3-4_Reproduction

3-4_Reproduction - Sexual Reproduction...

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Sexual  Reproduction By Kevin Laskey and Trisha Jhunjhnuwala
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Evolution of Sexual Reproduction:   Parazoa- Phylum Porifera (Sponges) is hermaphroditic and is  capable of regeneration / fragmentation Sperm carried by water currents to eggs in mesohyl Flagellated larvae develop and swim away to find new  location
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Radiata Phylum Cnidaria (jellyfish and corals) have both sexual and  asexual stages in life Zygote forms colonial polyp stage, which reproduces asexually  by budding Buds (medusa stage) can swim, create gametes, and undergo  fertilization to restart cycle Some jellyfish have reduced polyps and corals have no medusas 
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Acoelomates Phylum Platyhelminthes  (Flukes, tapeworms, etc.) Planarians are hermaphrodites  that usually reproduce  asexually Flukes reproduce larvae  asexually in snail host and  reproduce sexually in human  host Tapeworms have many  proglottids for reproduction;  larvae develop in food humans  eat
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Pseudocoelomates Phylum Rotifera All use parthenogenesis; some species consist of just females  produced in this way Some species create males that are there to fertilize female  eggs to survive harsh times Phylum Nematoda Internal fertilization; females are bigger than males and  produce 100,000 eggs per day
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Coelomates: Protosomes Phyla Bryzoa, Phorondia, Brachiopoda Colonial hermaphrodites that resemble deuterosomes in development Phylum Mollusca (Shellfish, snails, squids, octopus) H ave cilliated larvae called  trocophore Gastropods have torsion during development Phylum Annelida (earthworms) Hermaphrodites that can fragment and regenerate new organisms Can reproduce sexually by cross-fertilization; mucous cocoon of  embryos develop in soil Phylum Arthropoda (Insects, crustaceans, etc.) Insects have internal fertilization w/sperm deposited directly into  female or via sac Specialized sex organs and mostly mate once; metamorphosis almost  always present  Crustaceans have specialized appendages for sperm transfer Have at least 1 swimming larval stage 
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Coelomates: Deuterosomes Phylum Echinodermata (Sea stars, sea urchins) Release gametes into water and adults go through metamorphosis of  larvae Can regenerate limbs, but not whole organisms Subphylum Urochordata (tunicates) Larvae swim after fertilization, attach to surface, and undergo  metamorphosis to become colonial adult Subphylum Cephalochorda (lancelets) Developed via paedogenesis as they resemble tunicate larvae as adults Subphylum Agnatha (lampreys, hagfishes) Free swimming, filter feeding larvae that live in freshwater External fertilization like most other fish Class Chondrichthyes (sharks and rays) Internal fertilization; males have claspers to transfer sperm to female
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3-4_Reproduction - Sexual Reproduction...

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