Human Reproduction - HumanReproduction...

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    Human Reproduction
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    Stages of sexual reproduction Three distinct stages in this process: Gametogenesis (production of sex cells) Mating (getting the sex cells together) Fertilization (fusion of sex cells to form a  zygote) The processes of gametogenesis and fertilization are fairly similar among  all animals; however, there is considerable variation in mating  (question  to ponder: why might this be so?)
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    Gametogenesis Gametogenesis occurs in the gonads  (testes in males, ovaries in females) Testes (singular testis) produce sperm Ovaries produce ova (singular ovum) Gametes derived from germ cells  (rest  of body is comprised of somatic cells) Formation of germ cells begins during  embryonic development
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    Spermatogenesis Germ cell   Spermatogonium (2n)  Primary spermatocyte (2n)   2 Secondary  spermatocytes 2(n)   4 Spermatids (n) Note: Meiotic reduction division occurs  secondary spermatocytes; not  the second  meiotic division between secondary  spermatocytes and spermatids
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    Cytoplasmic contact required  during spermogenesis
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    Oogenesis While sperm are produced continuously  throughout mature male reproductive  lifespan, human ova are all produced during  fetal development A few hundred thousand ‘eggs’ (primary  oocytes arrested at prophase of meiosis 1)  are present in the ovaries at birth Only ~500 of these eggs (one per month) will  undergo meiosis to form a haploid ovum
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    Oogenesis Germ cell   oogonium (2n)   Primary  oocyte (2n)  (arrested stage present at  birth)    Secondary oocyte + first polar  body (n, first meiotic division)   ovum +  second polar body (n, second meiotic  division Note: spermatogenesis yields 4 haploid  sperm from one germ cell; oogenesis  one haploid ovum and two polar bodies
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    Sex requires male and female  gametes Dioecious  (two houses) animals have  Monoecious  (one house) animals have  both testis and ovaries within same  body (hermaphrodites) Hermaphrodites can be either  simultaneous  or  sequential
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    Sex-changing wrasses She’s the boss What are potential advantages to sex reversal in these fish?
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This note was uploaded on 05/23/2011 for the course BIOLOGY 1520 taught by Professor Davidgarton during the Fall '09 term at Georgia Institute of Technology.

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Human Reproduction - HumanReproduction...

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