Pressure gradient, Biology

Pressure Gradient

You know that air pressure is the weight of the atmosphere over a unit area of the earth's surface. The average air pressure at sea level is approximately 1 kilogram per square centimetre. At any point at sea level the air pressure is the same. We know that gravity which holds everything on earth's surface, also holds the atmospheric gases in an envelope
around the earth. Gravity compresses the atmosphere on the earth's surface so that air pressure decreases with increasing altitude.

Weather forecasters on the TV and Radio usually report air pressure in rnm i.e. in unit of length. This in fact refers to the height to which a column of mercury can rise in the barometer at a specific station at a given time. However, it is more appropriate to express pressure in millibars (mb). The average pressure at sea level is 1013.25 mb.

Let see what happens to the air pressure and density as we go higher up in the atmosphere. Air density which is the mass per unit volume also diminishes with altitude. Ninety-nine per cent of the atmosphere's mass lies between the earth's surface and an altitude of approximately 32 km. Approximately half of the atmosphere's mass lies between the surface of the earth and an altitude of 5.5 km. At this altitude the air pressure too remains only one-half of the pressure at sea level.

In most cases the reduction of pressure is not a limiting factor for the distribution of plants and animals at high altitudes. There arelother adverse conditions like low temperature, lack of food, unsuitable soil etc. Many species of beetles have been found in the highest meadows of Himalayas. While, earthworms have been found up to the snowline in the Andes mountains. However, for warm blooded vertebrates reduced air pressure and density
at high altitudes causes impairment in respiration.

The expansion and thinning of air accompanying the lower air pressure at high altitudes triggers physiological changes in human beings. For example, a person at high altitude may experience dizziness, headaches and shortness of breath, but gradually adjusts or acclimatises to the low oxygen levels. However, people cannot adjust to pressure at altitudes higher than approximately 5.5 km.

Relatively a slight change in the air pressure can trigger important changes in the weather. A large volume of air which is relatively uniform in terms of its temperature and water vapour content is called an air mass. As air masses move from one place to another, surface air pressure falls or rises causing changes in weather. As a general rule low pressure causes
stormy weather and when air pressure rises the weather improves.

Posted Date: 12/10/2012 7:01:36 AM | Location : United States







Related Discussions:- Pressure gradient, Assignment Help, Ask Question on Pressure gradient, Get Answer, Expert's Help, Pressure gradient Discussions

Write discussion on Pressure gradient
Your posts are moderated
Related Questions
Polyarthritis  1)  Gonococcal - Therapeutic trial of pencillin may help in diagnosis of gonococcal  infection.  2)  Viral infections such as rubella and hepatitis B may have

Q. What is the function of vitamin E? In which foods can it be found? Vitamin E is also known as tocopherol is a fat-soluble vitamin that participates as coenzyme in the respir

Wat is the excretory organ of lizard

Q. What are nerves? Axons extend all through the body inside nerves. Nerves are axon-containing structures presenting many axons and covered by connective tissue. The nerves co

Boiling Point There are certain properties of solutions  which are directly connected with vapour pressure and one of it is boiling point.  You must have observed that water bo

State the concept of type locus interaction Some of the major contributions included the concept of type locus interaction, the analysis of quantitative as opposed to qualitati

Which of the following pairs of functional groups CANNOT react with each other by a dehydration reaction? Select one: a. Carboxyl;Hydroxyl b. Carboxyl;Sulfhydryl c. Pho

Effect of pH or Nutrient Availability One of the greatest influence of pH on plant growth is through its effect on the nutrient availability. When base saturation is less than

Biochemistry : The chemistry  of  living organisms that covers all  the chemical reactions occurring  in our body.

Pheromones Serving Functions Other than Reproduction Besides sexual responses as described above pheromones mediate several other types of behaviour. Alarm pheromones have bee