Biology (Grades 9–10) Midterm — Units 5–6

Science Grades 9–10 20 multiple choice + 1 written

Free printable Biology midterm (Grades 9–10): 20 multiple-choice questions plus 1 written response covering Genetics, Evolution & Ecology. Answer key included — customize it in the Midterm Maker.

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Directions: Read each question carefully and choose the best answer. Answer the written response in complete sentences.

Covers: Genetics · Evolution & Ecology

Part 1: Multiple Choice

In a cross of AaBb × AaBb, what fraction of offspring are expected to be aabb?
1. A. 1/8
2. B. 3/16
3. C. 1/4
4. D. 1/16
A carrier mother (XᴴXʰ) and an unaffected father (XᴴY) have a son. What is the probability the son has hemophilia?
1. A. 0%
2. B. 25%
3. C. 50%
4. D. 100%
Red and white snapdragons are crossed and all offspring are pink. What inheritance pattern is this?
1. A. Complete dominance
2. B. Codominance
3. C. Incomplete dominance
4. D. Sex-linked inheritance
What phenotypic ratio is expected from a dihybrid cross of AaBb × AaBb with independent assortment?
1. A. 3:1
2. B. 1:1:1:1
3. C. 1:2:1
4. D. 9:3:3:1
A person with type AB blood has A antigens and B antigens on their red blood cells. What inheritance pattern is this?
1. A. Sex-linked inheritance
2. B. Polygenic inheritance
3. C. Incomplete dominance
4. D. Codominance
Two heterozygous plants (Aa × Aa) are crossed. What is the expected phenotypic ratio if A is completely dominant?
1. A. 1:1 dominant to recessive
2. B. 4:0 dominant to recessive
3. C. 3:1 dominant to recessive
4. D. 1:2:1 dominant to recessive
Crossing an organism that shows the dominant trait with a homozygous recessive organism to learn its genotype is called what?
1. A. A dihybrid cross
2. B. A karyotype
3. C. A pedigree
4. D. A test cross
Human height varies continuously across a wide range. This is largely because height is what?
1. A. A codominant trait
2. B. Influenced by many genes
3. C. A sex-linked trait
4. D. Controlled by one gene with two alleles
Why is red-green color blindness more common in males than in females?
1. A. The allele is dominant only in males
2. B. Females have no color-vision genes
3. C. Males have only one X chromosome
4. D. The allele is on the Y chromosome
What does Mendel's law of segregation state?
1. A. Genes on the same chromosome always stay together
2. B. Dominant alleles are more common
3. C. Offspring blend their parents' traits
4. D. The two alleles for a gene separate when gametes form
Primary succession begins in which type of area?
1. A. An area with no soil, such as new lava rock
2. B. An abandoned farm field
3. C. A mowed lawn
4. D. A forest after a wildfire
Producers in an ecosystem contain 10,000 kcal. Using the 10% rule, about how much energy reaches secondary consumers?
1. A. 5,000 kcal
2. B. 10 kcal
3. C. 100 kcal
4. D. 1,000 kcal
Which condition is required for natural selection to occur?
1. A. A population of identical individuals
2. B. Unlimited food and space
3. C. Individuals changing traits on purpose
4. D. Inherited variation among individuals
Which organisms convert nitrogen gas from the air into forms plants can use?
1. A. Green plants
2. B. Viruses
3. C. Nitrogen-fixing bacteria
4. D. Herbivores
Random changes in allele frequencies that have the greatest effect in small populations are called what?
1. A. Natural selection
2. B. Artificial selection
3. C. Genetic drift
4. D. Gene flow
In a population in Hardy-Weinberg equilibrium, 16% of individuals show the recessive phenotype. What is the frequency of the recessive allele?
1. A. 0.4
2. B. 0.84
3. C. 0.16
4. D. 0.6
What do homologous structures, such as the forelimbs of humans, cats, and whales, suggest?
1. A. The structures evolved separately
2. B. The species share a common ancestor
3. C. The species can interbreed
4. D. The species live in the same habitat
Which process removes carbon dioxide from the atmosphere?
1. A. Burning fossil fuels
2. B. Photosynthesis
3. C. Decomposition
4. D. Cellular respiration
A river splits a population in two. After many generations, the groups can no longer interbreed. What process occurred?
1. A. Convergent evolution
2. B. Artificial selection
3. C. Coevolution
4. D. Speciation through geographic isolation
Why do bacterial populations often become resistant to antibiotics over time?
1. A. Resistant bacteria survive treatment and pass on their resistance genes
2. B. Antibiotics make every bacterium stronger
3. C. Antibiotics teach bacteria to resist them
4. D. Bacteria decide to change their DNA

Part 2: Written Response

Using a specific example, explain how a change in an environment can lead to changes in a population over many generations. Then describe how energy and matter move differently through that ecosystem.

Answer Key — Biology (Grades 9–10) Midterm — Units 5–6

D — 1/16 1/4 aa × 1/4 bb = 1/16.
C — 50% Sons get the father's Y, and half get the mother's Xʰ.
C — Incomplete dominance Neither allele fully masks the other, producing a blend.
D — 9:3:3:1 Independent genes each give 3:1, combining to 9:3:3:1.
D — Codominance Both alleles are fully expressed at the same time.
C — 3:1 dominant to recessive Three of four offspring have at least one A allele.
D — A test cross Any recessive offspring reveal a heterozygous parent.
B — Influenced by many genes Polygenic traits, plus environment, produce a continuous range.
C — Males have only one X chromosome One recessive X-linked allele causes the trait in males.
D — The two alleles for a gene separate when gametes form Each gamete receives only one allele for each gene.
A — An area with no soil, such as new lava rock Primary succession starts where no soil exists; pioneer species begin it.
C — 100 kcal 10,000 → 1,000 (primary) → 100 (secondary).
D — Inherited variation among individuals Selection acts on heritable differences in survival and reproduction.
C — Nitrogen-fixing bacteria Bacteria in soil and root nodules convert N₂ into ammonia.
C — Genetic drift Chance events shift allele frequencies most in small populations.
A — 0.4 q² = 0.16, so q = √0.16 = 0.4.
B — The species share a common ancestor Shared bone patterns point to inheritance from a common ancestor.
B — Photosynthesis Producers take in CO₂ to build sugars.
D — Speciation through geographic isolation Isolation let the groups diverge until they became separate species.
A — Resistant bacteria survive treatment and pass on their resistance genes The antibiotic selects for bacteria that already carry resistance.

Written Response — Look-Fors

Accurate example (antibiotic resistance, finches, moths); variation, heritability, selection, change in allele frequency over generations; energy flows one way and is lost as heat (about 10% passed on); matter cycles (carbon, nitrogen).

Biology (Grades 9–10) Midterm — Units 5–6

Part 1: Multiple Choice

Part 2: Written Response

Written Response — Look-Fors

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