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Question 1

(a) Topic: 1.3 (features of organisms)                                                                                                                                                              (b) Topic: 1.3 (features of organisms)                                                                                                                                                              (c) Topic: 9.1 (circulatory systems)                                                                                                                                                                (d)  Topic: 9.1 (circulatory systems)                                                                                                                                                                (e) Topic: 9.3 (blood vessels)                                                                                                                                                                            (f) Topic: 9.3 (blood vessels)

(a) Fig. 1.1 is a photograph of a fish. Fig. 1.2 is a photograph of an amphibian.

State two visible features that distinguish the fish in Fig. 1.1 from the amphibian in Fig. 1.2.

(b) Fish, amphibians and mammals are all vertebrate groups. State the name of one other vertebrate group.

(c) Fig. 1.3 shows the circulatory system of a fish. Fig. 1.4 shows the circulatory system of an amphibian.

Describe the similarities and the differences between the circulatory systems of the fish and the amphibian in Fig. 1.3 and Fig. 1.4.

(d) Explain the advantages of the type of circulatory system in mammals compared with the type of circulatory system in fish.

(e) Explain how the structure of arteries and veins relates to the difference in the pressure of the blood transported by these vessels.

(f) Table 1.1 shows the names of some organs and the name of the main artery that brings blood to the organ. Complete Table 1.1.

▶️Answer/Explanation

Ans 

(a) any two from:
(fish has)
fins / no legs / no limbs ;
scales / scaly skin ;
operculum ;
deeper body / larger ratio of depth to length

(b) reptiles / birds

(c) total of four from:
similarities to max 3:
1 both have, heart / blood vessels / capillaries / arteries / veins ;
2 (heart with) one ventricle / no (visible) septum ;
3 both have valves (in the heart) ;
4 blood flows through atrium and then ventricle ;
5 no (visible) separation of oxygenated and deoxygenated blood ; differences to max 3:
6 fish have capillaries in gills and amphibians have capillaries in lung and skin ;
7 fish have a single circulatory system and amphibians have a (incomplete) double circulatory system ;
8 fish has a 2-chambered heart / amphibian has 3-chambered heart ;
9 amphibians have two atria / fish have one atrium ;
10 amphibians have a separate circuit to the, gas exchange surface / AW ;
11 fish have one valve (in heart) / amphibians have three valves (in heart)

(d) any three from:
1 ref. to double (rather than single) circulatory system ;
2 (allows / maintains) high(er) blood pressure (to tissues / body) ;
3 for faster / more efficient, transport, (named) substances / blood ;
4 supports fast(er), metabolism / respiration ;
5 allows lower pressure to lungs ;
6 (lower pressure) allows more time for, gas exchange / absorption of oxygen ;
7 prevents damage to lungs / AW ;
8 AVP

(e) total of four from:
arteries to max 3
1 idea of arteries have thick walls to, withstand / cope with / deal with, high pressure ;
2 arteries have (thick layer of) elastic tissue to, stretch / recoil (due to the changing pressure) ;
3 arteries have (thick layer of) muscular tissue to change pressure ;
4 arteries have narrow(er) lumen to maintain high pressure ;
5 veins have valves to prevent backflow of blood (due to low pressure) ;
6 veins have, thin walls / large lumen, to provide less resistance to blood flowing at low pressure / allow large volumes of blood / AW ;
7 veins have thin walls so blood is moved by contraction of (surrounding) muscles / AW

(f)

Question 2

(a) Topic: 14.4 (homeostasis)                                                                                                                                                                              (b) Topic: 14.4 (homeostasis)

(a) Fig. 2.1 shows the internal body temperature of a human and the external environmental temperature during six hours in one day.

(i) The internal body temperature range is from 36.4°C to 37.0°C. State the range of the external environmental temperature shown in Fig. 2.1.

(ii) Explain the results for the internal body temperature shown in Fig. 2.1.

(b) Fig. 2.2 shows a cross‑section through human skin.

Table 2.1 shows the names of some parts of the skin, the letter identifying the part in Fig. 2.2 and its role in maintaining internal body temperature. Complete Table 2.1.

▶️Answer/Explanation

Ans 

(a)(i) 28.0 (°C) to 39.0 (°C)

(a)(ii) any six from:
1 (internal temperature is maintained by) homeostasis / negative feedback ;
2 external temperature detected by, (thermo)receptors / sensory neurones, in the skin ;
3 (nerve) impulses (via sensory neurones) to the brain ;
4 change / increase / decrease in, blood / internal / core, temperature is detected by the brain ;
5 (nerve) impulses are sent (via motor neurones) to (effectors in) the skin ; 6, 7, and 8 when environmental temperature below body temperature / body is cold / before 3½ hours:
6 vasoconstriction / arterioles become narrow ;
7 decrease in blood flow (to capillaries), to / in, the skin ;
8 shivering / increase in metabolism (to generate heat) / hairs raised (to trap air for insulation) ; 9, 10 and 11 when environmental temperature above body temperature / body is hot / after 3½ hours:
9 (increase in) sweating / produce sweat ;
10 vasodilation occurs / arterioles widen ;
11 increase of blood flow (to capillaries), to / in, the skin ;
12 AVP

(b)

Question 3

(a) Topic: 8.2 (water uptake)                                                                                                                                                                              (b) Topic : 18.2 (adaptive features)

(a) Fig. 3.1 shows a drawing of a root hair cell and Fig. 3.2 shows a drawing of a palisade cell.

Explain the reasons for the difference in the numbers of mitochondria and chloroplasts between the root hair cell and the palisade cell, shown in Fig. 3.1 and Fig. 3.2.

(b) Fig. 3.3 is a photomicrograph of a cross‑section of part of a xerophyte leaf.

 

(i) Explain why the part labelled A in Fig. 3.3 is a tissue.

(ii) Describe two ways the structure labelled B in Fig. 3.3 is adapted for its function.

(iii) Describe one way the leaves of xerophytes are adapted to their environment.

(iv) Describe one way the roots of xerophytes are adapted to their environment.

▶️Answer/Explanation

Ans 

(a) total of five from:
mitochondria to max 4:
1 more in root hair cell / ORA ;
2 (site of) aerobic respiration ;
3 to, release / provide, energy ;
4 for active, transport / uptake, of, minerals / ions / named ion(s) ;
5 up/against, a concentration gradient ; chloroplasts to max 4:
6 in palisade only / none in root hair cell ;
7 no light reaches root hair cells / cells are underground or in soil ; ora
8 (site of) photosynthesis ;
9 contain chlorophyll ;
10 transfers / changes, energy from light to, energy in chemicals / ATP ;
11 to synthesise, glucose / carbohydrate

(b)(i) group of, same (type) / similar, cells ;
carry out a, specific / same / common, function / role / job / task

(b)(ii) any two from:
thick (cell) wall / (cell) wall with lignin ;
no end or cross walls / continuous tube / no cell contents / hollow ;
wide lumen / wide (tube) / large cross-sectional area / large (internal)
diameter / AW ;
pits (in the walls)

(b)(iii) any one from:
thick (waxy) cuticles ;
small (leaves) / small surface area / needle-like / AW ;
rolled / curled (leaves) ;
(leaves reduced to / leaves are) spines / spikes ;
hairs ;
fleshy / swollen ;
few stomata ;
sunken stomata / stomata in grooves

(b)(iv) deep / long shallow / widespread / spreading / roots cover a wide area

 

Question 4

(a) Topic: 21.2 (Biotechnology)                                                                                                                                                                          (b) Topic: 21.2 (biotechnology)

(a) A student investigated the effect of lactase on three different liquids:
• milk
• lactose‑free milk
• sucrose solution.
The student used an indicator to test for the presence of glucose. A sample of each liquid was tested before and after treatment with lactase. The indicator turned brown in the presence of glucose. The indicator remained blue in the absence of glucose. Table 4.1 shows the results of the tests.

(i) Explain the results for the three liquids shown in Table 4.1.

(ii) The student kept the solutions at a temperature that was close to the optimum during the investigation. Using your knowledge of the effect of temperature on enzyme activity, explain why this was important.

(b) As part of a balanced diet, some governments recommend that children drink milk that has vitamin D added to it.
(i) Suggest the dietary reasons for this advice.

(ii) Describe what is meant by a balanced diet.

▶️Answer/Explanation

Ans 

(a)(i) any three from:
row 1 – lactase breaks down lactose into glucose (and galactose in milk) ;
row 2 – lactose-free milk has already been treated with lactase (so glucose is already present) ;
row 3 – sucrose, is not broken down / does not contain lactose / AW ; lactase is specific for breakdown of lactose / AW
OR
lactose only fits into active site of, lactase / enzyme

(a)(ii) any four from:
1 at optimum temperature maximum enzyme activity or rate of reaction OR outside the optimum / when cold / when hot, reduced, enzyme activity / rate of reaction ;
2 at optimum temperature maximum, successful collisions / enzymesubstrate complexes (ESCs) OR outside the optimum / when cold / when hot, fewer, successful collisions / enzyme-substrate complexes (ESCs) ;
3 as temperature increases kinetic energy increases / ora ;
4 ref to denaturation at, high temperatures / temperatures above optimum ;
5 (so) shape of active site changes ;
6 (so) lactase is no longer complementary to the lactose ;
7AVP ; e.g. ref. to temperature as a standardised variable

(b)(i) any two from:
milk contains, calcium ;
calcium / vitamin D, required for, healthy / strong / AW, teeth / bones ;
(calcium / vitamin D) prevent, rickets / any symptom of rickets ;
AVP

(b)(ii) ref. to all nutrients / all food groups / AW ; idea of nutrients in the, correct / appropriate / healthy, proportions / amounts
OR
to provide suitable amount of energy for, level of activity / (stated) lifestyle(s)

 

 

Question 5

(a) Topic: 8.3 (transpiration)                                                                                                                                                                (b) Topic: 8.3 (transpiration)                                                                                                                                                                      (c) Topic: 6.2 (leaf structure)

Fig. 5.1 is a graph showing the effect of temperature on the rate of transpiration from the upper and lower surfaces of a leaf that is provided with a constant supply of water

(a) Describe the results shown in Fig. 5.1.

(b) Explain reasons for the shape of the graph for the upper surface of the leaf at X and at Y in Fig. 5.1.

(c) Suggest how the structure of the lower surface differs from the upper surface of the leaf used in this investigation.

▶️Answer/Explanation

Ans 

(a) any three from:
rate of transpiration increases and then remains constant with increasing
temperature ; ora
(the rate of transpiration) is higher from the lower surface ;
rates of both become constant at (nearly) the same temperature ;
transpiration from lower surface increases, at a greater rate / faster, than from
the upper surface (in X)

(b) total of four from:
X to max 3:
as temperature increases and rate increases
1 the rate of evaporation from the mesophyll (cells) increases ;
2 the rate of diffusion of water vapour (through the stomata / from the leaf) increases ;
3 particles / molecules, have more kinetic energy / move faster ;
4 temperature is the limiting factor (for transpiration) ;
5 more stomata opening / stomata open wider ; Y to max 3: as temperature increases and rate remains constant
6 rate of diffusion of water vapour through stomata at a maximum ;
7 evaporation from mesophyll (cells) at a maximum ;
8 rate of movement of water in xylem slows ;
9 rate of uptake of water is at a maximum ;
10 the stomata are, all / fully, open ;
11 humidity / light intensity / number of stomata, is the limiting factor

(c) more stomata on the lower surface / lower surface has a thinner cuticle ; ora

 

Question 6

(a) Topic: 19.4 (populations)                                                                                                                                                                    (b) Topic: 9.4 (blood)                                                                                                                                                                                  (c) Topic: 9.4 (blood)

(a) Polio is a viral disease that can cause nerve damage in humans. In one area, polio vaccination began in 1957. Fig. 6.1 shows the number of cases of polio in this area between 1950 and 1970.

(i) Calculate the percentage change in the number of cases of polio between 1950 and 1952 in Fig. 6.1. Give your answer to two significant figures. Space for working.

(ii) Explain how vaccination causes the results shown between 1958 and 1970 in Fig. 6.1.

(iii) Explain why the polio vaccine does not protect you from other diseases.

(b) Blood clotting helps to prevent some infections. Outline how a blood clot is formed and how it can prevent infections.

(c) State the name of the component of blood responsible for transporting blood cells.

▶️Answer/Explanation

Ans 

(a)(i) – 64 (%) / 64 (%) decrease

(ii) any five from:
1 (vaccination confers) active immunity ;
2 (vaccine contains) weakened / inactivated / dead / AW, virus / pathogen ;
3 (vaccine) stimulates (primary) immune response ;
4 lymphocytes produce antibodies ;
5 antibodies, destroy / agglutinate / immobilise / kill, virus / pathogen ;
6 antibodies, mark / attached to, virus / pathogen, so phagocytes destroy them ;
7 production of memory cells ;
8 long-term immunity / AW ;
9 herd immunity / protecting unvaccinated people ;
10 person to person transmission interrupted / prevents the spread of polio through the population / AW ;
11 AVP

(iii) any two from:
ref. to specificity (in context of antigen or antibody) ;
antibodies (produced in response to the polio vaccine) have a complementary
shape only to polio antigens ;
antibodies bind only to polio virus ;
idea that memory cells (produced by polio vaccine) are not activated by other
pathogens ;
AVP

(b) total of three from:(blood clot / scab) prevents entry of pathogens / pathogens trapped in mesh / (blood clot / scab) is a barrier to pathogens ;
max two from:
conversion of fibrinogen to fibrin ;
conversion of soluble (protein) to, insoluble / fibrous (protein) ;
forms, network of fibres / mesh ;
ref to role of platelets ;
formation of a scab

(c) plasma

Question 7

(a) Topic: 20.3 (eutrophication)                                                                                                                                                                        (b) Topic: 19.4 (populations)

Fig. 7.1 is a flowchart showing the stages of eutrophication.
(a) Complete Fig. 7.1.

(b) A scientist obtained a sample of the bacterial decomposers and grew them in a flask. The resources available for bacterial growth in the flask became limiting. The size of the bacterial population was estimated during the investigation and these data were plotted on a graph.
(i) State the name of the expected shape of the population growth curve that would be drawn on the graph.
(ii) State the name of the initial phase of bacterial growth.
(iii) State one factor, other than a lack of resources, that would cause bacteria to die during the death phase.

▶️Answer/Explanation

Ans 

(a) nitrate / ammonium / phosphate(s) / ions ;
algae / plants / producers ;
light ;
photosynthesise ;
(aerobic) respiration ;
dissolved

(b)(i) sigmoid(al)

(b)(ii) lag

(b)(iii) one from:
build-up of (named), toxins / waste / carbon dioxide ;
(change in) pH ;
high temperature ;
overcrowding ;
disease / virus attack

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