2. SEXUAL REPRODUCTION IN FLOWERING PLANTS
2020
SAY
1. Observe the
relationship between the first two terms and fill in the blank: (1)
Endothecium: Protection;
Tapetum: ......................
ü Answer:
Nutrition
2. Flowers are
classified into Chasmogamous and Cleistogamous flowers. (2)
(a)
Cleistogamous
flowers are autogamous. Justify.
(b)
Define autogamy.
ü Answer:
(a) Anthers and stigma lie close to each other. They
are not exposed.
(b) It is the transfer of pollen grains from the
anther to the stigma of the same flower.
3. Observe the
figure given below: (2)
(a)
Identify the
parts a, b, c.
(b)
Write the
functions of c.
ü Answer:
(a) a. Funicle, b. Micropyle, c. Integuments.
(b) Protective covering of ovule.
4. A typical angiosperm
embryo sac is 8-nucleate and 7-celled. (3)
(a)
Name the cells
that constitute egg apparatus.
(b)
Explain
monosporic type of embryo sac development.
ü Answer:
(a) Synergids and egg.
(b) In this, one of the megaspores is functional
while other three are degenerate.
2020
MARCH
1. How can you
differentiate true fruits from false fruits? (2)
ü Answer:
True fruit is developed from ovary.
False fruit is developed from any parts other than
ovary (e.g. from thalamus).
2. Define the
following terms: (3)
a.
Autogamy
b.
Geitonogamy
c.
Xenogamy
ü Answer:
(a) Autogamy: Transfer of pollen grains from the anther to the
stigma of the same flower.
(b) Geitonogamy: Transfer of pollen grains from the anther to the
stigma of another flower of the same plant.
(c) Xenogamy: Transfer of pollen grains from the anther to the
stigma of a different plant.
2019
SAY June
1. Observe the
relationship between the first two terms and fill in the blank. (1)
Funicle: Stalk of the ovule.
...................: Protective envelopes of the ovule.
ü Answer:
Integuments.
2. Wind
pollination is common in grasses. Write any three floral features in grasses
that help in wind pollination. (3)
ü Answer:
Pollen grains are light and non-sticky.
Well exposed stamens.
Large and feathery stigma.
3. Write any three
parts of a monocot embryo and write one peculiarity of each of these three
parts. (3)
ü Answer:
Scutellum: Single cotyledon.
Radicle: Lower end of the embryonal axis.
Coleorhiza: Sheath that encloses radicle.
2019
MARCH
1. The early
stages of embryo development are similar in both dicots and monocots. However,
mature embryos have differences. Write two major differences between dicot
embryo and monocot embryo. (2)
ü Answer:
Differences between dicot embryo and monocot embryo:
|
Dicot embryo |
Monocot embryo |
|
Two cotyledons |
One cotyledon |
|
Coleoptile absent |
Coleoptile present |
|
Coleorhiza absent |
Coleorhiza present |
2. Double
fertilization is a characteristic feature of angiosperms. (2)
a.
Which are the
events in double fertilization?
b.
Name the
triploid nucleus formed as a result of double fertilization.
ü Answer:
(a) Syngamy and Triple fusion.
(b) Primary Endosperm Nucleus (PEN).
3. Observe the
diagram of young anther given below. (3)
a.
Identify the
parts labelled as A, B, C and D.
b.
Which layer
nourishes the developing pollen grains?
ü Answer:
(a) A= Epidermis, B= Endothecium, C= Middle layers, D=
Tapetum.
(b) Tapetum.
2018
SAY June
1. Pollination by
water is seen in Zostera and Vallisnaria. Enumerate
its adaptations. (2)
ü Answer:
In Vallisneria, the female flower reaches the
surface of water by the long stalk and the male flowers or pollen grains are
released on to the surface of water.
In Zostera, female flowers remain
submerged in water. Pollen grains are long and ribbon like. They are carried inside
the water and reach the stigma.
2. Depending on
the source of pollen, pollination can be divided into three types. What are
they? Explain each. (3)
ü Answer:
(a) Autogamy (self-pollination): It is the transfer of pollen grains from the anther
to stigma of the same flower.
(b) Geitonogamy: It is the transfer of pollen grains from the anther
to the stigma of another flower of the same plant.
(c) Xenogamy: It is the transfer of pollen grains from anther to
the stigma of a different plant.
2018
MARCH
1. Synergids have
a special cellular thickening at micropylar tip. Write the name of name and
function of the structure. (2)
ü Answer:
Filiform apparatus. It guides pollen tube into the
synergids.
2. In angiosperms,
female gametophyte is known as embryo sac. Explain its development. (3)
ü Answer:
The functional megaspore develops into the female
gametophyte.
Nucleus of the functional megaspore divides
mitotically to form two nuclei. They move to the opposite poles, forming
2-nucleate embryo sac.
The nuclei again divide two times forming 4-nucleate
and 8-nucleate stages of the embryo sac.
These divisions are free nuclear.
After the 8-nucleate stage, cell walls are laid down
leading to the organization of the typical female gametophyte.
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