Learning Sheet Solution 4

1. Why are nutrient cycles in called biogeochemical cycles? A1. Nutrient cycles in nature are called biogeochemical cycles because the elements move cyclically from the environment to living organisms and back to the environment. 2. State the function of a reservoir in a . A2. The function of a reservoir in a nutrient cycle: It meets the deficit which occurs due to the imbalances in the state of influx and efflux of nutrients. Carbon cycle: Thus, they pass the carbon compounds along the . Most of the carbon these animals consume however is exhaled as carbon dioxide. 3. Outline salient features of carbon cycling in an ecosystem. A3. Salient features of carbon cycling are as follows 1. Carbon cycling occurs through atmosphere, ocean and through the living and dead organisms. 2. Most of the carbon is fixed by plants during the process of and returns to the atmosphere in the form of CO2 during respiration. 3. Burning of wood, forest fire and combustion of organic matter, fossil fuel, and volcanic activity are some other sources of releasing CO2 in the atmosphere. An outline of C‐cycle is depicted in the figure given below:

4. Explain the phosphorus cycle A4.  Weathering. Since the main source of phosphorus is found in rocks, the first step of the phosphorus cycle involves the extraction of phosphorus from the rocks by weathering.  Absorption by Plants and Animals.  Return to the Environment via . 5. The nutrients are never lost in the ecosystem but are recycled back in time and again the cycles continue indefinitely Answer the following questions on the basis of above information. (i) Name the different nutrient cycles and give example. (ii) Draw any cycle. (iii) What conclusion can be drawn from the above statement? A5. (i) There are mainly two types of nutrient cycles as follows: (a) Gaseous cycles‐ e.g. (a) Carbon cycle (b) Nitrogen cycle (b) Sedimentary cycles‐ e.g, (a) Sulphur cycle (b) Phosphorus cycle (ii)

(iii) Phosphorus Cycle (iii) The nutrients are never lost or destroyed in nature. They only change forms and returned back to in a cyclic manner. In this way the balance of nature is maintained. 6.What do you understand by ecological services? Explain in detail. A6. Ecosystem services. The products of ecosystem processes are named ecosystem services. Examples: The following services are provided by forests ecosystem. They (i) Purify air, (ii) Mitigate droughts and floods, (iii) Help in cycling of nutrients, (iv) Provide to a number of wildlife, (v) Act as storehouse of carbon, (vi) Influence the hydrological cycle and (vii) Maintain . The value of services of biodiversity is difficult to determine. Robert Constanza et al. have tried to put price tags on nature’s life‐support services. Researchers have estimated them to be 33 trillion US dollars a year, while our global gross production is only 18 trillion US dollars.