Question 1 of 10
The graph shows the change in a moth population over time. Dark moths increased after industrial pollution darkened tree bark. This is an example of:
AGenetic engineering
BSpontaneous generation
CNatural selection
DArtificial selection
Explanation
📌 This is the classic peppered moth example of natural selection.
Before pollution: light bark → light moths camouflaged → survived
After pollution: dark bark → dark moths camouflaged → survived
The environment selected for the trait that provided camouflage.
Before pollution: light bark → light moths camouflaged → survived
After pollution: dark bark → dark moths camouflaged → survived
The environment selected for the trait that provided camouflage.
Question 2 of 10
Why does the left ventricle have a thicker muscular wall than the right ventricle?
AIt must pump blood at higher pressure to reach the entire body
BIt contains valves that the right ventricle lacks
CIt receives more deoxygenated blood from the body
DIt is in direct contact with the lungs
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 3 of 10
The Hardy-Weinberg principle states that allele frequencies remain constant when:
Athe population is very small
Bnatural selection is strong
Cmutations are common
Dthere is no evolution occurring
Explanation
📌 Conditions: no mutation, no migration, random mating, large population, no natural selection.
Any violation → evolution occurs.
Any violation → evolution occurs.
Question 4 of 10
All three domains of life (Bacteria, Archaea, and Eukarya) share which structural feature?
ARibosomes for protein synthesis
BMulticellular organization
CChloroplasts for photosynthesis
DA membrane-bound nucleus
Explanation
All cellular life — Bacteria, Archaea, and Eukarya — uses ribosomes to build proteins. Distractors: a membrane-bound nucleus is found only in Eukarya (Bacteria and Archaea are prokaryotic). Multicellularity appears only in some Eukarya — most life is unicellular. Chloroplasts are organelles found only in plants and algae (a subset of Eukarya).
Question 5 of 10
In the food web below, what would happen if all the frogs were removed? 
AAll organisms die
BInsect population increases and snake population decreases
CNothing changes
DSnake population increases
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.
Question 6 of 10
Which graph correctly shows exponential growth?
AA
BB
CBoth
DNeither
Explanation
📌 Exponential growth = J-shaped curve (slow start, rapid increase)
Linear growth = straight line (constant rate)
Graph A shows exponential growth.
Linear growth = straight line (constant rate)
Graph A shows exponential growth.
Question 7 of 10
During which phase of the cell cycle does DNA replication occur? 
AM phase
BG1 phase
CG2 phase
DS phase
Explanation
📌 DNA replication occurs during S phase (Synthesis) of interphase.
Interphase: G1 → S → G2, then Mitosis.
Interphase: G1 → S → G2, then Mitosis.
Question 8 of 10
Lipids store roughly twice as much energy per gram as carbohydrates. Which property of lipid molecules best explains this?
ALong hydrocarbon chains contain many C–H bonds that can be oxidized to release energy
BThey contain more nitrogen atoms than carbohydrates
CThey are insoluble in water, so they take up less space when stored
DThey form longer polymer chains than carbohydrates
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
Which organelle is labeled X in the cell diagram below? 
AGolgi apparatus
BNucleus
CMitochondria
DEndoplasmic reticulum
Explanation
📌 Organelle X has the bean-shaped structure with inner folds (cristae) → Mitochondria
Mitochondria = powerhouse of the cell = produces ATP through cellular respiration
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
Mitochondria = powerhouse of the cell = produces ATP through cellular respiration
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
Question 10 of 10
Epigenetics studies how:
Agene expression changes without altering DNA sequence
Bcells divide
Corganisms evolve
DDNA sequence changes
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.