Biological Reproduction

In budding, a small outgrowth or bulge called a bud forms on the parent body. This bud gradually grows and develops into a new individual while remaining attached to the parent. Eventually, the bud detaches to live independently. This process is commonly observed in organisms like hydra and yeast.

Asexual reproduction is generally faster than sexual reproduction because it bypasses the complex processes of gamete formation, mating, and fertilization. It only requires mitotic cell division and involves a single parent. Options A, B, and D are all correct features of asexual reproduction - offspring are clones, divisions are mitotic, and only one individual is involved.

Organisms reproduce either asexually (without gamete fusion, producing clones) or sexually (involving gamete fusion and genetic recombination). These are the two fundamental modes of reproduction observed in nature. 'Bisexual' refers to organisms containing both male and female reproductive organs (like earthworms), not a mode of reproduction. 'Unisexual' describes separate male and female individuals, not a distinct reproductive mode.

In budding, the bud remains attached to and nutritionally dependent on the parent body during its growth and development. It's not independent - the bud receives nutrients through continuous cytoplasmic connection with the parent. Only after full development and constriction at the base does the bud separate to become independent. Options B, C, and D all correctly describe features of budding.

In budding, a new individual develops as an outgrowth (bud) on the parent body's surface. This bud forms due to repeated mitotic divisions at a specific site on the parent and gradually grows into a miniature version of the parent. Budding does not involve division of the entire parent body (longitudinal or transverse), nor does it involve spore formation. Hydra and yeast are classic examples of budding organisms.

Asexual reproduction in Spirogyra mirabilis takes place by aplanospores. Under unfavourable conditions, the protoplast of each vegetative cell shrinks and develops a wall around it to form an aplanospore. Each non-motile aplanospore germinates to form a new filament.

Under unfavourable conditions, the vegetative cells of S. farlowii develop thick-walled cells called akinetes. After getting favourable conditions, each akinete germinates into a new filament.

Sclariform conjugation takes place when filaments lie parallel to each other.

Scalariform conjugation takes place at night.

Zygospores are the product of sexual reproduction. It is the only diploid phase of Spirogyra cell cycle.

Two parallel strands of Spirogyra united with each other by a conjugation tube is referred to as aplanogametangia.

In spirogyra, gametes are nonflagellated. During conjugation, only the male gamete moves by amoeboid movement due to the activity of contractile vacuoles.

Scalariform conjugation requires association of two different filaments lined side by side either partially or throughout their length. One cell each from opposite lined filaments emits tubular protuberances known as conjugation tubes, which elongate and fuse to make a passage called the conjugation canal. 

In lateral conjugation, gametes are formed in a single filament. Two adjoining cells near the common transverse wall give out protuberances known as conjugation tubes, which further form the conjugation canal upon contact. The male cytoplasm migrates through the conjugation canal, fusing with the female. The rest of the process proceeds as in scalariform conjugation. Filaments showing lateral conjugation are always homothallic.