NCERT Solutions For Class 7 Science Chapter 12 Reproduction in Plants

In self-pollination, the pollens are deposited on the stigma of either the same flower or another flower on the same plant. In cross-pollination, pollens are deposited from one flower to another flower of the same kind, borne on another plant.

The process of fertilisation takes place after pollination. Pollens on reaching the stigma of the flower germinate to form pollen tubes that carry male gametes. One of the male gametes fuses with female gamete on reaching ovary forming zygote.

In asexual reproduction, single parent gives rise to the offspring without producing seeds whereas, in sexual reproduction two parents of opposite sex participate to produce a seed from which a new individual emerges.

Sexual reproduction is the process of producing offspring by an organism with involvement of male and female sexes. It involves fusion of male and female gametes that leads to the formation of zygote. The male and female gametes are produced by male and female flower parts, respectively. Male part of the plant is stamen that bears male gametes inside the pollens and female part of the plant is pistil that bears ovary containing female gamete or ovum. Pollens fall on stigma of the flower and germinate to form pollen tubes containing male gametes. Pollen tube enters the ovary releasing male gametes. One of the gametes fuses with ovum and undergo fertilisation to form zygote, completing the process of sexual reproduction.

(a) The reproductive part of a plant is the (iv) flower

(b) The process of fusion of the male and the female gametes is called (i) fertilisation

(c) Mature ovary forms the (iv) fruit

(d) A spore producing plant is (ii) bread mould

(e) Bryophyllum can reproduce by its (ii) leaves

The correctly matched contents of Column I with Column II are as follows:

Seed are carried by wind, water and animals for dispersal.

1. Some seeds, which are light and have wings or hair, are easily carried away by wind. For example, seeds of maple have wings and seeds of madar have hair.         
2. Some other seeds develop thick fibrous coating to acquire floating ability and are dispersed by water. For example, coconut seed has fibrous seed coat.
3. Some other plants produce seeds with hook-like structures or spines with the help of which they get attached to the bodies of animals and disperse to larger distances. For example, seeds of Xanthium and Urena have hooks and spines.

Various male and female reproductive parts of the flower can be sketched as follows:

There are four different methods of asexual reproduction which are as follows:

Fragmentation- In this process, an organism, like algae, breaks down into two or more fragments and each fragment gives rise to a new individual. For example, Spirogyra undergoes fragmentation as shown below:

Spore formation- Most of the fungi reproduce asexually by forming tiny spores, which germinate to give rise to new individuals in the following manner:


 

(a) Vegetative propagation

(b) Unisexual flower

(c) Self-pollination

(d) Fertilisation

(e) wind, water and animals