Problem 68 - Objective Biology for NEET

Question

How many of the following algae belong to the category of red algae? Polysiphonia, Gelidium, Laminaria, Spirogyra, Porphyra, Fucus, Chlamydomonas (a) 2 (b) 3 (c) 4 (d) 5

Step-by-Step Solution

Answer

(b) 3

Step 1: Identify red algae

Red algae comprise many species that are identifiable by their reddish color, attributed to the pigment phycoerythrin. This obscures the green color of the chlorophyll. The following species in the question are red algae: Polysiphonia, Gelidium, and Porphyra.

Step 2: Count the red algae

There are three species of red algae given in the exercise. They are Polysiphonia, Gelidium, and Porphyra.

Key Concepts

phycoerythrin

Phycoerythrin is a pigment found in red algae that gives these organisms their characteristic reddish color. This pigment is crucial for photosynthesis in red algae. It absorbs blue and green light, allowing red algae to thrive in deeper waters where these light wavelengths penetrate.
It masks the green hue of chlorophyll, commonly present in algae, resulting in the distinct red appearance of these species.

• Enables photosynthesis under low-light conditions
• Adaptation for survival in deeper marine environments

Understanding the function of phycoerythrin helps us know how red algae like Polysiphonia, Gelidium, and Porphyra sustain themselves and grow in diverse underwater habitats.

Polysiphonia

Polysiphonia is a genus of red algae, known for its filamentous and branching structure. It belongs to the Rhodophyta division, which is a group characterized by their red pigments due to phycoerythrin.
They are usually found attached to substrates like rocks in the intertidal zones. Polysiphonia species play an important role in marine ecosystems by providing habitat and food sources for a variety of marine organisms.

• Has a complex life cycle with alternation of generations
• Participates in nutrient cycling in marine environments

They are significant members of the red algae family, showing the adaptive nature of these organisms to various ecological niches.

Gelidium

Gelidium is another notable genus of red algae. These algae are typically found in warm waters and are widely utilized in commercial industries.
What sets Gelidium apart is its use in producing agar, a gelatinous substance employed in foods, laboratories, and various other industries.

• Thallus is cartilaginous, tough, and mostly erect
• Ecologically significant in rocky marine ecosystems

Gelidium species' economic importance highlights the diverse applications of red algae beyond their ecological roles.

Porphyra

Porphyra, often known as nori, is a widely recognized and cultivated genus of red algae, especially in the food industry. Its thin, delicate sheets are often used in sushi wraps and other culinary dishes.
Rich in nutrients such as vitamins, proteins, and minerals, Porphyra also contributes to marine ecosystems by providing habitat.

• Commonly farmed for consumption
• Supports coastal ecosystems

Porphyra demonstrates how red algae have become integrated into human diets, illustrating a direct link between aquatic ecosystems and human consumption.

chlorophyll in algae

Chlorophyll is a key molecule in photosynthesis, present in many algae, including red algae. It plays a vital role in converting light energy into chemical energy.
In red algae, the presence of chlorophyll is masked by phycoerythrin and other accessory pigments, making them appear red rather than green.

• Facilitates energy conversion in plants and algae
• Exists alongside pigments that absorb different light wavelengths

The interplay between chlorophyll and other pigments in red algae explains their adaptability and success in diverse underwater environments.