Biology Questions and Answers
by water; entomophily, pollen carried by
insects; ornitophily, pchiropterophily, pollen dissemination ollination by birds;by
bats.
Characteristicplant species relate to s of the flowers othe type off each
pollination usflowers are specialized ied by the plant. Coln bird and insectored (^)
attraction; nocturnal flowers generally
are white specialized iand perfumed, manyn pollination by bats; th (^) e
nectar is also a specialization to attract
pollinator animals; flan exaggerated amount of pollen oftenowers that produce
use the wind as pollinator; thof anthers more external or internale position
next to the nectar is a way to facilitate
the pollen dissemination the wind or by animals. respectively by
- How are the male
gametophytes and the male
gametes formed in
angiosperms?
In the anthers of each stamen pollen sacs. Within the pollen sacsthere are there (^)
are microspore mother cells, or
microspomeiosis forming microsporrocytes. These cells ues. Eachndergo
microspore by mitosis forms a pollen
grain coone tube cell. Tntaining he pollen grain is theone generative cell a nd
male gametophyte.
When pollination occurs agrain makes contact with the stigmand the pollen
(the apex of the pistil) the tube cellelongates its cytoplasm forming the (^)
pollen tube that grows towards the
ovary. forming two spThe generative cell derm nuclei (malividese
gametes) that migrate through the
pollen tube.
- How many cellular nuclei
does the pollen tube of
angiosperms have? What is
the ploidy of each of these
nuclei?
The pollen tube that is the mature malgametophyte of angiosperms has threee
cellular one tube cell nnuclei: ucleus.two sperm nuclei and
All thosgametophyte oe nuclei are part of the malef the plant and thus each (^)
of them is haploid (n).
- How is the female
gametophyte formed in
angiosperms?
In the flower ovary there are
megasporangia having a small opening, the micropylenclosed by a tegumente.
Within the megasporangium there is a
megasporocyte, or cell, that undergoes meiosismegaspor forminge mother
four megaspores of which three regress
and only one is functional. functional megaspore undergoes (three)The (^)
mitosis generating eight cells that as a
whole form the embryonic sac.
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