Ans. It is a type of asexual reproduction in which new plants are produced from roots, stems, leaves and buds. Since reproduction is through the vegetative parts of the plant, it is known as vegetative propagation. Most yeasts reproduce asexually by an asymmetric division process called budding. When water and nutrients are available algae grow and multiply rapidly by fragmentation.
Ans. Plants such as moss and ferns also reproduce by means of spores. Spores are asexual reproductive bodies. Each spore is covered by a hard protective coat to withstand unfavourable conditions such as high temperature and low humidity. So they can survive for a long time. Under favourable conditions, a spore germinates and develops into a new individual.
Ans. Yeast is a single-celled organism. The small bulb-like projection coming out from the yeast cell is called a bud. The bud gradually grows and gets detached from the parent cell and forms a new yeast cell. The new yeast cell grows, matures and produces more yeast cells. Sometimes, another bud arises from the bud forming a chain of buds. If this process continues, a large number of yeast cells are produced in a short time.
Ans. When ripe pollen from an anther of the same kind of flower catches on the stigma, each pollen grain sends out a tiny threadlike tube. The tube grows down through the style and pierces one of the ovules in the ovary. This pollen tube carries a male gamete to meet a female gamete in an ovule. Two gametes fuse together to form zygote. The process of fusion of male and female gametes (to form a zygote) is called fertilisation. The zygote develops into an embryo.
Ans. Generally pollen grains have a tough protective coat which prevents them from drying up. Since pollen grains are light, they can be carried by wind or water. Insects visit flowers and carry away pollen on their bodies. Some of the pollen lands on the stigma of a flower of the same kind. Some pollen of a flower may lands on the stigma of a flower of a different plant of the same kind. Pollen grain on the stigma grows a tiny tube, all the way down the style to the ovary. This pollen tube carries a male gamete to meet a female gamete in an ovule.
Image From NCERT
Image From NCERT
Ans. Seeds and fruits of plants are carried away by wind, water and animals.
i. Winged seeds such as those of drumstick and maple, light seeds of grasses or hairy seeds of aak (Madar) and hairy fruit of sunflower get blown off with the wind to far away places.
ii. Some seeds are dispersed by water. These fruits or seeds usually develop floating ability in the form of spongy or fibrous outer coat as in coconut. Some seeds are dispersed by animals, especially spiny seeds with hooks which get attached to the bodies of animals and are carried to distant places. Examples are Xanthium and Urena.
iii. Some seeds are dispersed when the fruits burst with sudden jerks. The seeds are scattered far from the parent plant. This happens in the case of castor and balsam.
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