MID TEST MATERIALS FOR GRADE XI

No. 1 - 3

Bird flu is an infection caused by avian (bird) influenza (flu) viruses. These flu viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, bird flu is very contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them.

Bird flu viruses do not usually infect humans, but several cases of human infection with bird flu viruses have occurred since 1997.
There are many different subtypes of type A flu viruses. These subtypes differ because of certain proteins on the surface of the flu A virus (hem agglutinin (HA) and neuraminidase (NA) proteins). There are 16 different HA subtypes and 9 different NA subtypes of flu A viruses. Many different combinations of HA and NA proteins are possible. Each combination is a different subtype. All subtypes of flu A viruses can be found in birds. However, when we talk about “bird flu” viruses, we are referring to that flu A subtypes that continue to occur mainly in birds. They do not usually infect humans, even though we know they can do so. When we talk about “human flu viruses” we are referring to those subtypes that occur widely in humans. There are only three known subtypes of human flu viruses (H1N1, H1N2, and H3N2); it is likely that some genetic parts of current human flu A viruses came from birds originally. Flu A viruses are constantly changing, and they might adapt over time to infect and spread among humans.

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No. 9 - 12

Atmosphere is a gas mixture. Nitrogen is about 4.5 of the air part. Oxygen is more than 1.5, and other gases in small amount are Argon, Neon, Helium, Krypton, Xenon, CO₂, Hydrogen, and Ozone.

It can be found amount of vapour coming from the seas, lakes and rivers as well. The solid substances in the earth control the above gases.

Atmosphere consists of five layers; they are troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

It protects the earth from ultraviolet and other sky materials. It is also used as the communication media.

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No. 20 - 21

One of the most deadly plants in the world is poison hemlock. This plant grows in many parts of the world. It is quite dangerous to humans; people can die if they eat it.

One thing that makes poison hemlock really dangerous is that it looks like some plants that people normally eat. Hemlock belongs to very much like parsley, and its roots look like carrots. People have died when they have made a mistake and have eaten poison hemlock when they thought that they were eating either parsley or carrot.