IB Biology Paper 2 Section B Exam 2025–2026
Accurate Real Exam Questions and Verified
Correct Answers JUST RELEASED
Outline a technique used for gene transfer. [5 marks] - answer>>>a. plasmid used for
gene transfer/removed from bacteria;
b. plasmid is a small/extra circle of DNA;
c. restriction enzymes/endonucleases cut/cleave DNA (of plasmid);
d. each restriction enzyme cuts at specific base sequence/creates sticky ends;
e. same (restriction) enzyme used to cut DNA with (desired) gene;
f. DNA/gene can be added to the open plasmid/sticky ends join gene and
plasmid;
g. (DNA) ligase used to splice/join together/seal nicks;
h. recombinant DNA/plasmids inserted into host cell/bacterium/yeast;
Explain how evolution may happen in response to environmental change with evidence
from examples. [8 marks] - answer>>>a. variation in population;
b. (variation is) due to mutation/sexual reproduction;
c. valid example of variation in a specific population;
d. more offspring are produced than can survive / populations over-populate;
e. competition / struggle for resources/survival;
f. example of competition/struggle for resources;
g. survival of fittest/best adapted (to the changed environment)/those with
beneficial adaptations / converse;
h. example of changed environment and adaptation to it;
i. favourable genes/alleles passed on / best adapted reproduce (more)
/converse;
j. example of reproduction of individuals better adapted to changed
environment;
k. alleles for adaptations to the changed environment increase in the population;
l. example of genes/alleles for adaptations increasing in a population;
m. evolution by natural selection;
n. evolution is (cumulative) change in population/species over time / change in
allele frequency;
Suitable examples are antibiotic resistance and the peppered moth but any genuine
evidence-based example of adaptation to environmental change can be credited.
,Draw a labelled diagram to show the structure of a sarcomere. [5 marks] -
answer>>>Award [1] for each structure clearly drawn and correctly labelled.
a. sarcomere - clearly indicated between Z lines (whether Z lines named or not);
b. Z lines - shown at the ends of a sarcomere;
c. actin (filaments) - drawn as thin lines attached to Z lines;
d. myosin (filaments) - drawn as thick lines interdigitating with thin/actin
filaments;
e. myosin heads - on both sides of at least one myosin filament;
f. light band and dark band - indicating regions of actin only and myosin plus actin;
Explain how an impulse passes along the axon of a neuron. [8 marks] - answer>>>a.
resting potential is -70 mV / relatively negative inside in comparison to the outside;
b. Na+/K+ pumps maintain/re-establish (the resting potential);
c. more sodium ions outside than inside (when at the resting potential);
d. more potassium ions inside than outside (when at the resting potential);
e. nerve impulse is an action potential that stimulates a (wave of) depolarization along
the membrane/axon;
f. if neuron is stimulated/threshold potential/-50 mV is reached sodium ion channels
open;
g. sodium ions diffuse/move in;
h. (Na+ move in) causing depolarization;
i. potassium ion channels open / potassium ions diffuse/move out;
j. (K+ move out) causing repolarization;
k. local currents / description of Na+ ion diffusion between depolarized region and next
region of axon to depolarize;
Accept any of the above points clearly explained in an annotated diagram
Describe the process of endocytosis. [5 marks] - answer>>>a. (plasma) membrane
encloses/engulfs solid particles/droplets of fluid/molecules;
b. fluidity of the membrane allows endocytosis;
c. plasma membrane forms pit/forms indentation/pulled inwards/invaginates;
d. membrane pinches off/seals back on itself/edges fuse;
e. vesicle/vacuole formed;
f. inside of plasma membrane becomes outside of vesicle membrane / converse;
g. vesicle breaks away from plasma membrane/moves into cytoplasm;
h. active process / endocytosis/vesicle formation requires energy;
, (plasma) membrane encloses/engulfs solid particles/droplets of fluid/molecules;
Accept any of the above points clearly described in an annotated diagram.
The leaves of plants are adapted for photosynthesis. Draw a labelled plan diagram of a
leaf to show the distribution of tissues in a leaf. [5 marks] - answer>>>a. epidermis -
shown and labelled on either the upper or lower surface or both;
b. upper and lower epidermis - both labelled;
c. palisade layer / palisade mesophyll;
d. spongy layer / spongy mesophyll;
e. xylem (in upper part of a major or minor vein);
f. phloem (in a major or minor vein); (accept whether upper or lower)
g. guard cells; (do not accept stoma or stomata only)
Do not penalize diagrams that show individual cells rather than tissues.
Explain how abiotic factors affect the rate of transpiration in terrestrial plants. [8 marks] -
answer>>>a. less transpiration/water loss as (atmospheric) humidity rises;
b. air spaces inside leaf are saturated/nearly saturated (with water vapour);
c. smaller concentration gradient with higher atmospheric humidity;
d. more transpiration/water loss as temperature rises/with more heat;
e. faster diffusion / more kinetic energy (of water molecules);
f. faster evaporation (due to more latent heat available);
g. more transpiration/water loss as wind (speed) increases;
h. humid air/water vapour blown away from the leaf;
i. increasing the concentration gradient (of water vapour);
j. more transpiration/water loss in the light;
k. light causes stomata to open / stomata closed in darkness;
l. low CO2 concentration inside leaf in bright light so stomata open wider;
Accept any of the points if clearly made on an annotated graph.
Describe the importance of water to living organisms. [5 marks] - answer>>>a. coolant in
sweat/in transpiration;
b. water has a high heat of vaporisation / heat taken when hydrogen bonds break;
c. water is cohesive so can pulled up/so can be moved under tension in xylem;
d. water is an excellent/universal solvent/dissolves many different substances;
e. medium for transport in blood/xylem/phloem;
f. medium for metabolic reactions / (metabolic) reactions happen dissolved in water;
Accurate Real Exam Questions and Verified
Correct Answers JUST RELEASED
Outline a technique used for gene transfer. [5 marks] - answer>>>a. plasmid used for
gene transfer/removed from bacteria;
b. plasmid is a small/extra circle of DNA;
c. restriction enzymes/endonucleases cut/cleave DNA (of plasmid);
d. each restriction enzyme cuts at specific base sequence/creates sticky ends;
e. same (restriction) enzyme used to cut DNA with (desired) gene;
f. DNA/gene can be added to the open plasmid/sticky ends join gene and
plasmid;
g. (DNA) ligase used to splice/join together/seal nicks;
h. recombinant DNA/plasmids inserted into host cell/bacterium/yeast;
Explain how evolution may happen in response to environmental change with evidence
from examples. [8 marks] - answer>>>a. variation in population;
b. (variation is) due to mutation/sexual reproduction;
c. valid example of variation in a specific population;
d. more offspring are produced than can survive / populations over-populate;
e. competition / struggle for resources/survival;
f. example of competition/struggle for resources;
g. survival of fittest/best adapted (to the changed environment)/those with
beneficial adaptations / converse;
h. example of changed environment and adaptation to it;
i. favourable genes/alleles passed on / best adapted reproduce (more)
/converse;
j. example of reproduction of individuals better adapted to changed
environment;
k. alleles for adaptations to the changed environment increase in the population;
l. example of genes/alleles for adaptations increasing in a population;
m. evolution by natural selection;
n. evolution is (cumulative) change in population/species over time / change in
allele frequency;
Suitable examples are antibiotic resistance and the peppered moth but any genuine
evidence-based example of adaptation to environmental change can be credited.
,Draw a labelled diagram to show the structure of a sarcomere. [5 marks] -
answer>>>Award [1] for each structure clearly drawn and correctly labelled.
a. sarcomere - clearly indicated between Z lines (whether Z lines named or not);
b. Z lines - shown at the ends of a sarcomere;
c. actin (filaments) - drawn as thin lines attached to Z lines;
d. myosin (filaments) - drawn as thick lines interdigitating with thin/actin
filaments;
e. myosin heads - on both sides of at least one myosin filament;
f. light band and dark band - indicating regions of actin only and myosin plus actin;
Explain how an impulse passes along the axon of a neuron. [8 marks] - answer>>>a.
resting potential is -70 mV / relatively negative inside in comparison to the outside;
b. Na+/K+ pumps maintain/re-establish (the resting potential);
c. more sodium ions outside than inside (when at the resting potential);
d. more potassium ions inside than outside (when at the resting potential);
e. nerve impulse is an action potential that stimulates a (wave of) depolarization along
the membrane/axon;
f. if neuron is stimulated/threshold potential/-50 mV is reached sodium ion channels
open;
g. sodium ions diffuse/move in;
h. (Na+ move in) causing depolarization;
i. potassium ion channels open / potassium ions diffuse/move out;
j. (K+ move out) causing repolarization;
k. local currents / description of Na+ ion diffusion between depolarized region and next
region of axon to depolarize;
Accept any of the above points clearly explained in an annotated diagram
Describe the process of endocytosis. [5 marks] - answer>>>a. (plasma) membrane
encloses/engulfs solid particles/droplets of fluid/molecules;
b. fluidity of the membrane allows endocytosis;
c. plasma membrane forms pit/forms indentation/pulled inwards/invaginates;
d. membrane pinches off/seals back on itself/edges fuse;
e. vesicle/vacuole formed;
f. inside of plasma membrane becomes outside of vesicle membrane / converse;
g. vesicle breaks away from plasma membrane/moves into cytoplasm;
h. active process / endocytosis/vesicle formation requires energy;
, (plasma) membrane encloses/engulfs solid particles/droplets of fluid/molecules;
Accept any of the above points clearly described in an annotated diagram.
The leaves of plants are adapted for photosynthesis. Draw a labelled plan diagram of a
leaf to show the distribution of tissues in a leaf. [5 marks] - answer>>>a. epidermis -
shown and labelled on either the upper or lower surface or both;
b. upper and lower epidermis - both labelled;
c. palisade layer / palisade mesophyll;
d. spongy layer / spongy mesophyll;
e. xylem (in upper part of a major or minor vein);
f. phloem (in a major or minor vein); (accept whether upper or lower)
g. guard cells; (do not accept stoma or stomata only)
Do not penalize diagrams that show individual cells rather than tissues.
Explain how abiotic factors affect the rate of transpiration in terrestrial plants. [8 marks] -
answer>>>a. less transpiration/water loss as (atmospheric) humidity rises;
b. air spaces inside leaf are saturated/nearly saturated (with water vapour);
c. smaller concentration gradient with higher atmospheric humidity;
d. more transpiration/water loss as temperature rises/with more heat;
e. faster diffusion / more kinetic energy (of water molecules);
f. faster evaporation (due to more latent heat available);
g. more transpiration/water loss as wind (speed) increases;
h. humid air/water vapour blown away from the leaf;
i. increasing the concentration gradient (of water vapour);
j. more transpiration/water loss in the light;
k. light causes stomata to open / stomata closed in darkness;
l. low CO2 concentration inside leaf in bright light so stomata open wider;
Accept any of the points if clearly made on an annotated graph.
Describe the importance of water to living organisms. [5 marks] - answer>>>a. coolant in
sweat/in transpiration;
b. water has a high heat of vaporisation / heat taken when hydrogen bonds break;
c. water is cohesive so can pulled up/so can be moved under tension in xylem;
d. water is an excellent/universal solvent/dissolves many different substances;
e. medium for transport in blood/xylem/phloem;
f. medium for metabolic reactions / (metabolic) reactions happen dissolved in water;
