SSC CGL 2024 Tier-I · 24 September 2024, Shift 2 · General Awareness · Question 1 of 100

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 10 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

Which types of gametes are found in Spirogyra?

(a)Isogamous and non-flagellated
(b)Heterogamous and flagellated
(c)Isogamous and flagellated
(d)Heterogamous and non-flagellated

Answer

Why

Correct — A. Spirogyra reproduces sexually by conjugation: two filaments lie side by side, a conjugation tube grows between them, and the contents of one cell pass across into the other.

The gametes that fuse are non-flagellated — they creep or flow rather than swim — and they are alike in size and shape, which is exactly what isogamous means.

Both halves of option (a) therefore hold: look-alike gametes, no flagella.

Why the others are wrong

(b)
Heterogamous and flagellated — Heterogamy needs gametes that differ in size or form, and Spirogyra's fuse as equals. No stage of its sexual cycle produces a flagellum either, so both halves fail.
(c)
Isogamous and flagellated — Isogamous is right, flagellated is not. That combination describes Chlamydomonas, whose similar-sized gametes carry flagella and swim to meet.
(d)
Heterogamous and non-flagellated — Half right — the gametes really are non-flagellated — but they are isogamous, not heterogamous, so the pair still fails.

Concept

Algae are grouped partly by what their fusing gametes look like. When the two are alike in size and shape the union is isogamous, when they differ it is anisogamous, and when a small motile gamete fuses with a large non-motile egg it is oogamous.

Motility is a second, independent axis: gametes may be flagellated and swim, or non-flagellated and move by flowing. Spirogyra sits at isogamous plus non-flagellated, Chlamydomonas at isogamous plus flagellated — same first term, opposite second.

Each option here pairs one term from each axis, so all four combinations appear. That is why guessing on the word isogamous alone leaves you with two live options.

Key facts

Spirogyra reproduces sexually by conjugation, and its gametes are non-flagellated.
Isogamous means the two fusing gametes are similar in size and shape.
Chlamydomonas has isogamous gametes that ARE flagellated, the standard contrast with Spirogyra.
Spirogyra belongs to Chlorophyceae, the green algae.

Study next

Isogamy, anisogamy and oogamy with one algal example for eachChlorophyceae, Phaeophyceae and Rhodophyceae — pigment, stored food and cell wallConjugation in Spirogyra, step by step

Common traps

Reading isogamous as if it also settled motility, when the two vary independently.
Assuming every algal gamete swims, which is true of Chlamydomonas but not of Spirogyra.

SSC keeps algae to one retrievable label per question — the pigment, the group or the gamete type. The brown-seaweed carotenoid was set the same way on 18 Sep 2024, 09:00, GA Q.11.

Related PYQs

No directly related past PYQ was found.