HESI A2 Biology 2024/2025 Master Review – 100%
Verified Questions with Scientific Reasoning
June 06, 2025
80 Original Biology Questions Covering Cell Biology, Genetics, Ecosystems, and Body
Systems
Question 1:
What is the primary source of energy for Earth’s ecosystems?
A Wind
B Sunlight
C Geothermal heat
D Tidal movement
Correct Answer: B
Explanation: Sunlight is the primary energy source for Earth’s ecosystems, driving
photosynthesis in producers like plants, which convert solar energy into chemical energy
for food chains.
Question 2:
Which organelle is responsible for protein synthesis in a cell?
A Mitochondrion
B Ribosome
C Golgi apparatus
D Nucleus
Correct Answer: B
Explanation: Ribosomes, found free in the cytoplasm or on the rough endoplasmic
reticulum, synthesize proteins by translating mRNA into amino acid chains.
Question 3:
In genetics, what term describes an organism with two identical alleles for a trait?
A Heterozygous
B Homozygous
1
, C Dominant
D Recessive
Correct Answer: B
Explanation: Homozygous refers to an organism with two identical alleles (e.g., AA or
aa) for a trait, influencing how the trait is expressed.
Question 4:
Which body system is primarily responsible for gas exchange?
A Circulatory system
B Respiratory system
C Digestive system
D Nervous system
Correct Answer: B
Explanation: The respiratory system, including lungs and alveoli, facilitates gas ex-
change, delivering oxygen to the blood and removing carbon dioxide.
Question 5:
What is the basic unit of life?
A Tissue
B Organ
C Cell
D Organism
Correct Answer: C
Explanation: The cell is the basic unit of life, the smallest structure capable of per-
forming all life processes, such as metabolism and reproduction.
Question 6:
During mitosis, what phase involves the separation of sister chromatids?
A Prophase
B Metaphase
C Anaphase
D Telophase
Correct Answer: C
Explanation: In anaphase of mitosis, sister chromatids are pulled apart to opposite
poles of the cell by spindle fibers, ensuring each daughter cell gets identical DNA.
Question 7:
2
, What type of symbiosis occurs when one organism benefits and the other is unaffected?
A Mutualism
B Commensalism
C Parasitism
D Predation
Correct Answer: B
Explanation: Commensalism is a symbiotic relationship where one organism benefits
(e.g., a bird nesting in a tree) while the other (the tree) is neither helped nor harmed.
Question 8:
Which molecule carries genetic information in cells?
A DNA
B RNA
C Protein
D Lipid
Correct Answer: A
Explanation: Deoxyribonucleic acid (DNA) stores and transmits genetic information,
encoding instructions for building proteins and determining traits.
Question 9:
What is the primary function of the circulatory system?
A Digest food
B Transport nutrients and oxygen
C Remove waste from cells
D Control body movement
Correct Answer: B
Explanation: The circulatory system transports nutrients, oxygen, and waste via blood,
vessels, and the heart, supporting cellular functions throughout the body.
Question 10:
What process allows plants to convert sunlight into chemical energy?
A Cellular respiration
B Photosynthesis
C Fermentation
D Transpiration
3
Verified Questions with Scientific Reasoning
June 06, 2025
80 Original Biology Questions Covering Cell Biology, Genetics, Ecosystems, and Body
Systems
Question 1:
What is the primary source of energy for Earth’s ecosystems?
A Wind
B Sunlight
C Geothermal heat
D Tidal movement
Correct Answer: B
Explanation: Sunlight is the primary energy source for Earth’s ecosystems, driving
photosynthesis in producers like plants, which convert solar energy into chemical energy
for food chains.
Question 2:
Which organelle is responsible for protein synthesis in a cell?
A Mitochondrion
B Ribosome
C Golgi apparatus
D Nucleus
Correct Answer: B
Explanation: Ribosomes, found free in the cytoplasm or on the rough endoplasmic
reticulum, synthesize proteins by translating mRNA into amino acid chains.
Question 3:
In genetics, what term describes an organism with two identical alleles for a trait?
A Heterozygous
B Homozygous
1
, C Dominant
D Recessive
Correct Answer: B
Explanation: Homozygous refers to an organism with two identical alleles (e.g., AA or
aa) for a trait, influencing how the trait is expressed.
Question 4:
Which body system is primarily responsible for gas exchange?
A Circulatory system
B Respiratory system
C Digestive system
D Nervous system
Correct Answer: B
Explanation: The respiratory system, including lungs and alveoli, facilitates gas ex-
change, delivering oxygen to the blood and removing carbon dioxide.
Question 5:
What is the basic unit of life?
A Tissue
B Organ
C Cell
D Organism
Correct Answer: C
Explanation: The cell is the basic unit of life, the smallest structure capable of per-
forming all life processes, such as metabolism and reproduction.
Question 6:
During mitosis, what phase involves the separation of sister chromatids?
A Prophase
B Metaphase
C Anaphase
D Telophase
Correct Answer: C
Explanation: In anaphase of mitosis, sister chromatids are pulled apart to opposite
poles of the cell by spindle fibers, ensuring each daughter cell gets identical DNA.
Question 7:
2
, What type of symbiosis occurs when one organism benefits and the other is unaffected?
A Mutualism
B Commensalism
C Parasitism
D Predation
Correct Answer: B
Explanation: Commensalism is a symbiotic relationship where one organism benefits
(e.g., a bird nesting in a tree) while the other (the tree) is neither helped nor harmed.
Question 8:
Which molecule carries genetic information in cells?
A DNA
B RNA
C Protein
D Lipid
Correct Answer: A
Explanation: Deoxyribonucleic acid (DNA) stores and transmits genetic information,
encoding instructions for building proteins and determining traits.
Question 9:
What is the primary function of the circulatory system?
A Digest food
B Transport nutrients and oxygen
C Remove waste from cells
D Control body movement
Correct Answer: B
Explanation: The circulatory system transports nutrients, oxygen, and waste via blood,
vessels, and the heart, supporting cellular functions throughout the body.
Question 10:
What process allows plants to convert sunlight into chemical energy?
A Cellular respiration
B Photosynthesis
C Fermentation
D Transpiration
3
