a) Why is locomotion necessary in higher animals? b) Explain how bony fish are adapted to their habitats.(16m)

-
  a)  Why  is  locomotion  necessary  in  higher  animals?
- Animals  move  in  order  to  look  for  food;  mates;  escape  danger/predators;
- look  for  shelter/ suitable  environmental  conditions;  (4  mks)

 b) Explain  how  bony  fish  are  adapted  to  their  habitats.(16m)
- Have  streamlined  bodies;  to  reduce  friction;  body  is  covered  with  scales;  which  overlap backwards;  to  reduce  friction;  skin  produces  mucus;  which  covers  the  body  making  it slippery;  reducing  friction;  have  swim  bladder;  which  stores  air;  for  buoyancy  hence  make the  fish  float;  myotomes/muscle  blocks;  that  contract  alternately;  for  forward  thrust  in  water; lateral  line  system;  on  either  side  of  the  body  which  is  sensitive  to  pressure  and  water currents;  possess  fins;  that  are  used  for  locomotion:  tail/caudal  fins;  for  propulsion;  dorsal; and  anal  fins;  prevent  rolling;  pectoral  fin;  used  for  breaking/steering;  prevents  yawing/side to  side  movement;  controls  pitching;  pelvic  fins;  for  steering/pitching;
 Max.  16  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