KCSE PIVOT BIOLOGY

How are sieve tube elements adapted to their function.[4m] Name the polysaccharides found in the following structures:[2m]    Exoskeleton Xylem vessels State three forces that maintain transpiration stream. [3m]       Name the tissue that is removed when the bark of a dicotyledonous plant is ringed.[1m]    What is the destination of materials translocated in plants.[2m]     An experiment was set-up as shown below to investigate a certain plant process:                                                                What process was being investigated above?[1m] With a reason in each case what observation was made if;             i.       ...

(i) Blood has two broad functions namely protective and transport. Describe how the blood protects the body. (4 marks) White blood cells; – engulf; and destroy bacteria/pathogen;  By producing antibodies; which neutralise bacterial toxins; Blood platelets; – Cause clotting; on fresh wounds preventing entry of bacteria into tissues prevent loss of blood, water; and mineral salts;.  (ii) Describe the structural adaptation of the mammalian heart to its function. (16m) It is muscular/has cardiac muscles; which are myogenic (do not need nervous stimulation) to pump blood; It is supplied by vagus and sympathetic nerves; which controls to rate of heart beat depending on body’s physiological requirements; It has triscupid valves; and bicuspid valves between atrium and ventricles which prevent back flow of the blood into the right and left ventricles respectively;. Presence of valvular tendons attached to the walls of ventricles and to the atria –ventricular walls...

 a) Give the functions of the skin in organisms. (6mks)  It protects the underlying tissues against mechanical injury, UV-light rays and entry of pathogens; (Rej. germs)  As an excretory organs, it enables organisms to eliminate excess water, ions and traces of urea;  As an sensory organ, it enables the organisms to be aware of deviations in pressure, touch and  temperature from the external environment;  It is a thermoregulator such that it enables the body to lose excess heat to lower its temperature back to norm or may enable the organisms to store its heat if the temperature is lower and hence raise it back to the norm;  It takes part in osmoregulation by enabling the body fluids to get rid of excess water or excess ions;  It takes part in the regulation of the pH of body fluids by enabling the body to get rid of either Hydrogen ions or bicarbonate ions;  (b) How is the mammalian skin modified to enable it perform its fu...

  a) Explain the factors that affect the rate of transpiration in plants. (12 mks)   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.  Wind; carries away moisture around the plant and increases the capacity for air to hold water; which then  increases the rate of water loss/transpiration in plants.   Higher relative humidity; reduces the capacity for air to hold water; which causes lowering of water  loss/transpiration in plants.  Higher amount of water in the soil; makes the plant to absorb excess water which increases the need  f or the plant to get rid of it through faster transpiration;  If the leaf is broader and has numerous and larger open stomata; the s...

 What is the role of the liver in the maintenance of a constant level of materials in the body. (20mks)  Regulation of blood sugar level; under the influence of insulin; and glucagon (hormones).  When there is excess sugar; the hormone insulin stimulates liver cells to convert it to glycogen; some blood sugar is converted to fats for storage;   When the blood sugar level is below normal: the hormone glucagon stimulates liver cells to convert glycogen to glucose;   Regulation of amino acids; excess amino acids; are deaminated; by the liver (cells) leading to  formation of urea; which is transported by the blood to the kidney; for elimination;    Production of heat: the liver is involved in the thermoregulation due to many metabolic, activities;  taking place in the liver cells a lot of heat is generated which is distributed to the entire body;   Detoxification of toxic substances; (s...

                     Adaptations of the Respiratory System to Gaseous Exchange The nostrils & inner passages of air are lined with ciliated epithelial cells; the cilia movements cause a sweeping action of mucus containing dust & pathogens; towards the pharynx for swallowing hence preventing their entry into the air ways; The nostrils & inner air passages have goblet cells which secrete mucus to trap dust particles, therefore cleaning the air; The lining of nostrils and air passages has a rich supply of blood, which keeps the incoming air warm and moist for faster diffusion in the lungs; The epiglottis  on top of the trachea prevent food, drinks and other solid particles from going in the trachea during swallowing; Lungs provide numerous alveoli; to provide a large surface area; for efficient gaseous exchange; Alveoli wall and blood capillary wall are made of squamous epithelium cells which are thin; to pr...

Explain how the mammalian heart is adapted to perform its function. (mks) - Muscular to pump blood over long distance; - Myogenic cardiac muscles which contract and relax rhythmically without fatigue; hence heart continues pumping; - Cardiac muscle fibres interconnected to form a network of fibre to ensure rapid and uniform spread of excitation throughout the walls of the heart; - Heart divided into 4 chambers which are hollow to accommodate more blood; - Ventricles have thicker walls than auricles to generate higher pressure to drive blood over long distance into more elaborate  circulation/to the lungs and to all body tissues;  - Walls of left ventricles are thicker than those of right ventricles to generate more pressure to pump blood to longer distance in the systemic circulation/rest of the body; - Longitudinal septum which separates the heart into two halves to prevent mixing of oxygenated and deoxygenated blood; - Valves to prevent ...

Describe how the mammalian heart is ADAPTED to its function                 (20mks) Explain how predators are ADAPTED to capture their prey. 14mks Describe how hydrophytes are ADAPTED to living in areas with abundant water.(8mks) Describe the ADAPTATIONs of seeds and fruits to dispersal.   20mks Describe how the xerophytes are ADAPTED to their habitats.        20mks Describe how the mammalian skin is ADAPTED to its functions.             ( 20mks) Describe how a male reproductive system is ADAPTED to its functions. 20mks Describe the ADAPTATIONs of wind pollinated flowers. (20mks) Describe how herbivorous mammals are ADAPTED to their mode of feeding. (16mks) Explain the ADAPTATIONs of respiratory surfaces to their functions. (10 marks) Explain how a body fish is ADAPTED for movement in its habitat.               (20mks) Describe h...