PRAXIS 5005 Science Mega Practice Exam | Real
Exam-Style Questions, Full Rationales, and A+
Graded Study Resource for Guaranteed Success
(Latest 2026 Edition)
Question 1
Which of the following best describes the primary function of mitochondria in a
eukaryotic cell?
(A) Protein synthesis
(B) Lipid storage
(C) ATP production
(D) Genetic material storage
Answer: C
Rationale: Mitochondria are known as the “powerhouses of the cell” because they
generate adenosine triphosphate (ATP) through cellular respiration.
Question 2
Which kingdom includes organisms that are multicellular, heterotrophic, and have cell
walls made of chitin?
(A) Plantae
(B) Animalia
(C) Fungi
(D) Protista
Answer: C
Rationale: Fungi are multicellular (except yeasts), heterotrophic (absorb nutrients), and
have cell walls containing chitin. Plantae have cellulose cell walls; Animalia lack cell
walls.
,Question 3
A student observes a plant’s leaves turning yellow. Which element deficiency is the
most likely cause?
(A) Nitrogen
(B) Phosphorus
(C) Potassium
(D) Calcium
Answer: A
Rationale: Nitrogen is a key component of chlorophyll. Deficiency causes chlorosis
(yellowing of leaves), especially in older leaves.
Question 4
What is the primary role of decomposers in an ecosystem?
(A) Convert sunlight into chemical energy
(B) Produce oxygen during photosynthesis
(C) Break down dead organic matter
(D) Control predator populations
Answer: C
Rationale: Decomposers (bacteria, fungi) recycle nutrients by breaking down dead
organisms and waste, making them available for producers.
Question 5
Which of the following is an example of a learned behavior?
(A) A baby grasping an object
(B) A turtle hatchling moving toward the ocean
(C) A dog sitting when commanded
(D) A spider spinning a web
Answer: C
Rationale: Learned behaviors are acquired through experience. Sitting on command is
trained; the others are innate (instinctual).
, Question 6
In a food web, which trophic level has the greatest biomass?
(A) Primary consumers
(B) Secondary consumers
(C) Tertiary consumers
(D) Producers
Answer: D
Rationale: Energy decreases at each trophic level. Producers (plants) have the highest
biomass, supporting all other levels.
Question 7
Which of the following is a density-dependent limiting factor?
(A) Flood
(B) Wildfire
(C) Competition for food
(D) Volcanic eruption
Answer: C
Rationale: Density-dependent factors (competition, disease, predation) intensify as
population density increases. Floods and fires are density-independent.
Question 8
A cell with 12 chromosomes undergoes mitosis. How many chromosomes will each
daughter cell have?
(A) 6
(B) 12
(C) 24
(D) 48
Exam-Style Questions, Full Rationales, and A+
Graded Study Resource for Guaranteed Success
(Latest 2026 Edition)
Question 1
Which of the following best describes the primary function of mitochondria in a
eukaryotic cell?
(A) Protein synthesis
(B) Lipid storage
(C) ATP production
(D) Genetic material storage
Answer: C
Rationale: Mitochondria are known as the “powerhouses of the cell” because they
generate adenosine triphosphate (ATP) through cellular respiration.
Question 2
Which kingdom includes organisms that are multicellular, heterotrophic, and have cell
walls made of chitin?
(A) Plantae
(B) Animalia
(C) Fungi
(D) Protista
Answer: C
Rationale: Fungi are multicellular (except yeasts), heterotrophic (absorb nutrients), and
have cell walls containing chitin. Plantae have cellulose cell walls; Animalia lack cell
walls.
,Question 3
A student observes a plant’s leaves turning yellow. Which element deficiency is the
most likely cause?
(A) Nitrogen
(B) Phosphorus
(C) Potassium
(D) Calcium
Answer: A
Rationale: Nitrogen is a key component of chlorophyll. Deficiency causes chlorosis
(yellowing of leaves), especially in older leaves.
Question 4
What is the primary role of decomposers in an ecosystem?
(A) Convert sunlight into chemical energy
(B) Produce oxygen during photosynthesis
(C) Break down dead organic matter
(D) Control predator populations
Answer: C
Rationale: Decomposers (bacteria, fungi) recycle nutrients by breaking down dead
organisms and waste, making them available for producers.
Question 5
Which of the following is an example of a learned behavior?
(A) A baby grasping an object
(B) A turtle hatchling moving toward the ocean
(C) A dog sitting when commanded
(D) A spider spinning a web
Answer: C
Rationale: Learned behaviors are acquired through experience. Sitting on command is
trained; the others are innate (instinctual).
, Question 6
In a food web, which trophic level has the greatest biomass?
(A) Primary consumers
(B) Secondary consumers
(C) Tertiary consumers
(D) Producers
Answer: D
Rationale: Energy decreases at each trophic level. Producers (plants) have the highest
biomass, supporting all other levels.
Question 7
Which of the following is a density-dependent limiting factor?
(A) Flood
(B) Wildfire
(C) Competition for food
(D) Volcanic eruption
Answer: C
Rationale: Density-dependent factors (competition, disease, predation) intensify as
population density increases. Floods and fires are density-independent.
Question 8
A cell with 12 chromosomes undergoes mitosis. How many chromosomes will each
daughter cell have?
(A) 6
(B) 12
(C) 24
(D) 48
