Question

In cyanobacteria, the reproduction is
(a) Vegetative
(b) Asexual and vegetative
(c) Asexual and sexual
(d) Sexual

Answer 1

Cyanobacteria or blue-green algae are photosynthetic bacteria. They can reproduce by producing spores such as endospores, exospores, and akinetes. They can also reproduce by fission and fragmentation.

Complete Step by Step Answer:
Cyanobacteria or blue- green algae can reproduce by various methods.
They can reproduce vegetatively by methods such as binary fission, fragmentation, or formation of hormogonia or hormospores.
They can reproduce by the production of asexual spores. Some examples of this method are endospore formation, exospore formation, and formation of akinetes.
Methods of vegetative reproduction:
- Binary fission: It is a type of simple cell division in which the genetic material replicates and the cell itself divides into two identical cells.
- Fragmentation: It is seen in the filamentous form of the bacteria when a fragment of the filament breaks apart and then grows into an individual organism. In this manner, all the individual fragments grow into individual organisms.
Methods of asexual reproduction:
- Akinetes or arthrospore formation: They are thick- walled, large reproductive cells. Akinetes have an outer wall exospore and an inner wall endospore. The akinetes germinate to form a new colony.
- Endospores: Some cyanobacteria develop endospores in which the protoplast of the cells divides and develops the endospores.
- Exospores: They are cut at the tip of some branches. They get separated from the main body and give rise to a new filament.
So, the correct answer is, ‘(b) Asexual and vegetative.’

Note:
- Sexual reproduction is completely absent in the cyanobacteria. - Cyanobacteria usually reproduce by vegetative methods like fragmentation when the condition is favourable and water is available. - When the methods are not unfavourable or water is not available, the cyanobacteria reproduce by spore formation such as akinetes, and endospores, and exospores. - These akinetes and spores lay dormant until favourable conditions and germinate as soon as the water is available to form the filament.