Biology CUET UG Test: Asexual Reproduction (Old NCERT) Free Online Test

In Amoeba, simple (irregular) binary fission occurs and nucleus is duplicated during this process. Binary fission involves mitosis and the resultant offsprings are genetically identical to the parent and to each other.

Bryophyllum (figure b) propogates vegetatively by adventitious leafbuds. Leaves of Bryophyllum carry on photosynthesis, their usual function, but in addition they have the capacity to produce one or more plants from the notches in their margins. It is also observed in Kalanchoe.

The figure represents asexual type of reproduction Offsprings resulting from this type of reproduction are genetically identical to parent, so they can be called clones. Development of an egg (ovum) into a complete individual without fertilization is known as parthenogenesis. It is observed in many invertebrates (rotifers, arthropods), insects bees, wasps) and some birds, etc.

When offspring are produced by a single parent with or without the involvement of gamete formation, the reproduction is called asexual. As a result, the offspring that are produced are not only similar to one another but are also the exact copies of their parent. Such a group of morphologically and genetically similar individuals is called clone. Asexual reproduction occurs usually in unicellular organisms, such as monerans, protists, plants and certain animals. It is faster than sexual reproduction. 

A. A sponge produces a tough coated dormant cluster of embryonic cells for development in more favourable conditions called Gemmules.
B. Yeast is a unicellular fungus. It reproduces asexually by the formation of spores. During the process of budding in yeast, the parent cell develops a small protuberance which grows in size.
C. Potato: Each eye of potato tuber is a bud which grows into a new potato plant when planted with a portion of the swollen tuber.
D. Offsets are one internode long runners which develop tuft of leaves at the apex. Example: Water hyacinth.

All the organisms shown in the figure reproduce asexually. (A) is Penicillium in which non-motile conidia are produced singly or in chains. Organism (B) is Chlamydomonas in which reproduction occurs by zoospores. In Hydra (C) and yeast (D), asexual reproduction takes place by budding

Ginger propagates vegetatively with the help of rhizome. Rhizomes are main underground stems which store food for perennation during unfavourable conditions These have buds for formation of new aerial shoots during favourable conditions.

Reproduction is a biological process in which an organism produces young ones (offspring) of the same species. It is one of the most important characteristics of the living organisms. Reproduction is essential for the survival of species but not for the survival of individuals.

Water hyacinth or "Terror of Bengal" is an aquatic plant which is one of the most invading weeds found growing in the standing water. It is also called as "blue devil" as it takes oxygen from the water which causes death of fishes. This plant was introduced in India for its beautiful flowers and shape of leaves. It can propagate vegetatively at a fast rate and spread all over the water body in a short time. It is very difficult to remove it from the water body.

Figure (i) shows longitudinal binary fission in Euglena, (ii) shows transverse binary fission in Paramecium and (iii) shows multiple fission in uncysted Amoeba.

Vegetative propagation is the formation of new plants from vegetative units such as buds, tubers, rhizomes, etc. This method produces a large number of population of clones in short time. It preserves purity, resistance and good qualities of race/variety indefinitely. Fleshy roots (root tubers) which develop adventitious buds also take part in vegetative propagation.
Example: Sweet potato.

The method of vegetative propagation described in the question is performed in Begonia and Bryophyllum plants.

Begonia and Bryophyllum plants can be propagated by stem cuttings, where 20-30 cm long pieces of one-year-old stems are cut and their lower ends are treated with root-promoting hormones such as auxins. These stem cuttings are then planted in soil, and after some time they develop adventitious roots, which grow from the base of the stem. The newly formed roots allow the stem cutting to grow into a new plant.

Lemon, orange, rose, and sugarcane can also be propagated through vegetative methods such as stem cuttings, but the specific method described in the question is not commonly used for these plants.

Vegetative propagation (vegetative reproduction) is the formation of new plants from vegetative units such as buds, tubers, rhizomes, etc. This term is used for asexual reproduction in plants. Plants with reduced power of sexual reproduction, long dormant period of seed or poor viability are multiplied easily through vegetative propagation.

Clone is population of genetically identical organisms or cells derived from a orignal single organismor cell by asexual reproduction.

Layering is a type of horticultural or artificial method of vegetative propagation in which adventitious roots are induced to develop on a soft stem while it is still attached to the plant. Bulbils are multicellular fleshy buds that take part in natural vegetative propagation.
Example: Oxalis, Agave, pineapple.

New buds arise from node, not from internode, hence a middle piece of sugarcane (internode) cannot serve as a vegetative propagule.

Zoospores are formed during favourable conditions with proper growth of the plant. Any cell except holdfast is capable of producing zoospores. The protoplast either develops into a single zoospore or undergoes division and forms 2, 4, 8, 16 or 32 units. Each unit contains a single nucleus and cytoplasm. These small units form zoospores.
The Chlamydomonas during sexual reproduction involves three stages. They are the;
- Gametogenesis:The process of gametogenesis occurs by repeated division of the protoplast giving rise to 16- 32 gametes from a single cell.
- Syngamy: It is the process of fusion of gametes as a result in the formation of zygote. These zygotes formed will then transform into zygospores.
- Zygospore formation: Zygospore are the spores which have thick walls to protect from the extreme environment. Under favourable conditions the zygospore germinates.

In sexually reproducing organisms, the male gamele is called the antherozoid or sperm and the known as the egg or ovum. They are not used for vegitative propagation.

New plantlets in potato and sugarcane arise from bud on stem. Tubers have buds over their nodes or eyes. The buds produce new plantlets when a stem tuber or a part of it having a node is placed in the soil. Sugarcane is propagated by planting segments of stems having atleast one node.

In binary fission, the parent organism divides into two halves, each half forming an independent daughters organism. Binary fission involves mitosis. The resultant  offspring are genetically identical to the parent and to each other.