NSAA 2020 Biology PART D

• A.none of them
• B.1 only
• C.2 only
• D.3 only
• E.1 and 2 only
• F.1 and 3 only
• G.2 and 3 only
• H.1, 2 and 3

Answer: H

• A.1 only
• B.2 only
• C.3 only
• D.4 only
• E.1 and 2 only
• F.1 and 3 only
• G.1 and 4 only
• H.2 and 4 only

Answer: F

• A.none of them
• B.1 only
• C.2 only
• D.3 only
• E.1 and 2 only
• F.1 and 3 only
• G.2 and 3 only
• H.1, 2 and 3

Answer: G

The diagram shows part of the carbon cycle.

Which row identifies the correct descriptions for boxes P, Q, R and S?

• A.CO2 in atmosphere: P, carbon-rich compounds in animals: Q, carbon-rich compounds in decomposers: R, carbon-rich compounds in plants: S
• B.CO2 in atmosphere: Q, carbon-rich compounds in animals: P, carbon-rich compounds in decomposers: S, carbon-rich compounds in plants: R
• C.CO2 in atmosphere: S, carbon-rich compounds in animals: Q, carbon-rich compounds in decomposers: R, carbon-rich compounds in plants: P
• D.CO2 in atmosphere: Q, carbon-rich compounds in animals: S, carbon-rich compounds in decomposers: P, carbon-rich compounds in plants: R
• E.CO2 in atmosphere: S, carbon-rich compounds in animals: R, carbon-rich compounds in decomposers: Q, carbon-rich compounds in plants: P
• F.CO2 in atmosphere: R, carbon-rich compounds in animals: S, carbon-rich compounds in decomposers: P, carbon-rich compounds in plants: Q
• G.CO2 in atmosphere: P, carbon-rich compounds in animals: R, carbon-rich compounds in decomposers: Q, carbon-rich compounds in plants: S
• H.CO2 in atmosphere: R, carbon-rich compounds in animals: P, carbon-rich compounds in decomposers: S, carbon-rich compounds in plants: Q

Answer: D

The diagram shows two human gametes, cell P and cell Q, fusing to form cell R.

Cell P carries an additional copy of one of its chromosomes so that it has one more chromosome than cell Q.

Cell R divides to form two cells S and T.

S and T grow into two separate individuals.

Using this information, which row shows the correct number of chromosomes in the nucleus of cell R and in the nucleus of cell T?

• A.cell R: 23, cell T: 24
• B.cell R: 24, cell T: 47
• C.cell R: 24, cell T: 48
• D.cell R: 46, cell T: 46
• E.cell R: 47, cell T: 24
• F.cell R: 47, cell T: 47
• G.cell R: 92, cell T: 47
• H.cell R: 93, cell T: 93

Answer: F

Pepsin and trypsin are both protease enzymes found in the human digestive system.

The graph shows how the activity of both enzymes varies with pH.

In the human digestive system:

1 pepsin is most active in the stomach.

2 trypsin would be inactive in the stomach.

3 pepsin could be a substrate for trypsin.

4 pepsin is most active at low acidity and trypsin most active at high acidity.

Which statements are correct?

• A.1 and 2 only
• B.1 and 3 only
• C.1 and 4 only
• D.2 and 3 only
• E.2 and 4 only
• F.3 and 4 only
• G.1, 2 and 3 only
• H.2, 3 and 4 only

Answer: G

• A.organ 1: kidney, organ 2: small intestine, organ 3: chambers of the right side of the heart
• B.organ 1: kidney, organ 2: chambers of the right side of the heart, organ 3: small intestine
• C.organ 1: small intestine, organ 2: kidney, organ 3: chambers of the right side of the heart
• D.organ 1: small intestine, organ 2: chambers of the right side of the heart, organ 3: kidney
• E.organ 1: chambers of the right side of the heart, organ 2: small intestine, organ 3: kidney
• F.organ 1: chambers of the right side of the heart, organ 2: kidney, organ 3: small intestine

Answer: F

• A.1 only
• B.2 only
• C.3 only
• D.1 and 2 only
• E.1 and 3 only
• F.2 and 3 only
• G.1, 2 and 3

Answer: F

• A.none of them
• B.1 only
• C.2 only
• D.3 only
• E.1 and 2 only
• F.1 and 3 only
• G.2 and 3 only
• H.1, 2 and 3

Answer: C

• A.none of them
• B.1 only
• C.2 only
• D.3 only
• E.1 and 2 only
• F.1 and 3 only
• G.2 and 3 only
• H.1, 2 and 3

Answer: B

• A.none of them
• B.1 only
• C.2 only
• D.3 only
• E.1 and 2 only
• F.1 and 3 only
• G.2 and 3 only
• H.1, 2 and 3

Answer: C

The graph shows the mass of product produced over time for an enzyme-controlled reaction in two different conditions, X and Y. All other variables were kept constant.

Which of the following could be correct for this graph?

1 Condition X is a higher pH than condition Y.

2 Condition X has less substrate supplied than condition Y.

3 Condition X is a lower pH than condition Y.

4 Condition X has more substrate supplied than condition Y.

• A.none of them
• B.1 and 2 only
• C.1 and 3 only
• D.1 and 4 only
• E.2 and 3 only
• F.2 and 4 only
• G.3 and 4 only
• H.1, 2, 3 and 4

Answer: C

A student investigated the endothermic reaction of photosynthesis in pondweed. The student set up the apparatus as shown in the diagram.

The experiment was left for 5 minutes and the distance moved by the gas bubble along a capillary tube of 2 mm diameter was recorded. Using these values, the rate of gas production is $2\text{mm}^3$ per minute.

Which row of the table is correct?

• A.total distance moved by the gas bubble during the experiment / mm: 0.5, reason why the reaction is described as endothermic: the reaction releases energy, observations if the light source was moved further from the pondweed: the gas bubble moves more slowly to the right
• B.total distance moved by the gas bubble during the experiment / mm: 0.5, reason why the reaction is described as endothermic: the reaction takes in energy, observations if the light source was moved further from the pondweed: the gas bubble moves more slowly to the left
• C.total distance moved by the gas bubble during the experiment / mm: 2.0, reason why the reaction is described as endothermic: the reaction releases energy, observations if the light source was moved further from the pondweed: the gas bubble moves more slowly to the left
• D.total distance moved by the gas bubble during the experiment / mm: 2.0, reason why the reaction is described as endothermic: the reaction releases energy, observations if the light source was moved further from the pondweed: the gas bubble moves more slowly to the right
• E.total distance moved by the gas bubble during the experiment / mm: 2.5, reason why the reaction is described as endothermic: the reaction takes in energy, observations if the light source was moved further from the pondweed: the gas bubble moves more slowly to the left
• F.total distance moved by the gas bubble during the experiment / mm: 2.5, reason why the reaction is described as endothermic: the reaction takes in energy, observations if the light source was moved further from the pondweed: the gas bubble moves more slowly to the right
• G.total distance moved by the gas bubble during the experiment / mm: 10.0, reason why the reaction is described as endothermic: the reaction releases energy, observations if the light source was moved further from the pondweed: the gas bubble moves more slowly to the left
• H.total distance moved by the gas bubble during the experiment / mm: 10.0, reason why the reaction is described as endothermic: the reaction takes in energy, observations if the light source was moved further from the pondweed: the gas bubble moves more slowly to the right

Answer: H

The abundance of a plant species in a habitat can be measured in different ways:

• the density (the number of that plant species per $m^2$)
• the frequency (the number of quadrats in which the plant species occurs)

The abundance of a plant species in a $100 m^2$ area of grassland was measured. The diagram below represents this area of grassland. Each black circle represents one individual of the plant species in this area of grassland.

Two different size quadrats were used to sample the area:

• large quadrat ($50 \text{ cm} \times 50 \text{ cm}$)
• small quadrat ($10 \text{ cm} \times 10 \text{ cm}$)

The area is sampled randomly, first using 10 large quadrats and then a second time using 10 small quadrats.

Which of the following statements is/are correct?

1 The overall density in the grassland calculated from sampling with either size quadrat will always be the same.

2 The overall density in the grassland calculated from sampling will always be 1 plant per $m^2$.

3 The frequency obtained using the small quadrat will always be lower than that obtained with the large quadrat.

• A.none of them
• B.1 only
• C.2 only
• D.3 only
• E.1 and 2 only
• F.2 and 3 only
• G.1 and 3 only
• H.1, 2 and 3

Answer: A

The diagram shows the changes in the volume of the ventricles, and the ECG trace that accompanies those changes, during two consecutive heart beats.

Which row is correct about the events happening at X, Y and Z?

• A.at X blood is being pumped into: aorta, at Y valves between atria and ventricles are: open, chambers of the heart contracting at Z: atria
• B.at X blood is being pumped into: aorta, at Y valves between atria and ventricles are: closed, chambers of the heart contracting at Z: atria
• C.at X blood is being pumped into: atria, at Y valves between atria and ventricles are: open, chambers of the heart contracting at Z: ventricles
• D.at X blood is being pumped into: atria, at Y valves between atria and ventricles are: closed, chambers of the heart contracting at Z: ventricles
• E.at X blood is being pumped into: pulmonary artery, at Y valves between atria and ventricles are: open, chambers of the heart contracting at Z: ventricles
• F.at X blood is being pumped into: pulmonary artery, at Y valves between atria and ventricles are: closed, chambers of the heart contracting at Z: ventricles
• G.at X blood is being pumped into: pulmonary vein, at Y valves between atria and ventricles are: open, chambers of the heart contracting at Z: atria
• H.at X blood is being pumped into: pulmonary vein, at Y valves between atria and ventricles are: closed, chambers of the heart contracting at Z: atria

Answer: A

The placenta is an organ that develops during pregnancy. One function of the placenta is to allow the exchange of gases between the mother and the developing foetus.

The diagram represents the maternal and foetal blood flow between P and Q in a section of the placenta of a healthy small mammal. The concentration of oxygen in both maternal and foetal blood was measured at regular distances along this section.

Which graph illustrates the concentration of oxygen in both maternal and foetal blood between P and Q?

• A.Graph A
• B.Graph B
• C.Graph C
• D.Graph D
• E.Graph E
• F.Graph F

Answer: C

• A.red blood cells in plasma: ✓, plant cells in a 0.5 mol dm⁻³ sucrose solution: ✓, red blood cells in water: x, plant cells in water: x
• B.red blood cells in plasma: x, plant cells in a 0.5 mol dm⁻³ sucrose solution: x, red blood cells in water: ✓, plant cells in water: ✓
• C.red blood cells in plasma: x, plant cells in a 0.5 mol dm⁻³ sucrose solution: ✓, red blood cells in water: ✓, plant cells in water: x
• D.red blood cells in plasma: x, plant cells in a 0.5 mol dm⁻³ sucrose solution: x, red blood cells in water: x, plant cells in water: ✓
• E.red blood cells in plasma: ✓, plant cells in a 0.5 mol dm⁻³ sucrose solution: ✓, red blood cells in water: ✓, plant cells in water: x
• F.red blood cells in plasma: ✓, plant cells in a 0.5 mol dm⁻³ sucrose solution: ✓, red blood cells in water: x, plant cells in water: ✓

Answer: C