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Structural Organisation in Animals — BIOLOGY STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 ScienceBIOLOGYStructural Organisation in Animals5 Marks
Question
Explain fertilization and development in pheretima.
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Answer

Fertilization and Development in Pheretima:
  • A mutual exchange of sperm occurs between two worms during mating. One worm has to find another worm and they mate juxtaposing opposite gonadal openings exchanging packets of sperms called spermatophores.
  • Mature sperm and egg cells and nutritive fluid are deposited in cocoons produced by the gland cells of clitellum. Fertilisation and development occur within the cocoons which are deposited in soil.
  • The cocoon holds the worm embryos. After about 3 weeks, each cocoon produces two to twenty baby worms with an average of four.
  • Earthworms development is direct, i.e., there is no larva formed.

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