(I) BLOOD HAS TWO BROAD FUNCTIONS NAMELY PROTECTIVE AND TRANSPORT. DESCRIBE HOW THE BLOOD PROTECTS THE BODY. (4 MKS) (II) DESCRIBE THE STRUCTURAL ADAPTATION OF THE MAMMALIAN HEART TO ITS FUNCTION. (16MKS)

-
(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; to prevent  atria-ventricular valves from turning inside out due to changes in the pressure in the ventricles.
  • Heart is supplied by coronary artery; which supplies food and oxygen to the cardiac muscles for their pumping action; the coronary vein in the heart removes metabolic wastes;
  • The heart is enclosed by the pericardial membrane; that secretes a fluid which lubricates it reducing friction on the walls as it pumps; The heart is divided into two by the atria –ventricular septum; that prevent mixing of oxygenated blood and deoxygenated blood;
  • The left ventricles has a thick muscular wall; to pump blood at higher pressure to the distant body tissues;.


Comments

Post a Comment

Popular posts from this blog

(a) Define digestion. [2 m] (b) Describe the digestion of a piece of ugali in a human digestive system from the mouth until its assimilation. [18mks]

-
(a) Define digestion It is break down of complex insoluble; v food substance into simple soluble food substances; v 2max (b) Describe the digestion of ugali; Digestion of ugali begins in the mouth;v ugali is chewed by the teeth to increase large surface areav for action of salivary amylase / ptyalin; vThe food mixes with saliva produced by salivary glands;v Saliva contains mucus and enzyme ptyalin. Mucus moistens, softens and lubricates the food;v ptyalin speeds up the conversion of starch to maltose;v ugali is made into bolus in the mouth;v The bolus moves along the oesophagus and prestalsis / by contraction and relaxation of circular and longitudinal muscles into the stomach;v The digestion continues until ugali become acidic since the stomach does not contain carbohydrase / carbohydrate digesting enzymes no digestion of ugali takes place here.v Ugali now...
Read more

Explain how structures of the human ear are adapted to their functions. (20 marks)

-
Image
The pinna;- is funnel shaped to trap sound waves; cartilaginous to maintain the funnel shape; collects and directs sound waves into the external auditory meatus ear; The external auditory canal; - a tube connected to the pinna that directs sound waves from the pinna to the eardrum lining the auditory canal; has hair that trap foreign particles; The canal contains wax-secreting cells; and hair which traps dust particles; and pathogenic bacteria hence prevent them from getting into the ear; The eardrum; - has a thin tough membrane; that easily vibrates when hit by sound waves; transferring them into vibrations. The ear ossiscles; - they act like a layer and they easily move forward and backward to amplify sound vibrations that hit them; The suspensory ligaments; - suspends the ear ossicles and prevents excessive vibration that would otherwise damage the inner parts of the ear; The eustachian tube - it connects the middle ear with the pharynx; and it equalises air pressure between...
Read more

EXPLAIN HOW ABIOTIC FACTORS AFFECT PLANTS. (20MKS)

-
 Explain how abiotic factors affect plants. (20mks) Abiotic factors. Wind; -On a windy day rate of transpiration increases since wind carries away water vapour leaving surrounding of leaves with low humidity; the lower the humidity the more the space in the atmosphere for water molecules to occupy. - Wind disperse fruits, seeds and spore; - Wind is an agent of pollination. - Strong winds break branches of trees and may even uproot some trees; Temperature; -Enzymes work best at optimum temperature; changes in temperature hence influence rate of photosynthesis/respiration; and other enzyme controlled biological reactions. -In aquatic environment temperature affects the percent of dissolved gases. Light; - green plants need light for photosynthesis; - some plants need light for flowering; photoperiodism; - some seeds (lettuce) require light for germination; - light affects opening and closing of stomata; which affects transpiration; gaseous exchange and photosynthesi...
Read more