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Biology Questions and Answers Form 2 - High School Biology Tests/Exams
Biology Questions and Answers Form 2 KCSE Revision Questions and Answers Biology Notes Form 2 1. a i Define transport Movement of substances from one pan of the body to another ii Explain the necessity of transport in plants and animals make nutrients move from one point to another movement of respiratory gases i. oxygen and carbon IV oxide elimination of metabolic wastes movement of hormones movement of water movement of salts aqa a2 biology essay help of enzymes b i Describe the structure and function of root hair root hairs are found near the root tip they are cells with elongated finger-like projections which are in contact with soil particles they are permeable to water and mineral salts hence are used to absorb Water and mineral salts There large number offers a large surface area for absorption of water and mineral salts, aqa a2 biology essay help.
photosynthesis transport turgidity w h helps in plant support solvent i. Attraction of water molecules to the Walls adhesion from the stem water enters the xylem of leaves water moves in the xylem vessels of the stem in a continuous uninterrupted water column up to the tree leaves Leaves once in the leaves water moves into the mesophyll cells by osmosis as water vaporizes from the spongy mesophyll cells their sap becomes more concentrated than the adjacent cells as the result water flows into the cell from other surrounding cells which in turn takes in water from xylem vessels within the leaf veins this creates a pull suction force called transpiration pull that pulls a stream of water from xylem vessels in the stem and roots.
The transpiration pull maintains a continuous column of water from the roots to the leaves. loss of water from plant to the atmosphere ii Name the sites through which transpiration takes place in a plant stomata stomatal transpiration lenticels lenticular transpiration cuticle cuticular transpiration iii State the aqa a2 biology essay help of transpiration to plants cooling the plant transport of water transport of mineral salts excretion of excess Water from plants excess transpiration causes wilting i Explain the structural factors that affect the rate of transpiration in plants number of stomata i, aqa a2 biology essay help.
the more the stomata the higher the rate and vice versa turgidity of the guard cells which control the opening and closing of stomata when they are open transpiration rate is high size of leaves where the larger the surface area the higher the rate of transpiration leaf fall leads to lower rate of transpiration and also drying of leaves reduces rate of transpiration Thin cuticle reduces distance through Which water vaporizes hence increase transpiration rate.
Absence of cuticle also increase rate of transpiration ii Explain the environmental factors that affect rate of transpiration in plants high temperature increases rate of transpiration and low temperature reduces the rate humidity when high increases rate and when low reduces the rate transpiration rate is higher in moving air wind than in still air high light intensity increases internal temperature hence higher rate of evaporation leading to higher rate of transpiration availability of water in the soil leads to more absorption hence more loss to the atmosphere atmospheric pressure when high leads to more evaporation and when low leads to low rate evaporation of water iii State the structural differences between xylem vessels and sieve tubes sieve tubes have cross wall while xylem vessels have none xylem vessels are lignified while sieve tubes are not Sieve tubes have cytoplasm elements while xylem vessels have none.
Water vapour accumulates in the depression of stomata lowering the water vapour concentration gradient leading to lower rate of evaporation rolling of leaves v State the factors that cause increase in the rate of transpiration from leaves increased light intensity low relative humidity temperature vi Explain how drooping of leaves on a hot sunny day is advantageous to a plant reduces surface area exposed to sun reducing cuticular transpiration c Explain how aquatic and terrestrial plants are adapted to deal with problems of transpiration a, aqa a2 biology essay help.
Mesophytes they grow in soils with enough water water loss is perfectly balanced by absorption of more from the soil no special adaptations b. small leaves all these adaptations are to reduce water loss c. Either cut a stem of a young plant or twig of a tree under water or else uproot a young herbaceous plant and wash the soil gently put some water in a beaker and add a dye i. eosin or red ink and place the cut stem or young plant in a beaker leave for time e. between 20 minutes and one hour cut a thin section of stem or leaf mount it on a slide and examine under a microscope observe and note the distribution of the dye or ink the aqa a2 biology essay help appears only in the xylem vessels ii.
OR use radio-active tracers, C14 in form of carbon ring a plant then put it in a container containing radio-active phosphorous solution The radio-active phosphorus is later detected in the leaves.
a i List the components of animal transport systems system of blood vessels in which materials are circulated round the body blood, a fluid medium which contains dissolved substances and cells the heart, a pumping mechanism which keeps blood in circulation ii Distinguish between closed and open circulatory systems closed system has blood vessels through which blood moves eg vertebrates open system has no blood vessels hence blood is in direct contact with tissues e.
g arthropoda iii What are the advantages of the closed circulatory system over open circulatory system? It receives blood from the whole body. The blood is pumped from the left atrium to the right ventricle To avoid flow back into the right atrium, a valve is present between the two chambers the tricuspid valve The right ventricle pumps blood to the lungs This is facilitated by the presence of pulmonary artery A valve is also present to avoid blood flowing back from the pulmonary artery to the right ventricle Blood from the lungs enters the heart through the pulmonary vein into the left atrium, aqa a2 biology essay help.
When the left atrium contracts, aqa a2 biology essay help, blood flows into the left ventricle Blood will not flow back into the left atrium because of the presence of bicuspid valve mitral The left ventricle is connected with the aorta and when it contracts, blood flows into the aorta for distribution into the whole body The heart muscle surrounding the left ventricle is thicker than that surrounding the right ventricle to be able to generate enough pressure to push blood to the whole body A pace-maker is present in the heart muscle to initiate and synchronise contractions.
For the heart muscle to be well nourished and be provided with enough oxygen and carbon IV oxide removal, it is supplied with blood by the coronary arteries and drained by the coronary veins iv Explain why blood leaving the lungs may not be fully oxygenated under ventilation of the lungs blockage of alveoli air sacs high cardiac frequency i.
high rate of pumping of blood in the heart e Describe the structure and functions of the blood vessels i. Arteries carry away blood from the heart carry oxygenated blood except pulmonary artery which takes blood from the heart to lungs for oxygen have thick, muscular walls are elastic have narrow lumen all these adaptations are required to withstand high pressure caused by heartbeat ii.
Capillaries link arterioles and venules to arteries and veins small in diameter to increase pressure resistance for materials to filter out thin walled as they consist of a single layer of cells to allow diffusion of substances e. g leucocytes to tissues thin walled to allow presence of intercellular spaces large number i. numerous to provide a large surface area for exchange of materials have sphincter muscles at the junction of the arterioles and capillaries to control movement of blood into them lie close to the body for easy exchange of materials iii.
Give the advantages of aqa a2 biology essay help mode of transport. list the major types of human blood groups O, with neither B nor A antigen AB, with both A and B antigens A, with type A antigen B, with type B antigen iii.
rhesus positive blood has the Rhesus Rh antigen rhesus negative lacks the Rhesus antigen vi What is blood transfusion? Introduction of blood from one person to another v Under what conditions would blood transfusion aqa a2 biology essay help necessary in people? during accidents during surgery in hospitals bleeding mothers when giving birth vi How can low blood volume be brought back to normal?
State the precautions that must be taken before blood transfusion blood must be disease free sterilized equipment must be used blood aqa a2 biology essay help the recipient and that of the donor must b compatible to both ABO and rhesus factor Fresh blood must be used, aqa a2 biology essay help. j i What is immunity? iii What are allergic reactions? Excessive sensitivity and reaction of an individual to certain substances in environment e. dust, pollen, perfumes, smoke etc.
vi How does an allergic reaction occur? a i What is gaseous exchange? The continuous exchange of oxygen and carbon Iv oxide between the organism and environment ii Why is gaseous exchange important to organisms?
to supply oxygen necessary for energy production to remove carbon IV oxide produced during respiration To remove Water vapour. Guard cells contain chloroplasts, aqa a2 biology essay help, unlike aqa a2 biology essay help other epidermal cells which enable photosynthesis to occur Inner walls of guard cells are thicker than the outer cells iii State the factors which affect stomatal opening water which when low stomata close and when high stomata keeps open light as stomata open in bright light and close in darkness temperature iv Name the theories suggesting the mechanism of opening and closing of stomata interconversion of starch and sugar pH theory mineral ion concentration v Describe the mechanism of opening and closing of stomata stomata close at night and open during daytime This comes about due to changes in turgidity as a result of pH changes in guard cells.
In the dark carbon dioxide accumulates in the intercellular spaces This raises concentration of carbonic acid The pH drops pH lowered Enzymes convert sugar into starch in guard cells Osmotic pressure in guard cells is lowered Water moves out of guard cells by osmosis making cells lose turgidity hence become flaccid The stomata close During day time there is aqa a2 biology essay help hence the production of sugar, carbon IV oxide concentration is lowered, pH increases, guard cells become turgid causing stomata to open.
During the day potassium ions concentrate in guard cells, raising their osmotic pressure and causes then to open In the night the concentration of potassium ions decreases increasing osmotic pressure in guard cells therefore causes stomata to open, aqa a2 biology essay help.
i What is the advantage of having stomata open during daytime and having them closed at night? opening in the daytime allows diffusion of carbon IV into the leaf for photosynthesis to take place and allows diffusion of oxygen out of the leaf transpiration also takes place, thus cooling the leaf and facilitating uptake of water and mineral slats Closing in the night is to conserve water in the plant especially when there is not enough water available in the soil.
d i List the types of respiratory surfaces of animals cell membrane aqa a2 biology essay help unicellular organisms e. Large surface area iii Describe gaseous aqa a2 biology essay help in protozoa example is amoeba small and have large surface area oxygen diffuses into the organism and carbon IV oxide diffuses out into Water simple diffusion of gases is enough to meet its respiratory requirements e i Make a labeled drawing of a fish gill ii How is a fish gill adapted to its function?
large surface area due to many filaments extensive vascularisation due to capillaries, aqa a2 biology essay help, for gaseous exchange thin filaments to facilitate diffusion of gases presence of rakers to filter solid particles gill bar is bony, hard and firm to support the filaments and rakers and for attachment of filaments and rakers iii Discuss gaseous exchange in bony fish example is tilapia the mouth opens and the floor of the mouth is lowered so that the volume in the mouth is increased and pressure is lowered water then enters into the mouth cavity the mouth is closed and the floor of the mouth raised so that the volume is reduced this raises the pressure, forcing water over gills and out through the operculum As water passes over the gills oxygen diffuses due to concentration gradient partial pressure into the blood stream.
In the body tissues, carbon IV oxide diffuses into the blood due to concentration gradient, and is transported to the gills and diffuses out into the water.
iv What is counter-flow system? Where water in which the fish lives flows in opposite direction across the gill. vi What is the advantage of counter-flow system? maintains a diffusion gradient so that there is maximum uptake of oxygen oxygen continues diffusing into blood and carbon iv oxide into Water f i Describe the mechanism of gaseous exchange in terrestrial insects example is cockroach air in the atmosphere contains oxygen air is drawn into the body of the insect through the spiracles due to movement of abdominal muscles these movements cause the opening of spiracles air moves through the trachea to tracheoles oxygen moves from the tracheoles into body cells by diffusion due to concentration gradient carbon iv oxide in the tissues diffuses into tracheoles due to concentration gradient From tracheoles carbon IV oxide moves into trachea and out through the spiracles into the air.
ii State how traceholes are adapted to gaseous exchange thin walls of tracheoles moist surface large surface area due to numerous tracheoles g i What is breathing?
Any process which speeds up the rate of gaseous exchange between an animal and its surrounding. in the mitochondria b i Draw and label a mitochondrion ii State the most important function of mitochondria to produce Adenosine triphosphate ATP which is the energy source of the Whole cell iii Give the functions of the labeled parts Outer membrane controls what enters and What leaves mitochondrion Cristae also called inner membrane increase surface are for attachment of enzymes this is Where cellular oxidation reactions occur Matrix enzymes are located here other reactions occur here c Explain the roles of enzymes in respiration they catalyse reactions i.
energy carbon iv oxide water e i What is anaerobic respiration occurs in the absence of oxygen e. yeast and certain bacteria release energy in the absence of oxygen ii What are obligate anaerobes?
are completely independent of oxygen iii What are facultative anaerobes? the demand for oxygen is more than supply leading to anaerobic respiration iv Why does lactic acid level reduce after exercise? lactic acid is oxidized to form carbon iv oxide and water some is converted to glucose some is converted into glycogen v State why accumulation of lactic acid during vigorous exercise lead to an increase in heartbeat lactic acid is poisonous to tissues and must be removed to increase supply of oxygen to tissues State the economic importance of anaerobic respiration brewing of alcohol biogas production compost manure formation silage formation baking bread production of dairy products fermentation of milk sewage treatment Fermentation of tea in industries.
What is oxygen debt? amount of oxygen required to convert accumulated lactic acid to water, carbon IV oxide and energy h i What is respiratory quotient RQ? Some energy locked up in intermediate products like ethanol in plants and lactic acid in animals substrate is completely oxidized in aerobic respiration iv Explain the disadvantages of anaerobic respiration Less energy produced in anaerobic respiration since food is partially oxidized while in aerobic respiration food is completely oxidized.
plants have lower rates of metabolism plants excrete non-poisonous products derived from carbohydrate metabolism unlike animals which produce toxic wastes derived from protein metabolism plants re-use some of their wastes like nitrogenous wastes used in protein synthesis plants store waste products in roots, fruits and leaves ii State the excretory products of plants and some of their uses to humans caffeine from tea and coffee is used in medicine and as a stimulant which is harmful to humans quinine used for treating malaria cocaine derived from leaves of cocoa plant used as a stimulant by addicts or as a local anesthesia, also causes damage to the brain, may cause addiction if not well used and is an illegal drug Tannins derived from barks of acacia wattle bark trees are used to make ink and tanning softening of leather.
Nicotine got from leaves of tobacco plant stimulates the central nervous, aqa a2 biology essay help, may cause addiction if much is used or consumed. It is used to make cigarettes, cigars and is poisonous, aqa a2 biology essay help. It is a precursor of lung cancer Cannabis sative bhang is used to make drugs Gum derived from glues is used for sticking substances and making certain jellies Rubber, a product of latex, got from rubber plant is sued to make tyres and synthetic fibres Morphine from opium poppy plant is a narcotic and illegal drug as it causes addiction Khat and miraa are used as stimulants Colchicines used in inducing polyploidy, cancer therapy, treatment of gouts in small quantities Papain used as meat tenderizer c i Describe excretion in unicellular organisms -examples are amoeba and paramecium -They have to remove waste products such as carbon IV oxide and nitrogenous substances e.
When it is cold, no sweat is produced, aqa a2 biology essay help, conserving water sweat contains water, sodium chloride, uric acid and urea hence the skin acts as an excretory organ Has hair, aqa a2 biology essay help. It lies flat to allow heat loss when temperature is high.
Arterioles vasodilate when temperatures are high to lose heat by radiation, aqa a2 biology essay help, and convention. Arterioles constrict when temperatures are low to conserve heat i. reduce heat loss Has sebaceous glands which secrete sebum, and antiseptic and water aqa a2 biology essay help that prevents drying and cracking the skin by making the skin supple e What is the role of lungs in excretion?
during respiration oxygen is used up in the body cells to produce energy carbon IV oxide is produced as a by-product the carbon IV oxide must be eliminated from the body elimination is through the lungs also, water vapour is formed and must be removed this removal is through the lungs the lung is therefore considered as an excretory organ as it removes carbon IV oxide and water vapour which are by-products of respiration f State the functions of the liver i.
Excretion in this function the liver is aided by the kidney deamination i. excess amino acids converted into urea and uric acid which is transported to skin and kidney for removal detoxification where harmful substances are converted into harmless ones in the liver and transported to kidneys for removal breakdown of worn out blood cells and haemoglobin and the residue excreted through the kidney to give urine a yellow tinge Breakdown of sex hormones after they have performed their function and the wasted are released through the kidney and bile.
a i Why is homeostatic control necessary? this provides a constant internal environment so that the cells of aqa a2 biology essay help body have the optimum best condition for their survival ii What is internal environment?
immediate surrounding of body cells refers to tissue fluid within an organism b i Why is constant body temperature maintained by mammals? most enzymes in the body function within a narrow range of temperature high temperature denatures enzymes low temperature inactivates and inhibits enzymes ii Explain the advantage gained by possessing a constant aqa a2 biology essay help temperature animals remain active despite fluctuations in environmental temperature higher chances of survival in various environments ie they colonize various environments chemical processes in their body continues at an optimum rate iii How do mammals regulate body temperature?
the body temperature of a mammal is kept constant to maintain this temperature the mammal must be able to balance its heat loss against the heat gain body temperature is controlled by the hypothalamus, a specialized part of the brain changes in the temperature within the body and the surrounding are detected by the hypothalamus it transmits impulses to the skin and the blood stream in response to temperature changes hypothalamus acts as a thermostat for the body a mammal loses heat by breathing out, urine, feaces, skin by radiation and by evaporation of sweat.
A mammal generates heat by the activity of its muscles, by general metabolism in respiration, or chemical activities In hot conditions the hypothalamus stimulates responses that increase heat loss from the body hence lowering the body temperature Such responses include sweating, vasodilation, keeping its hair flat on the surface of skin and reduction of metabolic rate In cold conditions the hypothalamus stimulates responses that generate heat gain in the body and reduce heat loss to the environment Such responses include shivering, vasoconstriction, raising its hair to trap a layer of air around the skin because still air is a good insulator of heat and by generation of heat by increasing metabolic rate.
iv Why does body temperature of a healthy person rise up to 37 C on a hot humid day? sweat evaporation is reduced hence cooling is less therefore more heat is retained in the body causing temperature to rise v Name the structures in the human body that detect external temperature changes temperature receptors end bulb corpuscles e. bulb of Krause warmth and organ of Ruffinni cold heat thermal receptors vi State the advantages that organisms with small surface area to volume ratio experience over those with larger heat loss slow hence their body temperature can increase to intolerable levels Heat gain from surrounding slower hence may remain inactive for a long time.
Need specialized and complex transport system and also gaseous exchange system Explain why individuals with smaller sizes require more energy per unit body weight than those with larger sizes.
surface area to volume ratio is higher in smaller individuals than larger ones, therefore smaller heat is lost faster by smaller ones than larger ones they therefore require more energy per unit body weight to maintain body temperature c i What is the meaning of osmoregulation? when a blood vessel is cut, there is exposure of blood platelets to the air this triggers fibrinogen to be converted to fibrin the fibrin forms a clot that prevents body fluids e.
blood from being lost therefore the clot conserves water and salts in the body g Describe the role of the following hormones in homeostasis i. Aldosterone concerned with regulation of ionic balance secreted by the cortex of adrenal glands it increases sodium ion uptake by the gut and aqa a2 biology essay help the reabsorption of sodium ions and therefore water in the kidneys this is accompanied by aqa a2 biology essay help of potassium ions this raises the overall level of sodium and lowers the overall level of potassium in the blood as sodium ions are absorbed in the blood, chlorine ions follow so as to neutralize the effect of sodium ions the production of aldosterone is regulated by the concentration of sodium ions which has an inhibiting effect, and a fall in sodium ions has a stimulating effect on the adrenal cortex the flow of aldosterone is stimulated by the adreno-cortic-tropic hormone ACTH produced in the anterior of the pituitary gland however, the main method of control is dependent on the fact that adrenal cortex itself is somehow aqa a2 biology essay help to the relative concentration of potassium and sodium in the blood ii.
Adrenaline produced by adrenal glands in high concentrations, it increases hydrolysis of glycogen and increases blood sugar it is usually released in emergency cases to increase glucose level for respiration this releases energy for the emergency h i Distinguish between diabetes mellitus and diabetes insipidus diabetes mellitus is a condition resulting from insufficient production of insulin causing hyperglucaemia and presence of glucose in urine diabetes insipidus is a condition whereby less or no antidiuretic hormone is secreted hence a high volume of water is passed out in urine in aqa a2 biology essay help condition called diuresis ii How can high blood sugar level in a person be controlled?
glucose molecules are actively reabsorbed in the proximal convoluted tubules iv When is glycogen which is stored in the liver converted into glucose and released into the blood? orange or red precipitate Positive result is an indication of diabetes mellitus Biology Diagrams and Images Biology Notes Form 1 Biology Notes Form 2 Biology Notes Form 3 Biology Notes Form 4 Biology Questions and Answers Form One Biology Questions and Answers Form Two Biology Questions and Answers Form Three Biology Questions and Answers Form Four KCSE Revision Notes Form 1 - Form 4 - Aqa a2 biology essay help Subjects Biology Notes FAQ Form Please aqa a2 biology essay help your question in the form below.
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