Part 1 — Algae: Basics, classification, structure, reproduction (Questions 1–25)

Part 1 — Algae: Basics, classification, structure, reproduction (Questions 1–25)

1. Which pigment is primary for photosynthesis in most green algae?
A. Phycoerythrin
B. Chlorophyll a
C. Fucoxanthin
D. Phycocyanin
Answer: B — Chlorophyll a.
Explanations:
A. Phycoerythrin — common in red algae (Rhodophyta), not primary in green algae.
B. Chlorophyll a — correct: chlorophyll a is essential and present in all oxygenic photosynthetic algae and plants.
C. Fucoxanthin — characteristic accessory pigment in brown algae (Phaeophyceae).
D. Phycocyanin — accessory pigment in cyanobacteria and some red algae; not primary in green algae.

2. Which group of algae stores food as laminarin and mannitol?
A. Chlorophyceae
B. Rhodophyceae
C. Phaeophyceae
D. Cyanophyceae
Answer: C — Phaeophyceae.
Explanations:
A. Chlorophyceae — store starch, not laminarin/mannitol.
B. Rhodophyceae — often store floridean starch (a different starch).
C. Phaeophyceae — correct: brown algae store laminarin (a polysaccharide) and mannitol (a sugar alcohol).
D. Cyanophyceae — cyanobacteria store cyanophycean starch (glycogen-like).

3. A filamentous green alga that shows intercalary growth and fragmentation is:
A. Chara
B. Spirogyra
C. Fucus
D. Volvox
Answer: B — Spirogyra.
Explanations:
A. Chara — a complex green alga (stonewort) with apical growth and calcified nodes, not filamentous fragmentation like Spirogyra.
B. Spirogyra — correct: filamentous, shows fragmentation and intercalary cell division.
C. Fucus — brown alga, not filamentous (thallus with holdfast, stipe, blade).
D. Volvox — colonial, spherical colonies, not filamentous.

4. Which algal group is most closely related to terrestrial plants based on chloroplast pigments and cell wall composition?
A. Rhodophyta
B. Phaeophyta
C. Chlorophyta
D. Chrysophyta
Answer: C — Chlorophyta.
Explanations:
A. Rhodophyta — red algae have different pigments and phylogeny.
B. Phaeophyta — brown algae are more distant; secondary endosymbiosis.
C. Chlorophyta — correct: green algae (Chlorophyta & Charophyceae) share chlorophylls a & b and cellulose in walls; Charophytes especially are close relatives of land plants.
D. Chrysophyta — golden algae, not closest to land plants.

5. Which structure in Chlamydomonas is used for locomotion?
A. Pseudopodium
B. Cilia
C. Flagella
D. Rhizoids
Answer: C — Flagella.
Explanations:
A. Pseudopodium — used by amoeboid protists, not by Chlamydomonas.
B. Cilia — shorter and many; Chlamydomonas has two long flagella, not cilia.
C. Flagella — correct: Chlamydomonas possesses two anterior flagella for swimming.
D. Rhizoids — anchoring structures in some algae/cryptogams; not locomotory.

6. Which of the following is a unicellular, colonial green alga forming spherical colonies?
A. Chlorella
B. Spirogyra
C. Volvox
D. Ulva
Answer: C — Volvox.
Explanations:
A. Chlorella — unicellular but not colonial spherical colonies.
B. Spirogyra — filamentous.
C. Volvox — correct: forms spherical colonies of many flagellated cells.
D. Ulva — multicellular sheet-like thallus (sea lettuce).

7. In the life cycle of Ulva (sea lettuce), the lifecycle showing morphologically similar haploid and diploid phases is called:
A. Haplontic
B. Diplontic
C. Heteromorphic alternation
D. Isomorphic alternation of generations
Answer: D — Isomorphic alternation of generations.
Explanations:
A. Haplontic — dominated by haploid stage, haploid individuals; not Ulva.
B. Diplontic — dominated by diploid stage; not Ulva.
C. Heteromorphic alternation — phases morphologically different; Ulva phases look alike.
D. Isomorphic alternation of generations — correct: Ulva gametophyte and sporophyte are morphologically similar.

8. Which algal group has a polysaccharide agar in its cell walls?
A. Chlorophyceae
B. Rhodophyceae
C. Phaeophyceae
D. Cyanophyceae
Answer: B — Rhodophyceae.
Explanations:
A. Chlorophyceae — cell walls mainly cellulose.
B. Rhodophyceae — correct: red algae contain agar and carrageenan in their cell walls.
C. Phaeophyceae — walls have alginates, not agar.
D. Cyanophyceae — prokaryotic cell walls with peptidoglycan-like material.

9. Which algal form exhibits siphonous (coenocytic) organization (large multinucleate cell without cross walls)?
A. Spirogyra
B. Caulerpa
C. Chlamydomonas
D. Ectocarpus
Answer: B — Caulerpa.
Explanations:
A. Spirogyra — filamentous with septate cells.
B. Caulerpa — correct: a large coenocytic (siphonous) green alga with multinucleate single cell forming complex thallus.
C. Chlamydomonas — unicellular.
D. Ectocarpus — filamentous brown alga with septate cells.

10. Which of following is NOT a feature of cyanobacteria?
A. Presence of peptidoglycan in cell wall
B. Chlorophyll a as primary pigment
C. Presence of membrane-bound chloroplasts
D. Nitrogen fixation in heterocysts (in some)
Answer: C — Presence of membrane-bound chloroplasts.
Explanations:
A. Presence of peptidoglycan — correct for cyanobacteria (prokaryotes).
B. Chlorophyll a — cyanobacteria have chlorophyll a (they perform oxygenic photosynthesis).
C. Presence of membrane-bound chloroplasts — incorrect for cyanobacteria; they are prokaryotic and lack membrane-bound organelles (chloroplasts).
D. Nitrogen fixation in heterocysts — some cyanobacteria have heterocysts for N fixation.

11. Accessory pigment phycobilin (phycoerythrin/phycocyanin) is characteristic of:
A. Green algae
B. Red algae and cyanobacteria
C. Brown algae
D. Diatoms
Answer: B — Red algae and cyanobacteria.
Explanations:
A. Green algae — their main accessory pigments are chlorophyll b, carotenoids.
B. Red algae and cyanobacteria — correct: phycobilins are major accessory pigments in red algae and cyanobacteria.
C. Brown algae — have fucoxanthin as major accessory pigment.
D. Diatoms — have fucoxanthin (golden-brown pigments).

12. Which algal group is commonly used as biofertilizer in rice fields because of nitrogen fixation?
A. Green algae (Chlorophyta)
B. Red algae (Rhodophyta)
C. Cyanobacteria (Blue-green algae)
D. Brown algae (Phaeophyceae)
Answer: C — Cyanobacteria.
Explanations:
A. Green algae — typically not nitrogen-fixing.
B. Red algae — marine, not used in rice fields.
C. Cyanobacteria — correct: genera like Anabaena, Nostoc fix atmospheric N2 and are used as biofertilizers in paddy fields.
D. Brown algae — marine; not applicable.

13. Which statement about alternation of generations in algae is TRUE?
A. All algae are diplontic.
B. All algae are haplontic.
C. Algae show different kinds of life cycles: haplontic, diplontic, and diplohaplontic.
D. Algae never show isomorphic alternation.
Answer: C.
Explanations:
A. False — not all are diplontic.
B. False — not all are haplontic.
C. True — algae exhibit varied life cycles including haplontic (many green algae), diplontic (some brown algae), diplohaplontic (Ulva).
D. False — some algae (Ulva) show isomorphic alternation.

14. Which algal group is most important commercially for agar production?
A. Chlorophyta
B. Phaeophyta
C. Rhodophyta
D. Chrysophyta
Answer: C — Rhodophyta.
Explanations:
A. Chlorophyta — not primary agar producers.
B. Phaeophyta — yield alginates, not agar.
C. Rhodophyta — correct: genera like Gelidium and Gracilaria are sources of agar and carrageenan.
D. Chrysophyta — golden algae, not agar sources.

15. Which of the following algal genera is used in genetic and molecular research due to its simple haploid lifestyle and ease of culture?
A. Spirogyra
B. Chlamydomonas
C. Laminaria
D. Fucus
Answer: B — Chlamydomonas.
Explanations:
A. Spirogyra — filamentous and less tractable.
B. Chlamydomonas — correct: a model green alga used in genetics, photosynthesis and flagellar studies.
C. Laminaria — brown alga, less used as model.
D. Fucus — brown alga, not a common lab model organism.

16. The alga responsible for harmful “red tides” and some fish kills is:
A. Ulva
B. Cyanobacteria (Anabaena)
C. Dinoflagellates (e.g., Gymnodinium)
D. Chlamydomonas
Answer: C — Dinoflagellates.
Explanations:
A. Ulva — causes green tides sometimes but not red tides.
B. Anabaena — cyanobacteria can cause freshwater blooms; not classical “red tide.”
C. Dinoflagellates — correct: many species cause red tides and harmful algal blooms (some produce toxins).
D. Chlamydomonas — freshwater unicellular green alga; not responsible for red tides.

17. Which of the following has haplontic life cycle (dominant haploid stage)?
A. Fucus
B. Polysiphonia (a red alga)
C. Chlamydomonas
D. Ulva
Answer: C — Chlamydomonas.
Explanations:
A. Fucus — diplontic (dominant diploid).
B. Polysiphonia — complex life cycle (triphasic) not strictly haplontic.
C. Chlamydomonas — correct: usually haplontic (vegetative haploid stage, zygote undergoes meiosis).
D. Ulva — isomorphic alternation (diplohaplontic).

18. Which algal class is mostly marine and multicellular with alternation of generations where the sporophyte produces unilocular sporangia, e.g., Laminaria?
A. Chlorophyceae
B. Phaeophyceae
C. Rhodophyceae
D. Euglenophyceae
Answer: B — Phaeophyceae.
Explanations:
A. Chlorophyceae — many freshwater or marine, but Laminaria is brown algal.
B. Phaeophyceae — correct: brown algae like Laminaria are marine, multicellular, often with alternation of generations.
C. Rhodophyceae — red algae, different life cycles.
D. Euglenophyceae — mostly freshwater unicellular euglenoids.

19. Which algal genus is a classical example of oogamous reproduction (large, non-motile egg; small motile sperm)?
A. Spirogyra
B. Volvox
C. Chara
D. Chlamydomonas
Answer: C — Chara.
Explanations:
A. Spirogyra — conjugation (isogamous-like transfer), not classical oogamy.
B. Volvox — oogamous in some; but Chara (stonewort) is classical multicellular oogamous plant-like alga and often emphasized as most plant-like.
C. Chara — correct: shows oogamy with multicellular structures (oogonia and antheridia) resembling early land plant reproduction.
D. Chlamydomonas — isogamous or anisogamous in some species; not as clearly oogamous.

20. Which statement about red algae (Rhodophyta) is CORRECT?
A. All possess flagellated stages.
B. They have chlorophylls a and b.
C. They often have complex life cycles with alternation of generations including a carposporophyte.
D. They store glycogen as food reserve.
Answer: C.
Explanations:
A. False — most red algae lack flagellated cells.
B. False — they possess chlorophyll a but not chlorophyll b; instead have phycobiliproteins.
C. True — many red algae have triphasic life cycles with gametophyte, carposporophyte, and tetrasporophyte.
D. False — they store floridean starch (a form of starch), not glycogen.

21. The major cell wall component of green algae is:
A. Agar
B. Alginic acid
C. Cellulose
D. Peptidoglycan
Answer: C — Cellulose.
Explanations:
A. Agar — red algae.
B. Alginic acid — brown algae.
C. Cellulose — correct: cellulose is a principal component of green algal cell walls (and land plants).
D. Peptidoglycan — in cyanobacteria (prokaryotes), not eukaryotic green algae.

22. Which algae are considered prokaryotes?
A. Chlorophyceae
B. Cyanobacteria (blue-green algae)
C. Rhodophyceae
D. Phaeophyceae
Answer: B — Cyanobacteria.
Explanations:
A. Chlorophyceae — eukaryotic.
B. Cyanobacteria — correct: they are prokaryotic photosynthetic organisms often called blue-green algae.
C. Rhodophyceae — eukaryotic red algae.
D. Phaeophyceae — eukaryotic brown algae.

23. Which algal group contains unicellular species that store oil and silica frustules (used as diatomaceous earth)?
A. Dinoflagellates
B. Diatoms (Bacillariophyceae)
C. Green algae
D. Brown algae
Answer: B — Diatoms.
Explanations:
A. Dinoflagellates — have cellulose plates, two flagella; not silica frustules.
B. Diatoms — correct: unicellular algae with silica cell walls (frustules); store lipids and chrysolaminarin.
C. Green algae — not silica-frustule-bearing.
D. Brown algae — multicellular, not diatoms.

24. Sexual reproduction in Spirogyra occurs by:
A. Conjugation
B. Oogamy
C. Syngamy
D. Isogamy by flagellated gametes
Answer: A — Conjugation.
Explanations:
A. Conjugation — correct: Spirogyra forms conjugation tubes between filaments for direct transfer of contents to form zygospore.
B. Oogamy — not typical for Spirogyra.
C. Syngamy — general term for fusion, but Spirogyra specifically undergoes conjugation.
D. Isogamy by flagellated gametes — Spirogyra gametes are non-flagellated and conjugate directly.

25. Which algal genus is known for alternation of generations where the multicellular sporophyte is morphologically different from gametophyte (heteromorphic)?
A. Ulva (isomorphic)
B. Laminaria (kelp)
C. Chlamydomonas
D. Spirogyra
Answer: B — Laminaria.
Explanations:
A. Ulva — isomorphic alternation (gametophyte and sporophyte similar).
B. Laminaria — correct: brown algae like Laminaria often show heteromorphic alternation (distinct sporophyte and gametophyte).
C. Chlamydomonas — haplontic unicellular.
D. Spirogyra — conjugation, not heteromorphic alternation. (more…)