Q10 of 805 Page 1

Plenty of algal bloom is observed in a pond in your locality.

(a) Write what has caused this bloom and how does it affect the quality of water.


(b) Suggest a preventive measure.


(a): Algal blooms are caused by Blue-green algae, which are actually bacteria (cyanobacteria). Some are due to excess nutrients like phosphate and Nitrogen.

• It affects the other creatures living in the water as it reduces the amount of oxygen(hypoxic condition)


• The harmful algae release toxins and kill the other organisms like fishes.


• Eutrophication (natural ageing of water body) is accelerated.


(b): Some of the preventive measures are as follows:


I. Reduce the use of fertilisers and manures on agriculture land.


II. Biomanipulation


III. Protect soil from erosion


IV. Artificial destratification


V. Treating sewage to remove the nutrients, nitrogen and phosphorus.


More from this chapter

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8

In an agricultural field there is a prevalence of the following organisms and crop diseases which are affecting the crop yield badly :

(a) White rust


(b) Leaf and stripe rust


(c) Black rot


(d) Jassids


Recommend the varieties of crops the farmers should grow to get rid of the existing problem and thus improve the crop yield.


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How does the application of the fungal genus, Glomus, to the agricultural farm increase the farm output?

 11

a) List the three stages the annuals and biennial angiosperms have to pass through during their life cycle.

(b) List and describe any two vegetative propagules in flowering plants.


 12

Draw a labelled diagrammatic sectional view of a human seminiferous tubule.