grade 7 life science

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oogpister
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131834
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grade 7 life science
Updated:
2012-01-31 21:45:30
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life science grade chapter
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GRADE 7 life science reproduction
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  1. where do sex cells form?
    reproductive organs
  2. egg
    the female sex cell

    forms in the ovary
  3. sperm
    the male sex cell

    forms in the testis
  4. fertilization
    proces in which an egg cell and sperm cell join together

    produces a new cell (zygote)
  5. sexual reproduction
    a type of reproduction in which the genetic materials from two different cells combine, producing an offspring.
  6. zygote
    a new cell that forms from fertilization
  7. following feritilization, what processes does the zygote go through?
    mitosis and cell division
  8. organisms that reproduce sexually form what two kinds of cells?
    body cells - similiar chromosomes, occur in pairs

    sex cells
  9. diploid cells
    cells that havepairs of chromosomes
  10. homologous chromosomes
    • pairs of chromosomes that have genes for the same traits
    • arranged in the same order
  11. why aren't chromosomes identical?
    because one chromosome is inherited from each parent
  12. why is having the correct number of chromosomes important?
    if a zygote has too many or too few chromosomes it will not develop properly
  13. haploid cell
    cells that have only one chromosome from each pair
  14. how do diploid cells differ from haploid cells?
    • in a "diploid" cell there are 2 copies of each chromosome
    • in a "haploid" cell there is only 1 copy of each chromosome

    Most of your body's cells are diploid. only the gametes, the sperm and the eggs, are haploid

    • diploid cells reproduce by mitosis
    • haploid cells reproduce by meiosis
  15. what process do organisms use to produce sex cells?
    miosis
  16. meiosis
    one diploid cell divides and makes four haploid cells

    meiosis only occurs during the formation of sex cells
  17. what happens to a reproductive cell before the beginning of meiosis I?
    • interphase:
    • cell grows and duplicates chromosomes
  18. what are the phases of meiosis I
    • prophase I
    • metaphase I
    • anaphase I
    • telophase I
  19. prophase I
    duplicated chromosomes form pairs

    homologous chromosomes form pairs

    membrane around nucleus breaks apart

    nucleolus disappears
  20. metaphase I
    • homologous chromosome pairs line up in middle of cell
    • spindle fiber attaches to each chromosome
  21. anaphase I
    chromosome pairs separate and are pulled toward opposite ends of cell

    (sister chromatids stay together)
  22. telophase I
    nuclear membrane forms around each group of duplicated chromosomes

    cytoplasm divides through cytokinesis, making 2 daughter cells

    sister chromatids remain together
  23. what happens during meiosis II?
    the 2 cells formed previously go through a second division of the nucleus and cytoplasm

    this reduction division results in a haploid gamete or spore
  24. phases of meiosis II
    • prophase II
    • metaphase II
    • anaphase II
    • telophase II
  25. prophase II
    chromsomes not copied again before prophase II, remain as thickened sister chromatids

    • nuclear membrane breaks apart
    • nucleolus disappears in each cell
  26. anaphase II
    sister chromatids of duplicated chromosomes are pulled away move towards opposite ends of cell
  27. metaphase II
    pairs of sister chromatids line up along middle of cell in single file
  28. telophase II
    nuclear membrane forms around each set of chromatids , which are again called chromosomes

    cyoplasm divides through cytokinesis and four haploid cells form.
  29. why is meiosis important?
    it ensures that the chromosome number of a species stays the same from generation to generation and creates genetic variation
  30. why is sexual reproduction beneficial?
    offspring inherit half their dna from each parent resulting in genetic variation among offspring
  31. independant assortment
    the inheritance of one trait does not influence the inheritance of another trait

    may be an advantage if the environment changes
  32. advantages of sexual reproduction
    selective breeding

    genetic variation
  33. disadvantages of sexual reproduction
    time and energy; growth and development, finding a mate
  34. asexual reproduction
    one parent organism produces offspring without meiosis and fertilization
  35. fission
    cell division in prokaryotes that forms two genetically identical cells
  36. describe fission
    • dna molocule copied
    • copy attaches to cell membrane
    • cell elongates, pulling copies apart
    • cell membrane pinches inward along the middle
    • cell splits and forms 2 new identical offspring
  37. types of asexual reproduction
    • fission
    • mitotic cell division
    • budding
    • animal regeneration
    • vegetative reproduction
    • cloning
  38. budding
    • a new organism grows by mitosis and cell division on the body of its parent.
    • bud is genetically identical to its parent, when large enough it can break from the parent and live on its own
  39. animal regeneration
    occurs when an offspring grows from a piece of its parent
  40. vegetative reproduction
    form of asexual reproduction in which offspring grow from a part of a parent plant

    typically involving structures such as roots, stems, and leaves
  41. cloning
    asexual reproduction performed in the laboratory that produces identical individuals from a cell or from a cluster of cells taken from a multicellular organism
  42. advantages of asexual reproduction
    enables organisms to reproduce without a mate

    enables some organisms to rapidly reproduce a large number of offspring
  43. disadvantages of asexual reproduction
    results in little genetic variation

    mutations will be passed to offspring, possibly affecting the offsprings ability to survive

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