(a) Draw a well labelled nitrogen cycle in nature.
(b) Describe one biological and one physical method of conversion of nitrogen to forms like nitrates and nitrities.
OR
(a) Draw a labelled carbon cycle in nature.
(b) Describe briefly two process by which carbon dioxide is returned back to the atmosphere.

(i) Make a neat and labelled sketch of nitrogen cycle in nature. (ii) Describe in brief the role of nitrogen fixing bacteria and of lightenng in fixing atmospheric nitrogen. OR (i) Draw a neat labelled sketch of carbon cycle in nature. (ii) What is green house effect? How does carbon dioxide cause global warming in the atmosphere.

With the help of a labelled diagram show (a) Nitrogen cycle in nature (b) Describe briefly any two processes involved in the cycling of N_(2) in the environment. OR With the help of a labelled diagram show the cycling of carbon in nature. What are the two ways in which carbon dioxide is fixed in the environment.

(a) Draw well labelled diagram of oxygen cycle in nature. (b) Explain in how many ways O_(2) is used up from the atmosphere and how it returns back to atmosphere.

(a) Describe is sequence the process of microsporogenesis in angiosperms. (b) Draw a labelled diagram of a two celled final structure formed.

(a) Describe is sequence the process of microsporogenesis in angiosperms. (b) Draw a labelled diagram of a two celled final structure formed.

(a). Name two metals which occur in nature in free state as well as in combined state. (b). Name one ore of manganese. Which compound of manganese is present in this ore? Also write, its chemical formula. (c) A zinc ore on heating in air forms sulphur dioxide. Describe briefly any two stages involved int eh conversion of this concentrated ore into zinc metal.

(a) Name two metals which are found in free state in nature. (b) What chemical process is used for extracting a metal from its oxide ore? Name one metal which is extracted by this method. (c) Describe the extraction of zinc metal from its sulphide ore as well as its carbonate ore. Write equations of all the reactions involved.

cosider the following conversions of nitrogen cycle. Which one of the following repersents biological oxidation Process?