Biological Reproduction

Spores - Thallophytes, bryophytes & pteridophytes have naked embryos that are called spores. The reproductive organs in these three groups are invisible and therefore they are called 'cryptogams' or “those with hidden reproductive organs”.

The homologous chromosomes bear a mark called chiasmata on the point were crossing over had taken place.

It is the sexual reproduction in which a bud arises from the main cell of body.

Imperfect fungi is the least understood group of fungi overall. Fungi imperfecti is called so because the complete sexual reproductive cycle is unknown. When the fungi has just been discovered, it is automatically placed in the imperfect fungi group. When the exact sexual cycle is found, the fungi is classified in one of the threadlike, sac, club or lichen. The scientific name is Deuteromycytes.

Binary fission produces two daughter cells, while huge number of cells is produced by multiple fission. Thus, option (1) is correct.

Spores are formed inside the sporangia and they are released when the wall breaks. The wall usually breaks on coming in contact with water and seldom on shaking. For release of spores, the lower hyphae or the parent fungus do not break their walls. Thus, (1) is correct.

Regeneration refers to formation of the entire organism from a part and for this, the cells of that part need to convert into the form in which they can divide and proliferate. This is a specialized function. Since, only one organism is involved, it is not a sexual mode of reproduction. Hence, only (3) is wrong.

Asexual reproduction involves only division of cells to form new individuals. This requires only one parent. Since two organisms are not involved, the role of gametes or their fusion is out of the logic. Also, reproduction cannot occur without a parent because a new organism is derived from the old (and not by magic). Hence, (3) is correct.

A bud is formed by proliferation of cells of the parent body. On maturity, it separates from parent by a constriction at the base. Since only one parent is involved, it is an asexual method. Clearly, here option (1) is incorrect because bud develops on parent and is not independent of it.

Under usual conditions, hydra reproduces by an asexual method, i.e. budding. Fission is limited to unicellular organisms while spores are formed in fungi. Thus, only (2) is correct.

Reproduction can occur through one parent (asexual) or through two parents (sexual). Further, some sexual reproducing organisms may contain both sexes in one (e.g. earthworm), i.e. they can be bisexual, or the sexes may be separate (e.g. humans), i.e. they are unisexual. Thus, it may be concluded that unisexual and bisexual modes are subtypes of sexual reproduction. But broadly, the reproduction is classified into sexual and asexual types only.

Tentacles are permanent parts of hydra. The bulge like projection is the bud and it is formed in both, hydra and yeast. Spores or bulbs are not formed in either of them. Hence, (4) is correct.

In asexual reproduction, the cells of parent organisms divide by mitosis to form identical cells. There is no change in DNA. Hence, no variations occur. Also, gametes do not play any role because this will bring new re-combinations of traits and it occurs only in sexual reproduction. Thus, (1), (3) and (4) are all incorrect about asexual reproduction. But as we know, spore formation is one of the methods of asexual reproduction. We can say that (2) is the most suitable answer.

Longitudinal or transverse divisions are features of binary fission and not related to budding. Bud appears as an outgrowth on the parent body and later forms an individual, which separates afterwards from the parent. Spores are not formed during any stage in budding method. Thus, only option (3) is correct.

Heterospory is defined as the production of two different types of spores, specifically microspores (small) and megaspores (large).