Animal Physiology: Systems, Homeostasis & Disease

12 methods · 18 questions

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The list-of-statements biology item (options none, 1 only, 1 and 2, all) is usually decided by finding the clause whose direction is wrong. The examiner's favourite traps invert cause and effect, flip an increase for a decrease, or assert a proportionality that the data break. Check the direction of each clause against the real mechanism or the numbers and discard any that runs backwards, which often leaves none or one standing.

Trigger: an MCQ whose answer options are combinations of numbered statements.

Instances:
(i) reversed cause and effect: air entering the lungs is the result of the ribcage moving, not its cause.
(ii) reversed sign: hard exercise lowers pH through lactic acid, it does not raise it.
(iii) false proportionality: blood output is directly proportional to heart rate only if their ratio is constant, but the output peaks then falls, so it is not; and check any percentage exactly, 4.0 to 5.0 is 25 percent, not 20.

Linked questions (3)

NSAA 2021 Section 1, Part D (Biology questions) · Q68

A person ran on a treadmill for 360 seconds. Their rates of aerobic and anaerobic respiration were measured at the start and at the end of the time. The table shows the results.

rate of aerobic respiration / arbitrary units rate of anaerobic respiration / arbitrary units time = 0 seconds 1.01 0.01 time = 360 seconds 5.77 3.67

Physiological changes occured in the person during this time.

Which of the following statements is/are correct during the 360 seconds?

1. There was an increase in pH that caused a change in the shape of the respiratory enzyme's active sites.
2. Part of the increase in the rate of cellular respiration may have been due to a temperature increase in the muscles.
3. More carbon dioxide needed to be removed from the muscle cells.

Anone of them
B1 only
C2 only
D3 only
E1 and 2 only
F1 and 3 only
G2 and 3 only
H1, 2 and 3

Worked solution

Answer:G

During the run the rate of anaerobic respiration rose from almost nothing to 3.67 units, producing lactic acid, which lowers the pH of the muscle; there was no increase in pH, so statement 1 is wrong.

Respiration releases heat, so working muscles warm up, and warmer enzymes work faster, so part of the rise in the rate of respiration may be due to the temperature increase: statement 2 is correct.

Aerobic respiration rose more than fivefold, so far more carbon dioxide was produced and had to be removed from the muscle cells: statement 3 is correct.

The answer is G.

NSAA 2022 Section 1, Part D (Biology questions) · Q61

Which of the following is/are correct when a healthy human breathes in?

1. The ribcage moves up and out because air enters the lungs.
2. The volume of the thorax decreases and the thoracic pressure increases.
3. Energy is required to contract the intercostal muscles but not the diaphragm.

Anone of them
B1 only
C2 only
D3 only
E1 and 2 only
F1 and 3 only
G2 and 3 only
H1, 2 and 3

Worked solution

Answer:A

When breathing in, the intercostal muscles and the diaphragm both contract: the ribcage moves up and out and the diaphragm flattens, so the volume of the thorax increases and the pressure inside it falls, drawing air into the lungs.

Statement 1 reverses cause and effect: the muscles moving the ribcage up and out is what draws air in, not the other way round. Statement 2 is wrong because the volume of the thorax increases and the pressure decreases on breathing in. Statement 3 is wrong because both the intercostal muscles and the diaphragm are muscles, and both need energy to contract.

None of the statements is correct.

The answer is A.

NSAA 2023 Section 1, Part D (Biology questions) · Q69

The table shows the relationship between heart rate and blood output from the left ventricle of a healthy human heart.

heart rate / beats per minute blood output each minute / dm^{3} 55 4.0 70 5.0 80 5.2 90 5.6 120 6.0 140 6.0 150 5.8 175 4.6

Which of the following statements is/are correct?

1. The volume of blood pumped out of the heart each minute is directly proportional to the heart rate.
2. When the heart rate increased from 55 to 70 beats per minute, the blood output from the heart increased by 20%.
3. Blood output from the heart to the lungs will be less than that to the rest of the body.

Anone of them
B1 only
C2 only
D3 only
E1 and 2 only
F1 and 3 only
G2 and 3 only
H1, 2 and 3

Worked solution

Answer:A

Statement 1 is wrong: if output were directly proportional to heart rate the two would rise together in a fixed ratio, but the output rises to a peak of

6.0 d m^{3}

and then falls at the highest rates, so it is not proportional. Statement 2 is wrong: the output rises from 4.0 to

5.0 d m^{3}

, an increase of

1.0 \div 4.0 = 0.25

, that is 25%, not 20%. Statement 3 is wrong: the right side of the heart pumps blood to the lungs and the left side to the rest of the body, and because they are in series they pump the same volume each minute, so the output to the lungs is not less.

None of the statements is correct.

The answer is A.