Which one of the following disorders is caused by the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule?
Sickle-cell anaemia results from a point mutation in the β-globin gene causing substitution of glutamic acid by valine at the sixth position.
Incomplete dominance is seen in Antirrhinum, co-dominance in ABO blood groups, pleiotropy in phenylketonuria and polygenic inheritance in human skin colour.
Molluscs generally respire through gills, reptiles through lungs, adult amphibians through lungs and skin, and Amoeba carries out cellular respiration.
Which of the following is not an example of convergent evolution?
Forelimbs of whales and bats are homologous organs that evolved from a common ancestor, representing divergent evolution. The other examples are analogous organs showing convergent evolution.
Arrange the following events occurring in Renin-Angiotensin mechanism in the correct order:
(A) Increase in blood pressure and glomerular filtration rate.
(B) Reabsorption of Na+ and water from distal parts of tubule due to aldosterone.
(C) Fall in glomerular filtration rate.
(D) Vasoconstriction by Angiotensin II and release of aldosterone.
(E) Renin converts angiotensinogen into Angiotensin I, followed by Angiotensin II.
A fall in GFR triggers renin release, producing angiotensin II, which causes vasoconstriction and aldosterone secretion. Aldosterone increases Na+ and water reabsorption, restoring blood pressure and GFR.
Choose the correct statements regarding population interactions between two species.
(A) In both parasitism and commensalism, only one species benefits and the other species is harmed.
(B) Both species benefit in mutualism.
(C) Both species benefit in commensalism.
(D) In parasitism, only one species benefits and the other species is harmed.
(E) In amensalism, one species is harmed and the other is unaffected.
Choose the correct answer from the options given below:
Mutualism benefits both species. In parasitism, one benefits while the other is harmed. In amensalism, one species is harmed whereas the other remains unaffected. Commensalism benefits one species without affecting the other.
In humans, respiration occurs in the following steps. Arrange these steps in the correct order.
(A) Diffusion of O2 and CO2 between blood and tissues.
(B) Diffusion of O2 and CO2 across the alveolar membrane.
(C) Pulmonary ventilation by which atmospheric air is drawn in and CO2-rich alveolar air is released out.
(D) Cellular respiration.
(E) Transport of gases by the blood.
Choose the correct answer from the options given below:
Respiration begins with pulmonary ventilation, followed by exchange of gases across the alveolar membrane, transport by blood, exchange between blood and tissues, and finally cellular respiration.
