Chapter 20, Problem 20A

Summary Introduction

Introduction :

Fungi are among the oldest and the largest group of organism on earth. All fungi are either unicellular or multicellular eukaryotic heterotrophs. Fungi have a cell wall composed of chitin. There are about 100,000 identified species of fungi. Most fungi reproduce through spores. A spore is the reproductive haploid cell that develops into a new organism without the fusion of gametes.

Answer to Problem 20A

Correct answer :

The correct answer is option (B) sporangium.

Explanation of Solution

Explanation/justification for the correct answer :

Option (B) sporangium. The diagram shows the fruiting body of a rhizopus fungus. Sporophore is the fruiting body of a spore-forming fungus. The classification of fungus is based on the kind of spore it produces. The sporophore bears a structure called sporangium. The sporangium is the sac or case in which spores are produced. So, the correct answer is option (B).

Explanation for incorrect answer :

Option (A) ascocarp. The fruiting body of an ascomycete fungus is called an ascocarp. The spores are produced at the tips of the hyphae. During sexual reproduction, the hyphae from opposite mating types fuse and one nucleus from each type pairs off in separate cells. Each cell contains two haploid nuclei. The hyphae eventually develops a reproductive structure called ascocarp. So, this is an incorrect option.

Option (C) ascus. The fruiting body of an ascomycete fungus is called an ascocarp. Within the ascocarp, the haploid nuclei fuses to form a zygote. The zygote divides by meiosis producing four haploid nuclei. These nuclei divide mitotically and form eight nuclei. The nuclei develop into spores in a sac like structure called ascus. So, this is an incorrect answer.

Option (D) ascophore. The fruiting body of an ascomycete fungus is called an ascocarp. Within the ascocarp, the haploid nuclei fuses to form a zygote. The zygote divides by meiosis producing four haploid nuclei. These nuclei divide mitotically and form eight nuclei. The nuclei develop into spores in a sac like structure called ascus. The spores produced by the ascus are called ascophores. Hence, this is an incorrect answer.