Question

In Spirogyra the sexual reproduction takes place by
A. Binary fission
B. Spore formation
C. Conjugation
D. Aplanospore formation

Answer 1

Hint: In order to solve this question, first we need to know types of reproduction in Spirogyra. Spirogyra is filamentous green algae which are commonly found in freshwater. There are more than 400 species of spirogyra which are included in order zygnemataceae.

Complete answer: Spirogyra also known as “water silk or pond silk” is free-floating green algae present in freshwater. It has a filamentous and unbranched structure. It lives in the stagnant water- pools, lakes, freshwater etc. Spirogyra shows three modes of reproduction- vegetative, asexual and sexual reproduction.
Vegetative reproduction happens through fragmentation. It is the preferred mode of reproduction in favorable condition. The vegetative filament after fragmentation results into a new filament.
Formation of azygospores, akinetes or aplanospores is asexual reproduction ways found in Spirogyra. Akinetes and aplanospores are non-motile spores which develop in a new filament. In binary fission, the fully grown parent cell splits into two halves, producing two offsprings.
Sexual reproduction in spirogyra takes place by the process called conjugation. Male cells become amoeboid and crawl across the tube. Sometimes, both male and female cells crawl across the tube and fusion takes place. These cells meet to form zygote which undergoes meiosis division to form new filament. In conjugation male and female strain fuses to form zygospore. Isogamous, i.e. male and female gametes of similar size, shape and structure fuse together in the sexual reproduction of paramecium.

So, the correct answer is C. Conjugation.

Note: Paramecium is a unicellular organism belonging to kingdom Protista. Other conjugating algae are mesotaeniaceae, basal green algae, desmidiales etc. These organisms grow as unbranched filaments which grow longer through normal cell division.