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Digestion and absorption

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Class 10 Class 12

Give reasons for the following:                                                                      
Nitrogenous fertilisers are not applied in fields where leguminous crops grow.


Nitrogenous fertilisers are not applied in fields where leguminous crops grow as the roots of leguminous crops contain nitrogen-fixing bacteria such as Rhizobium or Azotobacter, which fix the free nitrogen of the atmosphere into nitrates. Thus nitrogen is already made available to the plants and there is no need to add nitrogenous fertilisers. 


Expand the following:

DDT


Dichloro diphenyl trichloroethane


List any four disadvantages of using fossil fuels for the production of energy.


The four disadvantages of using fossil fuels for the production of energy are:

i. It releses high concentration of posinous gases like oxides of sulphur and nitrogen which may cause air pollution and acid rain.

ii. It results in the increase of concentration of Carbon dioxide in the enviroment and hence reults in global warming.

iii. When burnt in less oxygen large amount of toxic gas Carbon monoxide is released which may have adverse effect on the organisms.

iv. They are non-renewable resources of energy, their overuse may lead to depletion of these resources.


List three problems which arise due to the construction of big dams. Suggest a solution for these problems. 


The construction of big dams poses the following problems:

(i) Social problems as the construction displace a large number of peasants and tribals without adequate compensation or rehabilitation.

(ii) They create economic problems as they use up huge amounts of public money without the generation of proportionate benefits.

(iii) Environmental problems because they contribute enormously to deforestation and the loss of biological diversity.


State the meaning of inherited traits and acquired traits. Which of the two is not passed on to the next generation? Explain with the help of an example.


Inherited traits are those traits which can be passed from one generation to the next generation. These involve changes in the DNA.

Acquired traits - An acquired trait is a physical characteristic of an organism that is not passed down to offspring genetically. It is not coded in the organism's DNA and is a product of the environment's influence on the organism. These traits are acquired during the lifetime.

The acquired traits are not passed to the next generation. For example, if a person has increased the muscle strength and size by exercising regularly, then he/she cannot pass the same to their offspring.