatocyes (n)
  • Spermatids (n)
  • Sperm (n)
  • 4 haploid cells from one germ cell

7
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9
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10
Oogenesis
  • Primary Oocyte (2n)
  • Secondary Ooctye, Polar Body (n)
  • 1 Ootid, Polar bodies (n)
  • 1 Ovum (n)

11
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13
Sperm vs Ovum
  • Sperm
  • size - small
  • moves by flagellum
  • millions made per day
  • no food
  • produced in testes
  • Ovum
  • size - very large
  • no movement
  • fixed number
  • all made by 3rd month of development
  • Yolk (amnion) supplies food
  • Ovaries

14
Reproduction
  • Sexual
  • 2 parents for every offspring
  • Genetically diverse offspring
  • Asexual
  • 1 parent
  • Genetic clone
  • Hydra, sea stars, sponges, plants
  • Fission, budding, fragmentation, vegatative
    propagation

15
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16
  • Asexual reproduction
  • Advantages
  • Many offspring
  • Disadvantages
  • Little genetic diversity
  • Unable to handle changes in environment
  • Sexual Reproduction
  • Advantages
  • Genetic diversity
  • Many new combinations in a relatively short
    period of time
  • Disadvantages
  • Not as many offspring

17
Venn Diagram
  • Homologous chromosomes
  • somatic cells
  • gametes
  • 1 division
  • tetrads
  • cytokinesis
  • chromatids
  • Synapsis
  • unpaired chromosomes
  • diploid cells
  • crossing over
  • 2 divisions
  • haploid cells
  • ovum

18
I have, Who has?
  • On each slip of paper is a term and a definition.
  • One person will start by reading their definition
  • Someone else needs to answer (correctly) with
    their term. If its correct they will then read
    their definition
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