Biology EOC Questions

Sixty end-of-course biology questions, each built on a scenario such as an experiment, a genetic cross or a population count.

A student models one strand of DNA with letter beads in this order: A-T-G-C-C-A. Which bases belong on the matching strand, in the same order?

Pick an answer, then press Check answer. Then you see Correct or Not quite, with the reason. Keys: A to D pick, Enter checks.

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Unofficial practice questions, not affiliated with any state education agency. Bank checked October 7, 2026.

Next step Ohio's State Tests: more high school biologyScience practice by grade, 3 to 8

All 60 questions

Structures and Processes 15

  • A chemical stops a cell from copying a gene's DNA sequence into RNA. The cell's ribosomes are unharmed. Which step of making a protein has the chemical blocked? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Transcription", "Messenger RNA"
  • A fertilized frog egg divides many times. Weeks later the tadpole has muscle, nerve and skin cells. Tests show that all three kinds of cell carry the same DNA. What best explains how the cells differ? Next Generation Science Standards, HS-LS3 Heredity: Inheritance and Variation of Traits: core idea LS3.A (HS-LS3-1; also LS1.B, HS-LS1-4)
  • A liquid breaks down slowly on its own. A student adds a few drops of an enzyme, and the liquid breaks down rapidly. When that reaction ends, the student pours fresh liquid into the same tube and it breaks down rapidly again. Which statement fits the evidence? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Enzyme"
  • A plant grows in air whose carbon dioxide carries a traceable form of carbon. Days later the tracer is found in the plant's sugars, and later still in its proteins. What does this show? Next Generation Science Standards, HS-LS1 From Molecules to Organisms: Structures and Processes: core idea LS1.C (HS-LS1-6)
  • A runner's body temperature starts to rise during a race. Her sweat glands release sweat, and her temperature falls back toward its usual value. Which idea does this show? Next Generation Science Standards, HS-LS1 From Molecules to Organisms: Structures and Processes: core idea LS1.A (HS-LS1-3)
  • A stretch of messenger RNA that codes for part of a protein is 12 nucleotides long and has no stop signal. How many amino acids does this stretch code for? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Codon"
  • A student models one strand of DNA with letter beads in this order: A-T-G-C-C-A. Which bases belong on the matching strand, in the same order? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Base Pair", "Nucleotide"
  • A student watches a video of a human skin cell with 46 chromosomes dividing by mitosis. How many chromosomes does each of the two daughter cells have? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Mitosis", "Meiosis"
  • A substitution changes one base in a gene. The protein made from the gene now has one different amino acid and folds into a different shape. What does this result show? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Protein", "Substitution"
  • A water plant in a sealed tube of water is set under a bright lamp. Bubbles of gas rise from its leaves. When the lamp is switched off, the bubbling stops. Which gas is most likely in the bubbles, and why? Next Generation Science Standards, HS-LS1 From Molecules to Organisms: Structures and Processes: core idea LS1.C (HS-LS1-5)
  • Cells in a dish are treated with a chemical that stops their ribosomes from working. Tests show the cells still make messenger RNA. What can the cells no longer do? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Ribosome", "Translation"
  • Identical seedlings grow in two sealed jars with light and water. Jar 1 holds normal air. In jar 2 the carbon dioxide has been removed from the air. After two weeks only the seedlings in jar 1 have gained mass. What explains the result? Next Generation Science Standards, HS-LS1 From Molecules to Organisms: Structures and Processes: core idea LS1.C (HS-LS1-5)
  • In a model of the body, muscle cells make up muscle tissue, the tissue forms part of the heart, and the heart is one part of the circulatory system. Which idea does the model show? Next Generation Science Standards, HS-LS1 From Molecules to Organisms: Structures and Processes: core idea LS1.A (HS-LS1-2)
  • Sprouting seeds are sealed in a dark flask with gas sensors. Over one hour the oxygen level falls and the carbon dioxide level rises. Which process explains both changes? Next Generation Science Standards, HS-LS1, core idea LS1.C (HS-LS1-7); NOAA, "Carbon cycle" (carbon storage and exchange)
  • Students measure one classmate's heart rate: 70 beats per minute at rest, 130 after two minutes of jumping jacks, and 74 after five minutes of rest. Which claim do the data support? Next Generation Science Standards, HS-LS1 From Molecules to Organisms: Structures and Processes: core idea LS1.A (HS-LS1-3)

Ecosystems 15

  • A caterpillar eats 10 grams of leaf. It gains 1 gram of body mass, and 5 grams leave its body as solid waste. What happened to the other 4 grams of matter? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.B (HS-LS2-4)
  • A dam floods a forested valley for good. Ten years later, surveys find fish, water plants and ducks where forest species once lived. Which statement fits the evidence? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.C (HS-LS2-6)
  • A diagram of the carbon cycle has arrows between the air, plants, animals and soil. Which labeled arrow shows carbon moving from the air into living things? Next Generation Science Standards, HS-LS2, core idea LS2.B (HS-LS2-5); NOAA, "Carbon cycle" (carbon storage and exchange)
  • A lake has six native fish species. People release a fish from another continent. Ten years later, four native species are gone and the new fish makes up most of the catch. Which human-caused change does this show? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.C (HS-LS2-7)
  • A pond survey finds 50,000 insects that eat algae, 2,000 small fish that eat the insects and 40 large fish that eat the small fish. Why are there so few large fish? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.B (HS-LS2-4)
  • A sealed jar holds pond water, a water plant and a snail. It sits in a sunny window, and both organisms stay alive for weeks. Which pair of processes keeps carbon and oxygen moving between them? Next Generation Science Standards, HS-LS2, core idea LS2.B (HS-LS2-5); NOAA, "Carbon cycle" (carbon storage and exchange)
  • A small fire burns part of a grassland. Counts over the next five years show the same plant and insect species returning to their earlier numbers. What does this show? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.C (HS-LS2-6)
  • A table lists the hares and lynx counted in a forest over eight years. Each time the number of hares rises, the number of lynx rises a year or two later. When hares fall, lynx fall soon after. What best explains the pattern? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.A (HS-LS2-2)
  • A town wants less fertilizer washing into a stream. Plan A plants a strip of native grasses along the banks. Plan B paves the banks. In tests on a model stream, plan A cuts the runoff by 60 percent and plan B raises it. Which plan better meets the goal? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.C (HS-LS2-7)
  • An island herd holds steady near 200 deer. Then a hard winter kills many of the plants the deer eat, and the next count finds 120 deer. Which factor most directly lowered the number of deer the island could support? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.A (HS-LS2-1)
  • Bacteria live in mud at the bottom of a pond where sensors find no oxygen. They break down dead leaves and stay active all year. What does this show? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.B (HS-LS2-3)
  • Deer on an island are counted every year: 20, 45, 95, 160, 198, 201, 199. No deer arrive or leave. What does the leveling off near 200 suggest? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.A (HS-LS2-1)
  • In a meadow model, the grasses store 10,000 units of energy in a year. The grasshoppers that eat the grass store 1,000 units, and the birds that eat the grasshoppers store 100. What does the pattern show? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.B (HS-LS2-4)
  • Researchers watch a small fish species. A fish swimming alone is caught by predators in 6 of 10 trials. A fish swimming in a school of fifty is caught in 1 of 10 trials. What does the evidence support? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.D (HS-LS2-8)
  • Two bird species eat the same kind of seed on a small island. In years with few seeds, both populations shrink. Which interaction limits both populations? Next Generation Science Standards, HS-LS2 Ecosystems: Interactions, Energy, and Dynamics: core idea LS2.A (HS-LS2-2)

Heredity 15

  • A cell copies all of its DNA before it divides. The copying is very accurate, but tests find a few changed bases in the new copy. What are these changes, and why do they matter? Next Generation Science Standards, HS-LS3 Heredity: Inheritance and Variation of Traits: core idea LS3.B (HS-LS3-2)
  • A gene's code begins ATG-CCA-GGT and goes on for hundreds of bases. One base is deleted from the second group of three. How does this change the way the rest of the gene is read? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Frameshift Mutation", "Deletion"
  • A microscope video follows one diploid cell in a flower through all of meiosis. What does the video show at the end? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Meiosis"
  • A plant with red flowers is crossed with a plant with white flowers. The offspring have flowers with separate red patches and white patches. Which pattern of inheritance does this show? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Codominance"
  • A recessive trait is controlled by a gene on the X chromosome. In a study of one large family, 9 males and 1 female show the trait. What best explains why more males show it? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Sex Linked", "X Linked"
  • An insect species has 8 chromosomes in each body cell. How many chromosomes are in each of its egg or sperm cells? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Meiosis", "Haploid", "Gamete"
  • Cuttings from one plant, all genetically identical, are grown in two plots. The plants in rich soil average 90 centimeters tall. The plants in poor soil average 55 centimeters. What does the difference show? Next Generation Science Standards, HS-LS3 Heredity: Inheritance and Variation of Traits: core idea LS3.B (HS-LS3-3)
  • The heights of 500 students form a smooth, bell-shaped curve, with many values between the shortest and the tallest. Which explanation fits a trait with this kind of spread? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Polygenic Trait"
  • In a breed of guinea pig, black fur (B) is dominant over brown (b). Two guinea pigs have black fur. One has the alleles BB and the other Bb. Which statement is correct? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Genotype", "Phenotype"
  • In a family of dogs, neither parent shows a recessive coat trait, but one of their puppies does. What must be true of the parents? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Carrier", "Recessive"
  • In a plant species, purple flowers (P) are dominant over white (p). A Pp plant is crossed with a pp plant. What percent of the offspring are expected to have purple flowers? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Dominant", "Recessive"
  • In a plant species, tall (T) is dominant over short (t). A cross of two heterozygous plants (Tt × Tt) yields 400 seeds, and all of them sprout. About how many of the seedlings are expected to be short? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Recessive", "Dominant"
  • In a plant species, the allele for purple flowers (P) is dominant over the allele for white flowers (p). Two heterozygous plants (Pp) are crossed. What fraction of the offspring are expected to have white flowers? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Recessive", "Dominant", "Heterozygous"
  • Two brothers have the same parents but inherited different combinations of traits. Which event during meiosis creates new combinations of alleles on a chromosome? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Crossing Over", "Homologous Recombination"
  • Ultraviolet light causes a mutation in one skin cell of a lizard. Later the lizard has offspring. Will the offspring inherit this mutation? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Mutation"

Evolution 15

  • A bird population eats seeds. During a long drought only large, hard seeds are left. Birds with deeper beaks crack them more easily, and beak depth is inherited. What is expected in the next generations? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.C (HS-LS4-3)
  • A field is sprayed with one insecticide every year. In year 1 the spray kills 99 percent of a pest insect. By year 8 it kills only 30 percent. Tests show that the survivors pass their resistance to their offspring. What best explains the change? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.C (HS-LS4-4)
  • A fish lays thousands of eggs, but its lake has food for only a few hundred adults. The young differ in swimming speed, an inherited trait, and faster fish catch more food. Which outcome does natural selection predict? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.C (HS-LS4-2)
  • A frog species breeds only in cold mountain ponds. Over thirty years the ponds warm and dry up. The frogs' traits do not change fast enough, and in the end no frogs remain. Which statement fits the evidence? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.C (HS-LS4-5)
  • A river changes course and splits a squirrel population in two. For thousands of generations the two groups live under different conditions and never meet. Today they can no longer interbreed. What does this illustrate? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.C (HS-LS4-5)
  • A storm kills most of the 20 mice on a tiny island, at random. By chance, the 4 survivors all carry a rare allele for white feet, which does not affect survival. Generations later most of the mice have white feet. Which mechanism explains this? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Genetic Drift"
  • After a forest is cleared for farm fields, counts show field mice rising from 50 to 900 while a tree-nesting bird falls from 300 to 20. What does the evidence support? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.C (HS-LS4-5)
  • Every beetle in a population is the same shade of green, and the beetles are genetically identical for color. Birds eat the beetles. Can natural selection change the color of this population as it is now? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.B (HS-LS4-2)
  • In a series of rock layers, the shells of one kind of snail change gradually from smooth in the oldest layer to ridged in the youngest. What kind of evidence for evolution is this? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.A (HS-LS4-1)
  • On dark rocks, a lizard population is 20 percent dark and 80 percent light. Hawks catch light lizards more often. Color is inherited. Many generations later the population is 85 percent dark. What explains the change? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.C (HS-LS4-3)
  • One field is planted with a single, genetically uniform crop variety. A new fungus kills nearly every plant. A neighboring field planted with many varieties loses only some of its plants. What does this suggest? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Gene Pool"
  • One protein is 104 amino acids long in three species. The proteins of species A and species B differ at 1 position. Those of A and C differ at 20 positions. Which claim is best supported? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.A (HS-LS4-1)
  • The same gene is sequenced in four species. Species W differs from species X at 2 bases, from species Y at 15 bases and from species Z at 40 bases. By this evidence, which species shares the most recent common ancestor with W? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.A (HS-LS4-1)
  • Ten birds from a mainland population of many thousands settle a distant island. Centuries later, the island birds show far less genetic variety than the mainland birds. What explains the low variety? National Human Genome Research Institute, Talking Glossary of Genomic and Genetic Terms: "Founder Effect"
  • Three mammal species use their front limbs to fly, to swim and to run. X-ray images show the same set of bones, in the same order, in all three limbs. What does the shared bone pattern suggest? Next Generation Science Standards, HS-LS4 Biological Evolution: Unity and Diversity: core idea LS4.A (HS-LS4-1)

How it works

Unofficial biology EOC and biology state test practice: 15 questions on each of four life science topics. This is no state's test, and it is not affiliated with any state education agency.

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How the questions are built

Every question describes a scenario and asks what it shows, so you practice reading evidence instead of reciting definitions. Under each answer is the source it rests on: a core idea of the Next Generation Science Standards, an entry in the genetics glossary of the National Human Genome Research Institute, or NOAA's carbon cycle page. The organisms and numbers in the scenarios are made up.

  • Before you read the choices, find the one thing that changed in the scenario.
  • For a cross, write the four allele pairs on scratch paper, then count the ones the question asks about.

Questions and answers

What is on a biology EOC?

Each state publishes its own blueprint. The questions here follow the four high school life science ideas of the Next Generation Science Standards: structures and processes, ecosystems, heredity, and evolution.

Are these real EOC biology questions?

No. Every question was written for this site, and none comes from a state test, a released form or a state practice test. For official sample items, look on your state education agency's testing page.

How many questions are on the biology EOC?

There is no single number. Each state sets its own length, timing and passing score, and this page does not guess them. Your state education agency's testing page gives the figures for your test.

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