Question

According to the classification of algae, 'brown algae' are placed in which class?

• A. Chlorophyceae (Green)
• B. Rhodophyceae (Red)
• C. Phaeophyceae
• D. Cyanophyceae

Hint:

Remember the major classes of algae: \[ \boxed{ \begin{aligned} \text{Green algae} &\rightarrow \text{Chlorophyceae}\\ \text{Brown algae} &\rightarrow \text{Phaeophyceae}\\ \text{Red algae} &\rightarrow \text{Rhodophyceae} \end{aligned} } \] The pigment fucoxanthin is responsible for the brown colour of Phaeophyceae.

Answer 1

The Correct Option is C

Concept: Algae are chlorophyll-bearing, simple, autotrophic organisms that are classified mainly on the basis of their pigments, reserve food material and cell wall composition. The three major classes of algae are: \[ \boxed{ \begin{aligned} \text{Chlorophyceae} &\rightarrow \text{Green algae}\\ \text{Phaeophyceae} &\rightarrow \text{Brown algae}\\ \text{Rhodophyceae} &\rightarrow \text{Red algae} \end{aligned} } \] Brown algae possess the pigment fucoxanthin, which gives them their characteristic brown colour.

Step 1: Identify the pigments present in brown algae.
Brown algae contain \[ \boxed{\text{Chlorophyll }a,\;c\text{ and Fucoxanthin}.} \] Fucoxanthin masks the green colour of chlorophyll, making the algae appear brown.

Step 2: Determine their classification.
Based on the presence of fucoxanthin and other characteristics, brown algae are placed under \[ \boxed{\text{Phaeophyceae}.} \] Examples include: \[ \boxed{\textit{Sargassum},\;\textit{Laminaria},\;\textit{Fucus}.} \]

Step 3: Compare the options.

• Chlorophyceae → Green algae.

• Rhodophyceae → Red algae.

• Phaeophyceae → Brown algae.

• Cyanophyceae → Blue-green algae (Cyanobacteria).
Therefore, \[ \boxed{\textbf{Option (C)}} \] is the correct answer.