Science 3 Marks Question

(i) Vegetative propagation is the formation of new plants from vegetative parts of the plant such as roots, stems and leaves. 
(ii) The stems of plants normally bear buds in the axils which can be used in a vegetative propagation to produce new plants. New plants can be obtained from the stem of an existing plant by cuttings. A small part of stem having nodes and buds is removed by making a cut with a sharp knife. The lower end of stem cutting is buried in the moist soil. After a few days the cutting develops roots. The buds grows and produces a shoot.

List of wind pollinated flowers include
• Wheat
• Corn
• Barley
• Rice
• Rye

(i) Flowers are the reproductive parts of a plant. Functions of a flower are as follows.
1. It carry out sexual reproduction.
2. It forms male and female gametes.
3. It forms seeds and fruits.
(ii) Yes, flowers help in pollination and fertilisation. Flowers are essential for pollination and fertilisation because they attract pollinators have a structure that is specifically designed for pollination. These factors all work together to ensure that pollen is transferred from one flower to another which is necessary for fertilisation to occur.

The organisms covering the pond are algae. The massive growth of these algae form a dense layer on the surface of lake and water bodies. It makes water toxic to humans and organisms living inside the pond. It also reduces oxygen concentration in the water bodies.

The mode of dispersal of the seeds having following properties are as follows
(i) Seeds with wings - like seeds of drumstick and maple are light weight and can be blown away by air. Thus, these are dispersed by wind.
(ii) Small and light seeds like of grasses are also dispersed through wind.
(iii) Seeds with spines/hooks seeds of Xanthium, Urena have spines and hooks on them, these hooks or spines are attached to the fur of the animal body. When animals move to other places and rub their body with tree, etc. These seeds fall from their body and get dispersed. Therefore, these are dispersed through animals.

The seeds and their means of dispersal can be given as follows
(i) The seed of maple is dispersed by wind. It has winged seed which are light in weight.

(ii) Seed of oak or madar has hairy outgrowth which makes it lighter and can be dispersed by wind.

(iii) Seed of Xanthium have numerous spines on them which gets attached to the fur of animals. Hence, these are dispersed by animals.



None of the seed given in the figure is dispersed by water.

The four whorls of the flower are outermost whorl 'W' is green part which is called sepal. Inside sepal the next whorl is 'X' which is coloured and attractive part of the flower called petals. The 'Y' is the inner whorl of flower called stamen. It is the male reproductive part of a flower. It consist of two parts, i.e. anther and filament. The anther contains several pollen grain which have male gamete. The whorl 'Z' is the innermost part of the flower called pistil. It is the female reproductive part of flower. It consists of three parts, i.e. stigma, style and ovary. The ovary contains ovule which produces the female gametes or egg cell.

Yes, animals can pollinate flowers.
In this process, animals such as bees, butterflies, birds, or bats visit flowers to collect nectar or pollen for food.
While doing so, pollen grains from the male part (anther) stick to the body of the animal.
When the animal visits another flower, these pollen grains are transferred to the female part (stigma) of that flower.
This transfer of pollen helps in fertilization, leading to the formation of seeds and fruits, which ensures the reproduction of plants.

The difference between a zygote and an embryo is as follows:
A zygote is the single-celled structure formed immediately after the fusion of male and female gametes during fertilization.
An embryo is the developing multicellular stage that forms from the zygote after repeated cell divisions.
Thus, a zygote is the initial stage, while the embryo is the later stage of development that eventually grows into a new organism.

Benefits of Seed Dispersal
Some benefits of seed dispersal are
(i) Seed dispersal avoids overcrowding of young plants around their parent plants.
(ii) It helps in preventing competition between the plants and its own seedlings for sunlight, water and minerals.
(iii) It also enables the plant to grow into new habitats for wider distribution and provides them with better chance of survival.

The process by which the seeds are scattered to different place (far and wide from their parents) is called seed dispersal. The seeds and fruits are dispersed away through various agencies like air, water and animals. Sometimes dispersal takes place by the explosion or bursting of fruits.
If all the seeds of a plant were to fall at the same place and grow, there would be a severe competition for sunlight, water, mineral and space. As a result, the survival for the plants will be difficult and the plants who survive will not grow into healthy plants.

In this process, a small bulb-like projection called bud is formed on the parent body. The bud gradually grows in size and finally detaches itself from the parent plant. In this manner, a new individual is formed.
Yeast is a single-celled organism reproduced by the process of budding. Sometimes in yeast, another bud arises from the bud forming a chain of buds producing large number of yeast cells in short period of time.

Sugarcane and rose are propagated by stem cutting that is a method of vegetative propagation. In this, stem cutting with nodes is capable of growing into mature independent plants that are identical to their parents. Potato is an underground modified stem having bud called eyes, which sprout and develop into a new identical plant.
Thus, the plants which cannot produce seeds, can be propagated vegetatively with the help of vegetative parts such as stem, roots, buds and leaves.

The process in which the male gamete fuses with female gamete to form a new cell (i.e. zygote) is called fertilisation.
The process of fertilisation in plants is as follows
(i) When the pollen is deposited on the stigma of the pistil, it begins to germinate. After some time, a long pollen tube is developed from the pollen grain which passes through the style towards the female gametes in the ovary.
(ii) The male gametes move down the pollen tube and the tube enters the ovule present inside the ovary.
(iii) The tip of pollen tube bursts and the male gamete comes out of the pollen tube. Inside the ovary, the male gametes fuse with the female gametes present in the ovule to form a fertilised egg cell which is called zygote.
(iv) The zygote develops into an embryo which is a part of a seed that develops into a new plant.

The differences between self-pollination and cross-pollination are as follows

Self-pollination	Cross-pollination
Pollens are transferred to the stigma of same flower.	Pollens are transferred to the stigma of different flower.
Does not require pollinating agents.	Requires pollinating agents.
Occurs in papaya, corn, cucumber, etc.	Common in most of flowers like rose, China rose, etc.

The main differences between asexual and sexual reproduction are as follows

Asexual reproduction	Sexual reproduction
Only one parent is needed.	Two parents, a male and a female are required.
Offspring are identical to their parents.	Offspring exhibit variation with respect to their parents.
No seed is formed. Fragmentation, budding, spore formation, vegetative propagation are its different types.	Seeds are formed due to the fusion of male and female gametes.
Spirogyra, yeast, moulds and potato exhibit asexual reproduction.	Fruit bearing plants, like mango and China rose, reproduce sexually.