Question

In Mucor sp. usually isogamy occurs between __________
A. Same strains
B. + and – strains
C. Zygospores
D. Microspores

Answer 1

Mucor is a type of Fungi. Fungi are non-green, non-photosynthetic, thalloid, and heterotrophic plants. They are the largest kingdom after angiosperms. Fungi usually grow in warm, damp, and humid places. Their bodies are either unicellular or filamentous.

Complete answer:
Mucor belongs to the class Zygomycetes of Phycomycetes fungi. Zygomycetes are also known as the conjugation fungi as they reproduce through conjugation. They have filamentous and coenocytic bodies. Their cell wall is made up of chitin which is also known as the fungal cellulose. These fungi are mostly saprophytic, though some are parasitic too. Mucor is a terrestrial fungus that is found in hot and humid areas.
Mucor shows isogamy usually. Isogamy is the condition in which both the gametes are morphologically similar and they later fuse to form the zygote. Since, both the gametes are similar, they are labeled as ‘+’ and ‘-‘ strains. Therefore, the fusion is between the + and – strains of the gametes. The sexual reproduction in mucor occurs with the help of gametangial conjugation. The conjugation occurs between the hyphae of opposite strains but the same species. These two hyphae of opposite strains form a protuberance by fusion.
Thus, based on the above information we can conclude that in mucor species usually, isogamy occurs between + and – strains.

Hence, the correct answer is an option (B).

Note : The other methods of gametic fusion in fungi are as follows –
Anisogamy – When the male gametes are smaller than the female gametes. They fuse to form the zygote.
Oogamy – When the male gamete is smaller and flagellated whereas, the female gamete is large and non-motile due to the absence of flagella. They fuse to form the zygote known as the oospore.