Ecological Succession

Pioneer species are the first organisms to colonize a barren or disturbed habitat, initiating the process of ecological succession. These species are well-adapted to survive in harsh conditions and gradually prepare the environment for more complex communities to establish themselves.

Examples of pioneer species include lichens and mosses, which can grow on bare rock, and some hardy plants.

Other options:

• Key stone species: These species have a disproportionately large impact on their environment relative to their abundance but do not specifically initiate succession.
• Climatic species: These species thrive in a stable, mature ecosystem, not in bare areas.
• Endemic species: These species are native to a specific region but do not specifically play a role in initiating ecological succession.

Let's relate each item from Column I with the appropriate item from Column II:

Calotropis: This plant produces cardiac glycosides, which are toxic compounds used to deter herbivores and predators. Therefore, the correct match is:

• 1 → s (Cardioglycoside)

Pisaster: This is a genus of sea stars (starfish), and they are invertebrates. Therefore, the correct match is:

• 2 → p (Invertebrates)

Monarch butterfly: The Monarch butterfly is known for its distastefulness to predators due to toxins it accumulates from its diet, making it an unpalatable prey. Therefore, the correct match is:

• 3 → q (Distasteful)

Frogs: Frogs are often cryptically colored to blend into their surroundings and avoid being seen by predators. Therefore, the correct match is:

• 4 → r (Cryptically coloured)

Correct Matching:

1 → s (Cardioglycoside)
2 → p (Invertebrates)
3 → q (Distasteful)
4 → r (Cryptically coloured)

The correct answer is (B) : 1-s, 2-p, 3-q, 4-r.

Phytoplanktons: These are the pioneer species, microscopic organisms that can photosynthesize and form the base of the food chain.

Free-floating hydrophytes: These plants float on the water surface, such as Azolla and Pistia.

Rooted hydrophytes: These plants are rooted in the sediment but have leaves that float or emerge above the water, such as Nymphaea (water lily).

Reed swamps: As sediment accumulates, emergent plants like reeds and sedges establish, creating a swampy environment.

Marsh meadows: Further accumulation of sediment leads to the development of marshy areas with grasses and other herbaceous plants. Scrubs: With continued soil development and drainage, shrubs and bushes begin to colonize.

Trees: Finally, trees can establish, leading to a climax forest community.

Therefore, the correct answer is (D): Phytoplanktons → Rooted hydrophytes → Free floating hydrophytes → Reed swamps → Marsh meadows → Scrubs → Trees.

Here is why option D is the best answer: Phytoplankton are the pioneers. Rooted hydrophytes prepare the way for free floating. Free floating are not the second to colonize.

Reed swamps, marsh meadows, scrubs and trees is the correct order of terrestrial colonization.

The best option is (D), keeping in mind the relative order of aquatic succession.

The correct order is therefore (D) Phytoplanktons → Rooted hydrophytes → Free floating hydrophytes → Reed swamps → Marsh meadows → Scrubs → Trees.