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:
AArtificial selection
BGenetic engineering
CSpontaneous generation
DNatural 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 contains valves that the right ventricle lacks
BIt is in direct contact with the lungs
CIt receives more deoxygenated blood from the body
DIt must pump blood at higher pressure to reach the entire 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 3 of 10
In a DNA nucleotide, which component carries the genetic code through its specific sequence?
ADeoxyribose sugar
BPhosphate group
CHydrogen bond
DNitrogenous base
Explanation
The nitrogenous base (adenine, thymine, guanine, or cytosine) is the part of a DNA nucleotide that varies — its sequence along the strand IS the genetic code. The phosphate and deoxyribose sugar are identical in every nucleotide and form the structural 'backbone' of the DNA strand; they don't store information. Hydrogen bonds hold the two strands together at the bases but are not part of a single nucleotide.
Question 4 of 10
Alternative splicing allows:
Achromosomes to separate
Bmutations to be prevented
CDNA to be repaired
Done gene to code for multiple proteins
Explanation
📌 One gene → multiple proteins by including/excluding different exons. Increases protein diversity without needing more genes.
Question 5 of 10
Use the Punnett square to determine the probability of offspring with the homozygous recessive (aa) genotype.
A1/4 (25%)
B3/4 (75%)
C0
D1/2 (50%)
Explanation
Aa × Aa cross: AA, Aa, Aa, aa. Only one box (aa) shows the homozygous recessive: 1/4 = 25%.
Question 6 of 10
Epigenetics studies how:
Agene expression changes without altering DNA sequence
Borganisms evolve
Ccells divide
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.
Question 7 of 10
Which molecule carries energy from glucose breakdown to the electron transport chain?
AATP
BNADH
CCO2
DH2O
Explanation
📌 NADH and FADH2 are electron carriers. They transport high-energy electrons from glycolysis and Krebs cycle to the ETC.
Question 8 of 10
A theory in science is:
Athe same as a hypothesis
Ban untested guess
Ca proven fact that can never change
Da well-supported explanation based on extensive evidence
Explanation
📌 A scientific theory is well-tested, widely accepted, and explains a broad range of observations.
It is NOT just a guess — that's a hypothesis.
It is NOT just a guess — that's a hypothesis.
Question 9 of 10
During which phase of the cell cycle does DNA replication occur? 
AG1 phase
BG2 phase
CM 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 10 of 10
The carbon cycle involves:
Aonly the ocean
Bonly the atmosphere
Cthe movement of carbon through living and non-living systems
Donly living organisms
Explanation
📌 Carbon moves through: atmosphere (CO₂) → photosynthesis → organisms → respiration/decomposition → atmosphere.
Also: fossil fuels → combustion → atmosphere.
Also: fossil fuels → combustion → atmosphere.