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1) because of presence of sporopollelin. 2) because pollen tablets comprises of nutritive components which is given to athletes or race horses to increase their performance

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Give reasons why Most zygotes in angiosperms divide only after certain amount of endosperm is formed. Groundnut seeds are exalbuminous and Caster seeds are albuminous. Micropyle remains as a small pore in the seed coat of a seed. Integuments of an ovule harden and the water content is highly reduced as the seed matures. Apple and Cashew are not called true fruits.

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Explain double fertilization and trace the post fertilization events in sequential order leading to seed formation in a typical dicotyledonous plant.

Posted by Rachita T 4 years, 4 months ago

CBSE > Class 12 > Biology

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Sia ? 4 years, 4 months ago

pollen grain contain two male gemetes one fuses with egg and another fuses with central cell to form primary endosperm nucleus , the whole process is known as doible fertilisation.
after double fertilisation primary enfosperm nucleus is converted inro primary endosperm cell which is ised as food for developing seed.

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How are seeds advantageous to flowering plants ?

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Bishal Jyoti Baishya 4 years, 5 months ago

It's provide endosperm , which provides nutrition to the embryo

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Rachita T 4 years, 5 months ago

I don't think so....that I have repeated any of the question..

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Gaurav Bagga 4 years, 5 months ago

Why ru repeating the same questions?

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Describe in sequence the events that lead to the development of a 3-celled pollen grain from microspore mother cell in angiosperms

Posted by Rachita T 4 years, 4 months ago

CBSE > Class 12 > Biology

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Describe in sequence the events that lead to the development of a 3-celled pollen

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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How does pollen mother cell develop into a mature pollen grain ? Illustrate the stages a. with labelled diagrams

Posted by Rachita T 4 years, 4 months ago

CBSE > Class 12 > Biology

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Sia ? 4 years, 4 months ago

Pollen mother cells undergo meiosis to form a microspore tetrad (microspores arranged in a cluster of four cells) by the process called microsporogenesis.
- The microspores dissociate from each other and develop into pollen grains.
- The protoplast (pollen grain) then divides mitotically to form two unequal cells
- the bigger vegetative cell and smaller generative cell.

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Differentiate perisperm and endosperm giving one example of each .

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Sia ? 4 years, 4 months ago

Perisperm	Endosperm
Perisperm is the remnant of nucellus which are persistent. It encloses the embryo and provides nourishment to it in certain seeds.	Endosperm is the tissue formed after double fertilisation. It surrounds, stores food and provide nourishment to the embryo in an angiosperm seed.
It is diploid in nature.	It is triploid in nature because it is formed as a result of triple fusion.
Example- Black pepper	Example- Wheat

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How does geitonogamy differ from xenogamy

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Gaurav Bagga 4 years, 5 months ago

Geitonogamy is transfer of pollen grains from 1 flower to another flower of same plant. Genetically it is self pollination Xenogamy is transfer of pollen grains from one flower to another flower of different flower.

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Name the product of fertilization that forms the kernel of coconut. How does the a. Kernel differ from coconut water ? (a) Mention the similarity between autogamy and geitonogamy

Posted by Rachita T 4 years, 4 months ago

CBSE > Class 12 > Biology

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Sia ? 4 years, 4 months ago

The difference between kernel and coconut water is that kernel is the dried part of the coconut that can be eaten in soft or dried form. It is also used to make coconut oil. Coconut water is the byproduct of fertilization. It is the juice that is found inside the coconut. It is used as a drink.
Endosperm is a tissue that forms inside a seed in flowering parts after fertilization. It provides nutrition to the embryo and can also be the source of nutrition to other organisms.

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Write the cellular contents carried by the pollen tube. How does the pollen tube gain a. entry into the embryo sac ?

Posted by Rachita T 4 years, 4 months ago

CBSE > Class 12 > Biology

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How does the study of different parts of a flower help in identifying wind as its pollinating agent ?

Posted by Rachita T 4 years, 4 months ago

CBSE > Class 12 > Biology

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Sia ? 4 years, 4 months ago

Wind pollination requires that the pollen grains are light and sticky.
The flowers often possess well-exposed stamen and large feathery stigma.
Wind-pollinated flowers have a single ovule in each ovary.
These flowers have small calyx and corolla.

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Explain the function each of 9a) Coleorhiza (b) Germ pores

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Gaurav Bagga 4 years, 5 months ago

Coleorhiza is a region below the level of cotyledons which gives rise to root tip. Intine extends as pollen tube from germ pores

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State one advantage and one disadvantage of cleistogamy.

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Gaurav Bagga 4 years, 5 months ago

Advantage Assures set of seed formation. Disadvantage Continuous self pollination leads to inbreeding depression.

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Where is sporollenin present inplants ?state its significance with reference to its a. chemical nature.

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Bishal Jyoti Baishya 4 years, 5 months ago

In the extine layer of Pollengrain. 1. It can withstand with high temperatures 2. No enzymes can degrade them 3. Most organic resistant with environmental factors.

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Gaurav Bagga 4 years, 5 months ago

Baar baar ek hi sawal ka jawab nhi dunga

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Differentiate between geitonogamy and xenogamy in plants. Which one between the two will lead to inbreeding depression and why ?

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Asha As 4 years, 5 months ago

Geitonogamy leads to inbreeding depression because there is no variation.

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Nidhi Bharti 4 years, 5 months ago

In geitonogamy, the trasfer of pollen grains takes place from the anther of 1 flower to the stigma of a different flower of the same plant. But in Xenogamy the trasfer of pollen grains takes place from anther to stigma of different flower of different plant... Geitonogamy leads to inbreeding depression because in this both the flowers are genetically similar and thus continuous self pollination occurs which leads to inbreeding depression

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Partik Nehra 4 years, 5 months ago

Geitonogamy is type of pollination in which pollen from one flower transfer to stigma of another flower of same plant. While xenogamy is transfer of pollen of one plants to stigma of another plants of same species.xenogamy is genetically dissimilar. Geitonogamy cause inbreeding depression because it is genetically similar.

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Why is sporollenin considered the most resistant organic material ?

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Nidhi Bharti 4 years, 5 months ago

Because it is the toughest substance known. There is no microbe or enzyme found which can digest this substance

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Differentiate between albuminous and non-albuminous seeds, giving one example a. each.

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Keshav Kumawat 4 years, 5 months ago

Human resources management of digestive enzymes

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Nidhi Bharti 4 years, 5 months ago

Albuminous are the seeds in which the endosperm is not completely consumed by the developing embryo. Ex. Wheat, rice, gram Non Albuminous are the seeds in which no residual endosperm is left and thus is completely consumed by the developing embryo

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Explain giving two reasons why pollen grains can be best measured as fossils.

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Nidhi Bharti 4 years, 5 months ago

Because they have a tough outer member because of sporopollenin which makes it protected and hence the pollen grain do not get harmed for millions of years and thus can be measured as fossil

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Gaurav Bagga 4 years, 5 months ago

1) pollen grain consists of 2 protective layers outer exine made of sporopollelin and inner intine made of cellulose. 2) exine is thick layer composed of sporopollelin which is the most resistant organic matter known which cannot be decomposed with any microbe or fungus hence can be stored as fossils for many years

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If you squeeze a seed of orange, you might observe many embryos of different sizes. a. How is it possible ? Explain. (a) Mention any four strategies adopted by flowering plants to prevent self pollination. b. (b) Why is geitonogamy also referred to geneticalautogam

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology

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Gaurav Bagga 4 years, 5 months ago

Sorry Correction in b part Different flower but of same plant

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Gaurav Bagga 4 years, 5 months ago

Startegies adapted by flowering plants to prevent self pollination : 1) dichogamy - protandry and protogyny 2)self sterility 3) unisexuality 4)anther and stigma are at different positions on the same flower. b) geitonogamy also refered as geniticalautogam because morphologically it is self pollination but genetically it is self pollination because pollen grains which are transferred are of the same flower but on different plants respectively.

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Where does triple fusion take place in a flowering plant. Why is it so called ? Mention its significance

Posted by Rachita T 4 years, 5 months ago

CBSE > Class 12 > Biology