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Reproduction and Development

Types of reproduction. asexualbinary fissionbuddingameiotic parthenogenesissexualdioecy (separate sexes)?monoecy (hermaphroditism)?meiotic parthenogenesis, haplodiploidyconjugation. Generalized sexual lifecycle. . . . . . . . . . . . female. male. Ovum . sperm. (gametes, 1N)?. meiosis. 2N. f

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Reproduction and Development

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    1. Reproduction and Development General Zoology LS2014 11 February 2008 Following Hickman et al. 2008 Ch. 7 pp 138-157 Ch. 8 pp 159-181 Donald Winslow

    2. Types of reproduction asexual binary fission budding ameiotic parthenogenesis sexual dioecy (separate sexes)? monoecy (hermaphroditism)? meiotic parthenogenesis, haplodiploidy conjugation

    3. Generalized sexual lifecycle

    4. Figure 07.1

    5. The cost of sexual reproduction Half of all alleles are thrown away during meiosis! Males can’t produce eggs, so why have sons?

    6. From Hickman et al. 2006 (13th ed.)?

    7. The function of sexual recombination Increased variability—new combinations of alleles. Sexual populations better able to adapt to changing environment. (Group selection)?

    8. Somatic cells and germ line cells Germ line cells give rise to the gametes. Gametogenesis (spermatogenesis & oogenesis)? Oogenesis results in 3 polar bodies for each ovum. Somatic cells give rise to all the tissues of the body.

    9. Mechanisms of sex determination Y chromosomes In humans, presence of Y induces male development. Ratio of X chromosomes to autosomes In Drosophila flies, ratio of X chromosomes to autosomes determines whether male or female. Temperature In reptiles, temperature of nest often determines sex ratio of hatchlings.

    10. Levels of maternal physiological investment Ovipary Development takes place after female deposits egg. Ovovivipary Development takes place within mother’s body, but without nutritional investment from mother. Vivipary Development takes place within mother’s body, with nutritional investment from mother. Example: placental mammals

    11. Development Mechanisms of cellular differentiation Fertilization Cleavage Blastulation Gastrulation Neurulation Direct development and indirect development

    12. Mechanisms of cellular differentiation Cytoplasmic localization Gradients of molecules within cells determine developmental fate of daughter cells. Induction Adjacent cells determine the developmental fate of a cell.

    13. Fertilization and activation Prevention of polyspermy Fast block Change in membrane potential. Slow block Cortical reaction causes vitelline membrane to separate from cell membrane.

    14. Figure 08.04

    15. The Zygote Gray crescent Shows orientation of embryo within zygote Polarity Animal and vegetal poles Yolk Provides nutrition for developing embryo

    16. Patterns of cleavage Spiral cleavage Lophotrochozoan protostomes (annelids, molluscs, etc)? Superficial cleavage Ecdysozoan protostomes (nematodes, arthropods, etc)? Radial cleavage—primitive deuterostomes Discoidal meroblastic cleavage Reptiles, birds, most fishes Rotational holoblastic cleavage—mammals Mosaic vs regulative cleavage

    17. Figure 8-7

    18. Blastulation Blastula made up of blastomeres Inner cavity is called “blastocoel”

    19. Gastrulation Germ layer formation Coelom formation Schizocoely (protostomes)? Enterocoely (deuterostomes)? Fate of blastopore (or primitive streak)? Protostomes: blastopore becomes mouth Deuterostomes: blastopore becomes anus

    20. Figure 08.10

    21. Extraembryonic membranes Present in amniotic vertebrates Help embryo conserve water Amnion, chorion, allantois

    22. Neurulation Nervous system forms from ectoderm Induction by adjacent cells

    23. Direct and indirect development Direct development Embryo develops into adult-like individual Indirect development Embryo develops into larval stage May be several intermediate stages before adult

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