Biology 0610/41 October/November 2025: question paper and mark scheme
Cambridge IGCSE Biology (0610), Paper 4 Theory (Extended), October/November 2025. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
(a) Fig. 1.1 shows drawings of seven species of bacteria.
A B C
D E F
G not to scale
Fig. 1.1
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Use the key to identify each species of bacteria in Fig. 1.1.
Write the letter of each species (A to G) in the correct box beside the key.
One has been done for you.
key
(a) hair‑like structure or structures visible go to 2
1
(b) no hair‑like structures visible go to 4
(a) more than one hair‑like structure go to 3
2
(b) one hair‑like structure only Vibrio cholerae
(a) hair‑like structures attached at one end only Helicobacter pylori
3
(b) hair‑like structures attached all over Salmonella typhi
(a) bacteria have a spiral shape Treponema pallidum
4
(b) bacteria do not have a spiral shape go to 5
(a) bacteria are grouped to form a chain go to 6
5
(b) bacteria do not form a chain Staphylococcus aureus
(a) bacteria in the chain are cylindrical in shape Streptobacillus moniliformis
6
(b) bacteria in the chain are circular in shape Streptococcus pyogenes F
[3]
(b) (i) A cylinder‑shaped bacterium has a length of 2 μm and a diameter of 0.5 μm.
Calculate:
• the radius of this bacterium
• the volume of this bacterium.
Include the units in your answers.
Space for working.
radius ……
volume ……
[4]
(ii) State the name of the kingdom that bacteria belong to.
…… [1]
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(c) Fig. 1.2 is a diagram of a virus.
K
J
Fig. 1.2
(i) State the name of the parts labelled J and K in Fig. 1.2.
J ……
K ……
[2]
(ii) State two structures present in bacteria that are absent in viruses.
1 ……
2 ……
[2]
[Total:12]
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Mark scheme
1(a) 3 6 correct = 3
3 or 4 or 5 correct = 2
go to 2
1 or 2 correct = 1
go to 4
go to 3
Vibrio cholerae D
Helicobacter pylori B
Salmonella typhi E
Treponema pallidum C
go to 5
go to 6
Staphylococcus aureus A
Streptobacillus moniliformis G
Streptococcus pyogenes F
;;;
1(b)(i) radius: 0.25 um ; 4 MP1 correct radius calculated
volume: 0.39 um3 ;;; MP2 correct formula πr2h selected
MP3 correct volume calculated
MP4 correct units for both values
ecf from previous MP
1(b)(ii) prokaryote ; 1
1(c)(i) J protein coat ; 2
K genetic material ;
1(c)(ii) any two from: 2
cell wall ;
cell membrane ;
circular / loop of, DNA ;
plasmid ;
cytoplasm ;
ribosome ;
AVP ;; e.g. flagella
(a) Fig. 2.1 is a diagram of part of the human circulatory system.
The arrows show the direction of blood flow.
A lungs
B
heart
X
liver intestines
kidneys
D C
Fig. 2.1
(i) Complete Table 2.1 by naming the blood vessels in Fig. 2.1 and stating whether the blood in each vessel is oxygenated.
Table 2.1
carries oxygenated blood letter in Fig. 2.1 name of the blood vessel
(yes / no)
A
B
C
D
[4]
(ii) State the name of structure X in Fig. 2.1 and outline its function.
name ……
function ……
[2]
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(b) Fig. 2.2 is a diagram of part of a fish circulatory system.
The arrows show the direction of blood flow.
gills
heart
body
Fig. 2.2
(i) Describe how the structure of the fish heart in Fig. 2.2 differs from a human heart.
…… [2]
(ii) Explain the advantages of the type of circulatory system found in humans, compared
with the circulatory system shown in Fig. 2.2.
…… [4]
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(c) Fig. 2.3 is a photomicrograph of an arteriole.
P
magnification ×1430
Fig. 2.3
(i) Identify the structure labelled P in Fig. 2.3.
…… [1]
(ii) The magnification of the image is provided. Write the formula that would be used to calculate the actual diameter of the lumen of the arteriole in Fig. 2.3.
…… [1]
(iii) The actual diameter of the lumen of the arteriole shown in Fig. 2.3 is 0.0315 mm.
Convert 0.0315 mm to micrometres (μm).
…… μm [1]
[Total:15]
DFD
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Mark scheme
2(a)(i) 4 one mark for each correct row
name of the blood carries
letter on Fig. 6.1
vessel oxygenated blood
A pulmonary artery no
B aorta yes
C hepatic portal vein no
D renal vein no
;;;;
2(a)(ii) name: valve ; 2
function: prevents back flow of blood / AW ;
2(b)(i) any two from: 2 ora throughout
(only) two chambers ;
no, septum / left and right sides / AW ;
fewer valves ;
heart (chamber) walls of similar thickness (to each other) ;
fewer blood vessels (going to and from the heart) ;
2(b)(ii) any four from: 4
1 blood is pumped to the lungs then to the body / blood goes through
the heart twice in one complete journey / double circulation ;
2 oxygenated and deoxygenated blood, are kept separate / do not
mix / separated by septum ;
3 efficient, supply of blood / glucose / oxygen / nutrients (to, the
body / AW) ;
4 efficient, removal / carbon dioxide / urea / lactic acid (from, body / AW);
5 provides high(er) pressure (in body) ;
6 which allow a high, metabolic rate / rate of respiration ;
7 which allows filtration in kidneys (for excretion) ;
8 low(er) pressure in, pulmonary, artery / circuit / AW ;
9 to prevent damage to (capillaries in the) lungs ;
10 allow more time for, gas exchange / absorption of oxygen ;
11 AVP ;
e.g. larger / steeper, diffusion gradient
between capillaries and respiring
tissues / allows large body size / maintenance
of body temperature
2(c)(i) red blood cell ; 1
2(c)(ii) actual size = image size ÷ magnification ; 1
2(c)(iii) 31.5 (µm) ; 1
Fig. 3.1 is a diagram of the nitrogen cycle.
nitrogen in the atmosphere nitrogen fixation
A proteins in plants and animals
assimilation
plant and animal waste amino acids in plants decomposition and animals compound Y
B
nitrate ions in soil
Fig. 3.1
(a) (i) State the names of processes A and B in Fig. 3.1.
A ……
B ……
[2]
(ii) State two ways that nitrogen fixation can occur.
1 ……
2 ……
[2]
(iii) State the name of compound Y in Fig. 3.1.
…… [1]
(iv) State the name of an organ in animals, where assimilation and deamination of amino acids occurs.
…… [1]
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(v) Describe the process of deamination.
…… [2]
(b) Complete the sentences about pollution of the air by writing the appropriate words or phrases in the spaces provided.
Methane is a pollutant gas that contributes to the enhanced ……
and climate change. Methane is released into the atmosphere from cattle and from the
farming of …… crops.
…… is a gas that is absorbed by trees in the process
of …… . This gas is released into the atmosphere by the
…… of fossil fuels, where it also contributes to climate change.
[5]
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(c) Explain the process of eutrophication in aquatic ecosystems.
…… [6]
[Total:19]
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Mark scheme
3(a)(i) A denitrification ; 2
B nitrification ;
3(a)(ii) any two from: 2
lightning ;
bacteria ;
AVP ; e.g. Haber process
3(a)(iii) ammonia / ammonium (ions) ; 1
3(a)(iv) liver ; 1
3(a)(v) removal of nitrogen containing part 2
(of amino acids / protein) ;
urea is formed ;
3(b) greenhouse effect ; 5
rice ;
carbon dioxide ;
photosynthesis ;
burning / combustion ;
3(c) any six from: 6 A decomposers throughout for bacteria
1 untreated sewage / fertiliser / nutrients ;
2 increased availability of nitrates / ions / AW ;
3 causing algal bloom / algae reproduction ;
4 algae reduce (penetration of) sunlight (in the water) / AW ;
5 (so rooted) plants unable to photosynthesise ;
6 so plants die ;
7 bacteria, decompose / feed, on dead, plants or algae ;
8 so bacterial populations increase ;
9 bacteria respire aerobically ;
10 bacteria use up the oxygen in the water ;
11 organisms / fish , die / suffocate / migrate, due to lack of oxygen ;
Fig. 4.1 is a photograph of a bee on a flower. One of the bee’s legs is covered with pollen.
pollen
Fig. 4.1
(a) (i) State three features of flowers that attract pollinating insects such as bees.
1 ……
2 ……
3 ……
[3]
(ii) State one way that pollen grains are adapted for pollination by bees.
…… [1]
(b) Describe two ways the structure of a monocotyledonous plant differs from the structure of a dicotyledonous plant.
1 ……
2 ……
[2]
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(c) Fig. 4.2 is a diagram of a cross‑section of an insect‑pollinated flower.
Fig. 4.2
On Fig. 4.2, name and draw label lines to:
• the structure that supports an anther
• a structure that protects the flower bud
• an ovule.
[3]
(d) Describe sexual reproduction in a flower, from the release of pollen to the formation of a zygote.
[5]
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(e) Sexual reproduction also occurs in humans.
(i) State the name of the male gamete in a human.
…… [1]
(ii) State where gametes are formed in the human male reproductive system.
…… [1]
(iii) Human male gametes are haploid.
State the name of the process that produces haploid male gametes.
…… [1]
(iv) Describe the function of the prostate gland in the male reproductive system.
…… [1]
[Total: 18]
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Mark scheme
4(a)(i) any three from: 3
scent ;
nectar ;
large / colourful, petals ;
pollen (as a source of food) ;
AVP ; e.g. honey guides / ref. to landing
platforms / ref. to mimicking insects
4(a)(ii) any one from: 1
large ;
sticky / spiky / AW ;
4(b) any two from: 2
(monocots have)
narrow / strap / long/AW, leaves ;
parallel (leaf) veins ;
scattered vascular, tissue / bundles, (in the stem) ;
hollow stems ;
petals in multiples of three ;
fibrous roots ;
one cotyledon ;
pollen grains have one pore or furrow ;
AVP ;;
4(c) filament labelled ; 3
sepal labelled ;
an ovule labelled ;
4(d) any five from: 5
1 pollen (released) from the anther ;
2 pollen transferred to stigma ;
3 pollen tube, grows ;
4 (pollen tube goes) down / through, the style ;
5 ref. to ovule / ovary ;
6 pollen / male, nucleus travels down the (pollen) tube / style ;
7 pollen / male, and, ovule / female, nuclei fuse ;
8 fertilisation ;
9 AVP ; e.g. ref. to haploid nuclei or diploid zygote ;
4(e)(i) sperm (cell) ; 1
4(e)(ii) testis / testes ; 1
4(e)(iii) meiosis ; 1 A reduction division
4(e)(iv) make fluid / semen, for the sperm / male gametes, to swim / AW ; 1 A ref. to providing nutrients
A student investigated the effect of humidity on water vapour loss in plant leaves. As water vapour was lost, the mass of the leaves decreased.
Similar‑sized leaves were collected from one species of plant.
The leaves were divided into two groups, A and B. The leaves in group A were placed in a low humidity environment and the leaves in group B were placed in a high humidity environment. The leaves in each group were kept in their environment for 12 hours.
The temperature in each environment was maintained at 20 °C.
The mass of the leaves in each group was measured at the start of the investigation and then every hour throughout the 12‑hour period.
The student calculated the mass of water vapour lost as a percentage of the starting mass of the leaves for each group.
Fig. 5.1 shows the student’s results.
35
30
25 mass of water vapour lost from
20 the leaves as a percentage of the starting 15 mass
10
5
0
0 1 2 3 4 5 6 7 8 9 10 11 12
time / hours key
A low humidity environment
B high humidity environment
Fig. 5.1
(a) (i) State the name of the process by which water vapour is lost from plant leaves.
…… [1]
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(ii) Compare and explain the effects of high and low humidity shown in Fig. 5.1.
…… [5]
(iii) The students repeated the investigation at a temperature of 35 °C.
The leaves were kept in a low humidity environment.
Draw a line on the graph in Fig. 5.1 to predict the results of this investigation. [1]
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(b) Humans also lose water vapour from their bodies by sweating.
(i) Explain how sweating helps a person to maintain a constant internal body temperature.
…… [3]
(ii) State one other way that humans lose water vapour from their bodies.
…… [1]
[Total:11]
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Mark scheme
5(a)(i) transpiration / diffusion ; 1
5(a)(ii) any five from: 5 ora throughout
comparison
1 both lose mass ;
2 higher humidity, less water vapour is lost ;
3 ref. to steeper rate / greater water lost, initially (for both groups) ;
4 comparative data quote with units ;
explanation for high humidity
5 (higher humidity) greater amount of water vapour in the atmosphere ;
6 reduced water potential, gradient ;
7 less water vapour lost, through stomata / between guard cells ;
5(a)(iii) line drawn on the graph above the low humidity line ; 1
5(b)(i) any three from: 3
glands in the skin produce sweat ;
sweat on (the surface of) the skin evaporates ;
using / AW, heat / energy (from the body) ;
(internal) body temperature, decreases / returns, to a set point ;
ref. to homeostasis / negative feedback ;
5(b)(ii) expiration / AW ; 1
Fig. 6.1 is a diagram of a cell that shows how DNA is involved in protein synthesis.
free amino acids
growing protein chain
DNA mRNA ribosome
mRNA
Fig. 6.1
(a) State the name of the part of the cell that contains DNA.
…… [1]
(b) DNA controls cell function by controlling the production of proteins.
State the name of one type of protein.
…… [1]
(c) Using Fig. 6.1, explain how mRNA is involved in protein synthesis.
…… [3]
[Total: 5]
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Mark scheme
6(a) nucleus ; 1
6(b) any one from: 1
enzymes ;
membrane carriers ;
receptors for neurotransmitters ;
AVP ; e.g. insulin / glucagon / antibodies / keratin
/ haemoglobin
6(c) any three from: 3
(mRNA) is a copy of the gene / DNA / base sequence ;
gene / DNA, remains in the nucleus ;
(mRNA takes instructions) to cytoplasm / ribosome ;
mRNA, passes through / attaches to / ‘read by’, ribosome ;
base sequence determines sequence of amino acids (in the protein) ;
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Biology 0610/41 for October/November 2025 is out of 80 marks, with 1 hour 15 minutes to answer it, across 6 questions.
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