ESSAYS ON TRANSPORT IN PLANTS AND ANIMALS TRANSPORT IN PLANTS AND ANIMALS 1. Explain the environmental factors that increase rate of transpiration. - Increased light intensity; Increase in light intensity increase the rate of photosynthesis in guard cells; stomata open wider; more water lost; increase increases internal temperature of the leaf; air in sub-stomatal air chamber warms making water in the spaces to vapourise; more water lost; - Amount of water available in soil; with more water available in soil; mesophyll cells become saturated; giving more water to the intercellular spaces; guard cells become turgid; stomata open, rate of transpiration increases; - Higher temperature; Increases the kinetic energy; of water molecules which makes water turn into vapour on the leaf surfaces faster and hence increase rate of transpiration - Air currents / windy condition; Air sweeps away water vapour outside the leaf; creating steep diffusion gradient; more water vapour lost. - low humidity; When atmosphere is dry; there is more water in the intercellular spaces; increasing diffusion gradient; more water is therefore lost; 2. Explain the factors that affect the rate of transpiration in plants. - Higher temperature; increases the kinetic energy; of water molecules which makes water turn into vapour on the leaf surfaces faster and hence increase rate of transpiration - Higher light intensity; influences maximum opening of stomata which increases the surface area; over which transpiration occurs maximumly. - Wind; carries away moisture around the plant and create a higher saturation deficit; which then increases the rate of water loss/transpiration in plants. - Higher relative humidity; reduces saturation deficit; which lowers the rate of water loss/transpiration in plants. - Higher amount of water in the soil; makes the plant to absorb excess water which increases the need for the plant to get rid of it faster through transpiration; - Leaf size. If the leaf is broader and has numerous larger open stomata, the surface area over which water loss occurs is increased; causing increase in the rate of transpiration. 3. Explain how structural features in terrestrial plants affect their rate of transpiration. Plants in arid /semi arid /desert habitats have leaves covered with thick / waxy cuticles that are water proof/ impermeable to water ; allowing for reduced rate of transpiration ; sunken stomata ; in some desert/ semi arid areas plants have water vapour accumulating in the pits is not carried away by wind ;most plants have few or no stomata on the upper surface of the leaf/ more stomata on the lower surface sheltered by from direct sunlight; the fewer the stomata the less the water loss from the plant . some plant have small stomata / small stomata size ; thus reducing transpiration rate plants with small needle like / spine ; expose less surface area hence reduce the rate of transpiration leaves with shiny surfaces; reflect light resulting in reduce d leaf temperature thus reducing the rate of transpiration . Some plant have leaves covered with hairs /scales ; which trap a layer of moisture ; (on the leaf surface ) reducing the rate of transpiration . plants growing in wet habitats / mesophyets have athin layer of cuticle which allow high rate of transpiration broad leaves ; expose a large surface area ; many stomata on both sides of the leaves ; have a large stomata. 4. Trace the path followed by a molecule of glucose from the time of absorption in the ileum until it enters a muscle cell in the leg. Ileum → hepatic portal vein→liver→hepatic vein→inferior vena cava→vena cava→right auricle→right ventricle→pulmonary artery→lungs→pulmonary vein→left auricle→left ventricle→aorta→abdominal aorta→femoral artery→femoral arterioles→capillaries→ultrafiltration→tissues fluid→muscle cell. 5. Describe how mammalian heart is adapted to its function. - The heart has myogenic cardiac muscles that contract and relax rhythmically without fatigue, The muscles have intercalated discs to spread contractions throughout the heart. They have numerous mitochondria to release energy required for muscular contraction. - The coronary artery supply oxygen of nutrients to the heart muscles; - The coronary vein remove metabolic wastes from the heart muscles; - The heart has four chambers, the right and left auricles that pump blood into the right and left ventricles respectively, the right ventricle pumps blood to the lungs for oxygenation. The left ventricle has thick muscular walls which generate greater force that pump the blood to the rest of the body via aorta. - The heart has a thick muscular septum that separates the right and left chambers to prevent mixing of oxygenated and deoxygenated blood. - The bicuspid and tricuspid valves prevent back flow of blood into auricles when ventricles contract ; - Bicuspid and tricuspid valves have tendons / heart strings to prevent then from turning inside out when ventricles contract; - Semi lunar valves prevent back flow of blood into ventricles when they relax; - The right atrium has the pacemaker, sino-atrial node(ASN) which initiates and maintain heart beat. - Atrio-ventricular node (AVN) and purkinje tissues spread contractions in the walls of the ventricles - The vena cava and pulmonary vein bring blood back into heart - The pulmonary artery and Aorta drain blood out of heart - The vagus nerve slows down the rate of the heartbeat - The sympathetic nerve accelerates the rate of the heart beat - The heart is enclosed by pericardial membrane which prevents overdilation; It also secretes a fluid that lubricates the heart; The heart is covered by a layer of fats that prevent mechanical shock. 6. Explain how the various components of blood are adapted to perform their functions. i) Plasma - Consists of 90% water in which substances are suspended or dissolved. - Contain glucose, mineral salts, hormones, some enzymes, amino acids and lipids. ; plasma proteins. ii) Red blood cells - Have no nucleus to increase room for package of haemoglobin. This enables it carry more oxygen. - Haemoglobin has high affinity for oxygen; It readily combines with oxygen to form oxyhaemoglobin / - The cells are numerous to increase carrying capacity for oxygen and carbon (iv)oxide - Ability to change their shape enable them to squeezing through narrow capillaries - They have biconcave shape increase surface area over which gaseous exchange can take place. iii) White blood cells. (Leucocytes) - Number of cells increase with increase in infections thus increasing their efficiency - Use amoeboid movement to pass through the walls of the capillaries into infected area and to engulf pathogens. - Produce antibodies which destroy pathogens. - Produce anti-toxins which neutralize toxins produced by pathogens. iv)Platelets ( Thrombocytes) - Fragments of red large cells. - Cause clotting on fresh wounds preventing entry of bacteria and excessive loss of blood. 7. Describe the structure and functions of plasma and leucocytes as some of the components of blood. Plasma - Pale yellow liquid which is 90% water; - Has dissolved glucose, mineral salts, hormones, enzymes, amino acids, antibodies; - Acts as transport media for red blood cells; metabolic wastes to excretory organs; carbon (iv) oxide from respiring cells to the lungs; hormones from glands to sites of activity; transport of glucose/ mineral salts/ amino acids/ antibodies; - regulation of PH - distribution of heat leading to maintenance of body temperature White blood cells - Are nucleated; - have colorless cytoplasm; - are fewer than red blood cells; - manufactured in bone marrow; - fight pathogens in the following ways; engulf them, produce antibodies which destroy pathogens and antitoxins which neutralize toxins produced by pathogens. 8. Describe the process of blood clotting. When blood vessel is injured, platelets are exposed to air. They rupture on damaged tissue, releasing thromboplastin which neutralizes heparin (anti-clotting factor) and activates prothrombin to thrombin; in presence of calcium ions. Thrombin activates conversion of fibrinogen into fibrin which forms meshwork of fibres on the injured surface trapping red blood cells to form a clot. The clot dries up and forms a scab which stops further bleeding and prevent infection of the tissues. 9. Describe how oxygen is transported in the blood Oxygen is of high concentration in the lungs/ alveoli than in the blood capillaries; and it is easily diffuses into the red blood cells, where it combines with Haemoglobin; and forms an unstable compound called Oxyhaemoglobin; It is then transported in this form to respiring tissues; In the capillaries of the respiring tissues, Oxyhaemoglobin decomposes/dissociates, releasing oxygen which then diffuse into the tissues down the concentration gradient; Free haemoglobin goes back to the alveoli of the lungs to pick more oxygen. 10. Describe the absorption of water by plant roots It occurs in root hairs which are numerous and extended to give a large surface area for absorption. Between soil particles is a film of water which contains mineral salts forming a salt solution? Water enters the root hairs by osmosis because the root hair cells have high osmotic potential than the salt solution in the soil. -The absorption of water in to the epidermal cell makes them to have less osmotic potential than the adjacent cells of the cortex. -This difference causes the movement of water by osmosis from the epidermal cell to the adjacent cortex cell. -This process continues through the cortex cells until it reaches the epidermal cells. -At the endodermis there is the casparian strip which is impervious to water therefore controlling and guiding the flow of water into the xylem tissue. It uses energy to carry out this function. 11. Describe the forces involved in the movement of water to the leaves i) Capillarity -The size of a tube determines how far the water movers up. The narrower the tube the higher themovement. The xylem tissues are very narrow and so the water moves to greater heights. ii) Root pressure -It is created by osmotic pressure within the root tissue which pushes water into and up the xylem tissue iii) Transpiration pull -It is the pulling force that lifts up water from the roots to the top of the plant which occurs as a result of transpiration. iv) Cohesion -Is the force that holds together molecules of the same kind and keeps the water molecules together as they move up the xylem tissue. v) Adhesion Is the force that holds together different molecules of and this is the force that holds together the water molecules with the walls of the xylem tissue.
Posted on: Sat, 16 Aug 2014 09:26:53 +0000
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