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प्रश्न
Is the chromosome number of zygote, embryonal cells and adult of a particular organism always constant? How is the constancy maintained in these three stages?
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उत्तर
Mitosis is a cell division which results in the formation of two daughter cells from a cell with the same number of chromosomes. Zygote undergoes mitotic divisions to develop into an embryo which in turn, also undergoes mitotic divisions to become an adult. So, the constancy of chromosomes is maintained in these three stages.
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संबंधित प्रश्न
A student while observing an embryo of a pea seed in the laboratory listed various parts of the embryo as given below:
Testa, Tegmen, Radicle, Plumule, Micropyle, Cotyledon.
On examining the list the teacher remarked that only three parts are correct. Select three correct parts from the above list:
(a) Testa, Radicle, Cotyleddon
(b) Tegmen, Radicle, Micropyle
(c) Cotyledon, Plumule, Testa
(d) Radicle, Cotyledon, Plumule
Name the parts A, B and C shown in the following diagram and state one function of each.
State significance of pollination.
Name the parts labelled as A, B, C and D in the diagram given below:
What is the function of a flower?
Where is the female gamete formed in flowering plants?
Fill in the following blank with suitable word :
The female organ of reproduction in the flower is the...........
Fill in the following blank with suitable word :
The name of the structure in the flower in which the male gamete is formed is...........
In tobacco plant, the male gametes have 24 chromosomes.
What is the number of chromosomes in the female gamete?
When an insect sits on the flower of a plant then some particles A present in the top of little stalks in the flower attach to its body hair. When this insect now sits on the flower of another similar plant, then particles A attached to the hair of insect are put on the top of a flask-shaped organ at the centre of flower. The particle A grows a long tube b from the top of flask-shaped organ through which C moves down and reaches the bottom part of flask-shaped organ. Here C fuses with the nucleus of d contained in structure E. the fusion of C and D forms a new cell f which grows and develops into a seed of the plant.
(a) What are particles A? What is the process of transferring A from one flower to another flower of similar plant by the insect known as?
(b) What is the name of tube B?
(c) What is C which moves down through the tube B?
(d) Name D and E.
(e) What is F?
In what ways is fertilisation in a plant similar to fertilisation in a human?
Write one main difference between asexual and sexual mode of reproduction. Which species is likely to have comparatively better chances of survival – the one reproducing asexually or the one reproducing sexually? Give reason to justify your answer.
Fill in the blanks and rewrite the completed statements:
Lymph flows in _______________ direction.
Mention pollination types.
Pollen grains are formed by _________ division in locules of anthers.
The anther wall consists of four wall layers where ______
The ovule of an angiosperm is technically equivalent to ______
Pineapple fruit develops from ______.
Variations occur as a result of ______
State the post-fertilisation changes that lead to fruit formation in plants.
