Interaction and interdependenceIB Biology SL: Topic test

20 questions, 54 marks

IB Biology SL

Interaction and interdependence topic test

Total 54 marks

Name

Class

Date

1
A student investigates the activity of the enzyme amylase, which hydrolyses starch to maltose. Five test tubes containing identical starch solution and amylase solution are incubated at 10°C, 20°C, 30°C, 40°C and 50°C. Every 30 seconds a sample is tested with iodine solution, and the time taken for the iodine to stop turning blue-black (indicating no starch remains) is recorded. Results: 10°C, 480 s; 20°C, 210 s; 30°C, 95 s; 40°C, 60 s; 50°C, 310 s.
(a)
Which temperature gave the fastest rate of starch digestion, and what does this indicate about amylase?
[1 mark]
A40°C; this is close to amylase's optimum temperature, where successful collisions between enzyme and substrate are greatest without significant denaturation
B50°C; amylase works fastest at the highest temperature tested
C10°C; low temperature keeps the enzyme most stable
D30°C; the enzyme is only active over a narrow range around this single temperature
(b)
Which statement best explains why the reaction was slower at 50°C than at 40°C?
[1 mark]
AAt 50°C there was not enough substrate remaining
BAt 50°C the amylase became denatured, changing the shape of its active site so fewer substrate molecules could bind
CAt 50°C the amylase molecules moved too quickly to collide effectively with substrate
DAt 50°C the starch solution became more concentrated, slowing the reaction
(c)
Explain, in terms of substrate concentration, why the rate of reaction in the tube would be expected to decrease over the course of the 480 seconds at 10°C, even though the temperature does not change.
[2 marks]
Total for question 1: 4 marks
2
During a sprint, a runner's leg muscle cells briefly respire anaerobically once the local oxygen supply cannot keep pace with demand. A physiologist measures ATP production and lactate concentration in muscle samples taken immediately after (i) light jogging, where oxygen supply is adequate, and (ii) an all-out 100 m sprint, where oxygen supply is inadequate.
(a)
Which statement correctly compares aerobic and anaerobic cell respiration in the sprinter's muscle cells?
[1 mark]
AAnaerobic respiration produces more ATP per glucose molecule than aerobic respiration
BBoth types of respiration produce the same waste products
CAerobic respiration produces far more ATP per glucose molecule than anaerobic respiration, and requires oxygen and functioning mitochondria
DAerobic respiration does not require mitochondria, only anaerobic respiration does
(b)
Which waste product accumulates in the muscle cells specifically as a result of anaerobic respiration during the sprint?
[1 mark]
ACarbon dioxide
BWater
COxygen
DLactate
(c)
State two differences, other than ATP yield, between aerobic and anaerobic respiration in these muscle cells.
[2 marks]
Total for question 2: 4 marks
3
A student extracts pigments from spinach leaves and separates them by paper chromatography, using a solvent front that travelled 9.6 cm up the paper. Pigment 1 (green) travelled 8.6 cm, pigment 2 (yellow-green) travelled 7.9 cm, pigment 3 (yellow-orange) travelled 9.3 cm, and pigment 4 (blue-green) travelled 6.7 cm.
(a)
Calculate the Rf value of pigment 4, showing your working, and identify which of the four pigments is most likely to be carotene, given that carotene is known to have the highest Rf value of the main leaf pigments.
[3 marks]
(b)
Explain why photosynthetic pigments are separated by chromatography rather than being identified from a single measurement, and outline how a limiting factor, such as light intensity, could be investigated experimentally using a water plant, identifying the dependent and independent variables.
[4 marks]
Total for question 3: 7 marks
4
A person develops a bacterial throat infection. Chemoreceptors and other sensory pathways detect signals from the infection and, within the brain, the body's temperature set point is raised, triggering shivering and blood vessel constriction in the skin that raise core body temperature (a fever) from 37°C to 39°C over several hours. Meanwhile, in the lymph nodes of the neck, B-lymphocytes specific to antigens on the bacterium are activated with the help of helper T-lymphocytes, and begin to divide.
(a)
Explain how the nervous system coordinates the rise in body temperature described, and outline the role of the brain in this response.
[6 marks]
(b)
Explain the roles of helper T-lymphocytes and B-lymphocytes in producing an effective response to the bacterial antigens, and outline why this response will be faster if the same bacterium infects the person again in the future.
[6 marks]
Total for question 4: 12 marks
5
A physiologist measures the conduction speed of nerve impulses along several types of non-myelinated axon of different diameters, and also compares a myelinated and a non-myelinated fibre of similar diameter. Axon diameter 2 μm: 1.2 m s⁻¹. Axon diameter 10 μm: 4.0 m s⁻¹. Axon diameter 20 μm: 6.5 m s⁻¹ (non-myelinated). A myelinated axon of similar diameter (20 μm) conducts impulses at 70 m s⁻¹.
(a)
What relationship do the non-myelinated axon data suggest between axon diameter and conduction speed?
[1 mark]
AA negative correlation — speed decreases as diameter increases
BA positive correlation — speed increases as diameter increases
CNo correlation between the two variables
DConduction speed is constant regardless of diameter
(b)
Which statement best explains why the myelinated axon conducts impulses much faster than the non-myelinated axon of the same diameter?
[1 mark]
AMyelin insulates the axon, allowing the impulse to jump between the nodes of Ranvier along the fibre (saltatory conduction), which is faster than continuous conduction
BMyelinated axons have a wider lumen, allowing more ions to flow at once
CMyelinated axons use active transport of the impulse itself along the membrane
DMyelinated axons do not require ion pumps to generate a resting potential
(c)
State two roles of dendrites and the axon in a neuron's overall function of conducting an electrical impulse.
[2 marks]
Total for question 5: 4 marks
6
Ecology students estimate the population size of a beetle species in a meadow using capture–mark–release–recapture. On day 1 they capture and mark 84 beetles before releasing them. On day 3 they capture a second sample of 96 beetles, of which 24 carry a mark from the first capture.
(a)
Using the Lincoln index, what is the best estimate of the total beetle population in the meadow?
[1 mark]
A84
B96
C24
D336
(b)
Which assumption of the Lincoln index method, if violated by beetles dying between day 1 and day 3, would make the estimate less reliable?
[1 mark]
AMarked individuals must be a different species from unmarked ones
BThe marking method must change the colour of the whole beetle
CThe population is closed, with no significant deaths, births, immigration or emigration between sampling occasions
DSampling must occur on the same day for both captures
(c)
Suggest one reason the marking method used on the beetles should not affect their survival or behaviour, and state why random sampling is important when selecting the second sample of beetles.
[2 marks]
Total for question 6: 4 marks
7
In a grassland ecosystem, researchers measured the energy content of biomass at successive trophic levels over one year: producers (grasses), 22,000 kJ m⁻² yr⁻¹; primary consumers (grasshoppers), 2,100 kJ m⁻² yr⁻¹; secondary consumers (shrews), 190 kJ m⁻² yr⁻¹; tertiary consumers (owls), 15 kJ m⁻² yr⁻¹.
(a)
Calculate the percentage of energy transferred from producers to primary consumers, showing your working, and state the general term for this kind of loss of energy between trophic levels.
[3 marks]
(b)
Using the data, explain why an ecosystem such as this grassland could not support a fifth trophic level of consumers feeding on the owls, and outline why the biomass (rather than just the energy content) also decreases at each successive trophic level.
[4 marks]
Total for question 7: 7 marks
8
A student investigates the rate of aerobic cell respiration in a yeast suspension by measuring the volume of carbon dioxide gas collected in a gas syringe over 10 minutes, at four temperatures. At 15°C, 3.2 cm³ of gas was collected. At 25°C, 9.6 cm³. At 35°C, 15.8 cm³. At 55°C, 1.1 cm³.
(a)
Using collision theory and the concept of denaturation, explain the pattern of gas volumes collected across the four temperatures.
[6 marks]
(b)
Explain why gas is still produced even at 55°C, and describe how the student could determine whether the gas collected is a reliable measure of the rate of aerobic cell respiration, given that yeast can also respire anaerobically.
[6 marks]
Total for question 8: 12 marks

End of questions