2019 Bio paper

Question 1

The investigations were carried out in daylight.
The air bubble would not move if the investigations were done in the dark.
Explain why.

Answer 1

no photosynthesis
(so) stomata closed (as no
carbon dioxide needed)
(so) no transpiration

Question 2

Give one advantage of using an electron microscope compared with using a
light microscope.

Answer 2

Greater magnification and higher reolving power

Question 3

Explain how villi are adapted for efficient absorption of sugar molecules.

Answer 3

have (many) microvilli
* (to) increase surface area
* wall of villus only one cell thick or is thin
* capillaries are close to surface
* (so) short pathway
* good blood supply
* (to) transport food molecules away or to the body
* (and) maintain a diffusion gradient
* cells have many mitochondria
* (where) respiration takes place
* (where) energy is transferred
* (as) active transport requires energy
* energy is needed to absorb sugar / food / molecules

Question 4

People are encouraged to control their body mass with diet and exercise.
Describe how the balance between the mass of food eaten and the amount of
exercise a person does controls body mass.

Answer 4

increased energy intake
if more food eaten
* if exercise more, more
energy is transferred /
released
* if more energy is taken in
than is transferred body
mass increases
or
if less energy is taken in
than is transferred body
mass decreases
* if energy intake = energy
transferred body mass
stays the same

Question 5

0 5 . 1 How can oxygen production be used to show the rate of photosynthesis?

Answer 5

measure the volume of oxygen
produced in a given time
or
when more oxygen is produced
in a given time the rate of
photosynthesis is faster

Question 6

The light intensity you gave in Question 05.3 may not give the farmer maximum profit.
Explain why.

Answer 6

there is a cost for heating the
greenhouse
there is a cost for increasing the
carbon dioxide in the
atmosphere (of the greenhouse)
(therefore) the additional costs
might exceed the (additional)
sale price / profit

Question 7

0 5 . 5 Explain the results when the light intensity was 0 lux.

Answer 7

when there is no light there is no
photosynthesis
(so) no oxygen is produced
(but) respiration happens (all the
time) and oxygen is used
(therefore) the net / overall
oxygen production is negative

Question 8

The lamp gets warm when it is on. This causes the temperature of the water box
to increase.
0 1 . 3 Explain how an increase in temperature would affect the results of this investigation.

Answer 8

bubbles (of gas) would be
produced faster
(because) enzymes work faster

Question 9

0 1 . 4 Suggest one way the investigation could be improved so the temperature of the water

Answer 9

use an LED (lamp)
* place a tank / beaker of water
between the lamp and tube /
pondweed
* put the tube in a beaker of
water
* put the tube in a
(thermostatically controlled)
water bath
* place a piece of glass
between the lamp and tube /
pondweed

Question 10

Suggest two improvements to the investigation so the results would be more valid.
Do not refer to controlling the temperature of the water phot exp

Answer 10

measure the volume of gas
produced
* allow the pondweed time to
equilibrate
* repeat and calculate a mean
or
repeat and remove anomalies
* control the concentration of
carbon dioxide (in the water)
* use the same bulb / lamp