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100+ Free ILTS Science: Biology (239) Practice Questions

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Which of the following best describes the modern evolutionary synthesis (neo-Darwinism)?

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B
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D
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2026 Statistics

Key Facts: ILTS Science: Biology (239) Exam

240

Passing Scaled Score

ILTS Science: Biology (239) test page

$122

Test Fee (2026)

ILTS registration fee schedule

100 MC

Test Format

ILTS Science: Biology (239) test page

3h 15m

Testing Time

ILTS Science: Biology (239) test page

5 subareas

Content Domains

ILTS Science: Biology (239) test framework

37%

Disciplinary Core Ideas Weight

ILTS Science: Biology (239) test framework

23%

Science Process Skills Weight

ILTS Science: Biology (239) test framework

239

Test Code

ILTS Science: Biology (239) test page

ILTS Science: Biology (239) is Illinois' biology content licensure test, delivered by Pearson Evaluation Systems as a computer-based exam with 100 multiple-choice questions and a passing scaled score of 240. The test is weighted across five subareas: Science Process Skills 23%, Disciplinary Core Ideas 37%, Biochemistry, Cells, and Energetics 11%, Molecular Biology, Genetics, and Evolution 18%, and Ecology and the Unity and Diversity of Life 11%. The current public registration fee is $122 and candidates have 3 hours 15 minutes of testing time. This free 100-question bank mirrors the official subarea weighting so candidates can practice across every subarea.

Sample ILTS Science: Biology (239) Practice Questions

Try these sample questions to test your ILTS Science: Biology (239) exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1A biology teacher wants students to design an experiment testing whether light intensity affects the rate of photosynthesis in elodea. Which variable should students intentionally change to serve as the independent variable?
A.The intensity of light reaching the plant
B.The number of oxygen bubbles produced
C.The temperature of the water
D.The species of aquatic plant used
Explanation: The independent variable is the factor the experimenter deliberately manipulates. Because the hypothesis concerns the effect of light intensity, light intensity is the variable that must be changed across treatments while everything else is held constant.
2In a controlled experiment, what is the primary purpose of including a control group?
A.To provide a baseline for comparison against the experimental treatment
B.To increase the number of trials and reduce random error
C.To guarantee that the hypothesis will be supported
D.To eliminate the need for replication of the experiment
Explanation: A control group does not receive the experimental treatment and therefore establishes a baseline. Comparing the experimental group to the control allows the researcher to attribute observed differences to the manipulated variable rather than to other factors.
3A student measures the mass of a reactant as 12.0 g and a product as 11.7 g and concludes mass was lost. Which explanation best reflects sound scientific reasoning about this discrepancy in a closed-system reaction?
A.A gaseous product likely escaped or measurement error occurred, because mass is conserved
B.Mass is genuinely destroyed during chemical reactions
C.The law of conservation of mass applies only to physical changes
D.The reaction violated the first law of thermodynamics
Explanation: The law of conservation of mass states that matter is neither created nor destroyed in a chemical reaction. An apparent mass decrease usually means a gas escaped an unsealed system or there was measurement error, not that mass disappeared.
4Which of the following best distinguishes a scientific theory from a scientific hypothesis?
A.A theory is a broad, well-substantiated explanation supported by extensive evidence, while a hypothesis is a testable, tentative prediction
B.A theory is an unproven guess, while a hypothesis is an established fact
C.A theory cannot be tested, while a hypothesis can
D.A theory and a hypothesis are interchangeable terms in science
Explanation: In science, a theory is a comprehensive explanation of natural phenomena that has been repeatedly confirmed through observation and experiment. A hypothesis is a narrower, testable statement proposed before evidence is gathered.
5A researcher records bacterial colony counts of 20, 200, and 2000 over three days. Which type of graph best displays this exponential growth so that the trend appears as a straight line?
A.A semi-log plot with a logarithmic y-axis
B.A standard bar graph
C.A pie chart
D.A scatter plot with a linear y-axis and no trend line
Explanation: Exponential data spanning several orders of magnitude is best shown on a semi-log plot, where the y-axis uses a logarithmic scale. On this scale, exponential growth becomes a straight line, making the constant growth rate easy to identify.
6When teaching students to interpret a data table, which crosscutting concept emphasizes searching for repeated relationships that can guide further investigation?
A.Patterns
B.Stability and change
C.Energy and matter
D.Structure and function
Explanation: The crosscutting concept of Patterns focuses on recognizing recurring relationships in observed data. Identifying patterns prompts questions about cause and provides evidence that can be used to make predictions and design new investigations.
7A measurement of 0.00450 grams is recorded. How many significant figures does this value contain?
A.Three
B.Five
C.Six
D.Two
Explanation: Leading zeros are never significant, so the zeros before the 4 do not count. The digits 4, 5, and the trailing 0 (which is significant because it follows a decimal point) give three significant figures.
8Which laboratory safety practice is most appropriate when a student spills a small amount of dilute hydrochloric acid on a benchtop?
A.Neutralize the spill with a weak base such as sodium bicarbonate, then wipe it up while wearing gloves
B.Wipe it up immediately with a dry paper towel and bare hands
C.Add water to dilute it and let it evaporate on its own
D.Ignore it because the acid is dilute and therefore harmless
Explanation: A dilute acid spill should be neutralized with a mild base like sodium bicarbonate before cleanup, which raises the pH toward neutral and reduces the chemical hazard. Gloves and eye protection should be worn throughout.
9A class collects the following plant heights in centimeters: 10, 12, 12, 14, 17. What is the median height?
A.12
B.13
C.14
D.17
Explanation: The median is the middle value when data are ordered. With five ordered values (10, 12, 12, 14, 17), the third value, 12, is the middle and therefore the median.
10To investigate why some plants in a greenhouse grew taller than others, a teacher first guides students to develop a model. In science and engineering practices, what is the chief value of building a model of the system?
A.It makes relationships and variables explicit so predictions can be tested
B.It eliminates the need to collect any experimental data
C.It proves the hypothesis without further investigation
D.It replaces the requirement for peer review of conclusions
Explanation: Developing and using models is a core science and engineering practice because models represent the components and interactions of a system. By making variables and relationships explicit, a model generates testable predictions and clarifies what data are needed.

About the ILTS Science: Biology (239) Exam

The ILTS Science: Biology (239) test is the content-area assessment for the Illinois biology teaching endorsement. The computer-based test includes 100 multiple-choice questions organized into five subareas: Science Process Skills, Disciplinary Core Ideas, Biochemistry, Cells, and Energetics, Molecular Biology, Genetics, and Evolution, and Ecology and the Unity and Diversity of Life. The test is built on the Illinois Learning Standards and emphasizes science and engineering practices and crosscutting concepts.

Questions

100 scored questions

Time Limit

3 hours 15 minutes of testing (about 3 hours 30 minutes total appointment)

Passing Score

240 scaled score

Exam Fee

$122 (Illinois State Board of Education (ISBE) / Pearson)

ILTS Science: Biology (239) Exam Content Outline

23% of this test

Science Process Skills (Subarea I)

Practices of science and engineering including investigation design, scientific modeling, data analysis, and evidence evaluation; crosscutting concepts such as patterns, cause and effect, systems, and energy and matter; measurement and lab safety; and reading and literacy strategies that support science instruction and vocabulary development.

37% of this test

Disciplinary Core Ideas (Subarea II)

Foundational concepts across the sciences: chemistry (atomic structure, the periodic table, bonding, reactions, and equilibrium), physics (motion, forces, momentum, energy, waves, and circuits), biology (cells, genetics, and evolution), earth and space science (cosmology, plate tectonics, and the rock cycle), and environmental science (ecosystems, natural resources, climate, and human impacts), with engineering design applications.

11% of this test

Biochemistry, Cells, and Energetics (Subarea III)

Chemical bonding and biological macromolecules, functional groups, enzyme function and activation energy, thermodynamics, cellular respiration and photosynthesis, water properties, cell structure and organelle function, membrane transport and osmosis, and the cell cycle including mitosis and meiosis.

18% of this test

Molecular Biology, Genetics, and Evolution (Subarea IV)

The genetic code, DNA replication, transcription and translation, mutations, and biotechnology techniques such as gel electrophoresis; Mendelian inheritance, Punnett squares, pedigree analysis, blood types, and human genetic disorders; and evolutionary theory, natural selection, speciation, genetic drift, and Hardy-Weinberg equilibrium.

11% of this test

Ecology and the Unity and Diversity of Life (Subarea V)

Trophic interactions and energy flow, biomes, ecological succession, population dynamics and carrying capacity, species interactions, and biodiversity; plus the characteristics of life, homeostasis and feedback, reproduction and development, body systems, and biological classification within the three-domain system.

How to Pass the ILTS Science: Biology (239) Exam

What You Need to Know

  • Passing score: 240 scaled score
  • Exam length: 100 questions
  • Time limit: 3 hours 15 minutes of testing (about 3 hours 30 minutes total appointment)
  • Exam fee: $122

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

ILTS Science: Biology (239) Study Tips from Top Performers

1Allocate study time by subarea weight: Disciplinary Core Ideas is the heaviest at 37%, followed by Molecular Biology, Genetics, and Evolution at 18%
2Review the broad science content in Disciplinary Core Ideas, since it draws on chemistry, physics, earth and space science, and environmental science in addition to biology
3Practice interpreting data tables and graphs, designing experiments, and identifying variables because Science Process Skills makes up 23% of the test
4Master core biology relationships such as the central dogma, Mendelian ratios, photosynthesis and respiration, and Hardy-Weinberg equilibrium
5Use the provided on-screen calculator and periodic table during practice so the tools feel familiar on test day
6Connect content to crosscutting concepts and science and engineering practices, which the framework emphasizes throughout

Frequently Asked Questions

What is on the ILTS Science: Biology (239) test?

The test covers five subareas: Science Process Skills (23%), Disciplinary Core Ideas (37%), Biochemistry, Cells, and Energetics (11%), Molecular Biology, Genetics, and Evolution (18%), and Ecology and the Unity and Diversity of Life (11%). All are assessed through multiple-choice questions aligned to the Illinois Learning Standards.

How many questions are on the ILTS Biology (239) test and what is the format?

The computer-based test has 100 multiple-choice questions. There is no constructed-response or essay section on this content test, and an on-screen scientific calculator and periodic table are provided during testing.

What is the passing score for ILTS Science: Biology (239)?

You need a scaled score of 240 to pass, which is the standard passing score used across ILTS tests. Your raw number of correct answers is converted to a scaled score ranging from 100 to 300.

How much does the ILTS Biology (239) test cost in 2026?

The current registration fee for the ILTS Science: Biology (239) content test is $122. Always confirm the exact amount in your Pearson registration account before checkout, since fees can change and additional service fees may apply.

How long is the ILTS Biology (239) test appointment?

You have 3 hours and 15 minutes of testing time, with a total appointment of roughly 3 hours 30 minutes that includes a brief tutorial and nondisclosure agreement. Budget your time to answer all 100 multiple-choice questions.

Is a calculator allowed on the ILTS Biology (239) test?

The ILTS science tests provide an on-screen scientific calculator and a periodic table within the computer-based testing platform, so you do not bring your own calculator. Practice using the provided tools rather than memorizing every constant.