Question 1 of 10
Which graph correctly shows exponential growth?
ABoth
BB
CA
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 2 of 10
Use the Punnett square to determine the probability of offspring with the homozygous recessive (aa) genotype.
A1/2 (50%)
B1/4 (25%)
C0
D3/4 (75%)
Explanation
Aa × Aa cross: AA, Aa, Aa, aa. Only one box (aa) shows the homozygous recessive: 1/4 = 25%.
Question 3 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 form longer polymer chains than carbohydrates
CThey are insoluble in water, so they take up less space when stored
DThey contain more nitrogen atoms 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 4 of 10
Which organelle is labeled X in the cell diagram below? 
AGolgi apparatus
BMitochondria
CNucleus
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 5 of 10
Which pair of processes drives the most direct exchange of CO₂ between living organisms and the atmosphere?
ATranspiration (releases CO₂) and condensation (absorbs CO₂)
BPhotosynthesis (releases CO₂) and cellular respiration (absorbs CO₂)
CPhotosynthesis (absorbs CO₂) and cellular respiration (releases CO₂)
DNitrogen fixation (absorbs CO₂) and decomposition (releases O₂)
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
A theory in science is:
Athe same as a hypothesis
Ba proven fact that can never change
Can untested guess
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 7 of 10
In the food web below, what would happen if all the frogs were removed? 
AInsect population increases and snake population decreases
BNothing changes
CSnake population increases
DAll organisms die
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 8 of 10
Which molecule carries energy from glucose breakdown to the electron transport chain?
AH2O
BCO2
CATP
DNADH
Explanation
📌 NADH and FADH2 are electron carriers. They transport high-energy electrons from glycolysis and Krebs cycle to the ETC.
Question 9 of 10
A student designed an experiment to test how light affects plant growth. Identify the components of this experiment. 
AIndependent: light; Dependent: plant height
BIndependent: plant height; Dependent: light
CIndependent: temperature; Dependent: light
DIndependent: water; Dependent: soil
Explanation
📌 Independent variable = what you change (light)
Dependent variable = what you measure (plant height)
Control group = no light (to compare against)
Constants = same soil, water, temperature, pot size
Dependent variable = what you measure (plant height)
Control group = no light (to compare against)
Constants = same soil, water, temperature, pot size
Question 10 of 10
In a Punnett square cross Bb × Bb, what fraction of offspring are expected to be homozygous recessive (bb)?
A50%
B25%
C0%
D75%
Explanation
📌 BB:Bb:bb = 1:2:1
bb = 1/4 = 25%
bb = 1/4 = 25%