Question 1 of 10
In a Punnett square cross Bb × Bb, what fraction of offspring are expected to be homozygous recessive (bb)?
A75%
B25%
C0%
D50%
Explanation
📌 BB:Bb:bb = 1:2:1
bb = 1/4 = 25%
bb = 1/4 = 25%
Question 2 of 10
The carbon cycle involves:
Aonly the ocean
Bthe movement of carbon through living and non-living systems
Conly the atmosphere
Donly living organisms
Explanation
📌 Carbon moves through: atmosphere (CO₂) → photosynthesis → organisms → respiration/decomposition → atmosphere.
Also: fossil fuels → combustion → atmosphere.
Also: fossil fuels → combustion → atmosphere.
Question 3 of 10
Which class of biomolecule is built from nucleotide monomers?
ACarbohydrates
BLipids
CProteins
DNucleic acids (DNA and RNA)
Explanation
Nucleic acids (DNA, RNA) are polymers of nucleotide monomers — each nucleotide is a phosphate + sugar + nitrogenous base. Distractors: Proteins are polymers of *amino acids*. Carbohydrates are polymers of *monosaccharides* (e.g., glucose). Lipids are not true polymers — they assemble from fatty acids and glycerol but don't repeat a single monomer.
Question 4 of 10
Alternative splicing allows:
ADNA to be repaired
Bone gene to code for multiple proteins
Cchromosomes to separate
Dmutations to be prevented
Explanation
📌 One gene → multiple proteins by including/excluding different exons. Increases protein diversity without needing more genes.
Question 5 of 10
Which pair of processes drives the most direct exchange of CO₂ between living organisms and the atmosphere?
ANitrogen fixation (absorbs CO₂) and decomposition (releases O₂)
BPhotosynthesis (absorbs CO₂) and cellular respiration (releases CO₂)
CTranspiration (releases CO₂) and condensation (absorbs CO₂)
DPhotosynthesis (releases CO₂) and cellular respiration (absorbs CO₂)
Explanation
Photosynthesis consumes atmospheric CO₂ to build glucose (CO₂ → sugar), while cellular respiration breaks glucose back down to CO₂ and water. Together they form the short-term carbon cycle between the biosphere and atmosphere. Distractor B reverses the direction. Transpiration moves water vapor, not CO₂. Nitrogen fixation moves nitrogen, not carbon.
Question 6 of 10
Use the Punnett square to determine the probability of offspring with the homozygous recessive (aa) genotype.
A1/4 (25%)
B0
C1/2 (50%)
D3/4 (75%)
Explanation
Aa × Aa cross: AA, Aa, Aa, aa. Only one box (aa) shows the homozygous recessive: 1/4 = 25%.
Question 7 of 10
Why does the left ventricle have a thicker muscular wall than the right ventricle?
AIt contains valves that the right ventricle lacks
BIt is in direct contact with the lungs
CIt must pump blood at higher pressure to reach the entire body
DIt receives more deoxygenated blood from the body
Explanation
The left ventricle pumps oxygenated blood through the *systemic circuit* — every tissue in the body — which requires high pressure. The right ventricle only needs to push blood a short distance to the lungs (pulmonary circuit), so its wall is thinner. Distractors: the left ventricle pumps *oxygenated* blood, not deoxygenated. Both ventricles have valves (AV and semilunar). The right ventricle, not the left, is closer to the lungs.
Question 8 of 10
Lipids store roughly twice as much energy per gram as carbohydrates. Which property of lipid molecules best explains this?
AThey contain more nitrogen atoms than carbohydrates
BThey form longer polymer chains than carbohydrates
CThey are insoluble in water, so they take up less space when stored
DLong hydrocarbon chains contain many C–H bonds that can be oxidized to release energy
Explanation
Lipid fatty-acid tails are long chains of carbon–hydrogen bonds. Oxidizing each C–H bond releases energy, so the more C–H bonds per gram, the more energy is stored. Carbohydrates have fewer C–H bonds per carbon because oxygen atoms are already attached. Distractors: water insolubility relates to *where* lipids are stored, not how much energy they hold. Lipids aren't true polymers. Lipids contain almost no nitrogen — that's a feature of proteins and nucleic acids.
Question 9 of 10
Epigenetics studies how:
ADNA sequence changes
Borganisms evolve
Ccells divide
Dgene expression changes without altering DNA sequence
Explanation
📌 Epigenetics = changes in gene expression WITHOUT changing DNA sequence.
Mechanisms: DNA methylation, histone modification.
Affected by environment, diet, stress.
Mechanisms: DNA methylation, histone modification.
Affected by environment, diet, stress.
Question 10 of 10
In the food web below, what would happen if all the frogs were removed? 
AAll organisms die
BSnake population increases
CInsect population increases and snake population decreases
DNothing changes
Explanation
📌 If frogs are removed:
• Insects (grasshoppers) they ate would INCREASE (no predator)
• Snakes that ate frogs would DECREASE (less food)
• This demonstrates how removing one species affects the entire food web.
• Insects (grasshoppers) they ate would INCREASE (no predator)
• Snakes that ate frogs would DECREASE (less food)
• This demonstrates how removing one species affects the entire food web.