Biology Questions and Answers
- What is the embryonic sac?
Which are the cells that form
the embryonic sac? What are
their ploidies?
The embryonic sacgametophyte of angiosp is the femaleerms.
The embryonic saccells that remain n is composeext to the micropyld of threee,
two lateral oosphere (egg); one binucleatsynergids and the centraled cell, (^)
the polar nuclei, is placed in the central
region; three antipodal cellsopposite side to the micropyle. stay in the
Since all these cells come bfrom the functional megaspore they arey mitosis (^)
haploid (n).
- After pollination how does
fecundation occur in
angiosperms? In these plants
is fecundation dependent on
water?
After pollination ofrom the pollen tube unites with thne of the sperm neuclei
oosphere of the embryonic sac forming
the diploid (2n) zygote. The othersperm nucleus fuses with the polar (^)
nuclei of the embryonic sac originating triploid (3n) cell that by mitosis will turna
into the secondary endosperm of the
seed. The synergids and the antipodalcells degenerate after the fecundation
process.
Fecundatioindependent from water.n in these plants is
- What is the difference
between self pollination and
cross pollination? Which of
these two modes of
pollination contributes more
to the plant diversity?
Self pollination occurs when pollen
grains frthe pistilsom a fl of the same owering plant fall intoplant and thus (^)
gametes from the same individual unite
to form a occurs when pollinatorszygote. Cross pollination carry pollen (^)
grains frindividual om a pplants of lant to rthe same speach othecieser (^)
thus gametes of different individuals
form the zygote.
Since it promotes formation of zygotes
containing gindividuals (enes from differentnew gene combinatio (^) ns)
cross pollination contributes more to
biological diversity.
- What is dichogamy?
Dichogamy is thmaturation of female reproductivee phenomenon of the
structures operiod to the maturatiof the plant in a n of the maledifferent (^)
reproductive structures. Dichogamy
prevents self pollination cross pollination almost obligatory soand makes (^)
assisting in an evolutionary strategy to
promote genetic recombination.
- What are the typical
structures of the seed? What
is endosperm?
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