TOP MOST IMPORTANT QUESTIONS IN BIOLOGY FOR REDUCED SYLLABUS……
1. T.S of Anther OR Structure of microsporangium
2. The Megasporangium (Ovule) OR V.S of anatropus ovule
3. Female gametophyte or embryo sac or 7 celled 8 nucleate embryo sac
4. Define polyembryony? Write the significance of polyembryony.
Polyembryony: Ovule having more than one embryo is termed as polyembryony.
Significance of polyembryony:
Polyembryony plays an important role in plant breeding and horticulture.
Haploid embryos are used to raise homozygous diploids.
Adventive embryos are used to provide genetically uniform seedlings in some fruit trees.
5. Briefly explain the structure of pollen grain.
Pollen grains are spherical shaped structures measuring about
25-50 micrometers in diameter.
It has two-layers- the hard outer layer called the exine and the
inner layer called intine.
The exine is made up of one of the most resistant organic
material known as sporopollenin. It can withstand high
, temperatures and strong acids and alkali.
The inner wall of the pollen grain called the intine is a thin
, and continuous layer made up of cellulose and pectin.
Pollen grain exine has prominent apertures called germ pores where sporopollenin is absent.
The cytoplasm of pollen grain is surrounded by a plasma membrane contains two cells, the
vegetative cell and generative cell.
6. What are Cleistogamous flowers? Write their significance.
The flowers which do not open at all are called Cleistogamous flowers.
In such flowers, the anthers and stigma lie close to each other, When anthers dehisce in the flower
buds, pollen grains come in contact with the stigma to effect pollination.
Significance: Cleistogamous flowers are invariably autogamous as there is no chance of cross-pollen
landing on the stigma.
Cleistogamous flowers produce assured seed-set even in the absence of pollinators.
7. What is Pollination? Mention any four features of wind pollinated flowers.
POLLINATION: The process of transfer of pollen grains from anther to stigma is called Pollination.
Wind pollination also requires that the pollen grains are light and non-sticky so that they can be
transported through wind currents.
They often possess well-exposed stamens and large often-feathery stigma to easily trap air-borne
pollen grains.
Wind pollinated flowers often have a single ovule in each ovary and numerous flowers packed into
an inflorescence.
Wind-pollination is quite common in grasses.
8. Describe the outbreeding devices that prevent autogamy.
Outbreeding devices is the method of promoting the plant to undergo cross pollination. Flowering plants
have developed many devices to discourage self-pollination and to encourage cross-pollination.
Some of the mechanisms that plants have developed as outbreeding devices are described below;
Dicliny: Dicliny or unisexuality is a condition in which the flowers are either staminate (male) or
pistilate (female).
Self-sterility: Pollen grains of a flower do not germinate on the stigma of the same flower due to
presence of similar self-sterile gene e.g., Tobacco, potato.
Dichogamy: The stigma and anther mature at different times. Dichogamy is further divided into
Protandry- the androecium matures earlier than the gynoecium and Protogyny- the gynoecium
matures earlier than androecium.
Herkogamy: The natural physical barrier prevents the pollen of the same flower entering the ovary.
9. Write the events of development of female gametophyte in correct order OR Describe the process of
megasporogenesis with a neat labelled diagram
Ans: Megasporogenesis:
The process of formation of megaspores from the megaspore mother cell (MMC)
is called megasporogenesis.
The female gametophyte is formed within the nucellus of the ovule by undergoing sequential cell
divisions. The angiospermic female gametophyte is a 7-celled and 8-nucleate structure.
1. T.S of Anther OR Structure of microsporangium
2. The Megasporangium (Ovule) OR V.S of anatropus ovule
3. Female gametophyte or embryo sac or 7 celled 8 nucleate embryo sac
4. Define polyembryony? Write the significance of polyembryony.
Polyembryony: Ovule having more than one embryo is termed as polyembryony.
Significance of polyembryony:
Polyembryony plays an important role in plant breeding and horticulture.
Haploid embryos are used to raise homozygous diploids.
Adventive embryos are used to provide genetically uniform seedlings in some fruit trees.
5. Briefly explain the structure of pollen grain.
Pollen grains are spherical shaped structures measuring about
25-50 micrometers in diameter.
It has two-layers- the hard outer layer called the exine and the
inner layer called intine.
The exine is made up of one of the most resistant organic
material known as sporopollenin. It can withstand high
, temperatures and strong acids and alkali.
The inner wall of the pollen grain called the intine is a thin
, and continuous layer made up of cellulose and pectin.
Pollen grain exine has prominent apertures called germ pores where sporopollenin is absent.
The cytoplasm of pollen grain is surrounded by a plasma membrane contains two cells, the
vegetative cell and generative cell.
6. What are Cleistogamous flowers? Write their significance.
The flowers which do not open at all are called Cleistogamous flowers.
In such flowers, the anthers and stigma lie close to each other, When anthers dehisce in the flower
buds, pollen grains come in contact with the stigma to effect pollination.
Significance: Cleistogamous flowers are invariably autogamous as there is no chance of cross-pollen
landing on the stigma.
Cleistogamous flowers produce assured seed-set even in the absence of pollinators.
7. What is Pollination? Mention any four features of wind pollinated flowers.
POLLINATION: The process of transfer of pollen grains from anther to stigma is called Pollination.
Wind pollination also requires that the pollen grains are light and non-sticky so that they can be
transported through wind currents.
They often possess well-exposed stamens and large often-feathery stigma to easily trap air-borne
pollen grains.
Wind pollinated flowers often have a single ovule in each ovary and numerous flowers packed into
an inflorescence.
Wind-pollination is quite common in grasses.
8. Describe the outbreeding devices that prevent autogamy.
Outbreeding devices is the method of promoting the plant to undergo cross pollination. Flowering plants
have developed many devices to discourage self-pollination and to encourage cross-pollination.
Some of the mechanisms that plants have developed as outbreeding devices are described below;
Dicliny: Dicliny or unisexuality is a condition in which the flowers are either staminate (male) or
pistilate (female).
Self-sterility: Pollen grains of a flower do not germinate on the stigma of the same flower due to
presence of similar self-sterile gene e.g., Tobacco, potato.
Dichogamy: The stigma and anther mature at different times. Dichogamy is further divided into
Protandry- the androecium matures earlier than the gynoecium and Protogyny- the gynoecium
matures earlier than androecium.
Herkogamy: The natural physical barrier prevents the pollen of the same flower entering the ovary.
9. Write the events of development of female gametophyte in correct order OR Describe the process of
megasporogenesis with a neat labelled diagram
Ans: Megasporogenesis:
The process of formation of megaspores from the megaspore mother cell (MMC)
is called megasporogenesis.
The female gametophyte is formed within the nucellus of the ovule by undergoing sequential cell
divisions. The angiospermic female gametophyte is a 7-celled and 8-nucleate structure.
