Question Video: Identifying the Reproductive Method Displayed by Spirogyra Biology • Third Year of Secondary School

Video Transcript

Spirogyra is a filamentous algae that grows in freshwater. What reproductive process is happening in the figure? (A) Sexual reproduction by lateral conjugation. (B) Asexual reproduction by lateral conjugation. (C) Asexual reproduction by budding. (D) Sexual reproduction by scalariform conjugation. Or (E) sexual reproduction by budding.

Spirogyra are able to reproduce both sexually and asexually. Under favorable environmental conditions, Spirogyra reproduces asexually by budding, which produces offspring that are genetic copies of a single parent. When environmental conditions are not favorable, Spirogyra reproduces sexually through a process called conjugation, combining DNA of one individual with another. The goal of this process is to incorporate genes into the offspring that will allow them to fare better under the adverse environmental conditions.

With this information, we can already eliminate answers (B) and (E), because Spirogyra use budding in asexual reproduction and conjugation in sexual reproduction. As we can see two individuals participating in this process, which indicates sexual reproduction, we can eliminate answer choice (C) as well.

Now we need to figure out whether the image shows lateral conjugation or scalariform conjugation. When one filament is involved in conjugation, this is known as lateral conjugation. In this process, adjacent cells in the same filament combine their genetic material to form a zygote. When two filaments are involved in conjugation, it is known as scalariform conjugation. In this process, two adjacent filaments connect via conjugation tubes through which male gametes travel to the female gamete at the opposite filament.

In the image provided by the question, we can see two parallel filaments and the conjugation tubes that run between them. The word “scalariform” comes from the Latin word that literally means ladder form. And as we can see in this image, the conjugation tubes between the two filaments look somewhat like the rungs of a ladder.

Now we can answer this question correctly. We can deduce that the reproductive process the image shows is (D) sexual reproduction by scalariform conjugation.