Algae Classification Practice Questions
20 free Algae Classification practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following is a colonial form of algae?
- A Ulothrix
- B Spirogyra
- C Volvox
- D Chlamydomonas
Correct answer: Volvox
Volvox is a classic example of a colonial green alga. In contrast, Ulothrix and Spirogyra are filamentous, and Chlamydomonas is a unicellular form.
The cell wall of Phaeophyceae (brown algae) is typically covered on the outside by a gelatinous coating of:
- A Carrageen
- B Algin
- C Agar
- D Cellulose
Correct answer: Algin
Brown algae possess a cellulosic cell wall that is usually covered by a hydrocolloid substance called algin. This gelatinous coating helps protect the algae from desiccation and mechanical stress.
In which class of algae is the food stored as a complex carbohydrate called floridean starch?
- A Chlorophyceae
- B Phaeophyceae
- C Rhodophyceae
- D Cyanophyceae
Correct answer: Rhodophyceae
Floridean starch is the characteristic storage polysaccharide of Rhodophyceae (red algae). Its structure is very similar to amylopectin and glycogen.
Pyrenoids, which are found in the chloroplasts of most green algae, contain:
- A Both protein and starch
- B Only starch grains
- C Only oil droplets
- D Only protein bodies
Correct answer: Both protein and starch
Pyrenoids are specialized subcellular compartments in the chloroplasts of Chlorophyceae. They contain protein besides starch and function as centers for carbon fixation.
Which of the following algae produces large amounts of carrageen, a hydrocolloid used commercially?
- A Brown algae
- B Green algae
- C Red algae
- D Blue-green algae
Correct answer: Red algae
Carrageen is a water-holding substance (hydrocolloid) extracted specifically from certain red algae. Along with algin (from brown algae), it is widely used in the food and pharmaceutical industries.
Isogamous reproduction with non-flagellated (non-motile) gametes is found in:
- A Spirogyra
- B Ulothrix
- C Volvox
- D Fucus
Correct answer: Spirogyra
Spirogyra exhibits isogamy where both gametes are similar in size but lack flagella. In Ulothrix, the isogamous gametes are flagellated.
Which group of algae is characterized by having two unequal, laterally attached flagella?
- A Chlorophyceae
- B Phaeophyceae
- C Rhodophyceae
- D Bacillariophyceae
Correct answer: Phaeophyceae
Members of Phaeophyceae produce biflagellate zoospores or gametes that have two unequal flagella attached laterally. Green algae typically have 2-8 equal, apical flagella.
The plant body of a typical brown alga consists of a holdfast, a stalk called the ______ and a leaf-like photosynthetic organ called the ______.
- A Stipe, frond
- B Seta, capsule
- C Radicle, plumule
- D Rhizoid, thallus
Correct answer: Stipe, frond
The thallus of large brown algae like kelps is differentiated into a holdfast (attachment), a stipe (stalk), and a frond (photosynthetic lamina).
Agar-agar, used in labs to grow microbes and in ice creams, is obtained from which two genera?
- A Laminaria and Sargassum
- B Gelidium and Gracilaria
- C Chlorella and Spirulina
- D Porphyra and Dictyota
Correct answer: Gelidium and Gracilaria
Gelidium and Gracilaria are red algae (Rhodophyceae) from which agar is commercially extracted. Agar is an important solidifying agent in microbiology and food technology.
What is the reason for the red color of Rhodophyceae?
- A Predominance of fucoxanthin
- B Predominance of chlorophyll a
- C Predominance of anthocyanins
- D Predominance of r-phycoerythrin
Correct answer: Predominance of r-phycoerythrin
Red algae appear red because of the abundance of the pigment r-phycoerythrin in their bodies. This pigment allows them to absorb blue light, which penetrates deeper into the ocean.
In Chlorophyceae, the major pigments are:
- A Chlorophyll a and b
- B Chlorophyll a and c
- C Chlorophyll a and d
- D Chlorophyll a and fucoxanthin
Correct answer: Chlorophyll a and b
Green algae (Chlorophyceae) possess chlorophyll a and b, which are the same pigments found in higher plants. This gives them their characteristic grass-green color.
Which type of life cycle is generally observed in most algae like Volvox and Spirogyra?
- A Diplontic
- B Haplontic
- C Haplo-diplontic
- D Diplohaplontic
Correct answer: Haplontic
Most algae have a haplontic life cycle where the dominant phase is the free-living haploid gametophyte. The diploid phase is represented only by the single-celled zygote.
Ectocarpus and Kelps are examples of which class of algae?
- A Chlorophyceae
- B Rhodophyceae
- C Phaeophyceae
- D Cyanophyceae
Correct answer: Phaeophyceae
Ectocarpus (filamentous) and Kelps (massive branched forms) belong to Phaeophyceae. They are found primarily in marine habitats.
Flagella are completely absent in both vegetative and reproductive stages of:
- A Green algae
- B Brown algae
- C Red algae
- D Both a and b
Correct answer: Red algae
Rhodophyceae (red algae) are unique among the major algal groups because they lack flagellated stages entirely. Even their gametes and spores are non-motile.
A unicellular alga rich in proteins and used as a food supplement by space travelers is:
- A Chlorella
- B Sargassum
- C Gelidium
- D Ulothrix
Correct answer: Chlorella
Chlorella is a unicellular green alga that is exceptionally high in protein. It is widely used as a nutritional supplement and has been studied for use in space missions.
The variation in size and form of brown algae ranges from simple branched filamentous forms to massive bodies called:
- A Corals
- B Kelps
- C Strobes
- D Mycelium
Correct answer: Kelps
Brown algae show great variation in size. Kelps represent the most massive forms, sometimes reaching heights of up to 100 meters in the ocean.
Mannitol and Laminarin are stored food materials in which group?
- A Red algae
- B Green algae
- C Brown algae
- D Blue-green algae
Correct answer: Brown algae
Phaeophyceae store food as complex carbohydrates, specifically laminarin or mannitol (a sugar alcohol). This is a diagnostic feature of the class.
Sexual reproduction where a small, motile male gamete fuses with a large, non-motile female gamete is called:
- A Isogamous
- B Anisogamous
- C Oogamous
- D Zoogamous
Correct answer: Oogamous
Oogamy is the fusion between one large, static female gamete (egg) and a smaller, usually motile male gamete (sperm). Examples include Volvox and Fucus.
Which alga exhibits a diplontic life cycle, serving as an exception to the general rule in its group?
- A Ectocarpus
- B Polysiphonia
- C Fucus
- D Chlamydomonas
Correct answer: Fucus
While most algae are haplontic, Fucus (a brown alga) is an exception as it follows a diplontic life cycle. Ectocarpus and Polysiphonia are haplo-diplontic.
The inner and outer layers of the cell wall in Chlorophyceae are composed of ______ and ______ respectively.
- A Cellulose, Pectin
- B Pectin, Cellulose
- C Chitin, Cellulose
- D Cellulose, Algin
Correct answer: Cellulose, Pectin
Green algae have a rigid cell wall with a chemical composition similar to land plants. The inner layer consists of cellulose and the outer layer is made of pectose (pectin).