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SUMMARY II

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How Living Organisms Breathe

♥ We breathe by ventilating our lungs regularly with fresh air.

♥ Air is sucked into the lungs when the ribs rise and when the diaphragm falls. The air is pushed out when the ribs fall and the diaphragm rises.

♥ The air we expire contains much more carbon dioxide and water vapour than the air we inspire.

♥ The composition of the air changes in the millions of microscopic air sacs called alveoli which are found at the ends of the bronchial tree branches.

♥ Oxygen is carried all over the body by the blood to the tissues where it is used in a process called respiration.

♥ Respiration releases energy and produces carbon dioxide, a waste which must be eliminated from the body.

♥ The more energy we need the more we respire. Therefore, we breathe faster and deeper to obtain more oxygen and excrete more carbon dioxide.

 

The Breathing System of Insects

♥ Insects use a breathing system of tubes called tracheae.

♥ The tracheae transport air directly to the tissues which are respiring, such as muscles and nerves.

♥ The air enters and leaves the tracheae by spiracles which are found along the side of the insect's body. Insects do not breathe through their mouths.

♥ This system works slowly, which is one reason why insects are never very large.

 

Animals which Breathe through their Skin

♥ Animals with permeable skins may breathe through their skin but they lose a lot of water in this way.

♥ Large animals which breathe through their skins transport the gases around their bodies in their blood stream.

 

Breathing Underwater

♥ In water there is much less oxygen than in air but the animal will not dry out, even if it breathes through its skin.

♥ Aquatic animals can easily breathe through their skins but this may not be enough to give then all the oxygen that they need.

♥ Therefore, many aquatic animals have gills which give them a large surface for breathing.

♥ Usually the gills combine with the blood system to transport the oxygen around the body. Some aquatic insects combine their gills with the tracheal system.

♥ Not all animals which live in water have gills. Some breathe air at the surface

 

How Plants Breathe

♥ All plants respire just as animals do. Oxygen is absorbed and carbon dioxide is produced.

♥ Green plants also carry out photosynthesis which produces oxygen and absorbs carbon dioxide. If we want to study respiration in these plants we must block out the light.

♥ Plants do not breathe as animals do. They have no lungs, gills or tracheae. They exchange gases directly with the air or water that surrounds their leaves, stems and roots.

 

Living without Oxygen

♥ Yeasts can respire without oxygen. This is called fermentation or anaerobic respiration and it produces alcohol and carbon dioxide.

♥ Certain bacteria can respire without oxygen. These bacteria produce lactic acid.

♥ Some parts of our body can tolerate anaerobic respiration for short periods. Other parts need oxygen all the time.

 

Feeding in Green Plants

♥ The body of a plant is made of three things: water, mineral salts and organic matter.

♥ A plant needs a constant supply of water which it absorbs through its roots.

♥ The water absorbed by the plant is used to support the plant and to replace water lost from the leaves by transpiration.

♥ Plants also use minerals which are dissolved in the water that they take from the soil. These minerals are very important for healthy growth of a plant.

♥ Plants make the organic matter in their bodies by photosynthesis.

♥ For photosynthesis plants need the green pigment chlorophyll, light energy, carbon dioxide gas and some water.

♥ Photosynthesis also produce oxygen gas as well as organic matter. So in the light plants absorb carbon dioxide and release oxygen.

 

Plants which Feed in Different Ways

♥ Some plants do not make the green pigment chlorophyll, so they cannot build the organic matter in their bodies by photosynthesis.

♥ These non-green parasitic plants get there food from other plants by sucking the sap from the vessels in their stems.

♥ Lichens are formed by an association of a fungus with a plant called an alga. The fungus protects and supports while the green alga makes the food for the partnership by photosynthesis.

♥ Some green plants are carnivorous. They feed on insects which they trap with their leaves. These plants need the minerals in the insects' bodies because the soil where they grow does not have enough minerals for them.

 

How Feeding and Breathing are Connected

How Feeding and Breathing are Connected: Summary © Shirley Burchill

 

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