Surface Area To Volume Ratio - Mark Scheme Answers (studymind)

Question 1

The oxygen dissociation curve for haemoglobin shifts to the right during vigorous exercise.

Explain the advantage of this shift. 3m

Answer 1

1. Lower affinity for oxygen / releases more oxygen / oxygen is released quicker /
   oxygen dissociates / unloads more readily;
2. (To) muscles / tissues / cells
3. (For) high / rapid respiration;

Question 2

(i) Explain how the body shape of a Weddell seal is an adaptation to living in a
cold environment.

Answer 2

1. Small SA:VOL;
2. (So) reduces heat loss / (more) heat retained;

Question 3

Describe and explain the changes in the rate of blood flow to the different
organs during a long dive.

Answer 3

1. Brain is the same, others fall
2. Brain controls other organs / remains active / needs constant supply of oxygen;
3. Lungs not used / are used less / seal is not breathing / heart rate decreases / heart pumps less / blood diverted to muscles;

Question 4

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs.

Details of breathing are not required.

Answer 4

1. Trachea and bronchi and bronchioles;
2. Down pressure gradient;
3. Down diffusion gradient;
4. Across alveolar epithelium.
5. Across capillary endothelium / epithelium.

Question 5

(a) One theory of translocation states that organic substances are pushed from a high
pressure in the leaves to a lower pressure in the roots.
Describe how a high pressure is produced in the leaves.

Answer 5

1. Water potential becomes lower / becomes more negative (as sugar enters phloem)
2. Water enters phloem by osmosis;
3. Increased volume (of water) causes increased pressure.

Question 6

During their experiment, the scientists ensured that the rate of photosynthesis of
their plants remained constant.
Explain why this was important.

Answer 6

1. Rate of photosynthesis related to rate of sucrose production;
2. Rate of translocation higher when sucrose concentration is higher.

Question 7

The scientists concluded that some translocation must occur in the spaces in the
cell walls.
Explain how the information in the figure above supports this conclusion.

Answer 7

1. Rate of translocation does not fall to zero / translocation still occurs after

120 minutes;
2. But sucrose no longer able to enter cytoplasm of phloem cells.

Question 8

(a) Describe and explain the mechanism that causes forced expiration.

Answer 8

1. Contraction of internal intercostal muscles;
2. Relaxation of diaphragm muscles / of external intercostal muscles;
3. Causes decrease in volume of chest / thoracic cavity;
4. Air pushed down pressure gradient.

Question 9

Suggest how the environmental conditions have resulted in adaptations of
systems using Model A rather than Model B.

Answer 9

1. Water has low(er) oxygen partial pressure/concentration (than air);
2. So (system on outside) gives large surface area (in contact with
   water)
3. Water is dense(r) (than air);
4. (So) water supports the systems/gills;

Question 10

Mammals such as a mouse and a horse are able to maintain a constant
body temperature.
Use your knowledge of surface area to volume ratio to explain the higher
metabolic rate of a mouse compared to a horse.

Answer 10

1. (Smaller so) larger surface area to volume ratio;
2. More/faster heat loss (per gram/in relation to body size);
3. (Faster rate of) respiration/metabolism releases heat;

Question 11

Describe the relationship between size and surface area to volume ratio of organisms.

Answer 11

As size increases, ratio (of surface area to volume) decreases;

Question 12

Explain why oxygen uptake is a measure of metabolic rate in organisms.

Answer 12

(Oxygen used in) respiration, which provides energy / ATP;

Question 13

A student who looked at these results said that they could not make a
conclusion about the relationship between stage of development and
metabolic rate.
Use information in the table to explain reasons why they were unable to
make a conclusion.

Answer 13

1. No information about egg;
2. So cannot compare all stages (in Table 2);
3. No statistical information / test / t-test / comparison of standard
   deviations;

Question 14

Name the process by which oxygen reaches the cells inside the body of a
tubifex worm.

Answer 14

(Simple) diffusion;

Question 15

Using the information provided, explain how two features of the body of
the tubifex worm allow efficient gas exchange.

Answer 15

1. Thin/small so short diffusion pathway;
2. Flat/long/small/thin so large surface area to volume ratio/surface area: volume;