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19) the two main gases exchaged are oxygen and carbon dioxide . carbon dioxide is absorbed by the blood capilleries from the lungs alveoli by diffusion oxygen is transferd from lungs to the body cells in the form of oxy- hymoglobin
Answer:
19)Oxygen is absorbed by the blood capillaries from the lungs alveoli by diffusion while carbon-dioxide is absorbed by the lungs alveoli from blood capillaries by diffusion.
Oxygen is transported from lungs to the body cells in the form of oxy-hemoglobin.
Carbon dioxide is carried physically dissolved in the blood and is transported in the form of carbaminohaemoglobin.
20)The main components of the transport system in human beings are the heart, blood, and blood vessels.
• The heart pumps oxygenated blood throughout the body. It receives deoxygenated blood from the various body parts and sends this impure blood to the lungs for oxygenation.
• Being a fluid connective tissue, blood helps in the transport of oxygen, nutrients, CO2, and nitrogenous wastes.
• The blood vessels (arteries, veins, and capillaries) carry blood either away from the heart to various organs or from various organs back to the heart.
21)(a)Artificial kidney is often a synonym for dialysis, but may also, refer to renal replacement therapies (with exclusion of kidney transplantation) that are in use and/or in development. This article deals with bio-engineered kidneys/bio-artificial kidneys that are grown from renal cell lines/renal tissue.
(b)The process of getting back a full organism from its body part is called regeneration. Regeneration is carried out by specialized cells. From this mass of cell,different cells undergo changes to become various cell types and tissue. These changes take place in an organised sequence called as development.
22)(a)Electrical resistivity (also called specific electrical resistance or volume resistivity) and its inverse, electrical conductivity, is a fundamental property of a material that quantifies how strongly it resists or conducts electric current. A low resistivity indicates a material that readily allows electric current.
(b)Tungsten metal is selected for making filaments of incandescent lamp bulbs because tungsten can sustain high temperatures and it has high melting point, combined with the fact that it also has high resistivity.
23)Long-sightedness affects the ability to see nearby objects. You may be able to see distant objects clearly, but closer objects are usually out of focus.The medical name for long-sightedness is hyperopia or hypermetropia.
Long sight can occur at any age but it tends to become more noticeable above the age of 40 years. In rare cases, long sight is caused by other conditions such as diabetes, small eye syndrome (microphthalmia), cancers around the eye and problems with the blood vessels in the retina.
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24)(a) The main cause is the industrial burning of coal and other fossil fuels, the waste gases from which contain sulphur and nitrogen oxides which combine with atmospheric water to form acids is called acid rain.
(b) A food chain is a series of organisms where all the organismsare dependent on next organism as a source of food. The series of organism take part at various biotic levels to form a food chain.