Reproduction & Development 1 Marine Invertebrate Zoology Reproduction and Development
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Marine Invertebrate Zoology
Reproduction and Development
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Asexual reproduction
Reproduction in the absence of fertilization (without union of gametes)
Parthenogenesis
Parthenogenesis – eggs develop to adulthood in the absence of fertilization (some arthropods, and rotifers)
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Parthenogenesis
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Sexual Reproduction
Patterns of Sexuality– Gonochoristic or
dioecious The parents are of 2
different sexes
Hermaphroditism – both male and female sex organs
– Simultaneous or sequential
– Protandric– Protogynous
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Getting the “Boys” to the Party
Internal fertilization– Direct – Indirect
Methods of transfer vary across phyla
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Sexual Reproduction
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Broadcast Spawning & External Fertilization
Requires the precise timing of gamete release
Successful fertilization is dependent on:
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Larval Forms
The product of external and some internal fertilization usually results in a free-living, swimming larvae that grows and differentiates in the plankton
– Most larvae are ciliated for locomotion, and food collection
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Advantages for Free-living Larvae
Transitions between phases of complex life cycles usually requires metamorphosis (abrupt morphological, physiological, and ecological changes)
Cost of Delaying Metamorphosis
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