Name any two organisms which can occupy more than one trophic level in an ecosystem.
Human being (man) and birds (sparrow) can be frequently seen in more than one trophic level, in an ecosystem.
In the North East region of India, during the process of jhum cultivation, forests are cleared by burning and left for regrowth after a year of cultivation. How would you explain the regrowth of forest in ecological term?
Forests that are cleared by burning and left for regrowth will show secondary succession. Since, soil is already present, the buried seeds oen to germinate. Due to wind dispersal and some other natural forces, new seeds will be brought into the area and new species will colonise the forest again.
Climax stage is achieved quickly in secondary succession as compared to primary succession. Why?
The rate of ecological succession is quicker in secondary succession as compared to primary succession as the soil (substratum) is already available for further succession. While in primary succession, the succession starts from bare rocks. Which take time for first colonisation by plants as there is no nutrient holding mechanisms.
Among bryophytes, lichens and fern which one is a pioneer species in a xeric succession?
The species that invade a bare area are called pioneer species. In a xeric succession, the pioneer species are usually lichens then bryophytes which are succeeded by ferns and some other bigger plants.
Lichen produces lichen acid and carbonic acid which corrodes rock surface and release minerals required for growth. The corroded rock accumulate soil particle by wind and provides substrate for Bryophytes and ferms.
What is the ultimate source of energy for the ecosystems?
Solar radiation is the ultimate source of energy for the ecosystem except deep hydrothermal ecosystem.