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Biology · 2024 · 2 marks
CBSE 2024 · Region 2 · Set 1 · Q17
(a) Name any two copper releasing intra-uterine devices. State two reasons that make them effective contraceptives.
(a)
Name any two copper releasing intra-uterine devices. State two reasons that make them effective contraceptives.
OR
(b)
Name any two outbreeding devices that flowering plants have developed and explain how they help in encouraging cross-pollination.
Marking-scheme solution
Copper releasing IUDS – CuT, Cu-$\displaystyle 7$, Multiload – $\displaystyle 375$
Cu+ released from IUDs suppress sperm motility, reduces fertilising capacity of sperms, increase phagocytosis of sperms
Unisexuality - production of unisexual flowers, prevent self pollination,
Release and receptivity of stigma are not synchronized, either pollen is released
before the stigma becomes receptive or stigma becomes receptive much before the release of pollen,
Anther and stigma are placed at different positions, so that the pollen cannot come
in contact with stigma,
Self-incompatibility/genetic incompatibility, genetic mechanism and prevents self-
pollen from fertilizing the ovule by inhibiting pollen germination or pollen tube growth in the pistil.
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