EST II BIOLOGY HARD PRACTICE MOCK EXAM 60 Questions | 60 Minutes

 

EST II BIOLOGY

HARD PRACTICE MOCK EXAM
60 Questions   |   60 Minutes

Directions:

Choose the best answer for each question. Each question has five answer choices: A, B, C, D, and E.

Some questions require you to interpret an experiment, identify variables, analyze observations, predict results, or use biological evidence to reach a logical conclusion.

Recommended practice: Complete all 60 questions before checking the answers.

CELL STRUCTURE AND CELLULAR PROCESSES

1. A student observes a cell under a microscope. The cell has a nucleus, mitochondria, and a cell membrane, but no cell wall or chloroplasts. Which conclusion is most appropriate?

A) The cell is definitely a bacterium.

B) The cell is most likely an animal cell.

C) The cell is definitely a plant cell.

D) The cell must be a fungal cell.

E) The cell cannot perform cellular respiration.

Answer: B) The cell is most likely an animal cell.

2. Which observation provides the strongest evidence that a structure is a eukaryotic cell?

A) It contains DNA.

B) It contains ribosomes.

C) It contains a membrane-bound nucleus.

D) It has a cell membrane.

E) It produces proteins.

Answer: C) It contains a membrane-bound nucleus.

3. A cell is placed in a solution with a lower solute concentration than the cell. What will most likely happen?

A) Water moves out of the cell by osmosis.

B) Water moves into the cell by osmosis.

C) Solute moves into the cell by active transport only.

D) The cell immediately stops all metabolic activity.

E) No water movement occurs.

Answer: B) Water moves into the cell by osmosis.

4. A red blood cell is placed in distilled water. After several minutes, the cell swells and eventually bursts. Which explanation best accounts for the observation?

A) Water entered the cell because the surrounding solution was hypotonic.

B) Water left the cell because the surrounding solution was hypertonic.

C) Glucose entered the cell by active transport.

D) Proteins left the cell through the nucleus.

E) ATP production caused the cell to expand.

Answer: A) Water entered the cell because the surrounding solution was hypotonic.

5. A scientist adds a chemical that prevents ATP production in a cell. Which process would be most directly affected?

A) Simple diffusion

B) Osmosis

C) Active transport

D) Movement of oxygen down its concentration gradient

E) Passive diffusion of carbon dioxide

Answer: C) Active transport

6. Why are mitochondria particularly numerous in muscle cells?

A) Muscle cells need large amounts of DNA.

B) Muscle cells require substantial ATP for contraction.

C) Mitochondria store oxygen for the bloodstream.

D) Mitochondria produce glucose for muscles.

E) Mitochondria prevent muscle cells from dividing.

Answer: B) Muscle cells require substantial ATP for contraction.

7. A student examines two cells. Cell X contains many ribosomes, while Cell Y contains relatively few ribosomes. Which cell would most likely be specialized for producing large quantities of proteins?

A) Cell X

B) Cell Y

C) Both equally

D) Neither cell

E) It cannot be determined because ribosomes contain DNA.

Answer: A) Cell X

8. A researcher observes that a substance crosses a cell membrane without ATP use and moves from an area of high concentration to an area of low concentration. Which process is most likely occurring?

A) Active transport

B) Endocytosis

C) Exocytosis

D) Passive transport

E) Protein synthesis

Answer: D) Passive transport

9. Which organelle modifies, sorts, and packages many proteins for transport within or outside the cell?

A) Ribosome

B) Golgi apparatus

C) Mitochondrion

D) Nucleolus

E) Centriole

Answer: B) Golgi apparatus

10. A drug blocks the function of lysosomes in a cell. Which result is most likely?

A) The cell becomes unable to produce DNA.

B) Cellular waste and damaged components accumulate.

C) Oxygen can no longer enter the cell.

D) Ribosomes stop containing RNA.

E) Glucose can no longer enter through the cell membrane.

Answer: B) Cellular waste and damaged components accumulate.

ENERGY, ENZYMES, AND METABOLISM

11. During cellular respiration, the majority of ATP in a typical eukaryotic cell is produced during:

A) Glycolysis

B) The citric acid cycle

C) Oxidative phosphorylation

D) Fermentation

E) DNA replication

Answer: C) Oxidative phosphorylation

12. A plant is kept in complete darkness for several days. Which process can continue as long as the plant has sufficient stored materials?

A) Photosynthesis only

B) Cellular respiration

C) Light-dependent reactions

D) Production of oxygen from water using light

E) Chlorophyll excitation

Answer: B) Cellular respiration

13. An enzyme normally works best at pH 7. A researcher changes the solution to pH 2, and the reaction rate falls sharply. What is the most likely explanation?

A) The enzyme's structure or active site was altered.

B) The enzyme became a carbohydrate.

C) The substrate became DNA.

D) ATP was automatically produced.

E) The enzyme concentration necessarily increased.

Answer: A) The enzyme's structure or active site was altered.

14. A student investigates how temperature affects an enzyme. The reaction rate is measured at 10°C, 20°C, 30°C, 40°C, and 80°C. The rate increases from 10°C to 40°C but is almost zero at 80°C. What is the best explanation?

A) The enzyme was probably denatured at 80°C.

B) The substrate disappeared because temperature creates matter.

C) Enzymes always work better at higher temperatures.

D) The enzyme became a lipid.

E) ATP cannot exist above 40°C.

Answer: A) The enzyme was probably denatured at 80°C.

15. A student places equal amounts of starch into two test tubes. One receives active amylase and the other receives boiled amylase. Both are kept at the same temperature. After 20 minutes, the active-amylase tube contains much less starch. What is the purpose of the boiled-amylase tube?

A) It is the experimental variable.

B) It is a control for the experiment.

C) It increases the enzyme concentration.

D) It prevents starch from dissolving.

E) It measures temperature.

Answer: B) It is a control for the experiment.

16. In the experiment in Question 15, which variable is the dependent variable if the student measures the amount of starch remaining after 20 minutes?

A) Presence of active amylase

B) Temperature

C) Amount of starch remaining

D) Type of test tube

E) Time kept in the experiment

Answer: C) Amount of starch remaining

17. A plant's rate of photosynthesis increases as light intensity increases, but eventually reaches a plateau. What is the most reasonable explanation for the plateau?

A) Light is no longer a limiting factor.

B) The plant has stopped cellular respiration.

C) Chlorophyll has disappeared completely.

D) The plant no longer contains enzymes.

E) Photosynthesis cannot occur in plants.

Answer: A) Light is no longer a limiting factor.

18. A student places an aquatic plant under a lamp and counts bubbles of gas produced each minute. At greater distances from the lamp, fewer bubbles are produced. What does the experiment most directly suggest?

A) Increasing light intensity can increase the rate of photosynthesis under these conditions.

B) Light prevents photosynthesis.

C) The bubbles must be nitrogen from the air.

D) Photosynthesis requires darkness.

E) Distance from the lamp has no effect on light intensity.

Answer: A) Increasing light intensity can increase the rate of photosynthesis under these conditions.

CELL DIVISION AND GENETICS

19. What is the main biological significance of mitosis in multicellular organisms?

A) It produces genetically different gametes.

B) It reduces chromosome number by half.

C) It produces genetically similar cells for growth and repair.

D) It always produces four daughter cells.

E) It occurs only in reproductive organs.

Answer: C) It produces genetically similar cells for growth and repair.

20. A species has 24 chromosomes in its body cells. How many chromosomes should normally be present in one of its gametes?

A) 6

B) 12

C) 24

D) 36

E) 48

Answer: B) 12

21. Two heterozygous organisms with genotype Aa are crossed. What is the probability that their offspring will have genotype aa?

A) 0%

B) 10%

C) 25%

D) 50%

E) 75%

Answer: C) 25%

22. In a genetic cross, the phenotype of a heterozygous organism is intermediate between the phenotypes of both homozygous organisms. This pattern is called:

A) Complete dominance

B) Codominance

C) Incomplete dominance

D) Polygenic inheritance

E) Sex-linked inheritance

Answer: C) Incomplete dominance

23. A father has genotype X^NY and a mother has genotype X^NXⁿ for an X-linked recessive trait. What is the probability that a son will inherit the recessive allele?

A) 0%

B) 25%

C) 50%

D) 75%

E) 100%

Answer: C) 50%

24. A DNA molecule contains 30% adenine. Approximately what percentage of the molecule is guanine?

A) 10%

B) 20%

C) 30%

D) 40%

E) 70%

Answer: B) 20%

25. Which statement best explains why a mutation in a DNA sequence can change a protein?

A) DNA determines the sequence of RNA and ultimately the amino acid sequence of proteins.

B) DNA is directly converted into lipids.

C) Mutations always destroy the entire chromosome.

D) Proteins are made directly from glucose.

E) RNA has no relationship to protein production.

Answer: A) DNA determines the sequence of RNA and ultimately the amino acid sequence of proteins.

26. A mutation changes one DNA base but does not change the amino acid encoded by the gene. Which type of mutation is most likely?

A) Silent mutation

B) Frameshift mutation

C) Chromosomal deletion

D) Nondisjunction

E) Gene duplication

Answer: A) Silent mutation

27. A scientist compares DNA sequences from four species. Species A and B differ by 3 DNA bases, while Species A and D differ by 35 bases. Which conclusion is best supported?

A) A and B are necessarily the same species.

B) A and B likely share a more recent common ancestor than A and D.

C) A and D must live in the same habitat.

D) DNA mutations never occur.

E) A and B cannot evolve independently.

Answer: B) A and B likely share a more recent common ancestor than A and D.

EVOLUTION AND NATURAL SELECTION

28. Which statement correctly describes natural selection?

A) Individual organisms develop useful traits because they need them.

B) Organisms consciously choose which genes to pass on.

C) Individuals with heritable traits that improve survival or reproduction tend to leave more offspring.

D) All mutations are beneficial.

E) Evolution always makes organisms more complex.

Answer: C) Individuals with heritable traits that improve survival or reproduction tend to leave more offspring.

29. A population of insects is treated repeatedly with the same pesticide. Initially, most insects die, but after many generations, a large fraction survives. What is the best explanation?

A) The insects intentionally changed their genes.

B) Resistant individuals survived and reproduced, increasing resistance in the population.

C) The pesticide created identical resistance in every insect.

D) Natural selection stopped occurring.

E) The insects stopped reproducing.

Answer: B) Resistant individuals survived and reproduced, increasing resistance in the population.

30. Which observation would provide the strongest evidence that two species share a common evolutionary ancestor?

A) They live in different ecosystems.

B) They have identical diets.

C) They possess highly similar DNA sequences and homologous structures.

D) They have different body sizes.

E) They compete for food.

Answer: C) They possess highly similar DNA sequences and homologous structures.

31. A population becomes separated into two groups by a newly formed mountain range. After thousands of generations, the groups can no longer successfully reproduce with each other. This is most consistent with:

A) Artificial selection

B) Genetic drift only

C) Speciation

D) Photosynthesis

E) Stabilizing homeostasis

Answer: C) Speciation

32. Which situation is most likely to produce genetic drift?

A) A very large population experiences random changes in allele frequencies.

B) A small population is reduced dramatically by a random natural disaster.

C) Individuals with favorable traits reproduce more successfully.

D) A population experiences gene flow every generation.

E) All organisms reproduce at exactly the same rate.

Answer: B) A small population is reduced dramatically by a random natural disaster.

PLANT BIOLOGY

33. Which structure controls gas exchange in most leaves?

A) Xylem

B) Phloem

C) Stomata

D) Root hairs

E) Meristems

Answer: C) Stomata

34. A plant is watered normally but kept in soil that lacks nitrogen. Which symptom would most likely develop?

A) Increased protein production

B) Reduced growth because nitrogen is needed for amino acids and other molecules.

C) Increased chlorophyll production

D) Immediate root death in every case

E) Increased DNA replication

Answer: B) Reduced growth because nitrogen is needed for amino acids and other molecules.

35. A plant's leaves lose water rapidly on a hot, dry day. Which response would help reduce water loss?

A) Opening all stomata widely

B) Closing stomata

C) Increasing transpiration

D) Increasing leaf temperature

E) Stopping all cellular respiration permanently

Answer: B) Closing stomata

36. A student removes all leaves from one plant but leaves another plant intact. Both plants receive the same amount of water and light. After several days, the plant without leaves has much less stored carbohydrate. What is the best explanation?

A) Leaves are major sites of photosynthesis.

B) Roots cannot absorb water without leaves.

C) Leaves produce nitrogen from sunlight.

D) Leaves are the only structures containing DNA.

E) Photosynthesis occurs only in roots.

Answer: A) Leaves are major sites of photosynthesis.

37. A ring of bark is removed from around a tree trunk, while the xylem remains intact. Several weeks later, sugars accumulate above the ring. Which tissue was most directly disrupted?

A) Xylem

B) Phloem

C) Epidermis only

D) Root hairs

E) Guard cells

Answer: B) Phloem

HUMAN BIOLOGY AND PHYSIOLOGY

38. Which organ is primarily responsible for filtering the blood and producing urine?

A) Liver

B) Kidney

C) Pancreas

D) Spleen

E) Stomach

Answer: B) Kidney

39. During intense exercise, a person's breathing rate increases. What is the primary reason?

A) Cells need more oxygen and produce more carbon dioxide.

B) The lungs produce ATP directly.

C) The blood stops carrying carbon dioxide.

D) Muscles stop cellular respiration.

E) The kidneys require additional oxygen for digestion.

Answer: A) Cells need more oxygen and produce more carbon dioxide.

40. A person eats a meal containing a large amount of starch. Which substance begins the digestion of starch in the mouth?

A) Pepsin

B) Amylase

C) Lipase

D) Bile

E) Trypsin

Answer: B) Amylase

41. Which hormone helps lower blood glucose concentration after a carbohydrate-rich meal?

A) Insulin

B) Glucagon

C) Adrenaline

D) Thyroxine

E) Growth hormone

Answer: A) Insulin

42. A student measures blood glucose before and after a meal:

Time	Blood Glucose
Before meal	90 mg/dL
30 minutes	135 mg/dL
60 minutes	120 mg/dL
120 minutes	95 mg/dL

Which conclusion is best supported by the data?

A) Blood glucose remained constant.

B) Blood glucose increased after the meal and later moved toward its original level.

C) The meal permanently increased blood glucose.

D) The body stopped regulating glucose.

E) Blood glucose decreased immediately after the meal.

Answer: B) Blood glucose increased after the meal and later moved toward its original level.

43. Which system is primarily responsible for transporting oxygen, nutrients, hormones, and wastes throughout the body?

A) Digestive system

B) Circulatory system

C) Skeletal system

D) Reproductive system

E) Integumentary system

Answer: B) Circulatory system

44. A person has a blockage in a coronary artery. Which tissue is most directly threatened by reduced blood flow?

A) Heart muscle

B) Skin only

C) Bone marrow only

D) Stomach lining only

E) Hair follicles

Answer: A) Heart muscle

45. When body temperature rises above the normal range, sweating helps restore homeostasis primarily because:

A) Sweat production creates heat.

B) Evaporation of sweat removes heat from the body.

C) Sweat increases blood glucose.

D) Sweat prevents all blood flow to the skin.

E) Sweat stops cellular respiration.

Answer: B) Evaporation of sweat removes heat from the body.

46. A person touches a hot surface and immediately pulls the hand away before consciously thinking about the pain. Which structure coordinates this rapid response?

A) Spinal cord

B) Stomach

C) Pancreas

D) Kidney

E) Thyroid gland

Answer: A) Spinal cord

IMMUNITY, DISEASE, AND MICROBIOLOGY

47. Which statement best distinguishes a virus from a typical living cell?

A) Viruses contain genetic material.

B) Viruses can contain proteins.

C) Viruses generally require host cells to reproduce.

D) Viruses can mutate.

E) Viruses can evolve.

Answer: C) Viruses generally require host cells to reproduce.

48. Antibiotics are generally ineffective against viruses because:

A) Viruses are larger than bacteria.

B) Viruses lack the bacterial structures and processes targeted by many antibiotics.

C) Viruses contain no genetic material.

D) Antibiotics increase viral reproduction.

E) Viruses are always harmless.

Answer: B) Viruses lack the bacterial structures and processes targeted by many antibiotics.

49. A patient receives a vaccine containing a harmless form or component of a pathogen. Later, the patient encounters the actual pathogen. Why can the immune response be faster?

A) The vaccine permanently kills all pathogens in the environment.

B) Memory cells can recognize the pathogen and support a faster response.

C) Vaccines prevent all mutations.

D) The vaccine replaces all white blood cells.

E) The immune system stops producing antibodies.

Answer: B) Memory cells can recognize the pathogen and support a faster response.

50. In an experiment, Group A receives a vaccine while Group B receives a placebo. Later, both groups are exposed to the same pathogen. Group A has fewer infections. Which is the independent variable?

A) Number of infections

B) Exposure to the pathogen

C) Whether participants received the vaccine or placebo

D) Immune response after infection

E) Number of participants who became sick

Answer: C) Whether participants received the vaccine or placebo

ECOLOGY AND ENVIRONMENT

51. In the food chain grass → rabbit → fox, which organism receives the least amount of energy from the original sunlight?

A) Grass

B) Rabbit

C) Fox

D) Grass and rabbit equally

E) Sunlight is not involved.

Answer: C) Fox

52. Why does energy decrease at higher trophic levels?

A) Energy is destroyed by consumers.

B) Much of the energy is used for metabolism and released as heat.

C) Producers consume all available energy.

D) Predators cannot perform cellular respiration.

E) Energy is converted entirely into DNA.

Answer: B) Much of the energy is used for metabolism and released as heat.

53. A lake receives excessive fertilizer runoff from nearby farms. Algae rapidly increase, and several days later many fish die. Which explanation best connects these events?

A) Algae produce unlimited oxygen for fish.

B) Excess nutrients can cause algal growth followed by oxygen depletion as organisms decompose.

C) Fertilizer directly converts fish into algae.

D) Fish cannot live in water containing algae.

E) Nutrient runoff always increases biodiversity.

Answer: B) Excess nutrients can cause algal growth followed by oxygen depletion as organisms decompose.

54. A researcher counts the number of bacteria in a culture every hour:

Hour	Bacteria
0	100
1	200
2	400
3	800

If the pattern continues for one more hour, approximately how many bacteria should be expected?

A) 900

B) 1,000

C) 1,200

D) 1,600

E) 3,200

Answer: D) 1,600

55. A population of deer increases rapidly after predators are removed. Several years later, food becomes scarce and the deer population falls sharply. Which concept best explains the decline?

A) Carrying capacity and resource limitation

B) Photosynthesis

C) Genetic dominance

D) Artificial selection

E) Protein synthesis

Answer: A) Carrying capacity and resource limitation

56. Two species occupy the same habitat and depend heavily on the same limited food source. If the food becomes scarce, what is most likely to increase?

A) Competition

B) Photosynthesis

C) Mutualism automatically

D) Carrying capacity for both species automatically

E) Genetic similarity

Answer: A) Competition

57. A student wants to determine whether fertilizer concentration affects plant growth. Four groups of identical plants receive different fertilizer concentrations. All groups receive the same amount of water, light, and soil. Plant height is measured after four weeks. Which is the dependent variable?

A) Fertilizer concentration

B) Amount of water

C) Amount of light

D) Plant height after four weeks

E) Type of soil

Answer: D) Plant height after four weeks

58. In the experiment in Question 57, the plants receiving the highest fertilizer concentration grow less than the plants receiving a moderate concentration. Which conclusion is best supported?

A) More fertilizer always produces more growth.

B) Fertilizer has no effect on plants.

C) Under these experimental conditions, excessive fertilizer may reduce plant growth.

D) Water was the independent variable.

E) The plants did not need sunlight.

Answer: C) Under these experimental conditions, excessive fertilizer may reduce plant growth.

59. A scientist studies whether temperature affects bacterial growth. Two identical bacterial cultures are placed at 20°C and 40°C. However, the 40°C culture receives twice as much nutrient solution. The scientist observes faster growth at 40°C. Why is the conclusion that temperature caused the difference weak?

A) Temperature can never affect bacteria.

B) The experiment has more than one independent variable.

C) Bacteria cannot grow in nutrient solution.

D) The dependent variable was temperature.

E) The cultures were necessarily identical.

Answer: B) The experiment has more than one independent variable.

60. A student performs an experiment to test whether a particular fertilizer increases plant growth. The student uses 20 identical plants, randomly divides them into two groups, gives one group the fertilizer and the other group no fertilizer, and keeps light, water, soil, and temperature the same. After four weeks, the fertilizer group is significantly taller. Which conclusion is best supported?

A) The fertilizer definitely works for every plant species under every condition.

B) The fertilizer caused the observed increase in growth under the conditions tested.

C) Water had no role in plant growth.

D) The control group should also have received fertilizer.

E) The experiment proves that fertilizer is necessary for all plants to survive.

Answer: B) The fertilizer caused the observed increase in growth under the conditions tested.

EST II Biology Practice Resource

This is an original hard-level Biology practice examination created for EST II preparation. It is not an official EST examination and does not reproduce official EST questions.