Textbook Solutions: Reproduction in Plants | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests PDF Download

A. Choose the correct option.

1.
Ans: (a)

2.
Ans: (d)

3.
Ans: (b)

4.
Ans: (d)

5.
Ans: (c) 

B. Fill in the blanks with the correct words.

1. 
Ans: Flowering plants multiply sexually.

2.
Ans: One parent is involved in asexual reproduction.

3. 
Ans: Characteristics of the parent plant are preserved when they multiply vegetatively.

4.
Ans: Flowers are the reproductive organs of a plant.

5. 
Ans: Pistil is the female reproductive part of a flower.

6. 
Ans: The transfer of pollen grains from the anther to the stigma is called pollination.

C. Give two examples for each of the following.

1.
Ans: Plants that multiply with the help of spores: ferns and mosses

2.
Ans: Plants that multiply through their roots: Dahlia and sweet potato

3.
Ans: Plants that multiply through their stems: grasses and strawberry

4.
Ans: Underground stems: turmeric and ginger

5.
Ans: Plants that multiply through stem cuttings: sugar cane and rose

6.
Ans: Plants that multiply through layering: grapes and jasmine

7.
Ans: Flowers that get pollinated by wind: wheat and rice

8.
Ans: Insect-pollinated flowers: sweet pea and jasmine

9.
Ans: Flowers pollinated by water: sea grass and water lily

10.
Ans: Seeds dispersed by wind: maple and dandelion

D. Answer the following questions.

1.
Ans: Plants reproduce in different ways depending on the type of plant and its specific structure. They reproduce through asexual means, vegetative reproduction, and sexual reproduction. In asexual reproduction, a single parent produces progeny and it is common in simple plants like algae and fungi. The plant body divides into two or more parts. In vegetative reproduction, any part of the plant, other than the reproductive part, can give rise to a new individual plant. This can occur naturally or be induced artificially. In sexual reproduction, both male and female parents take part in producing offspring. The reproductive cells fuse together forming a zygote, which grows into a seed and then into a new plant.

2.
Ans: Asexual reproduction is the process by which a single parent body produces young ones. It is commonly seen in simple plants like algae and fungi. The plant body simply divides into two or more parts. On the other hand, sexual reproduction is the process by which both the parent bodies, male and female, take part in producing young ones. The male and female parts of the plant produce reproductive cells, which fuse together forming a single cell called the zygote. This zygote grows and develops into a seed which when planted, gives rise to a new plant.

3.
Ans: In the process of budding, yeast, a single-celled organism, produces a small, bulb-like outgrowth called a bud at one end. The nucleus of the cell divides into two, with one of these nuclei passing into the bud. As the bud grows in size, it eventually detaches from the parent plant and grows into a new individual.

4.
Ans: Fragmentation and spore formation are methods of asexual reproduction. Fragmentation occurs in plants such as the algae, Spirogyra. A part of the parent body detaches from the parent plant and develops into a new individual plant. Spore formation is observed in plants like ferns and mosses. These plants multiply with the help of spores which are produced by the parent plant in large numbers. These spores germinate under favourable conditions to grow into new plants.

5.
Ans: Plants reproduce vegetatively through their roots, stems, and leaves. Some plants like Dahlia, sweet potato, and Asparagus reproduce through their roots. Some plants have underground stems that can produce new plants. These stems are swollen because of the food stored in them. The plant Bryophyllum develops small buds on the margins of their leaves which fall off from the parent plant and grow into new plants. Sometimes, vegetative reproduction is induced artificially by humans through methods like cutting, grafting, and layering.

6.
Ans: A complete flower contains four main parts: sepals, petals, stamens, and pistils. Sepals are thin green leaf-like structures that protect the inner soft parts of the flower. Petals are the thin brightly coloured parts of a flower. Stamens represent the male reproductive part of a plant and are made up of anthers, attached to slender structures called filaments. The anthers contain pollen grains which have male gametes. Pistil represents the female reproductive part of a plant and is made up of a sticky head called stigma, a thin style, and a swollen base called ovary. The female gametes or egg or ovum are present within the ovules inside the ovary.

7.
Ans: Pollination is the process by which pollen grains reach the stigma of the pistil. Two ways in which flowers pollinate are self-pollination and cross-pollination. In self-pollination, the pollen grains get transferred from the stamen to the stigma of the same flower. In cross-pollination, the pollen grains from the stamen of one flower get transferred to the stigma of another flower of the same kind.

8.
Ans: Several agents bring about pollination. Some common agents are wind, water, and insects. Wind helps to blow away pollen grains from the anthers of one flower to the stigma of another flower. Water helps in the transport of pollen grains to the stigma of the receiving flower in aquatic plants. Insects are attracted by brightly coloured flowers or by their sweet smell. When the insects sit on the flowers, pollen from the flower sticks to their body parts and are then transported to the stigma of another flower which the insects visit later.

9.
Ans: Fertilization is the process by which the male and female reproductive cells fuse together to form a zygote. After fertilization, several changes take place in the flower leading to the formation of fruit and seed. The sepals, petals, and stamens dry up and fall off from the flower. The ovary swells to form the fruit and the ovules become the seeds. Inside each ovule, the zygote develops into the embryo which gives rise to the future plant.

10.
Ans: Flowers that are pollinated by insects often have unique features such as bright colours and sweet fragrances to attract insects. They also have sticky pollen or specialized structures to attach pollen to the visiting insects. Some flowers even have shapes and structures that specifically match with the body parts of the visiting insects, ensuring successful pollination.

11.
Ans: A fruit is the mature ovary of a flower that contains seeds, while a seed is the mature ovule after fertilization. Plants produce seeds after the process of fertilization where the male and female reproductive cells fuse to form a zygote. This zygote develops into an embryo inside the ovule which then matures into a seed.

12.
Ans: Seed dispersal is the process by which seeds get scattered far away from the mother plant. This process is essential because it helps in reducing competition and aids in survival and germination of seeds. It ensures that the seeds will have enough space, sunlight, and water to grow.

13.
Ans: Different plants disperse their seeds by different means. Some seeds are dispersed by wind, like dandelion and maple, because they are light and possess hair or wings. Some seeds are dispersed by water, like coconut, because they have a spongy outer coat which helps them float. Some seeds are dispersed by animals, like mango and cocklebur, because they either have fleshy fruits that are eaten by animals or they have hooks that get caught in the fur of animals.