<p>The following events take place during conjugation in spirogyra 1. The protoplasm of each of the conjugating cell separate from the cell wall to form a Gamete; the gamete of one filament passes through the conjugation tube to meet the gamete of the other filament 2. The zygote soon become surrounded by thick brown wall to become zygospore which burst after a short rest and germinate to produce a new filament 3. The nuclei of the gametes fuse to form a zygote 4. The protuberance meet and where they touch the cell-wall disappear so that a conjugation tube joining the two cell is formed 5. protuberance appear on the wall of the cell of two filament of spirogyra lying side by side opposite one another. Now what is the correct sequence in which the above sequence occur?</p>

Question 69 of 782

The following events take place during conjugation in spirogyra 1. The protoplasm of each of the conjugating cell separate from the cell wall to form a Gamete; the gamete of one filament passes through the conjugation tube to meet the gamete of the other filament 2. The zygote soon become surrounded by thick brown wall to become zygospore which burst after a short rest and germinate to produce a new filament 3. The nuclei of the gametes fuse to form a zygote 4. The protuberance meet and where they touch the cell-wall disappear so that a conjugation tube joining the two cell is formed 5. protuberance appear on the wall of the cell of two filament of spirogyra lying side by side opposite one another. Now what is the correct sequence in which the above sequence occur?

A. 1,2,3,4,5
B. 1,2,4,5,3
C. 3,4,5,2,1
D. 5,4,1,3,2

Correct Answer: D

Explanation

The correct option for the sequence of events during conjugation in Spirogyra is D. 5, 4, 1, 3, 2. Let's break down the reasoning behind this answer step-by-step. Step-by-Step Explanation

Understanding Conjugation in Spirogyra:
Spirogyra is a filamentous green alga that reproduces sexually through a process called conjugation. This involves the fusion of gametes from two different filaments.
Sequence of Events:
Step 5: Protuberances appear on the wall of the cells of two filaments lying side by side.
- This is the initial step where the two filaments of Spirogyra come into close proximity. The cells develop protuberances (outgrowths) that will eventually facilitate the fusion of gametes.
Step 4: The protuberances meet, and where they touch, the cell wall disappears, forming a conjugation tube.
- Once the protuberances touch, the cell walls at the point of contact dissolve, creating a conjugation tube. This tube allows the gametes to move from one filament to the other.
Step 1: The protoplasm of each conjugating cell separates from the cell wall to form a gamete.
- In this step, the protoplasm (the living part of the cell) detaches from the cell wall, and each cell transforms into a gamete. This is crucial for the next step where the gametes will move through the conjugation tube.
Step 3: The nuclei of the gametes fuse to form a zygote.
- After the gametes have moved through the conjugation tube, they come into contact, and their nuclei fuse. This fusion results in the formation of a zygote, which is a diploid cell that will develop into a zygospore.
Step 2: The zygote becomes surrounded by a thick brown wall to become a zygospore, which bursts after a short rest and germinates to produce a new filament.
- The zygote is then encased in a protective wall, forming a zygospore. After a period of dormancy, the zygospore will germinate, leading to the formation of a new filament of Spirogyra.

Why Other Options Are Incorrect

Option A (1, 2, 3, 4, 5):
This sequence is incorrect because it starts with the formation of gametes (Step 1) before the protuberances even appear (Step 5). The protuberances must form first to allow for the conjugation tube to develop.
Option B (1, 2, 4, 5, 3):
This option incorrectly places the formation of gametes (Step 1) before the protuberances (Step 5) and also incorrectly suggests that the zygote forms before the nuclei fuse (Step 3).
Option C (3, 4, 5, 2, 1):
This option incorrectly starts with the fusion of nuclei (Step 3) before any gametes are formed or the conjugation tube is established. The sequence of events must logically follow the physical processes of conjugation.

Revision Summary

Conjugation in Spirogyra involves the formation of protuberances on adjacent filaments.
The protuberances meet, leading to the formation of a conjugation tube.
Gametes are formed from the protoplasm of the cells, which then fuse to create a zygote.
The zygote develops into a zygospore, which eventually germinates to form a new filament.

This structured understanding of the conjugation process in Spirogyra will help you remember the correct sequence of events and the biological significance of each step.