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Chapter 43

Chapter 43. Animal Reproduction. Reproduction. Produce copies of self Continue survival of species Ensure survival of personal genetics. Asexual Reproduction. Fragmentation Sponges, some annelids, starfish Organism breaks apart, pieces become new organisms. Asexual Reproduction. Budding

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Chapter 43

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  1. Chapter 43 Animal Reproduction

  2. Reproduction • Produce copies of self • Continue survival of species • Ensure survival of personal genetics

  3. Asexual Reproduction • Fragmentation • Sponges, some annelids, starfish • Organism breaks apart, pieces become new organisms

  4. Asexual Reproduction • Budding • Hydras, cnidarians • Creates bud that breaks off and becomes new organism • Transverse fission • Some protists, planaria • Constricts, splits in half

  5. Asexual Reproduction • Parthenogenesis • “virgin birth” • Eggs produced by mitosis, not meiosis • Egg not fertilized by male • Some insects and arthropods (bees, ants, water fleas) • Some reptiles (komodo dragons, geckos, whiptails) • Some fish, sharks • Same species can reproduce sexually as well

  6. Sexual Reproduction • More “costly” to make and care for gametes • Potential mate needs to be found and possibly courted • Pheromone production • Time and energy in searching • May be time & injury risk when competing • Timing of gamete formation must synchronize between sexes • Neural & hormonal mechanisms in both parents • Overall more complex, more resources needed • So why do it?

  7. Sexual Reproduction • Great genetic variation! • Humans • 22 pairs of homologous chromosomes (X & Y non-homologous) • 8,388,608 combinations of homologous chromosomes • 70,368,744,000,000 possible variations of offspring • Including crossing over in meiosis I, there are 4,951,760,200,000,000,000,000,000,000 possible variations! IN ANY SINGLE CHILD!!! • Many variations possible, some could enhance survival of organism

  8. Sexual Reproduction • External fertilization • Sperm and egg unite outside of female • Must be in very wet environment • Sperm & eggs released into water • Marine invertebrates • Sperm deposited onto eggs • Many fish, amphibians • Internal fertilization • Sperm and egg unite within female

  9. Male Reproductive Systems • Testes (internal or external) • Sperm • Motile, allows movement through fluid towards ova • Copulatory organs • For internal fertilization • Penis—mammals • Usually internal until copulation • Most contain bone (baculum/os penis)

  10. Male Reproductive Systems • Copulatory organs (cont.) • Clasper • Chondricthyes • Inserted into female • Hemipenis (pl. hemipenes) • Snakes, lizards • Paired organs • Often barbed • Internal, everted into female during copulation

  11. Male Reproductive Systems • Copulatory organs (cont.) • Cloaca • Pass sperm through direct cloacal contact • Most birds • Waterfowl have penis-like organ (phallus)

  12. Female Reproductive Systems • Ovaries • Oviduct (Fallopian tube) • Uterus • Eggs/Ova

  13. Female Reproductive Systems • Eggs • Protect & nourish growing embryo • Aquatic animals • Gelatinous, thin-walled eggs • Allow water to diffuse through egg wall • Fish, amphibians

  14. Female Reproductive Systems • Eggs (cont.) • Land animals • Thick shell • Water impermeable (prevent dehydration) • Reptiles—leathery shell • Usually buried or laid underground to preserve warmth • Birds—hard shell • Requires incubation (warmth from parent)

  15. Female Reproductive System • Eggs (cont.) • Amnion—fluid sac to cushion & prevent dehydration • Allantois—stores metabolic wastes • Yolk sac—food source for embryo

  16. Sexual Reproduction • Hermaphrodite • Animal has male and female sex organs • Self-fertilization • Inseminates itself • Tapeworms • Cross-fertilization • Inseminate others • Slugs, snails, earthworms

  17. Sexual Reproduction • Hermaphrodite (cont.) • Sequential hermaphrodites • Born as one sex, can change sex later in life • Mostly fish, some crustaceans • Clownfish harem • Large female, several males • Remove female, one male will become female • Wrasses • Largest fish always male • When male dies, female may turn into male

  18. Sexual Reproduction • Oviparous • Egg laying • Little or no embryonic development within mother • Young hatch from eggs • Most insects, arachnids • Most fish, reptiles, amphibians • All birds, monotremes

  19. Sexual Reproduction • Viviparous • Embryo develops within mother • No egg around embryo • Nourished by mother • Live birth • Most mammals • Rare in other animals, but exists

  20. Sexual Reproduction • Ovoviviparous • Eggs develop within mother • Embryo nourished by yolk sac, not mother • Live birth • Some fish (guppies, mollies, swordtails) • Some sharks, reptiles, amphibians, invertebrates

  21. Placenta • Most mammals • None in monotremes or marsupials • Feeds & nourishes fetus • Filters and eliminates wastes • Blood does not directly connect between mother & fetus • Produces progesterone to maintain pregnancy • Specific shape and attachments vary between species

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