How are the leaves of higher plants adapted to their functions?

-
  Broad  and  flattened  lamina;  to  increase  surface  area;  for  absorption  of  light;  thin  blade;  to reduce  distance  for  diffusion  of  gases  and  penetration  of  light  waves;  transparent  epidermis  and cuticle;  to  allow  light  to  penetrate  to  tissues;  cuticle  layer  absent  on  stomata;  to  allow  for  gaseous exchange;  one-cell  thick  epidermal  layer;  to  reduce  the  distance  over  which  sunlight  penetrates; palisade  cells  have  numerous  chloroplasts  containing  chlorophyll;  to  trap  maximum  amounts  of light  energy;  have  stomata  on  the  epidermis;  to  allow  for  gaseous  exchange;  and  control  of  water loss  through  transpiration;  palisade  layer  have  elongated  cells  located  at  right  angles  to  the  leaf surface;  for  maximum  absorption  of  light  energy;  spongy  mesophyll;  consists  of  spherical  and loosely-packed  cells;  to  create  air  spaces;  which  communicate  with  the  atmosphere  through stomata;  for  purposes  of  gaseous  exchange  and  control  of  water  loss;  veins  have  conducting tissues:  xylem;  for  movement  of  water  and  dissolved  mineral  salts;  phloem;  for  translocation  of manufactured  food;  Max.  20  mks 

Comments

Post a Comment

Popular posts from this blog

DESCRIBE THE ADAPTATIONS OF THE ILEUM TO ITS FUNCTION (20 MARKS)

-
Has secretory glands/crypts of lieberkuhn which secretes enzymes (maltase/sucrase/lactase/peptidase/lipase to complete digestion of sugars/proteins/lipids. Goblet cells secrete mucus which allows for smooth movement of food and protect wall of ileum from action of digestive enzymes Very long to provide large surface area for absorption. Highly folded/coiled to slow movement of food to allow more time for digestion/absorption/ and to increase surface area for absorption. Has numerous villi which increase surface area for absorption/microvilli which further increase surface area for absorption. Ileum wall/villi have thin epithelium which is only one cell thick to reduce distance over which digested food has to diffuse. Villi are highly vascularised/have a rich network of blood capillaries for rapid transport from small intestines and maintain a steep concentration gradient for rapid absorption. Villi have lacteals for absorption of fatty acids and glycerol Cells of ileum wall h...
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

KCSE 2010 Q8. Describe how a finned fish such as Tilapia moves in water. (20 marks)

-
The following describes how  a finned fish such as Tilapia moves in water . v       Water is denser than air. The density of water supports fish and provides a medium in which it swims. v       It has a streamlined body; reducing resistance, thus easily swims in the water. v       The scales overlap pointing backwards allowing water to pass over the fish without obstruction. Mucus is also secreted over the scales reducing friction during movement. v       They have a flexible backbone onto which segments of muscle blocks, myotomes, are attached. The muscles contract and relax bringing about undulating movements. v       The fish have fins that help in steering and balancing fish during swimming. v       The pectoral and pelvic fins are paired. They are used for braking, steering and v   ...
Read more