question_answer

Explain the process of hydrarch succession.

Or

Give the significance of predation in nature in detail.

Answer:

Process of hydrarch succession is as follows

(a) Plankton stage It is the pioneer stage of hydrosere. Spores of this stage reach the water body through wind or animals. First phytoplanktons appear followed byzooplanktons.

(b) Submerged stage They are rooted in the mud and form dense growth.

(c) Submerged free - floating stage Floating plants begin to appear with the rise in shallowness, of the pond, Later on, free - floating plants like Lemna, Azolla, Wolffia, etc., grow profusely to cover the water surface.

(d) Reed swamp stage Amphibious plants grow where the water body becomes shallow, e.g. Typha, Sdrpus, etc.

(e) Marsh - Meadow stage The shapes built up by reed swamp stage are invaded by Carex, Cyperus, grasses like Themeda and herb like Campanula.

(f) Woodland stage With time, many smaller species of trees invade the area and finally climax community appears.

Or

Significances of predation are as follows

(a) Control of prey population The predator keeps the population of the prey under check, so that an equilibrium is maintained. The prey also maintains its optimum activity and efficiency since only weak and sick individuals are removed by the predators.

(b) Biological control of weeds and pests It is largely based on predator prey relation. Opuntia turned out to be a serious weed in Australia. It was brought under control when its natural herbivore Cactoblastis was introduced.

(c) Maintenance of species diversity Predators also help in maintaining species diversity in a community by reducing the intensity of competition among competing prey species.

(d) Vegetation Predation helps in growth of vegetation all over the globe by restricting the population of herbivores.