Transport of water in plants
The survival of plants is dependent on a number of factors which include water, minerals, gases, and nutrients they receive. The movement of gas, water, and nutrients in plants are carried out in components. They take in carbon dioxide from the air through the stomata present in their leaves and they absorb compounds of nitrogen, phosphorus, etc., from the soil by their roots. If the distance to be traversed is relatively small, diffusion process occurs. As the distances increases in tall trees, a well-developed transportation system arises as these movements of substances have to be facilitated with extreme care.
The amount of energy required by plants is lower compared to that of animals, hence there is a requirement of slower transportation. In plants, a tube-like passage made up of vascular tissues called xylem and phloem are two modes of transportation. Water and minerals travel upwards through the xylem, while phloem transport synthesized food to other parts of the plant. The movement of water and other nutrients from one part of a plant to another is called translocation. Water gets absorbed by osmosis while minerals by active transport. The method used in the upward movement of water through the xylem is determined by the cohesion-tension theory. Here the driving force of transport is transpiration. In this process, cohesion is responsible for driving more water through the xylem and excess water molecules are pulled up by the pulling force which later evaporates through the tiny pores of stomata.
Transport of minerals in plants
Like water, minerals are also necessary for plants to survive. About 16 minerals are necessary for plants. These minerals are present in soil in the form of inorganic salts such as nitrates and phosphates. In soil, these minerals get dissolved in water and are absorbed by roots along with water. From roots, the minerals are transported to various parts of a plant along with water by xylem vessels by same procedure as described earlier.
Thus, in plants both water and minerals are transported from roots to upper parts (stems, leaves, flowers and fruits) by xylem vessels.
Transport of water in animals
A healthy sedentary adult living in a temperate climate should drink at least 1.5 liters of water per day . This level of water intake balances water loss and helps keeping the body properly hydrated. The water you consume through food and drinks follows a very precise route to arrive in your cells, of which it is a vital constituent.
After passing through the stomach, water enters the small intestine, where it is largely absorbed in the first sections, the duodenum and jejunum. The rest passes into the colon. It crosses the intestinal mucous membrane into the bloodstream, then into the interstitial tissues that make up the framework of every organ, to arrive in the cells.
Blood brings nutritional elements to cells (minerals, vitamins, protein components, lipids and carbohydrates). Waste products are then removes through urines. Water plays also an essential function in helping the regulation of temperature.
Transport of minerals and other nutrients in animals
In all leaving beings the nutrients and gases are transported to and from all parts of the body. This is essential to carry on various life processes. In case of unicellular and small multicellular organisms transport takes place by diffusion. However, in large multicellular organisms, as the distances between different body parts have increased, they need an elaborate and efficient system for transportation of materials. In large animals, such a system is called circulatory system in which a fluid circulates in all parts of the body. In many invertebrates this fluid is the haemolymph, where as in all vertebrates and in some higher invertebrates this fluid is the blood.
Open Circulatory System
Many invertebrates e.g. arthropods have open circulatory system.In this system the blood is pumped from the heart into the blood vessel. The blood vessels in turn, empty themselves into open spaces called sinuses. In the sinuses, the blood is in direct contact with the tissues, and after exchange of materials with the tissues it re-enters the heart for circulation again.
Closed Circulatory System
Closed circulatory system is more elaborate, complicated and efficient as compared to the open circulatory system. The closed circulatory system consists of a muscular, and contractile pumping organ, the heart with its incoming (veins) and outgoing (arteries) blood vessels. The blood remains confined in the blood vessels while circulating in the whole body e.g. earthworm, man etc.
In closed circulatory system, the heart pumps blood into the blood vessels (arteries) which take away the blood from the heart to the tissue. In the tissues, the arteries divide and subdivide into very fine branches, called the capillaries. The walls of capillaries are just one cells thick, and in them the blood is in close contact with the tissue cells. Exchange of materials with tissues is carried out here.
The capillaries join and form bigger blood vessels called venules. These venules in turn join to from the veins, which ultimately transport blood back to the heart.
General Plan Of Circulatory System Of Vertebrates
In vertebrates, the circulatory system is always of closed type. The closed circulatory system is further of two types, (a) single circuit circulation, (b) double circuit circulation.
For instance in fishes the circulation is of single type. In it, only the deoxygenated blood circulates through the heart. The deoxygenated or the venous blood from all tissues of the body enters the sinus venous, from where it passes into the single auricle or atrium. From the atrium it goes in the ventricle.
From the ventricle, the blood is pumped into the gills for oxygenation. The oxygenated blood from the gills is directly distributed to all parts of the body. As the blood circulates once through the heart, therefore, this type of circulation id called single circuit circulation.
In land vertebrates, with the introduction of lung respiration, double-circuit circulation evolved.
The evolution of double circuit circulation led to the division of atrium and ventricle, each into two chambers. The atrium divided into right and left atria (plural of atrium) and likewise the ventricle also divided into two chambers. In amphibians, the ventricle is not divided and in most reptiles, the division of the ventricle is incomplete. In some reptiles and in all birds and mammals, the division of the ventricle is complete. So in these animals, oxygenated and deoxygenated bloods are completely separated from each other and there is no mixing of these two types of blood. This increases the efficiency of the circulatory System in vertebrates is highly developed and among them mammals have the most efficient circulatory system.
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