Give Reasons: 
  1.  Oxygen given out during photosynthesis comes from water.
  2. The need to limit the size of the family is more vital today
  3. In summer, urine is slightly thicker in winter.
  4. Man can live without food for a number of days but he cannot survive without oxygen for more than a few minutes.
  5. Environmental pollution is a recent problem.
  6. A higher rate of transportation is recorded on a windy day rather than on a calm day.
  7. Leguminous plants act as natural fertilizers.
  8. Why one usually feels dizzy at high altitudes.
  9. All lives will come to an end if there are no green plants.
  10. One feels thirsty after having a meal rich in salt.
  11. Why should we breathe through nose not by mouth?
  12. Transpiration is vital for the life of plant
  13. Explain briefly how the rate of transpiration is by:
  • Intensity of light.
  • Humidity of the atmosphere.


Dear Student,
1)During photosynthesis water molecules dissociated into H+and OH- . The H+ is essential to reduce NADP+ into NADPH .which is essential for the reduction of CO2 .Two OH molecule combine to form H2O and O2. Four OH radical combines to form H2O and O2
Hence O2 comes out during photosynthesis comes from H2O and not from CO2.
2)Of course yes if day by day family will increasing then all resources (food , water , fuel, trees ) will get finished because  people need it every time.
3) in summer sweating takes place and water losses from our body so two maintain the water balance in the body only harmful nitrogenous waste removed from the body that's why urine is thick in summer.
4) A body that does not have food can survive for quite a long time by subsisting on the fat reserves in the body and, eventually, the glycogen reserves in the liver and the proteins in the muscles. The first two to three days without food, the body will depend solely on the fat reserves to run the muscles of the body. Unfortunately, these fatty acids can’t cross the blood-brain barrier. The brain relies on the glycogen reserves to send glucose to the brain. After day three, the liver begins to synthesize ketones (short strand fatty acids) that can cross the blood-brain barrier. The ketone stage can last for up to two weeks. Once the fat reserves are used up, the body will begin breaking down the musculature into proteins that can be converted into amino acids that are then transformed into glucose. Muscles break down quickly, within one week. Once this process has completed there is no other internal source of energy and the body dies. Oxygen is possibly our most basic human need. People can begin to experience brain damage after as few as five minutes without oxygen. Hence, without oxygen survival is only for minutes but without food it is for few days.
5)  Environmental pollution represents an obstacle to the economical exploitation of coal deposits. In industrialized countries, the rules for protection of the environment are stricter than in developing countries. Thus, to get a license to open mines involves lengthy procedures which in turn cause delay.  Consequently, ecological problems can be totally prevented, but these arw costly.
6)The wind is one of the external factors that increase the rate of transpiration. The wind carries away the moisture present in the atmosphere by making it dry enough so that it can absorb more water vapours from the plants. This result in high rate of transpiration in a windy atmosphere than on a calm day.
7)Nitrogenous fertilizers are not added in the soil in which leguminous plants are grown because the nitrogen fixing bacteria, Rhizobium reside in their root nodules.
The bacteria fix atmospheric nitrogen into soluble forms which can be readily absorbed by the plants. The nitrogen fixed gets into the soil and makes it fertile. The leguminous plants utilize some of the nitrogen compounds, leaving behind the rest in the soil. So, the soil is already rich in nitrogenous compounds, there is no need for fertilizers.
8) High-altitude illness, or sickness, is a condition that can occur when your body doesn’t get enough oxygen. Places with high altitudes have less oxygen than places with lower altitudes. When you go from low to high altitudes, your body has a hard time adjusting to the change in oxygen levels.
9) Yes if there were no green plants all life on earth would come to an end & earth would become a barren place because plants provide oxygen which is important for all organisms to live.secondly plants give us food which is our basic necessity.plants also bring rain which is important for us too. so if plants were not there we could not survive too.
10)  After taking food  salt is added to body .As the saltier blood circulates through the body, it makes the fluid outside of our body cells saltier than the fluid inside the cells.
The cells notice the change right away. That’s because the extra salt outside acts like a magnet, pulling water out of the cells. The cells try to hold in the water and they send chemical messengers to the brain, protesting the saltiness of the fluid around them.

Please ask other question seperately.
Hope it helps!

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The?oxygen released during photosynthesis comes from?the splitting of water?during?the light-dependent reaction. 3. Remember, the electrons lost from the reaction center in photo-system II must be replaced. The splitting of water serves to replace these lost electrons
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It is so because all the catbon dioxide is consumed by plants for photosynthesis Hence o2 is release by hydrolysis of H2O
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