Plant Kingdom Test - 4

All the Bryophytes exhibit haplo-diplontic life cycle. It is an intermediate condition where both the phases are multicellular. In Bryophytes, a dominant, independent, erect phase is represented by a haploid gametophyte. This alternates with short-lived, multicellular sporophyte which is partially or fully dependent on the gametophyte for nutrition and support.

Option (B) is incorrect as angiosperms exhibit diplontic life cycle.

Option (C) is incorrect as gymnosperms also exhibit diplontic life cycle.

Option (D) is incorrect as algae exhibit haplontic life cycle.

Kelps exhibit haplo-diplontic life cycle. The diploid sporophyte is represented by a dominant, independent body which alternates with multicellular, short living gametophyte.

Option (B) is incorrect as Volvox exhibits haplontic life cycle and not diplontic life cycle.

Option (C) is incorrect as Spirogyra also exhibits haplontic life cycle and not haplo-diplontic life cycle.

Option (D) is incorrect because Lycopsida exhibits haplo-diplontic life cycle and not haplontic life cycle.

In haplontic life cycle the dominant, photosynthetic phase is free living gametophyte. The haploid spores produced by the sporophytic body are formed by meiosis in the zygote which again divide mitotically and form the haploid, free living gametophyte.

Option (A) is incorrect as diploid sporophyte is the dominant, independent, photosynthetic phase in diplontic life cycle.

Option (B) is incorrect because just the zygote is not the dominant phase of any life cycle in plants.

Option (D) is incorrect because thalloid is just a simple structure that lacks specialized tissues of higher plants like stem, leaves, xylem, phloem, etc. However, it isn’t the dominant phase of any life cycle in plants.

Pinus is a gymnosperm. It shows alternation of generation. Being a gymnosperm, diploid sporophyte is the dominant phase. Sporophyte is differentiated into root, stem and leaves. This implies the number of chromosomes in a leaf cell is also diploid (2n). We know that double fertilisation is absent in gymnosperms. Therefore the endosperm directly develops from megaspore. So, the number of chromosomes in an endosperm will be haploid (n) that is 8.

The fungi bodies consist of long, slender thread-like structures called hyphae.

The network of hyphae is known as mycelium. Some hyphae are continuous tubes filled with multinucleated cytoplasm – these are called coenocytic hyphae.

The cell walls of fungi are composed of chitin and polysaccharides.

Basidiospores are responsible for sexual reproduction in fungi.

Sexual spores are called ascospores which are produced endogenously in sac-like asci (singular ascus).

These asci are arranged in different types of fruiting bodies called ascocarps. Some examples are Aspergillus, Claviceps and Neurospora.

The fusion of two vegetative or somatic cells of different strains or genotypes.

The resultant structure is dikaryotic which ultimately gives rise to basidium.

Karyogamy and meiosis take place in the basidium producing four basidiospores.