MCQs Based On Environment – (56)

Correct Option: 3. The alga provides food and the fungus retains moisture
Explanation: Lichens are a classic example of symbiosis — a mutually beneficial relationship between two different organisms. In this case:
• The alga (or cyanobacterium) carries out photosynthesis, producing carbohydrates (food).
• The fungus, which lacks chlorophyll, cannot make its own food but is excellent at absorbing and retaining moisture and nutrients from the environment.
• The fungus provides a protective structure and a moist environment that allows the alga to survive in harsh conditions (like on rocks or tree trunks).
• This cooperation allows lichens to survive in nutrient-poor and extreme habitats where neither organism could live alone.

Correct Option: 2. Bryophytes
Explanation: Bryophytes are non-vascular plants, meaning they lack the vascular tissues (xylem and phloem) found in more advanced plants.
• They do not have true roots, stems, or leaves. Instead, they have rhizoids — hair-like structures that help in anchorage but not in water absorption.
• Bryophytes include mosses, liverworts, and hornworts.
• They thrive in moist and shady environments because their reproduction (via spores) requires water for fertilization — the male gametes need water to swim to the female gametes.
• Since they lack vascular tissues, they cannot transport water efficiently over long distances and must absorb it directly from the environment.

Correct Option: 2. The seeds are exposed without any covering
Explanation: The word “Gymnosperm” is derived from Greek:
• Gymnos = naked
• Sperma = seed
This means “naked seed”, and here’s why:
• In gymnosperms, the ovules are not enclosed within an ovary.
• The seeds develop openly on the surface of cone scales (carpels), instead of being enclosed within a fruit like in angiosperms.
• Examples include Pine (Pinus), Cycas, and Gnetum.
• Since there is no ovary, gymnosperms do not form true fruits — the seeds are directly exposed to the environment, making them vulnerable but evolutionarily significant.

Correct Option: 1. Eastern Himalayas and Northeast India
Explanation: Pteridophytes are the first vascular plants in evolution, having true roots, stems, and leaves, and vascular tissues (xylem and phloem).
• They reproduce via spores, not seeds.
• Moisture is essential for their reproduction, as sperm must swim to the egg.
• Therefore, they thrive in moist, shady environments like rainforests, mountain slopes, and stream banks.
• In India, the Eastern Himalayas and Northeast India offer the ideal climate: high rainfall, dense canopy cover, and high humidity, making them rich in pteridophytic diversity.
• Common pteridophytes in these areas include ferns, horsetails (Equisetum), and club mosses (Lycopodium).

Correct Option: 3. Sonneratia and Avicennia
Explanation: The Sunderbans, located in the delta region of the Ganges and Brahmaputra rivers, is the largest mangrove forest in the world and a UNESCO World Heritage site.

• The mangrove ecosystem is zoned according to tidal influence.
• In the lowest tidal zones, which are frequently flooded by seawater, species like:
(1) Sonneratia
(2) Avicennia
are the pioneer species — they tolerate high salinity and waterlogging.

• These trees have special adaptations, such as:
(1) Pneumatophores (aerial roots) for oxygen intake in waterlogged soil.
(2) Salt glands or ultrafiltration mechanisms to deal with salinity.

• Higher up in the tidal zone, you find species like Rhizophora, Bruguiera, and Excoecaria, followed by palms like Phoenix and Nypa at the uppermost levels.