Biology MCQ

A human-dominated biosphere is often referred to as the Noosphere, which signifies the sphere of human thought and activity influencing the environment. Term Noosphere was coined by Vladimir Vernadsky, and he describes it as the "sphere of human thought" and the increasing influence of human intellect and technology on the Earth. 

The atmosphere is an integral part of the earth. It surrounds the earth from all sides. Generally it extends upto about 1600 kilometres from the earths surface. 97 percent of the total amount of weight of the atmosphere is limited upto the height of about 30 kilometres. The atmosphere can be divided into five layers according to the diversity of temperature and density.
(a) Troposphere  (b) Stratosphere (c) Mesosphere (d) Ionosphere (e) Exosphere

1. TROPOSPHERE: The environmental temperature decreases with increasing height of atmosphere. It decreases at the rate of 10C at the height of 165 metre. This is called Normal lapse rate.
2. STRATOSPHERE: The temperature remains almost the same in the lower part of this layer upto the height of 20 kms. After this the temperature increases slowly with the increase in the height. The temperature increases due to the presence of ozone gas in the upper part of this layer. 
3. MESOSPHERE: Temperature goes on decreasing and drops upto – 100 degree Celcius.
4. IONOSPHERE: The temperature starts increasing again with increasing height in this layer.
5. EXOSPHERE: Gases are very sparse in this sphere due to the lack of gravitational force. Therefore, the density of air is very less here.

The height of this layer is about 18 kms on the equator and 8 kms on the poles. The main reason of higher height at the equator is due to presence of hot convection currents that push the gases upward.

The height of this layer is about 18 kms on the equator and 8 kms on the poles. The main reason of higher height at the equator is due to presence of hot convection currents that push the gases upward.

This layer is spread upto the height of 50 kms from the Earth’s surface. Its average extent 40 kms.

It spreads upto the height of 85 kms. from the surface of the earth.

(i) This is the fourth layer of the atmosphere. It is located above the mesosphere.
(ii) This layer spreads upto the height of 500 kms. from the surface of the earth.
(iii) The temperature starts increasing again with increasing height in this layer.
(iv) Electrically charged currents flows in the air in this sphere. Radio waves are reflected back on the earth from this sphere and due to this radio broadcasting has become possible. Ions are found in abundance in ionosphere. Ionosphere reflects back the radio waves to the earth and make possible the communication system

(i) This is the last layer of the atmosphere located above ionosphere and extends to beyond 500 km above the earth.
(ii) Gases are very sparse in this sphere due to the lack of gravitational force. Therefore, the density of air is very less here.

This is the lowest layer of the atmosphere. This is the most important layer of the atmosphere because all kinds of weather changes take place only in this layer. Due to these changes development of living world take place on the earth. The air never remains static in this layer. Therefore this layer is called changing sphere or troposphere.

The upper limit of the troposphere is called tropopause. This is a transitional zone. In this zone characteristics of both the troposphere and ionosphere are found.

The ionosphere is located within the thermosphere, meaning it's a part of the thermosphere. The thermosphere is a broader atmospheric layer, while the ionosphere specifically refers to the region within the thermosphere where ionization occurs due to solar radiation. 

The stratopause is the atmospheric boundary between the stratosphere and the mesosphere, characterized by a temperature maximum. It's located at approximately 50 kilometers (31 miles) above the Earth's surface. In this region, the temperature stops decreasing with altitude (as it does in the stratosphere below) and begins to increase again in the mesosphere above. In the stratosphere, temperature generally decreases with increasing altitude. However, at the stratopause, the temperature begins to increase with altitude as you move into the mesosphere. 

The ozone layer, which absorbs ultraviolet radiation, is primarily located within the stratosphere. This absorption contributes to the temperature increase in the stratosphere with altitude, and the subsequent temperature maximum at the stratopause. 

The mesopause is the boundary between the mesosphere and thermosphere layers of Earth's atmosphere, characterized by the lowest temperatures in the atmosphere, typically around -90°C. It's a crucial region for understanding atmospheric dynamics and space weather.