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California CAST · High School · Science

California High School CAST Science Practice Test

Build California High School CAST Science readiness with five focused 10-question practice sets covering life science, physical science, Earth and space science, environmental systems, engineering, and data.

High School CAST Science practice sets

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

Science skills covered

  • Population dynamics, ecosystems, mutations, meiosis, natural selection, photosynthesis, decomposers, speciation, alleles, and homeostasis
  • Particle motion, reaction energy, reaction rates, conservation of atoms, circuits, graphs, gravity, waves, and catalysts
  • Mantle convection, plate tectonics, greenhouse gases, stars, redshift, tides, carbon cycling, ice cores, solar energy, and radioactive dating
  • Food webs, wetlands, eutrophication, fisheries, biodiversity, stormwater, climate feedbacks, conservation, ocean chemistry, and data scales
  • Engineering optimization, repeated trials, extrapolation, controlled variables, model revision, correlation, uncertainty, unexpected results, constraints, and outliers

How to use this page

Complete one 10-question set at a time. Identify the evidence, explain the mechanism, and review every solution before moving to the next set.

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.

Select a test

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

1. Test

California High School CAST Science Practice Questions

A 10-question California High School CAST Science practice set on high school life science and ecosystems, with answers and explanations.

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 population has a high birth rate and a low death rate. What will most likely happen if resources remain available?

Please select an answer first.

Correct answer: A

The correct answer is The population will increase..

  1. Identify the science idea: Determine whether the task focuses on life, physical, Earth and space, environmental, or engineering science.
  2. Use the evidence: When births exceed deaths and resources support survival, population size increases.
  3. Check the choice: Make sure the answer explains the mechanism, pattern, or evidence rather than only repeating a detail.

When births exceed deaths and resources support survival, population size increases.

2. QuestionMultiple choice

Why can a change in one species affect many other species in an ecosystem?

Please select an answer first.

Correct answer: B

The correct answer is Species are connected through food webs and resource relationships..

  1. Identify the science idea: Determine whether the task focuses on life, physical, Earth and space, environmental, or engineering science.
  2. Use the evidence: Changes to one population can alter predation, competition, and energy flow through a food web.
  3. Check the choice: Make sure the answer explains the mechanism, pattern, or evidence rather than only repeating a detail.

Changes to one population can alter predation, competition, and energy flow through a food web.

3. QuestionMultiple choice

A mutation changes the amino acid sequence of a protein. What is one possible result?

Please select an answer first.

Correct answer: C

The correct answer is The protein may fold differently and have a changed function..

  1. Identify the science idea: Determine whether the task focuses on life, physical, Earth and space, environmental, or engineering science.
  2. Use the evidence: A changed amino acid sequence can affect protein structure and function.
  3. Check the choice: Make sure the answer explains the mechanism, pattern, or evidence rather than only repeating a detail.

A changed amino acid sequence can affect protein structure and function.

4. QuestionMultiple choice

Why does meiosis increase genetic variation in offspring?

Please select an answer first.

Correct answer: D

The correct answer is It produces cells with different combinations of genetic material..

  1. Identify the science idea: Determine whether the task focuses on life, physical, Earth and space, environmental, or engineering science.
  2. Use the evidence: Meiosis and the events associated with it create varied combinations of alleles.
  3. Check the choice: Make sure the answer explains the mechanism, pattern, or evidence rather than only repeating a detail.

Meiosis and the events associated with it create varied combinations of alleles.

5. QuestionMultiple choice

Which evidence best supports the idea that natural selection occurred in a population?

Please select an answer first.

Correct answer: A

The correct answer is A heritable trait became more common as it improved survival in a specific environment..

  1. Identify the science idea: Determine whether the task focuses on life, physical, Earth and space, environmental, or engineering science.
  2. Use the evidence: Natural selection changes trait frequencies when heritable differences affect survival or reproduction.
  3. Check the choice: Make sure the answer explains the mechanism, pattern, or evidence rather than only repeating a detail.

Natural selection changes trait frequencies when heritable differences affect survival or reproduction.

6. QuestionMultiple choice

A plant receives light energy and uses carbon dioxide and water to make sugar. What process is occurring?

Please select an answer first.

Correct answer: B

The correct answer is Photosynthesis.

  1. Identify the science idea: Determine whether the task focuses on life, physical, Earth and space, environmental, or engineering science.
  2. Use the evidence: Photosynthesis stores light energy in chemical energy within sugar molecules.
  3. Check the choice: Make sure the answer explains the mechanism, pattern, or evidence rather than only repeating a detail.

Photosynthesis stores light energy in chemical energy within sugar molecules.

7. QuestionMultiple choice

What is the primary role of decomposers in an ecosystem?

Please select an answer first.

Correct answer: C

The correct answer is They return matter to the environment by breaking down dead organisms..

  1. Identify the science idea: Determine whether the task focuses on life, physical, Earth and space, environmental, or engineering science.
  2. Use the evidence: Decomposers break down organic matter and help recycle nutrients.
  3. Check the choice: Make sure the answer explains the mechanism, pattern, or evidence rather than only repeating a detail.

Decomposers break down organic matter and help recycle nutrients.

8. QuestionMultiple choice

A population becomes separated by a physical barrier for many generations. What could eventually occur?

Please select an answer first.

Correct answer: D

The correct answer is The populations may diverge genetically and become separate species..

  1. Identify the science idea: Determine whether the task focuses on life, physical, Earth and space, environmental, or engineering science.
  2. Use the evidence: Isolation can reduce gene flow and allow populations to diverge over time.
  3. Check the choice: Make sure the answer explains the mechanism, pattern, or evidence rather than only repeating a detail.

Isolation can reduce gene flow and allow populations to diverge over time.

9. QuestionMultiple choice

Why can an allele that is harmful in one environment be neutral or helpful in another?

Please select an answer first.

Correct answer: A

The correct answer is The effect of a trait can depend on environmental conditions..

  1. Identify the science idea: Determine whether the task focuses on life, physical, Earth and space, environmental, or engineering science.
  2. Use the evidence: Selection depends on how a trait interacts with the conditions in which organisms live.
  3. Check the choice: Make sure the answer explains the mechanism, pattern, or evidence rather than only repeating a detail.

Selection depends on how a trait interacts with the conditions in which organisms live.

10. QuestionMultiple choice

Which statement best explains homeostasis in an organism?

Please select an answer first.

Correct answer: B

The correct answer is The organism maintains relatively stable internal conditions despite external changes..

  1. Identify the science idea: Determine whether the task focuses on life, physical, Earth and space, environmental, or engineering science.
  2. Use the evidence: Homeostasis uses regulatory processes to keep internal conditions within a suitable range.
  3. Check the choice: Make sure the answer explains the mechanism, pattern, or evidence rather than only repeating a detail.

Homeostasis uses regulatory processes to keep internal conditions within a suitable range.

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Frequently asked questions about California High School CAST Science Practice Test

Which Science skills are covered?

The page covers high school life science, physical science, Earth and space science, environmental systems, engineering practices, data analysis, and scientific reasoning.

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.