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Biology 30 · Diploma prep

Sample diploma exam

A full-length exam in the diploma format: 48 multiple-choice and 12 numerical-response questions of equal value, mostly in context-based sets, weighted to the same blueprint the real exam uses. Give yourself 3 hours, then read every solution — they are written out in full, starting on their own printed page.

These questions were written for this site. Alberta's own exams are secured; for real released items, use the links on the diploma prep page.

Sample Diploma Exam

Biology 30 · maddyhelps.com

Name
Date
Score
/ 60

Time: 3 hours, as on the real exam. Every student may take up to 6 hours if they need it.

You will need one approved calculator and the Biology 30 data pages. Questions come in sets: read the information box before the questions that refer to it.

Multiple choice: choose the best of the four answers. Numerical response: write your answer in the boxes, first digit on the left, unused boxes blank, and a 0 before the decimal point for answers between 0 and 1. Read the recording instruction under each one — some are sequences, some are any order.

Use the following information to answer question 1 and numerical-response question 1.

A student's hand touches a hot pan. The hand is pulled away before the student is aware of any pain.

1. The hand is pulled away before the pain is felt because the

  1. A. reflex is completed through the spinal cord, while the impulse that produces awareness of pain must still travel to the cerebrum
  2. B. impulse for the reflex travels along myelinated neurons, while the pain impulse is carried by the endocrine system
  3. C. cerebellum processes the reflex faster than the cerebrum processes pain
  4. D. pain receptors in the skin are slower to depolarize than the motor neurons that move the hand

Numerical Response

1. Four structures involved in the reflex above are listed below. 1 Motor neuron 2 Sensory neuron 3 Interneuron in the spinal cord 4 Pain receptor in the skin When these structures are arranged in the order the impulse travels through them, the order is ___, ___, ___, and ___.

(Record all four digits of your answer in the numerical-response section on the answer sheet.)

Use the following information to answer question 2.

A neuron has a resting membrane potential of −70 mV. When it is stimulated past threshold, the membrane potential rises to +40 mV and then falls back below −70 mV before returning to rest.

2. The rise from −70 mV to +40 mV is caused by

  1. A. the sodium-potassium pump moving sodium ions out of the neuron
  2. B. sodium ions diffusing into the neuron
  3. C. chloride ions diffusing into the neuron
  4. D. potassium ions diffusing out of the neuron

Use the following information to answer question 3.

Some insecticides block the enzyme acetylcholinesterase at the neuromuscular junction.

3. Exposure to such an insecticide would most likely cause

  1. A. no effect, because acetylcholine would be reabsorbed by the muscle
  2. B. a reduced response, because the receptors on the muscle would be destroyed
  3. C. continuous stimulation of the muscle, because acetylcholine would remain bound to the receptors
  4. D. muscle paralysis, because no neurotransmitter could be released from the synaptic knob

Use the following information to answer questions 4 and 5.

After a meal high in carbohydrates, a person's blood glucose concentration rises above its normal range and returns to normal about two hours later.

4. The change that returns blood glucose to its normal range is

  1. A. the release of glucagon from the alpha cells of the pancreas, which converts glycogen into glucose
  2. B. the release of insulin from the anterior pituitary, which reduces the absorption of glucose in the small intestine
  3. C. the release of ADH from the posterior pituitary, which increases the excretion of glucose in the urine
  4. D. the release of insulin from the beta cells of the pancreas, which increases the uptake of glucose by body cells and its storage as glycogen

5. The return of blood glucose to its normal range is an example of

  1. A. negative feedback, because the response reverses the original change
  2. B. an antagonistic reflex arc controlled by the spinal cord
  3. C. a tropic response controlled by the anterior pituitary
  4. D. positive feedback, because the response increases the original change

Use the following information to answer numerical-response question 2.

Six hormones are listed below.

  • 1 FSH
  • 2 Insulin
  • 3 LH
  • 4 ADH
  • 5 TSH
  • 6 Glucagon

Numerical Response

2. The hormones above that are released by the anterior pituitary gland are numbered ___, ___, and ___.

(Record all three digits of your answer in any order in the numerical-response section on the answer sheet.)

Use the following information to answer question 6.

A hiker becomes dehydrated during a long walk on a hot day.

6. As the hiker becomes dehydrated, the secretion of ADH will

  1. A. increase, and less water will be reabsorbed by the kidneys
  2. B. increase, and the volume of urine produced will decrease
  3. C. decrease, and the volume of urine produced will decrease
  4. D. decrease, and more water will be reabsorbed by the kidneys

Use the following information to answer questions 7 and 8.

A person walks from a brightly lit room into a dark theatre. At first they can see almost nothing, but after several minutes they can make out the seats and the aisle.

7. The improvement in vision after several minutes in the dark is mainly due to

  1. A. the optic nerve sending impulses to the cerebellum instead of the cerebrum
  2. B. the cones becoming more sensitive as they regenerate their pigment
  3. C. the rods regenerating rhodopsin, which allows them to respond to dim light
  4. D. the lens becoming rounder to focus the dim light on the retina

8. As the person walks into the dark theatre, the pupils dilate. This response is caused by

  1. A. contraction of the circular muscles of the iris, under conscious control
  2. B. contraction of the ciliary muscles, which also flattens the lens
  3. C. relaxation of the suspensory ligaments attached to the cornea
  4. D. contraction of the radial muscles of the iris, under the control of the autonomic nervous system

9. When a person shifts their focus from a distant sign to a book held close, the

  1. A. ciliary muscles contract, the suspensory ligaments slacken, and the lens becomes rounder
  2. B. cornea changes shape to bend the light more sharply
  3. C. retina moves closer to the lens to shorten the focal length
  4. D. ciliary muscles relax and the lens becomes flatter

Use the following information to answer questions 10 and 11.

An infection damages the semicircular canals of a person's inner ear but leaves the cochlea unaffected.

10. The most likely result of this damage is

  1. A. loss of the sense of taste, with normal hearing
  2. B. difficulty with balance when the head turns, with normal hearing
  3. C. an inability to equalize pressure across the eardrum
  4. D. hearing loss in one ear, with normal balance

11. In a healthy ear, sound vibrations travel from the eardrum to the receptor cells in the order

  1. A. eardrum → ossicles → oval window → fluid in the cochlea → hair cells
  2. B. eardrum → oval window → ossicles → hair cells → fluid in the cochlea
  3. C. eardrum → Eustachian tube → cochlea → ossicles → hair cells
  4. D. eardrum → semicircular canals → ossicles → oval window → hair cells

Use the following information to answer questions 12 to 15.

In a 28-day menstrual cycle, the concentration of LH in the blood rises sharply around day 14. Estrogen has been rising through the days before, and progesterone rises after day 14 and then falls near day 28.

12. The sharp rise in LH around day 14 causes

  1. A. the fertilized egg to implant in the wall of the uterus
  2. B. the endometrium to be shed as menstruation
  3. C. a mature follicle to release its egg from the ovary
  4. D. the pituitary gland to stop producing FSH permanently

13. The rise in estrogen before day 14 triggers the LH surge rather than suppressing it. This relationship is an example of

  1. A. negative feedback, because the rising hormone reduces the response
  2. B. an antagonistic pair of hormones acting on the same target
  3. C. a tropic hormone acting directly on the endometrium
  4. D. positive feedback, because the rising hormone increases the response

14. The progesterone that rises after day 14 is secreted by the

  1. A. developing follicle, and it thickens the endometrium before ovulation
  2. B. corpus luteum, and it maintains the endometrium in case of pregnancy
  3. C. placenta, and it prevents the corpus luteum from breaking down
  4. D. anterior pituitary, and it stimulates the ovary to release a second egg

15. If the egg released on day 14 were fertilized and implanted, the hormone that would prevent the corpus luteum from breaking down is

  1. A. ADH, secreted by the posterior pituitary
  2. B. testosterone, secreted by the ovary
  3. C. hCG, secreted by the developing embryo
  4. D. FSH, secreted by the anterior pituitary

Use the following information to answer numerical-response question 3.

Four events of the menstrual cycle are listed below.

  • 1 The corpus luteum secretes progesterone
  • 2 FSH stimulates a follicle to develop
  • 3 The endometrium is shed
  • 4 An LH surge causes ovulation

Numerical Response

3. Beginning with day 1 of the cycle, the order in which these events occur is ___, ___, ___, and ___.

(Record all four digits of your answer in the numerical-response section on the answer sheet.)

Use the following information to answer question 16.

A combined oral contraceptive contains synthetic estrogen and progesterone.

16. This contraceptive prevents pregnancy mainly because the synthetic hormones

  1. A. block the sperm from reaching the oviduct
  2. B. prevent the endometrium from being shed each month
  3. C. destroy the follicles that are present in the ovary
  4. D. suppress FSH and LH by negative feedback, so no follicle matures and ovulation does not occur

17. In a healthy female reproductive system, fertilization usually occurs in the

  1. A. ovary
  2. B. oviduct
  3. C. uterus
  4. D. cervix

Use the following information to answer question 18.

An adult male is given a course of anabolic steroids, which act in the body like testosterone.

18. A likely consequence of this treatment is a

  1. A. decrease in LH and FSH secretion, which reduces sperm production
  2. B. increase in LH and FSH secretion, which increases sperm production
  3. C. decrease in the number of interstitial cells, which increases testosterone
  4. D. increase in GnRH secretion by the hypothalamus

Use the following information to answer numerical-response question 4.

Four stages of early human development are listed below.

  • 1 Blastocyst
  • 2 Zygote
  • 3 Gastrula
  • 4 Morula

Numerical Response

4. When these stages are arranged in the order they occur, the order is ___, ___, ___, and ___.

(Record all four digits of your answer in the numerical-response section on the answer sheet.)

Use the following information to answer questions 19 and 20.

A human embryo implants in the endometrium about six days after fertilization. The placenta forms from tissue of both the embryo and the mother.

19. In the placenta,

  1. A. the amnion transfers nutrients directly from the uterus to the fetal digestive system
  2. B. maternal and fetal blood mix freely, which allows nutrients to be shared
  3. C. maternal and fetal blood remain separate, and materials are exchanged by diffusion
  4. D. fetal blood is filtered by the mother's kidneys before returning to the fetus

20. The fluid-filled sac that surrounds the fetus and cushions it against physical shock is the

  1. A. chorion
  2. B. amnion
  3. C. yolk sac
  4. D. allantois

Use the following information to answer questions 21 and 22.

A drug is known to interfere with the development of the limbs and heart of a fetus.

21. Exposure to this drug would be expected to cause the most severe damage if it occurred during

  1. A. the third trimester, when the fetus is gaining the most mass
  2. B. the second trimester, when fetal movement begins
  3. C. labour and delivery, when the fetus is under the most stress
  4. D. the first trimester, when organogenesis is occurring

22. All of the cells of the fetus carry the same genes, yet a nerve cell and a muscle cell differ in structure and function. This is because

  1. A. different genes are expressed in different cell types, which is cell differentiation
  2. B. mutations during cleavage give each cell type a different genome
  3. C. meiosis in the embryo produces cells with different combinations of chromosomes
  4. D. each cell type loses the genes it does not need during cell division

Use the following information to answer questions 23 and 24.

A human body cell contains 46 chromosomes. It passes through interphase and then divides.

23. The DNA of this cell is replicated during

  1. A. prophase
  2. B. the S phase of interphase
  3. C. metaphase
  4. D. cytokinesis

24. If this cell divides by mitosis rather than meiosis, the daughter cells will be

  1. A. four cells, each with 23 chromosomes and genetically different from one another
  2. B. four cells, each with 46 chromosomes and genetically identical to the parent cell
  3. C. two cells, each with 46 chromosomes and genetically identical to the parent cell
  4. D. two cells, each with 23 chromosomes and genetically identical to the parent cell

Use the following information to answer questions 25 and 26.

During meiosis, homologous chromosomes pair up and segments are exchanged between non-sister chromatids.

25. This exchange of segments is called crossing over, and it occurs during

  1. A. prophase I
  2. B. metaphase II
  3. C. anaphase II
  4. D. telophase I

26. Crossing over is significant because it

  1. A. doubles the number of chromosomes in each gamete
  2. B. repairs mutations that occurred during replication
  3. C. ensures that each gamete receives identical genetic information
  4. D. produces new combinations of alleles on a chromosome, increasing genetic variation in the gametes

Use the following information to answer questions 27 and 28.

A karyotype of a newborn shows 47 chromosomes, with three copies of chromosome 21.

27. This karyotype is most likely the result of

  1. A. polyploidy, in which an entire extra set of chromosomes is present
  2. B. crossing over between chromosome 21 and its homologue
  3. C. nondisjunction, in which a pair of chromosomes failed to separate during meiosis
  4. D. a frameshift mutation in a gene on chromosome 21

28. A gamete produced by the nondisjunction described above would contain

  1. A. 22 chromosomes
  2. B. 24 chromosomes
  3. C. 46 chromosomes
  4. D. 47 chromosomes

Use the following information to answer questions 29 and 30.

In pea plants, the allele for tall stems (T) is dominant over the allele for short stems (t). Two tall plants are crossed, and some of their offspring are short.

29. The genotypes of the two parent plants must be

  1. A. TT and TT
  2. B. TT and Tt
  3. C. Tt and Tt
  4. D. Tt and tt

30. To determine whether a particular tall plant is TT or Tt, a breeder should cross it with a plant that is

  1. A. tall (TT), because all the offspring will then show the parent's genotype
  2. B. tall (Tt), because the offspring ratio will be 3:1 either way
  3. C. from a different species, so the alleles can be tracked
  4. D. short (tt), because any short offspring shows the tall parent carries a recessive allele

Use the following information to answer question 31 and numerical-response question 5.

In one species of flower, plants homozygous for the red allele (C^R C^R) have red flowers, plants homozygous for the white allele (C^W C^W) have white flowers, and heterozygous plants (C^R C^W) have pink flowers.

31. This pattern of inheritance is called

  1. A. incomplete dominance
  2. B. codominance
  3. C. multiple alleles
  4. D. sex linkage

Numerical Response

5. Two pink-flowered plants are crossed. The expected phenotypic ratio of the offspring is ___ red : ___ pink : ___ white.

(Record all three digits of your answer in the numerical-response section on the answer sheet.)

Use the following information to answer question 32.

A woman with blood type O has children with a man whose blood type is AB.

32. The possible blood types of their children are

  1. A. AB or O only
  2. B. A, B, AB or O
  3. C. O only
  4. D. A or B only

Use the following information to answer numerical-response question 6.

Red-green colour blindness is a sex-linked recessive trait carried on the X chromosome. A woman who is a carrier has children with a man who has normal colour vision.

Numerical Response

6. The probability that any one of their children is colour blind is ___ %.

(Record your answer in the numerical-response section on the answer sheet.)

33. Sex-linked recessive disorders appear more often in males because males

  1. A. have only one X chromosome, so a single recessive allele is expressed
  2. B. inherit the X chromosome from both parents
  3. C. carry the allele on the Y chromosome, which is never masked
  4. D. have a higher mutation rate on the X chromosome

Use the following information to answer question 34.

In a pedigree, two parents who do not show a particular trait have a daughter who does. The trait appears in both males and females in the family.

34. The most likely mode of inheritance for this trait is

  1. A. sex-linked dominant
  2. B. autosomal recessive
  3. C. autosomal dominant
  4. D. sex-linked recessive

Use the following information to answer question 35 and numerical-response question 7.

In a plant, round seeds (R) are dominant over wrinkled seeds (r), and yellow seeds (Y) are dominant over green seeds (y). Two plants that are heterozygous for both traits are crossed.

35. The expected phenotypic ratio of the offspring is

  1. A. 9 : 3 : 3 : 1
  2. B. 3 : 1
  3. C. 1 : 2 : 1
  4. D. 1 : 1 : 1 : 1

Numerical Response

7. If this cross produced 160 offspring, the expected number of offspring with wrinkled, green seeds is ___.

(Record your answer in the numerical-response section on the answer sheet.)

Use the following information to answer questions 36 and 37.

Before a cell divides, its DNA is replicated. Each new molecule of DNA contains one original strand and one newly made strand.

36. The enzyme that separates the two strands of the original DNA molecule by breaking the hydrogen bonds between the bases is

  1. A. DNA helicase
  2. B. DNA polymerase
  3. C. DNA ligase
  4. D. RNA polymerase

37. Replication in which each new molecule keeps one original strand is described as

  1. A. semiconservative
  2. B. conservative
  3. C. dispersive
  4. D. complementary

Use the following information to answer numerical-response question 8.

A sample of double-stranded DNA is analyzed and found to contain 30% adenine.

Numerical Response

8. The percentage of guanine in this sample of DNA is ___ %.

(Record your answer in the numerical-response section on the answer sheet.)

Use the following information to answer questions 38 and 39.

In a eukaryotic cell, a gene is transcribed and the resulting molecule leaves the nucleus and binds to a ribosome.

38. The molecule that leaves the nucleus and binds to the ribosome is

  1. A. mRNA
  2. B. tRNA
  3. C. rRNA
  4. D. DNA

39. At the ribosome, the amino acid that is added to the growing polypeptide is determined by

  1. A. the order in which amino acids are dissolved in the cytoplasm
  2. B. the sequence of bases on the rRNA of the small ribosomal subunit
  3. C. the pairing of a tRNA anticodon with the next mRNA codon
  4. D. the pairing of a tRNA codon with the next DNA triplet

Use the following information to answer numerical-response question 9.

A short strand of mRNA has the base sequence AUG–GCU–UCA–UUU. Four amino acids are listed below.

  • 1 Alanine (GCU)
  • 2 Methionine (AUG)
  • 3 Phenylalanine (UUU)
  • 4 Serine (UCA)

Numerical Response

9. The order in which these amino acids are joined into the polypeptide is ___, ___, ___, and ___.

(Record all four digits of your answer in the numerical-response section on the answer sheet.)

Use the following information to answer question 40.

In one form of sickle cell disease, a single base in the gene for hemoglobin is replaced by a different base, and the hemoglobin produced contains one different amino acid.

40. This type of mutation is a

  1. A. deletion, which shifts the reading frame for every codon that follows
  2. B. insertion, which adds an extra amino acid to the chain
  3. C. nondisjunction, which changes the number of chromosomes
  4. D. substitution, which changes at most one codon

Use the following information to answer question 41.

Human insulin is produced commercially by inserting the human insulin gene into bacterial plasmids and growing the bacteria in large tanks.

41. This process is possible because

  1. A. bacterial ribosomes use a different genetic code, which is more efficient
  2. B. the genetic code is essentially universal, so bacteria read the human gene and make human insulin
  3. C. bacteria naturally produce insulin, and the human gene increases the amount
  4. D. the plasmid changes the human gene into a bacterial gene before it is expressed

Use the following information to answer numerical-response question 10.

A biologist samples a beetle population living in a patch of forest floor with an area of 12 m². She estimates that the patch contains 1 800 beetles.

Numerical Response

10. The population density of the beetles is ___ beetles/m².

(Record your answer in the numerical-response section on the answer sheet.)

Use the following information to answer numerical-response question 11.

A population of 2 000 deer increases by 160 individuals over one year.

Numerical Response

11. The per capita growth rate of this population over the year is ___.

(Record your answer to the nearest hundredth in the numerical-response section on the answer sheet.)

Use the following information to answer questions 42 to 44.

A small number of rabbits is released onto an island with abundant food and no predators. The population grows rapidly at first, then levels off and fluctuates around 4 000 rabbits.

42. The value of 4 000 rabbits represents the

  1. A. carrying capacity of the island for rabbits
  2. B. biotic potential of the rabbit population
  3. C. per capita growth rate at equilibrium
  4. D. minimum viable population of the rabbits

43. The change from rapid growth to a levelling off is best described as a change from

  1. A. open growth to closed growth, as the island fills with predators
  2. B. a density-independent pattern to a density-dependent pattern of reproduction
  3. C. exponential growth to logistic growth, as environmental resistance increases
  4. D. logistic growth to exponential growth, as the biotic potential increases

44. Once the rabbit population is near 4 000, an outbreak of a contagious disease spreads quickly through the population. This disease is

  1. A. a density-independent factor, because it affects the same proportion of the population at any density
  2. B. a density-independent factor, because it is a biotic factor
  3. C. an example of biotic potential, because it changes the birth rate
  4. D. a density-dependent factor, because it has a greater effect as the population becomes more crowded

Use the following information to answer question 45.

A tapeworm lives in the intestine of a moose, absorbing nutrients from the moose's digested food.

45. The relationship between the tapeworm and the moose is best described as

  1. A. competition, because both organisms use the same food source
  2. B. parasitism, because one organism benefits and the other is harmed
  3. C. mutualism, because both organisms benefit from the relationship
  4. D. commensalism, because one organism benefits and the other is unaffected

Use the following information to answer question 46.

A forest fire removes the trees from an area but leaves the soil intact. Over the following decades, grasses appear first, then shrubs, then trees.

46. This sequence is an example of

  1. A. primary succession, because pioneer species colonized the area
  2. B. a climax community establishing without succession
  3. C. secondary succession, because soil was already present
  4. D. primary succession, because the community was destroyed

Use the following information to answer question 47.

A population of bacteria is treated with an antibiotic. A small number of the bacteria survive, and their descendants are no longer affected by the antibiotic.

47. The best explanation for this observation is that

  1. A. the antibiotic caused the surviving bacteria to develop resistance because they needed it
  2. B. the surviving bacteria learned to break down the antibiotic and passed the behaviour on
  3. C. the antibiotic caused a mutation in every surviving bacterium at the same time
  4. D. variation for resistance already existed in the population, and the antibiotic selected for the individuals that had it

Use the following information to answer question 48 and numerical-response question 12.

In a large population of plants that is in Hardy–Weinberg equilibrium, 16% of the plants show the recessive phenotype.

Numerical Response

12. The frequency of the dominant allele in this population is ___.

(Record your answer to the nearest tenth in the numerical-response section on the answer sheet.)

48. For this population to remain in Hardy–Weinberg equilibrium, it must have

  1. A. a constant mutation rate that replaces the alleles lost to selection
  2. B. random mating, no migration, no mutation, no natural selection, and a large population size
  3. C. random mating, steady migration, and a small population size
  4. D. non-random mating and strong natural selection against the recessive phenotype

Answer key · Sample diploma exam

Biology 30 · maddyhelps.com

Multiple choice
1. A · 2. B · 3. C · 4. D · 5. A · 6. B · 7. C · 8. D · 9. A · 10. B · 11. A · 12. C · 13. D · 14. B · 15. C · 16. D · 17. B · 18. A · 19. C · 20. B · 21. D · 22. A · 23. B · 24. C · 25. A · 26. D · 27. C · 28. B · 29. C · 30. D · 31. A · 32. D · 33. A · 34. B · 35. A · 36. A · 37. A · 38. A · 39. C · 40. D · 41. B · 42. A · 43. C · 44. D · 45. B · 46. C · 47. D · 48. B

Numerical response
1. 4231 · 2. 135 · 3. 3241 · 4. 2413 · 5. 121 · 6. 25 · 7. 10 · 8. 20 · 9. 2143 · 10. 150 · 11. 0.08 · 12. 0.6

Question 1 — A. reflex is completed through the spinal cord, while the impulse that produces awareness of pain must still travel to the cerebrum

A withdrawal reflex is integrated in the spinal cord — receptor, sensory neuron, interneuron, motor neuron, effector — so the muscle responds before the impulse reaching the cerebrum produces the conscious sensation of pain. The reflex does not wait for the brain.

Numerical Response 1 — 4231

The impulse starts at the receptor (4), travels along the sensory neuron (2) into the spinal cord, passes through the interneuron (3), and leaves along the motor neuron (1) to the effector muscle: 4, 2, 3, 1. Sequencing questions are marked on the order, so a reversed answer earns nothing.

Question 2 — B. sodium ions diffusing into the neuron

At threshold the voltage-gated sodium channels open and Na⁺ rushes in down its concentration and charge gradient, making the inside of the neuron positive. That is depolarization. Potassium leaving is repolarization, which comes next.

Question 3 — C. continuous stimulation of the muscle, because acetylcholine would remain bound to the receptors

Acetylcholinesterase breaks acetylcholine down so the synapse can reset. Blocking it leaves acetylcholine in the cleft, so the muscle keeps being stimulated — twitching, then sustained contraction. Nothing stops the neuron releasing the neurotransmitter.

Question 4 — D. the release of insulin from the beta cells of the pancreas, which increases the uptake of glucose by body cells and its storage as glycogen

High blood glucose stimulates the beta cells of the islets of Langerhans to release insulin, which moves glucose into cells and stores it as glycogen in the liver. Glucagon does the opposite job, when glucose is low.

Question 5 — A. negative feedback, because the response reverses the original change

The rise in glucose triggers a response that lowers glucose, which switches the response off — a change reversed by its own effect is negative feedback. Positive feedback amplifies a change instead, like the LH surge or oxytocin during labour.

Numerical Response 2 — 135

FSH, LH and TSH are tropic hormones released by the anterior pituitary. Insulin and glucagon come from the pancreas, and ADH is made in the hypothalamus and released from the posterior pituitary — a favourite exam distinction. Any order of 1, 3 and 5 is correct.

Question 6 — B. increase, and the volume of urine produced will decrease

Osmoreceptors in the hypothalamus detect the rise in blood solute concentration, so more ADH is released from the posterior pituitary. ADH makes the collecting duct more permeable to water, so more water is reabsorbed and a smaller volume of more concentrated urine is produced.

Question 7 — C. the rods regenerating rhodopsin, which allows them to respond to dim light

Bright light bleaches rhodopsin in the rods. In the dark it is regenerated over several minutes, and the rods — the receptors that work in dim light, in shades of grey — become sensitive again. Cones need bright light and give colour vision.

Question 8 — D. contraction of the radial muscles of the iris, under the control of the autonomic nervous system

The iris controls pupil size automatically: radial muscles contract to widen the pupil in dim light, circular muscles contract to narrow it in bright light. The ciliary muscles and suspensory ligaments change the shape of the lens for focusing, which is accommodation — a different job.

Question 9 — A. ciliary muscles contract, the suspensory ligaments slacken, and the lens becomes rounder

For near vision the ciliary muscles contract, which releases the tension in the suspensory ligaments and lets the elastic lens bulge into a rounder shape that refracts light more. The cornea does most of the refraction but cannot change shape.

Question 10 — B. difficulty with balance when the head turns, with normal hearing

The semicircular canals detect rotational movement of the head — dynamic equilibrium — while the cochlea converts sound vibrations into impulses. Damage to one does not affect the other. Equalizing pressure is the Eustachian tube's job.

Question 11 — A. eardrum → ossicles → oval window → fluid in the cochlea → hair cells

The eardrum vibrates, the three ossicles amplify the vibration and pass it to the oval window, which sets the fluid in the cochlea moving, which bends the hair cells of the organ of Corti and generates impulses along the auditory nerve.

Question 12 — C. a mature follicle to release its egg from the ovary

The LH surge triggers ovulation. FSH grows the follicle earlier in the cycle; implantation, if it happens at all, is about a week later.

Question 13 — D. positive feedback, because the rising hormone increases the response

For most of the cycle estrogen holds FSH and LH down, but once estrogen passes a high threshold it flips to stimulating the surge — the change amplifies itself, which is positive feedback. It is one of the few positive feedback loops in the course, along with oxytocin during labour.

Question 14 — B. corpus luteum, and it maintains the endometrium in case of pregnancy

After ovulation the empty follicle becomes the corpus luteum, which secretes progesterone to maintain the thickened endometrium. If no embryo implants, the corpus luteum breaks down, progesterone falls, and the lining is shed — the fall near day 28.

Question 15 — C. hCG, secreted by the developing embryo

Human chorionic gonadotropin from the chorion of the embryo keeps the corpus luteum secreting progesterone through the first trimester, until the placenta takes over. hCG in urine is what a pregnancy test detects.

Numerical Response 3 — 3241

Day 1 is the start of menstruation (3), FSH then grows a follicle during the follicular phase (2), the LH surge causes ovulation around day 14 (4), and the corpus luteum secretes progesterone through the luteal phase (1).

Question 16 — D. suppress FSH and LH by negative feedback, so no follicle matures and ovulation does not occur

Steady high levels of estrogen and progesterone are read by the hypothalamus and pituitary as "already ovulated", so GnRH, FSH and LH stay low and no follicle matures. It works through feedback, not by blocking sperm.

Question 17 — B. oviduct

Sperm meet the egg in the upper oviduct (fallopian tube). The resulting zygote divides as it travels down and implants in the uterus about a week later, so the uterus is where development happens, not fertilization.

Question 18 — A. decrease in LH and FSH secretion, which reduces sperm production

High testosterone-like levels feed back negatively on the hypothalamus and anterior pituitary, lowering GnRH, LH and FSH. Since FSH drives sperm production in the seminiferous tubules, sperm counts fall — the reason steroid use can cause infertility.

Numerical Response 4 — 2413

Fertilization gives the zygote (2), cleavage produces the solid ball of cells called the morula (4), a fluid-filled cavity makes it a blastocyst (1), which implants, and gastrulation then forms the three germ layers (3).

Question 19 — C. maternal and fetal blood remain separate, and materials are exchanged by diffusion

Fetal capillaries sit in pools of maternal blood, but the two circulations stay separate. Oxygen, nutrients, carbon dioxide and wastes cross by diffusion, which is also why drugs and some viruses can reach the fetus.

Question 20 — B. amnion

The amnion encloses the amniotic fluid that cushions the fetus and keeps its temperature steady. The chorion forms the fetal side of the placenta.

Question 21 — D. the first trimester, when organogenesis is occurring

Organs form during the first trimester, so a teratogen has the greatest structural effect then — often before a pregnancy is noticed. Later exposure tends to affect growth and function rather than the basic structure of organs.

Question 22 — A. different genes are expressed in different cell types, which is cell differentiation

Differentiation is a matter of which genes are switched on, not which genes are present. Genes are not lost — that is why a differentiated nucleus can be reprogrammed, as in cloning.

Question 23 — B. the S phase of interphase

Replication happens in the S (synthesis) phase of interphase, before division begins, which is why each chromosome is already two sister chromatids when it condenses in prophase.

Question 24 — C. two cells, each with 46 chromosomes and genetically identical to the parent cell

Mitosis is one division producing two diploid, genetically identical cells for growth and repair. Four genetically different haploid cells is the result of meiosis, which makes gametes.

Question 25 — A. prophase I

Crossing over happens in prophase I, while homologous chromosomes are synapsed as tetrads. By meiosis II there are no homologous pairs left to exchange segments.

Question 26 — D. produces new combinations of alleles on a chromosome, increasing genetic variation in the gametes

Crossing over recombines alleles that were on the same chromosome, so gametes carry combinations neither parent's chromosome had. With independent assortment and random fertilization, it is one of the three main sources of variation.

Question 27 — C. nondisjunction, in which a pair of chromosomes failed to separate during meiosis

Nondisjunction is the failure of homologous chromosomes (meiosis I) or sister chromatids (meiosis II) to separate, giving a gamete with an extra chromosome. Fertilization then produces a trisomy — three copies of one chromosome, not of every chromosome, which would be polyploidy.

Question 28 — B. 24 chromosomes

A normal human gamete has 23 chromosomes. If one pair fails to separate, the gamete that receives both members has 24, and the gamete that receives neither has 22. The 24-chromosome gamete plus a normal 23 gives a zygote with 47.

Question 29 — C. Tt and Tt

A short offspring is tt, so it received a t allele from each parent. Both parents are tall, so both must be Tt. A Tt × Tt cross gives the classic 3 tall : 1 short ratio.

Question 30 — D. short (tt), because any short offspring shows the tall parent carries a recessive allele

That is a test cross. Crossing with the homozygous recessive means every offspring gets a t from that parent, so the phenotypes of the offspring reveal the unknown genotype: all tall suggests TT, while any short offspring proves Tt.

Question 31 — A. incomplete dominance

The heterozygote shows a blended intermediate phenotype, which is incomplete dominance. In codominance both alleles appear fully and separately in the heterozygote, as in blood type AB.

Numerical Response 5 — 121

C^R C^W × C^R C^W gives 1 C^R C^R : 2 C^R C^W : 1 C^W C^W, which is 1 red : 2 pink : 1 white. With incomplete dominance the phenotypic ratio matches the genotypic ratio, unlike the 3:1 of complete dominance.

Question 32 — D. A or B only

The mother is ii and the father is I^A I^B, so every child receives i from the mother and either I^A or I^B from the father: type A (I^A i) or type B (I^B i). Neither AB nor O is possible — a standard question in paternity contexts.

Numerical Response 6 — 25

X^C X^c × X^C Y gives X^C X^C, X^C X^c, X^C Y and X^c Y. Only the last is colour blind — one of four, or 25% of all children, which is half of the sons and none of the daughters.

Question 33 — A. have only one X chromosome, so a single recessive allele is expressed

A male is X^c Y, so there is no second X that could carry a dominant allele to mask the recessive one. A female needs two copies of the recessive allele to show the disorder.

Question 34 — B. autosomal recessive

Two unaffected parents with an affected child means the trait is recessive and both parents are carriers. Sex linkage is unlikely because an affected daughter would need an affected father, who does not show the trait, and because the trait appears in both sexes.

Question 35 — A. 9 : 3 : 3 : 1

RrYy × RrYy is the classic dihybrid cross: 9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green. The ratio 1:1:1:1 comes from a dihybrid test cross instead.

Numerical Response 7 — 10

Wrinkled and green is the double recessive, rryy, which is 1 of the 16 boxes in the Punnett square. 1/16 × 160 = 10 offspring.

Question 36 — A. DNA helicase

Helicase unzips the double helix. DNA polymerase then adds complementary nucleotides to each exposed strand, and ligase joins the fragments on the lagging strand.

Question 37 — A. semiconservative

Semiconservative: half of each new molecule is conserved from the parent molecule. It is also why each original strand acts as a template, so the base sequence is copied faithfully.

Numerical Response 8 — 20

Adenine pairs with thymine, so thymine is also 30%, accounting for 60% of the bases. The remaining 40% is guanine and cytosine, which pair with each other in equal amounts: 20% guanine and 20% cytosine.

Question 38 — A. mRNA

Transcription copies a gene into messenger RNA, which carries the message out of the nucleus to a ribosome. tRNA brings amino acids to the ribosome, and DNA never leaves the nucleus.

Question 39 — C. the pairing of a tRNA anticodon with the next mRNA codon

Each tRNA carries one specific amino acid and has an anticodon that base-pairs with a complementary mRNA codon, so the order of codons sets the order of amino acids. That is why a change in one base can change one amino acid.

Numerical Response 9 — 2143

Read the codons in order: AUG is methionine (2), GCU is alanine (1), UCA is serine (4), UUU is phenylalanine (3). On the real exam the codon table is on the data pages, so this kind of question is about reading it correctly, not memorizing it.

Question 40 — D. substitution, which changes at most one codon

One base swapped for another is a substitution (point mutation), and it affects only the codon it falls in — sometimes not even that, if the new codon codes for the same amino acid. Insertions and deletions shift the reading frame and usually ruin everything downstream.

Question 41 — B. the genetic code is essentially universal, so bacteria read the human gene and make human insulin

The same codons specify the same amino acids in nearly all organisms, so bacterial ribosomes translate the human gene correctly. Restriction enzymes cut the gene and the plasmid so they can be joined by ligase, which is what makes the DNA recombinant.

Numerical Response 10 — 150

Dp = N/A = 1 800 ÷ 12 = 150 beetles/m². The equation is on the data pages; choosing area rather than volume, and reporting the units, is the part that is on you.

Numerical Response 11 — 0.08

cgr = ∆N/N = 160 ÷ 2 000 = 0.08. Per capita growth rate has no units — it is a rate per individual. Because the answer is between 0 and 1, the 0 before the decimal point must be recorded.

Question 42 — A. carrying capacity of the island for rabbits

Carrying capacity (K) is the number of individuals an environment can sustain over time. Biotic potential is the maximum rate of reproduction under ideal conditions, which is what the early rapid phase approaches.

Question 43 — C. exponential growth to logistic growth, as environmental resistance increases

With unlimited resources growth is exponential — a J-shaped curve. As food, space and disease begin to limit the population, environmental resistance rises and the curve flattens into the S-shaped logistic form at carrying capacity.

Question 44 — D. a density-dependent factor, because it has a greater effect as the population becomes more crowded

Disease, competition, predation and parasitism all bite harder in a crowded population, so they are density dependent. Weather events such as drought or a hard frost hit the same proportion regardless of density, so they are density independent.

Question 45 — B. parasitism, because one organism benefits and the other is harmed

The tapeworm gains nutrients and the moose loses them, which is parasitism. Mutualism would be lichen (fungus and alga) and commensalism would be barnacles riding on a whale.

Question 46 — C. secondary succession, because soil was already present

Secondary succession follows a disturbance that leaves soil behind, so it is much faster. Primary succession starts on bare rock, lava or sand where lichens and mosses must build soil first.

Question 47 — D. variation for resistance already existed in the population, and the antibiotic selected for the individuals that had it

Natural selection acts on variation that is already there. The antibiotic does not create resistance — it removes the bacteria that lack it, leaving the resistant ones to reproduce. Saying an organism develops a trait because it needs one is the classic misconception.

Numerical Response 12 — 0.6

The recessive phenotype is q² = 0.16, so q = √0.16 = 0.4, and p = 1 − q = 0.6. Record the 0 before the decimal point. Taking 0.16 as q itself is the usual error.

Question 48 — B. random mating, no migration, no mutation, no natural selection, and a large population size

All five conditions must hold for allele frequencies to stay constant, which is why real populations rarely are in equilibrium — the equation is most useful as a baseline for detecting that evolution is happening.