Question

Stages of hydrarch are

(a) Marsh meadow stage,

(b) Reed swamp stage,

(c) Submerged plant stage,

(d) Phytoplankton stage,

(e) Submerged free floating stage.

ldentify the correct sequence.

• A. d, c, e, b, a
• B. c, e, a, b, d
• C. b, d, c, a, e
• D. d, e, c, b, a

Answer 1

The correct option is A d, c, e, b, a

The various stages of hydrarch are:

(i) Phytoplankton stage- This constitutes the pioneer community. Some blue-green algae, diatoms and bacteria etc. are the first organisms to colonise the primitive medium of the pond.

(ii) Rooted submerged stage- As a result of death and decomposition of phytoplankton and their mixing with the slit, brought from the surrounding land by rain waters and by wave action of pond water, there develops a soft mud at the bottom of the pond. This new habitat becomes suitable for the growth of rooted hydrophytes.

(iii) Rooted floated stage- They all are rooted hydrophytes with their large leaves floating on the water surface. Water level by now become very much decreased.

(iv) Reed swamp stage- This stage is also known as the amphibious stage. The plants have well developed rhizomes and form very dense vegetation. The water level is by now very much reduced and finally become unsuitable for these plants.

(v) Sedge-meadow stage- The mesic conditions approach the area and marshy vegetation disappears gradually.

(vi) Woodland stage- By the time of disappearance of marshy vegetation, the soil becomes drier for most time the year. Terrestrial plants now invade this area.

(vii) Forest stage- This is a climax community. Several trees rapidly invade the woodland community.

Therefore, the correct answer is option A.