Chapter 30, Problem 1TYK

Summary Introduction

Introduction:

Organisms belonging to the kingdom fungi are popularly known as recyclers. These are multicellular eukaryotic heterotrophs, generally covered with a polysaccharide known as chitin, which provides rigidity to their outer wall. Fungal phyla can be categorized into many groups on the basis of characteristics such as evolution from single-celled to multicellular organisms, mode of nutrition, and aspects of reproduction.

Answer to Problem 1TYK

Correct answer:

The lineages leading to fungus and plants diverged a billion years ago and the fungal phyla, which are broadly classified into monophyletic and paraphyletic that includes Basidiomycota, Ascomycota, Glomeromycota, and Zygomycota group.

Explanation of Solution

Explanation for the correct answer:

Option (a) states that the lineages of fungus diverged from the plants billion years ago but they are related in numerous ways with each other. Fungi are heterotrophic eukaryotes that can be divided into two body forms, single-celled, yeast and multicellular fungus that has a slender filament, hypha. It is generally used in procuring food. The group of hyphae is known as mycelium. They are divided into small compartments by walls known as septa in multicellular fungal species. However, in few species, there are no septa as the nuclei growing in hyphae divide without cytokinesis and thus they are known as Coenocytic. So, it does not depict the current phylogenetic relationship and features among the fungi. Hence, option (a) is correct.

Option (c) states that the three phyla, which are Ascomycota, Glomeromycota, and Basidiomycota, are monophyletic, whereas Zygomycota is paraphyletic, and recent studies also suggest that the chytridiomycota should be reconsidered as a separate phylum that does not show any phylogenetic relationship features among fungi. Hence, the option (c) is correct.

Explanation for the incorrect answer:

Option (b) states that chytrids may have a close relation with the earliest fungi as they are the only fungi that produces spores propelled by flagella. All the chytrids have aquatic habitat, reproduce asexually as well as sexually, and are in a paraphyletic group exhibiting the current relationship among features of fungi. So, it is an incorrect option.

Option (d) states that there are different reproductive adaptations, which are evolved in different lineages of fungal phyla such as Zygomycota, which is a sexually reproducing species. It reproduces by zygospores and feeds on detritus present in soil; Ascomycota are the species that produce sac-like structure called asci, a reproductive structure. There are species of Ascomycota that reproduce asexually by producing conidia; Basidiomycota reproduces asexually by budding or fragment detachment of hypha and sexually by producing haploid spores. So, it is an incorrect option.

Option (e) states that basal fungal group constitutes mostly living members of cryptomycota, which are single-celled intracellular parasites. They can help in depicting the earliest branching of fungi. Hence, they can give some light on the phylogenetic features among fungi. So, it is an incorrect option.

Hence, options (b), (d), and (e) are incorrect.

Conclusion

It can be concluded that even if fungal phyla have a close relationship with plants in numerous ways, it does not show any phylogenetic relationship and features among fungi. There are three phyla, which are Ascomycota, Basidiomycota, and Glomeromycota that are monophyletic, whereas Zygomycota is a paraphyletic.