Biology Paper 2
暂无描述。系统推荐的高质量记忆内容，适合每天坚持背诵学习。
卡片预览 (8 张)
Water lilies have stomata on the upper surface of the leaves. Explain why water lilies have no stomata on the lower surface of the leaves.
• lower surface of leaf is not in contact with air • so gas exchange cannot occur
Describe how this sugar is transported from the leaves to the flowers of the water lily
• in the phloem • dissolved in water • by translocation • using active transport
One water lily plant was brought from America 10 years ago and planted in the lake shown in Figure 2. Explain why this non-indigenous plant now covers the whole surface of the lake.
• because conditions allowed adaption to the conditions • it outcompeted the natural plants • therefore it reproduces
Describe how starch is broken down into glucose.
• enzymes like amalyse • starch fits into the active site • bonds between glucose molecules in starch broken
The food is mashed before the trypsin is added. Explain the advantage of mashing the food before adding the trypsin.
• to increase the surface area of the food • so trypsin will break down more protein
Explain how one structure of a vein helps the blood return to the heart.
• veins contain valves • which prevent the backflow of blood
The stroke volume for person B before exercising was 61ml per beat. Calculate the cardiac output for person B before exercising. Give your answer in litres per minute.
• 65 x 61 = 3965 • 3965 / 1000 = 3.965 litres
The cardiac output for person A during exercise was 5.5 litres per minute. Explain why the heart rate for person A needed to be higher than the heart rate for person B during exercise.
• person A had a lower stroke volume • pumps less blood out per beat • so needed to have a higher heart rate to get a similar cardiac output