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Solutions for Biology, Class 8, ICSE
Assertion (A): The edible portion of potato plant is the root as it grows and develops under the soil.
Reason (R): The root is swollen due to the storage of food material which is rich in starch.
Both A and R are false.
Explanation — The edible part of the potato is a modified stem called a tuber, not a root, even though it grows underground. The swelling occurs due to food storage, but it's the stem, not the root, that stores starch.
Assertion (A): Carrot is a biennial plant which stores food material in its roots in the first year.
Reason (R): This food is utilized in the second year to produce flowers and viable seeds, i.e. to reproduce sexually.
Both A and R are true.
Explanation — Carrot is a biennial plant, meaning it completes its life cycle in two years. In the first year, it stores food in its roots, which is then used in the second year for flowering and seed production, enabling sexual reproduction.
Assertion (A): Calyx is the outermost whorl of a flower which consists of large, fragrant and brightly coloured petals.
Reason (R): As petals are brightly coloured and fragrant, they can be noticed by insects easily and help in cross pollination.
A is false and R is true.
Explanation — Calyx, the outermost whorl of a flower consists of tiny leaf-like green structures called sepals, for providing the inner parts of flower with necessary protection.
Corolla, the second inner whorl of the flower is made up of petals that are large, fragrant and brightly coloured. They can be noticed by insects easily and help in cross pollination.
Assertion (A): Micropropagation is the propagation or multiplication of plants by a special technique called 'tissue culture'.
Reason (R): It is called 'micropropagation' because this technique is applicable to micro-organisms only.
A is true and R is false.
Explanation — Micropropagation involves growing plant cells, tissues, or organs in a laboratory setting to produce plantlets. These plantlets are then transferred to the soil.
Assertion (A): Vallisneria is a good example of wind-pollinated flower, even though the plant is aquatic.
Reason (R): Both male and female flowers of Vallisneria float on the surface of water and get pollinated with the help of wind.
Both A and R are false.
Explanation — Vallisneria, an aquatic plant, is a good example of water-pollinated flower. Both male and female flowers of Vallisneria float on the surface of water and get pollinated with the help of water.
Fill in the blanks by selecting suitable words:
(unisexual, fertilisation, fruit, stamen, anther, bisexual, pollination, seed, ovary)
A flower that bears both the male and the female parts is known as ............... flower.
A flower bearing only male or female parts is known as ............... flower.
Transfer of pollen grains from the anther to the stigma is known as ...............
Fusion of male cell with female cell is called ...............
The ovule develops into a ...............
The ovary of the flower develops into a ...............
A flower that bears both the male and the female parts is known as bisexual flower.
A flower bearing only male or female parts is known as unisexual flower.
Transfer of pollen grains from the anther to the stigma is known as pollination.
Fusion of male cell with female cell is called fertilization.
The ovule develops into a seed.
The ovary of the flower develops into a fruit.
Difference between Self pollination and Cross pollination on the basis of definition:
| Property | Self pollination | Cross pollination |
|---|---|---|
| Definition | The process of transfer of pollen grains from the anthers to the stigma of the same flower, or another flower of the same plant is called self pollination. | The process of transfer of pollen grains from anther of one flower to stigma of other flower of different plants of the same species. |
Difference between Pollen grain and Ovule on the basis of location in the flower:
| Property | Pollen grain | Ovule |
|---|---|---|
| Location in the flower | Located in anther (androecium) | Located in ovary (gynoecium) |
Difference between Sepals and Petals on the basis of function:
| Property | Sepals | Petals |
|---|---|---|
| Function | It protects the flower at bud stage. | It attracts insects for pollination. |
Difference between Chlorella and Spirogyra on the basis of mode of asexual reproduction:
| Property | Chlorella | Spirogyra |
|---|---|---|
| Mode of asexual reproduction | Multiple fission | Fragmentation |
Difference between Vallisneria and Trapa on the basis of kind of pollinating agent:
| Property | Vallisneria | Trapa |
|---|---|---|
| Kind of pollinating agent | Water | Insects |
Draw a neat and labelled diagram of the section of a typical flower. From the parts labelled by you, name the parts matching the description given below :
(a) This part attaches the flower to the shoot.
(b) The flattened part of the pedicel.
(c) The outermost whorl of the flower.
(d) The male reproductive organ of the flower.
(e) The part of carpel which receives pollen grains.
Below labelled diagram shows the section of a typical flower:
(a) This part attaches the flower to the shoot — Pedicel
(b) The flattened part of the pedicel — Thalamus
(c) The outermost whorl of the flower — Calyx
(d) The male reproductive organ of the flower — Androecium
(e) The part of carpel which receives pollen grains — Stigma
(a) develops into a fruit — Ovary
(b) develops into a seed — Ovule
(c) produces pollen grains — Anther
(d) attracts insects for pollination — Petals
(e) connects stigma to the ovary — Style
Artificial vegetative propagation
Reason — Grafting is a process of joining two plants together to grow as one and is one of the methods of Artificial vegetative propagation.
Grafting
Reason — Grafting is the most suitable method for developing a desired variety of Guava as it combines the qualities of two different plants of related species, ensuring better yield and uniform fruit quality.
Flowers borne on the shoot system of a plant serve as reproductive part. Which of the following reasons supports this statement ?
P. Flowers bear stamens and carpels.
Q. Flowers make the plant attractive.
R. Flowers produce fruits with seeds.
Only P and R
Reason — Flowers contain stamens (male reproductive organs) and carpels (female reproductive organs) which are essential for fertilization. Flowers develop into fruits after fertilization, and these fruits contain seeds, which are the next generation of plants.
Flowers indeed make the plant look attractive, but this does not serve the purpose of being the reproductive part of a plant.
Mamta is curious to study different kinds of pollination among flowers present in her garden. She has performed artificial pollination in the following ways :
P. Pollination within a flower.
Q. Pollination between flowers of same plant.
R. Pollination between two flowers of two different plants of same species.
S. Pollination between two flowers of two different plants of the different species.
Which of the ways given abo explains 'cross-pollination'?
Only R
Reason — Cross-Pollination occurs between two flowers on different plants of the same species.
Cross-pollination is considered better than self-pollination because it produces healthier and more viable seeds. But it cannot occur by itself. Cross-pollination occurs with the help of certain agents like wind, water, insects, etc. Which of the following features of flowers are not suitable for insect-pollination ?
P. Flowers are usually small and of dull colours.
Q. Flowers are not scented and do not produce nectar.
R. Flowers produce sticky pollen grains.
Only P and Q
Reason — Large flowers of brightly coloured petals, that are scented, produce nectar as food for insects, and produce sticky pollen grains are suitable for pollination by insects.
Two features of flowers which favour pollination by insects are —
Two characteristics of flowers in which pollination occurs by wind are —
Gardener prefer to grow certain crops by vegetative method because of the following reasons:
Artificial pollination is practiced by plant breeders for developing new varieties. The breeders select two different varieties of a crop plant with desired characteristics. For example, one variety maybe high yielding while the other maybe disease-resistant. Cross breeding between them is done by artificial pollination. Many high-yielding varieties of rice, wheat, maize, etc. have been produced by this process.