It is my holiday home work so plz help me

1 why should we need sunlight everyday or in the form of energy
2 who discover pathogen for the first time.
3 what are the requirement for good health.
4 what are the functions of heamoglobin.
5 write short note on green house effect with suittable example.
6 how are clouds forms.
7 why fertile soil necessary for crop production.
8 what is pollution . Name its type , and how it can we prevent or cantrol peastical - an type of pollution.



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Sunlight (ultra violet part) is a good source for D3 vitamin for our body.  Our body produces the vitamin from the sunlight falling on the skin.  Deficiency of D vitamin is not good for us.

Blood pressure may be reduced by exposure to sunlight, as dilation of blood vessels may happen.  Perhaps the infrared radiation present in sunlight also helps brain function better. 


Indian doctor-expert-inventors of old times, Charaka, Sushruta and Vaghbhata wrote in Ayurveda about pathogens being invisible and causing diseases and infections. Girolamo Fracastroro in 16the century and Francesco Redi worked on the subject.

Discovery of micro organisms and pathogens by pioneer of microbiology – in the 17th century – by Anton Van Leewenhoek is probably first. Nicolas Andry and Rchard Bradley proposed theories on the pathogens. Agostino Bassi proved by experiments that pathogens cause diseases.



 We require two types of nutrients.  Macro nutrients are needed in big quantities and micro nutrients in small amounts.  We need to eat sufficient amount of fibrous foods (micro nutrients) for good digestion purpose.

We need to drink water – about 2 litres each day.  We need small amounts of salt too, but large amounts are dangerous.

Macro nutrients consist of carbohydrates, proteins, vitamins and fats.  Vitamins are needed for the organs to function well and increase our body defense.  Fats and carbohydrates give us immediate energy through metabolsm.  Proteins help us to grow.

  We need to eat fruits, vegetables, pulses, rice or wheat, milk and eggs   We need to eat regularly and in sufficient quantities, but not excess.  We need to also breathe in fresh and clean air.  We need to keep our environment clean.  Sufficient exercise is essential  to keep the body fit and healthy.



 Haemoglobin is a protein in the red blood cells in our body.  It contains iron. Colour of blood is due to haemoglobin. It transports oxygen from the lungs to all the cells/tissues in the body for aerobic metabolism. Haemoglobin also carries carbon dioxide from respiration of cells back. In kidneys, haemoglobin regulates iron metabolism activity. Haemoglobin also carries nitric oxide gas in it, which helps expansion and contraction of the veins. Thus blood pressure is also monitored by it.

Sufficient amount of haemoglobin in our blood is essential. Otherwise a person may become anaemic. New blood cells are formed in bone marrows.  Red blood cells have a life time of 4 months.


  There are various green house gases in our atmosphere. They are carbon dioxide, water varpour, nitrous oxide, ozone, methane etc. They absorb the radiation from the Sun and emit it in all directions. They emit the radiation in thermal infrared range. This radiation is emitted towards Earth’s surface and the atmosphere near our surface, the temperatures are increasing  gradually.  This heating effect is called greenhouse effect.

   Greenhouse effect is not same was the green house used for growing plants more efficiently. Without the greenhouse effect on Earth, the temperatures on Earth’s surface would be very low.

6.  Clouds are in the troposphere of our atmosphere, just a few km above our surface.  They are mainly a group of tiny drops/droplets or frozen ice particles of water.  Often clouds contain some particles (aerosols) of other chemicals also suspended in air/atmosphere. When water from Earth’s surface evaporates due to Sun’s heat, it raises higher.  Damp air is lighter than dry air.  When the air in atmosphere is saturated  or  when air cools down, the water vapour  forms clouds that is visible.  When the droplets are big enough, then it rains.

 We say that the process of condensation of water in atmosphere is the cause for formation of the clouds.

7.  A fertile land / soil consists of nutrients that are required by plants to grow.  A infertile soil does not contain any useful nutrition for plants.  Hence fertile soil is needed. Fertile soil contains  potassium, phosphorous, nitrogen etc. Many minerals (small but necessary quantities) are also present like copper, iron, cobalt, boron, chlorine, magnesium, manganese, sulphur, zinc etc. Often we use fertilizers as the soil does not contain minerals and nutrients in sufficient quantities.

 There are many microorganisms in fertile soil that help the plants to grow.   Often soil needs to be a little acidic or a little alkaline.


Pollution is contamination – mixing of impurities – chemically or physically in to substances, causing negative and undesired consequences. The impurities are called pollutants.  We have water (bodies) pollution, energy pollution, sound pollution, air pollution etc.

 We control the emissions into air. We need to control chemical effluents (from factories) into air, water bodies, and soil.

We must recycle, reuse and reduce in a biodegradable way. Sound pollution (noise) can be controlled. Vehicular emissions is controlled by stricter regulations.

Good, practical and economic non-polluting methods  for manufacturing need to be invented.
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