a the maintenance of a constant internal environment in a mammal
b an animal whose temperature mainly fluctuates as a result of behavioural responses
c response to a change that increases the degree of change
d part of the brain which detects changes in the temperature and water potential of the blood
e series of reactions that form urea in the liver
2 Describe the difference between:
a receptors and effectors
Receptors detect, change/physical and chemical parameters, but effectors cause change Receptors are sensory, neurones/structures, but effectors are, muscles/glands
2 Describe the difference between:b excretion and osmoregulation
Excretion is getting rid of waste products of metabolism plus named example Osmoregulation is homeostatic control of water potential of body fluids
2 Describe the difference between: blood in the renal artery and blood in the renal vein.
Renal artery blood has: More oxygen Less carbon dioxide More urea Less optimal water potential Less optimal salt concentration ORA
i A pregnancy testing kit contains a testing ‘stick’ to detect a hormone in the urine. Explain how the stick detects this pregnancy hormone.
(Testing for) human chorionic gonadotrophin/hCG Hormone small so can pass from blood into filtrate (at Bowman’s capsule) Monoclonal/immobilised, antibodies/immunoglobulin, on stick Antibodies attached to, marker/dye Hormone, binds/complementary, to antibody (triggers) appearance of colour/line becomes visible
ii The urine of some high profile athletes has been tested and found to contain abnormally high levels of banned steroids or their metabolites. The pressure on these elite athletes to succeed in their sport leads some of them to resort to the use of these performance-enhancing steroids. Comment on whether the use of steroids should be permitted in sport.
Fairness/giving unfair advantage/does not give an ‘even playing field’ Idea of health risks/dangerous/unhealthy/fatal/side effects Specified health risk Idea of distrust of ‘outstanding’ performances/does not reflect athlete’s natural talent/sport should reflect athlete’s natural talent Idea of pressure to keep up with rival competitors Idea that can train for longer (without tiring)/can respire longer (without tiring)/can recover from injury quicker/can build up muscle mass
iii Name the kidney tissue within which the glomeruli are situated.
ii Describe and explain how the mass and concentration of urea changes between the Bowman’s capsule and the ureter.
Mass decreases from, Bowman’s capsule/filtrate, to, ureter/urine Due to reabsorption of nearly half by diffusion (in proximal convoluted tubule) Concentration increases from, Bowman’s capsule/filtrate, to, ureter/urine Due to relatively more water reabsorbed so urea dissolved in smaller volume
5 a Explain why the homeostatic control of oxygen, carbon dioxide, glucose, and temperature are necessary in a mammal.
To ensure enough O2 for respiration (in all cells) Because CO2 is acidic and change in pH, affects/denatures, enzymes To ensure enough glucose for respiration Because too high a temperature denatures enzymes and too low slows down their activity
b Describe how homeostatic control of temperature and water in a mammal are interlinked.
If temperature rises sweating causes body to lose water (and salts) Kidneys compensate by, producing a more concentrated urine/reabsorbing more water from distal convoluted tubule Due to effects of, ADH/anti-diuretic hormone