Give reasons for the following:
(ii) Urine is slightly thicker in summer than in winter.
During summer, more water is lost in the form of sweat, so there is more reabsorption of
water from the kidney tubules into the blood so as to maintain the concentration of the blood. Thus, the urine is more concentrated and thicker to prevent excessive loss of water ad maintain osmotic balance.
In winter, perspiration is highly reduced, so smaller amounts of water
is reabsorbed by the kidney tubules, making the urine more dilute.
With reference to the human ear, answer the following questions:
(ii) Name the three small bones present in the middle ear. What is the biological term
for them collectively?
Give reasons for the following:
People living in hilly regions usually suffer from simple goitre.
(b) Give reasons for the following:
(iii) Potato cubes when placed in water become firm and increase in size.
Give reasons for the following:
(v) Photosynthesis is considered as a process supporting all life on Earth.
With reference to the functioning of the eye, answer the following questions:
(i) What is power of accommodation of the eye?
With reference to the human ear, answer the following questions:
(i) Give the technical term for the structure found in the inner ear.
Give reasons for the following:
(iv) A matured mammalian erythrocyte lacks nucleus and mitochondria.
With reference to the functioning of the eye, answer the following questions:
(iv) Name the cells of the retina and their respective pigments which get activated (1)
in dark and (2) in light
