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California CAST · Grades 5, 8 & High School · Science

California CAST Science Practice Test

Build California CAST Science readiness with five focused 10-question practice sets covering life science, physical science, Earth and space science, engineering, and data analysis for Grades 5, 8, and high school.

CAST Science practice sets

This California CAST Science Practice Test page provides five short practice sets with 10 original multiple-choice questions each. The sets offer supplemental review across life science, physical science, Earth and space science, engineering and design, scientific practices, systems, and data analysis.

Science skills covered

  • Photosynthesis, natural selection, cells, heredity, ecosystems, energy flow, mutations, evolution, and experimental variables
  • Chemical and physical change, thermal energy, circuits, atomic structure, reactions, waves, collisions, work, and ions
  • Plate tectonics, climate, Moon phases, greenhouse gases, fossils, tides, volcanic ash, renewable resources, and redshift
  • Controlled experiments, engineering criteria and constraints, models, repeated trials, efficiency, controls, and claim-evidence-reasoning
  • Associations, systems, phase changes, surface energy, biodiversity, gas relationships, conservation of matter, simulations, carrying capacity, and uncertainty

How to use this page

Complete one 10-question set at a time. Identify the evidence, describe the mechanism, and review every explanation before moving to the next set. Use the grade-specific pages when you want more focused practice for Grade 5, Grade 8, or high school.

This is supplemental State Test Practice, State Assessment Practice, and Standardized Test Practice. It does not replace current California Department of Education guidance, official CAST blueprints, accommodations, or testing schedules.

For the broader California assessment hub, visit California State Assessments.

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5 Tests
1. Test2. Test3. Test4. Test5. Test

1. Test

California CAST Science Practice Questions

A 10-question California CAST Science practice set on life science, with answers and explanations for Grades 5, 8, and high school review.

Read each science task carefully, choose one answer, and review the explanation after responding.

10 Questions
0/10 Questions0 %
Correct 0
Incorrect 0
Unanswered 10
1. QuestionMultiple choice

A plant is placed in sunlight and produces more sugar than an identical plant kept in darkness. Which process explains the difference?

Please select an answer first.

Correct answer: A

The correct answer is Photosynthesis uses light energy to make sugar..

  1. Identify the science idea: Determine whether the task focuses on a life, physical, Earth and space, engineering, or data concept.
  2. Use the evidence: Photosynthesis uses light energy, water, and carbon dioxide to produce sugars, so light availability affects the result.
  3. Check the choice: Make sure the answer explains the observed pattern, mechanism, or evidence rather than merely repeating a detail.

Photosynthesis uses light energy, water, and carbon dioxide to produce sugars, so light availability affects the result.

2. QuestionMultiple choice

A population of bacteria becomes resistant to an antibiotic over several generations. Which explanation best fits natural selection?

Please select an answer first.

Correct answer: B

The correct answer is Resistant bacteria survive treatment and reproduce more often..

  1. Identify the science idea: Determine whether the task focuses on a life, physical, Earth and space, engineering, or data concept.
  2. Use the evidence: Bacteria with inherited resistance are more likely to survive and pass the trait to offspring.
  3. Check the choice: Make sure the answer explains the observed pattern, mechanism, or evidence rather than merely repeating a detail.

Bacteria with inherited resistance are more likely to survive and pass the trait to offspring.

3. QuestionMultiple choice

Which structure controls many activities of a eukaryotic cell?

Please select an answer first.

Correct answer: C

The correct answer is Nucleus.

  1. Identify the science idea: Determine whether the task focuses on a life, physical, Earth and space, engineering, or data concept.
  2. Use the evidence: The nucleus contains genetic material and helps regulate cell activities.
  3. Check the choice: Make sure the answer explains the observed pattern, mechanism, or evidence rather than merely repeating a detail.

The nucleus contains genetic material and helps regulate cell activities.

4. QuestionMultiple choice

Two parents have brown eyes, but their child has a recessive eye-color trait. What must be true for this outcome?

Please select an answer first.

Correct answer: D

The correct answer is Both parents carried a recessive allele..

  1. Identify the science idea: Determine whether the task focuses on a life, physical, Earth and space, engineering, or data concept.
  2. Use the evidence: A child can express a recessive trait when each parent contributes a recessive allele.
  3. Check the choice: Make sure the answer explains the observed pattern, mechanism, or evidence rather than merely repeating a detail.

A child can express a recessive trait when each parent contributes a recessive allele.

5. QuestionMultiple choice

Why are decomposers important in an ecosystem?

Please select an answer first.

Correct answer: A

The correct answer is They return matter from dead organisms to the environment..

  1. Identify the science idea: Determine whether the task focuses on a life, physical, Earth and space, engineering, or data concept.
  2. Use the evidence: Decomposers break down organic matter and return nutrients to soil and water.
  3. Check the choice: Make sure the answer explains the observed pattern, mechanism, or evidence rather than merely repeating a detail.

Decomposers break down organic matter and return nutrients to soil and water.

6. QuestionMultiple choice

In a food web, what usually happens to available energy at higher trophic levels?

Please select an answer first.

Correct answer: B

The correct answer is Less energy is available at each higher level..

  1. Identify the science idea: Determine whether the task focuses on a life, physical, Earth and space, engineering, or data concept.
  2. Use the evidence: Energy is transferred inefficiently, so less usable energy reaches higher trophic levels.
  3. Check the choice: Make sure the answer explains the observed pattern, mechanism, or evidence rather than merely repeating a detail.

Energy is transferred inefficiently, so less usable energy reaches higher trophic levels.

7. QuestionMultiple choice

A mutation changes one DNA base in a gene but does not change the resulting protein. What is a likely explanation?

Please select an answer first.

Correct answer: C

The correct answer is The changed codon still codes for the same amino acid..

  1. Identify the science idea: Determine whether the task focuses on a life, physical, Earth and space, engineering, or data concept.
  2. Use the evidence: Because multiple codons can code for the same amino acid, a base change can be silent.
  3. Check the choice: Make sure the answer explains the observed pattern, mechanism, or evidence rather than merely repeating a detail.

Because multiple codons can code for the same amino acid, a base change can be silent.

8. QuestionMultiple choice

Which evidence best supports the idea that a population evolved over time?

Please select an answer first.

Correct answer: D

The correct answer is The frequency of an inherited trait changes across many generations..

  1. Identify the science idea: Determine whether the task focuses on a life, physical, Earth and space, engineering, or data concept.
  2. Use the evidence: Evolution is supported by inherited trait frequencies changing in a population across generations.
  3. Check the choice: Make sure the answer explains the observed pattern, mechanism, or evidence rather than merely repeating a detail.

Evolution is supported by inherited trait frequencies changing in a population across generations.

9. QuestionMultiple choice

A student compares the number of pill bugs in light and dark areas while keeping moisture and temperature constant. What is the independent variable?

Please select an answer first.

Correct answer: A

The correct answer is Light level.

  1. Identify the science idea: Determine whether the task focuses on a life, physical, Earth and space, engineering, or data concept.
  2. Use the evidence: The independent variable is the factor deliberately changed: the light level.
  3. Check the choice: Make sure the answer explains the observed pattern, mechanism, or evidence rather than merely repeating a detail.

The independent variable is the factor deliberately changed: the light level.

10. QuestionMultiple choice

Why does genetic variation help a population respond to environmental change?

Please select an answer first.

Correct answer: B

The correct answer is Some individuals may have traits that improve survival in the new conditions..

  1. Identify the science idea: Determine whether the task focuses on a life, physical, Earth and space, engineering, or data concept.
  2. Use the evidence: Variation provides differences that natural selection can act on when conditions change.
  3. Check the choice: Make sure the answer explains the observed pattern, mechanism, or evidence rather than merely repeating a detail.

Variation provides differences that natural selection can act on when conditions change.

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Frequently asked questions about California CAST Science Practice Test

Which grades does this CAST Science practice page support?

This hub provides mixed supplemental practice for the California CAST assessment areas used in Grade 5, Grade 8, and high school. Grade-specific pages can provide more targeted review.

How many questions are included?

There are five practice sets with 10 questions each, for 50 questions in total. Each set can be completed separately.

Are these official CAST questions?

No. These are original supplemental practice questions. Check the latest California Department of Education information for official materials, standards, accommodations, and policies.