A-level Biology: Exchange of Substances, Energy Transfers, Responses of Organisms

A student correctly plotted the right ventricle pressure on the same grid as the left ventricle pressure in Figure 3 Describe one way in which the student's curve would be similar to and one way it would be different from the curve shown in Figure 3. (2) - - The position of the peaks would occur at the same time - Student's curve would occur at a lower pressure - as right ventricle only exerts enough pressure to pump blood to the lungs At P on Figure 3, the pressure in the left ventricle is increasing. At this time, the rate of blood flow has not yet started to increase in the aorta Use evidence from Figure 3 to explain why. (2) - - The pressure in the aorta is higher than in the ventricles at this point causing the semi-lunar valve to close - ∴ blood flow cannot move into the aorta At Q on Figure 3 there is a small increase in pressure and in rate of blood flow in the aorta. Explain how this happens and its importance (2) - - Aorta contains lots of elastin fibres that allows it to maintain blood pressure via elastic recoil - Elastic recoil causes an increase in pressure by forcing the blood forwards - this ensures blood will reach tissues for gas exchange Calculate how many times greater the mean growth rate per day was using 37.5g potassium nitrate than using 37.5g ammonium sulphate. Assume the mean biomass of the spinach plants at the start of the investigation was 0.5g per pot (1) - 1. From graph: biomass of KNO3 at 37.5g = 4.9g biomass of NH3SO4 at 37.5g = 3.7g 2. 4.9-0.5 = 4.4g 3.7-0.5 = 3.2g 3. 4.4/3.2 = 1.375 = 1.4 x greater (1dp)