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AP Biology AP Biology Practice Test 2025

AP BiologyModel questions
120marks
180min
10questions

This is the official AP Biology AP Biology question paper for 2025, as set in the Model questions examination. It carries 120 full marks and a time allowance of 180 minutes, across 10 questions. On Kekkei you can attempt this AP Biology past paper online with a timer, get instant AI feedback and step-by-step solutions, and track the topics where you lose marks — completely free. Whether you are revising for your AP Biology AP Biology exam or solving previous years' question papers, this 2025 paper is a great way to practise under real exam conditions.

LevelAP Biology
SubjectAP Biology
Year2025 BS
Exam sessionModel questions
Full marks120
Time allowed180 minutes
Questions10, all with step-by-step solutions
A

Multiple Choice

Select the best answer.

10 questions·1 mark each
1Multiple choice1 mark

Primary site of ATP production in eukaryotic cells?

  • a

    Ribosome

  • b

    Mitochondrion

  • c

    Golgi apparatus

  • d

    Endoplasmic reticulum

Correct answer: b

Mitochondrion

Mitochondria produce most ATP via oxidative phosphorylation.

The correct answer is (b) Mitochondrion.

cell-biologyorganelles
2Multiple choice1 mark

Tt×TtTt \times Tt. Fraction phenotypically tall (TT dominant)?

  • a
    14\frac{1}{4}
  • b
    12\frac{1}{2}
  • c
    34\frac{3}{4}
  • d
    11
Correct answer: c
34\frac{3}{4}

3/4 tall (TT + Tt).

The correct answer is (c) 34\frac{3}{4}.

geneticsmendelian-inheritance
3Multiple choice1 mark

Which describes stabilizing selection?

  • a

    Intermediate phenotypes have highest fitness

  • b

    One extreme has highest fitness

  • c

    Both extremes have higher fitness

  • d

    All phenotypes equal fitness

Correct answer: a

Intermediate phenotypes have highest fitness

Intermediate phenotypes favored; reduces variation.

The correct answer is (a).

evolutionnatural-selection
4Multiple choice1 mark

Percentage of energy transferred between trophic levels?

  • a

    1%

  • b

    10%

  • c

    50%

  • d

    90%

Correct answer: b

10%

~10% (10% rule).

The correct answer is (b) 10%.

ecologyenergy-pyramids
5Multiple choice1 mark

Rapid depolarization in action potential caused by:

  • a

    K+^+ efflux via voltage-gated channels

  • b

    Ca2+^{2+} influx via ligand-gated channels

  • c

    Na+^+ influx via voltage-gated Na+^+ channels

  • d

    Na+^+/K+^+-ATPase active transport

Correct answer: c

Na+^+ influx via voltage-gated Na+^+ channels

Voltage-gated Na+^+ channels open; Na+^+ influx.

The correct answer is (c).

physiologynervous-system
6Multiple choice1 mark

Enzyme that unwinds DNA double helix during replication?

  • a

    Helicase

  • b

    DNA polymerase

  • c

    Ligase

  • d

    Topoisomerase

Correct answer: a

Helicase

Helicase breaks H-bonds between base pairs.

The correct answer is (a) Helicase.

molecular-biologydna-replication
7Multiple choice1 mark

Purpose of denaturation step in PCR?

  • a

    Activate DNA polymerase

  • b

    Allow primers to bind

  • c

    Synthesize new strands

  • d

    Separate DNA strands by breaking hydrogen bonds

Correct answer: d

Separate DNA strands by breaking hydrogen bonds

~95 C separates DNA strands by breaking H-bonds.

The correct answer is (d).

biotechnologypcr
8Multiple choice1 mark

Where does photolysis of water occur in photosynthesis?

  • a

    Stroma

  • b

    Thylakoid membrane, at Photosystem II

  • c

    Inner mitochondrial membrane

  • d

    Thylakoid membrane, at Photosystem I

Correct answer: b

Thylakoid membrane, at Photosystem II

At Photosystem II in thylakoid membrane.

The correct answer is (b).

cell-biologyphotosynthesis
9Multiple choice1 mark

Process that removes introns from pre-mRNA?

  • a

    DNA methylation

  • b

    Polyadenylation

  • c

    RNA splicing by the spliceosome

  • d

    5' capping

Correct answer: c

RNA splicing by the spliceosome

Spliceosome performs RNA splicing.

The correct answer is (c).

geneticsgene-expression
10Multiple choice1 mark

Hardy-Weinberg: q=0.3q=0.3. Heterozygote frequency?

  • a

    0.09

  • b

    0.21

  • c

    0.30

  • d

    0.42

Correct answer: d

0.42

2pq=2(0.7)(0.3)=0.422pq=2(0.7)(0.3)=0.42.

The correct answer is (d) 0.42.

evolutionhardy-weinberg

Frequently asked questions

Where can I find the AP Biology AP Biology question paper 2025?
The full AP Biology AP Biology 2025 (Model questions) question paper is available free on Kekkei. You can read every question online and attempt the paper under timed exam conditions.
Does the AP Biology 2025 paper come with solutions?
Yes. Every question on this AP Biology past paper includes a step-by-step solution, plus instant AI feedback when you attempt it on Kekkei.
How many marks is the AP Biology AP Biology 2025 paper?
The AP Biology AP Biology 2025 paper carries 120 full marks and is meant to be completed in 180 minutes, across 10 questions.
Is practising this AP Biology past paper free?
Yes — reading and attempting this AP Biology past paper on Kekkei is completely free.