Official Biology Clep Test - College Board

In which of the following ways do social insects

benefit most from having several types or castes

within the species?

(A) Each colony is able to include a large number of individuals.

(B) The secretions or odors produced by the protective caste are an effective defense.

(C) The division of the species into castes ensures the survival of the fittest.

(D) Large numbers of the worker caste can migrate to start new colonies.

(E) The specialized structure of each caste permits division of labor and greater

efficiency.

(E)The division of the species into castes ensures the survival of the fittest

2. The greatest diversity of structure and of methods of locomotion is exhibited in the individuals of

(A) a class

(B) a family

(C) an order

(D) a species

(E) a phylum

(E) a phylum

3. Of the following, which is an example of a

mutualistic relationship?

(A) The protozoan Trichonympha digesting wood in the gut of a termite

(B) The sporozoan Plasmodium reproducing in human blood cells and liberating toxins into

the human body

(C) Two species of Paramecium deriving food from a common Laboratory culture

(D) Rabbits being eaten by foxes

(E) Humans inadvertently providing food for cockroaches

(A) The protozoan Trichonympha digesting wood in the gut of a termite

4. Evidence that multicellular green plants may

have evolved from green algae is best supported

by the fact that in both

(A) the gametophyte generation is dominant

(B) the sporophyte generation is dominant

(C) chlorophylls a and b are photosynthetic pigments

(D) xylem vessels are pitted and spiraled

(E) male gametes are nonflagellated

(C) chlorophylls a and b are photosynthetic pigments

5. All of the following statements concerning the

light-capturing reactions of photosynthesis are

true EXCEPT

(A) An initial event is the excitation of electrons

in chlorophyll by light energy.

(B) The excited electrons are raised to a higher

energy level.

(C) If not captured, the excited electrons drop

back to their initial energy levels.

(D) If captured, some of the energy of the excited electrons is used to split carbon dioxide into carbon and oxygen.

(E) Light is absorbed by pigments that are embedded in membranes.

(D) If captured, some of the energy of the excited electrons is used to split carbon dioxide into carbon and oxygen.

6. Which of the following statements best explains

the hypothesis that the development of sexual

reproduction has resulted in acceleration of the

rate of evolution?

(A) Mutations are more likely to occur in spermatogenesis and oogenesis than in mitotically dividing cells.

(B) Sexual reproduction results in more

offspring than does asexual reproduction.

(C) Those members of a species that are best

adapted to their environment are most likely to be successful in sexual reproduction.

(D) Mutations usually do not occur in the

production of spores or in cells dividing by

fission.

(E) Sexual reproduction is more likely to result

in genetic recombination than is asexual

reproduction.

(E) Sexual reproduction is more likely to result

in genetic recombination than is asexual

reproduction.

7. A frog skeletal muscle contracts in response to

an electrical stimulus. Increase of the stimulus

intensity by 50 percent will increase the strength

of response nearly 50 percent. If the intensity is

again increased 50 percent, the response will

increase only about another 25 percent. Further

increase in the stimulus intensity produces no

further increase in response.

The observations above are best explained by

which of the following?

(A) A muscle functions with an all-or-none

mechanism.

(B) Muscle-fiber sarcolemma is electrically

resistant.

(C) The fibers of a muscle do not all contract at

the same rate.

(D) The fibers of a muscle fatigue at varying rates.

(E) The fibers of a muscle have varying thresholds for response.

(E) The fibers of a muscle have varying thresholds for response

8. Nitrogen-containing waste products are excreted

as the result of the metabolism of which of the

following?

(A) Proteins

(B) Fats

(C) Simple sugars

(D) Starch

(E) Cellulose

(A) Proteins

9. Deposits of coal in Greenland and the Antarctic

indicate that

(A) these regions once contained numerous

mollusks that deposited carbohydrates in

their shells

(B) the Earth's crust in these regions contains

vast amounts of limestone

(C) these regions were once thickly vegetated

(D) there is a rich store of dissolved carbon

dioxide in the seas surrounding these regions

(E) a geologic uplift of coral rock and ocean bed has recently occurred in these regions

(C) these regions were once thickly vegetated

10. Thirst, loss of weight, and sugar in the urine

result from the undersecretion of a hormone by

which of the following glands?

(A) Thyroid

(B) Parathyroid

(C) Pancreas

(D) Adrenal

(E) Thymus

(C) Pancreas

11. Considering the role of mitochondria in cells,

mitochondria would likely be most abundant in

which of the following?

(A) Mature red blood cells

(B) Callous cells of the skin

(C) Cells of the heart muscle

(D) Epithelial cells of the cheek lining

(E) Fat cells

(C) Cells of the heart muscle

12. All of the following statements about enzymes

are true EXCEPT

(A) A single enzyme molecule can be used over and over again.

(B) Most enzymes are highly specific with

regard to the reactions they catalyze.

(C) Some enzymes contain an essential nonprotein component.

(D) Enzymes can function only within living cells.

(E) Most enzymes are denatured by high

temperatures.

(D) Enzymes can function only within living cells.

13. Which of the following is critical in limiting the

size to which an animal cell may grow?

(A) The ratio of cell surface to cell volume

(B) The abundance of mitochondria in the cytoplasm

(C) The chemical composition of the cell membrane

(D) The presence of an inelastic cell wall

(E) The relative number of nucleoli

(A) The ratio of cell surface to cell volume

14. Which of the following best describes the

effect on heart action of the stimulation of the

parasympathetic nerve fibers of the vagus nerve?

(A) There is a decrease in the volume of blood pumped and an increase in the heartbeat rate.

(B) There is an increase in the volume of

blood pumped without a decrease in the

heartbeat rate.

(C) There is a prolonged acceleration in the

heartbeat rate.

(D) There is a decrease in the heartbeat rate.

(E) There is an increase in the blood pressure.

(D) There is a decrease in the heartbeat rate.

15. If poorly drained soils encourage the growth

of bacteria that convert nitrate to nitrogen, the

effect on higher plants will be to

(A) increase lipid production

(B) decrease protein production

(C) increase carbohydrate production

(D) produce unusually large fruits

(E) stimulate chlorophyll production

(B) decrease protein production

16. A patient is placed on a restricted diet of water, pure cooked starch, olive oil, adequate minerals, and vitamins. If a urinalysis several weeks later reveals the presence of relatively normal amounts of urea, the urea probably came from the

(A) food eaten during the restricted diet

(B) withdrawal of reserve urea stored in the liver

(C) chemical combination of water, carbon

dioxide, and free nitrogen

(D) deamination of cellular proteins

(E) urea synthesized by kidney tubule cells

(D) deamination of cellular proteins

17. Shown above is the absorption spectrum of a compound of biological importance. If a person with normal human color vision viewed this compound under ordinary white light, what color would it appear to be?

(A) Red

(B) Blue

(C) Green

(D) Black

(E) White

(C) Green

18. The codon for a particular amino acid is

5'CAU3'. The DNA sequence that complements

this codon is

(A) 3'CAU5'

(B) 3'GTA5'

(C) 3'GTT5'

(D) 3'GUA5'

(E) 3'GUT5'

(B) 3'GTA5'

19. Viral DNA would be most likely to contain

genes that code for

(A) regulatory hormones

(B) viral-coat protein

(C) viral-ribosome proteins

(D) glycolytic enzymes

(E) restriction enzymes

(B) viral-coat protein

20. Which of the following statements about

imprinting is NOT true?

(A) The capacity for imprinting may be limited to a specific and brief period in the early life of the organism.

(B) The behavior pattern associated with imprinting is the result of reward or punishment.

(C) The behavior resulting from imprinting is difficult to reverse in later life.

(D) A gosling imprinted by a moving wooden

decoy may exhibit courting behavior to the

decoy in later life.

(E) Odors and sounds may serve as stimuli

for imprinting.

(B) The behavior pattern associated with imprinting is the result of reward or punishment.

21. Which of the graphs below illustrates the effect of substrate concentration on the initial rate of reaction when a limited amount of enzyme is present?

Graph that is low on the bottom left gradually rising to the upper right corner where it settles off

22. Which of the following is the final electron

acceptor in the mitochondrial electron transport

system?

(A) ADP + Pi

(B) ATP

(C) NAD or FAD

(D) Pyruvate

(E) O2

(E) O2

23. In a eukaryotic cell, glycolysis occurs in which of the following parts of the cell?

(A) Chloroplast

(B) Cytosol

(C) Nucleolus

(D) Mitochondrion

(E) Ribosome

(B) Cytosol

24. The clotting process in blood is initiated by

(A) erythrocytes

(B) lymphocytes

(C) hemoglobins

(D) platelets

(E) neutrophils

(D) platelets

25. Which of the following membranes is correctly

matched to its function?

(A) Allantois .. food absorption

(B) Yolk sac .. embryonic bladder

(C) Amnion .. gas exchange

(D) Dura mater .. brain protection

(E) Peritoneum .. heart protection

(D) Dura mater .. brain protection

26. Which of the following statements best describes

the movement of energy in an ecosystem?

(A) Radiant energy is converted into chemical

energy in plant photosynthesis and then

released as heat energy during cellular

respiration.

(B) Energy cycles within an ecosystem.

(C) Plants get energy from the nutrients in the soil.

(D) The animals in an ecosystem absorb the

radiant energy of the Sun and use it to make

organic molecules such as proteins.

(E) Some chemoautotrophic bacteria release

energy that can then be used by soil animals

to make food.

(A) Radiant energy is converted into chemical energy in plant photosynthesis and then released as heat energy during cellular respiration.

27. Which of the following elements is correctly

linked to its role in a living organism?

(A) Calcium .. component of proteins

(B) Carbon .. component of lipids

(C) Magnesium .. neuron action potential

(D) Potassium .. component of ATP

(E) Zinc .. component of carbohydrates

(B) Carbon .. component of lipids

28. Mistletoe is attached to the branches of trees

such as sweet gum, from which it obtains water

and some nutrients. Due to this association,

tree growth may be diminished. Which of the

following terms describes the relationship

between the two plants?

(A) Commensalism

(B) Competition

(C) Mutualism

(D) Parasitism

(E) Predation

(D) Parasitism

29. AMP is which type of molecule?

(A) A nucleotide

(B) A peptide

(C) A phospholipid

(D) A disaccharide

(E) A tripeptide

(A) nucleotide

30. Which of the following is generally true about

bacterial viruses?

(A) They infect animal cells only.

(B) They have a protective capsid made of chitin.

(C) They inject their nucleic acids into the cells that they infect.

(D) They produce haploid gametes in meiosis.

(E) They carry out glycolysis but not the Krebs (citric acid) cycle

(C) They inject their nucleic acids into the cells that they infect.

31. A typical photosynthetic eukaryotic cell

contains which of the following?

I. Ribosomes

II. Chloroplasts

III. Mitochondria

(A) II only

(B) I and II only

(C) II and III only

(D) I and III only

(E) I, II, and III

(E) I, II, and III

32. Which of the following pairs of organisms are

most closely related?

(A) Mus bufo and Bufo americanus

(B) Lynx lynx and Alces alces

(C) Panthera leo and Felis concolor

(D) Odocoileus virginianus and Colinus virginianus

(E) Canis latrans and Canis lupus

(E) Canis latrans and Canis lupus

33. Which of the following is an example of a

testcross?

(A) AA x Aa

(B) A? x AA

(C) A? x Aa

(D) A? x aa

(E) aa x aa

(D) A? x aa

34. The process by which a zygote is formed

(A) Fertilization

(B) Meiosis

(C) Mitosis

(D) Pollination

(E) Nondisjunction

(A) Fertilization

35. The process by which the nuclei of somatic (body) cells divide

(A) Fertilization

(B) Meiosis

(C) Mitosis

(D) Pollination

(E) Nondisjunction

(C) Mitosis

36. The process by which haploid cells are formed from diploid cells

(A) Fertilization

(B) Meiosis

(C) Mitosis

(D) Pollination

(E) Nondisjunction

(B) Meiosis

37. Birds are most closely related to which class?

(A) Amphibians

(B) Bony fish

(C) Cartilaginous fish

(D) Mammals

(E) Reptiles

(E) Reptiles

38. Which class includes animals that have a moist skin as the primary organ for gas exchange in

the adults?

(A) Amphibians

(B) Bony fish

(C) Cartilaginous fish

(D) Mammals

(E) Reptiles

(A) Amphibians

39. Which class includes whales?

(A) Amphibians

(B) Bony fish

(C) Cartilaginous fish

(D) Mammals

(E) Reptiles

(D) Mammals

40. Members of which class produce milk for their

young in specialized skin glands?

(A) Amphibians

(B) Bony fish

(C) Cartilaginous fish

(D) Mammals

(E) Reptiles

(D) Mammals

41. Which class includes snakes?

A) Amphibians

(B) Bony fish

(C) Cartilaginous fish

(D) Mammals

(E) Reptiles

(E) Reptiles

42. The most probable explanation for the relative masses of the first- and second-order consumers

is that

(A) each link in the food chain of an ecosystem

has less available energy than the previous

link has

(B) only a small fraction of sunlight that reaches

the Earth is transformed into chemical

energy by photosynthesis

(C) the total energy of the decomposers is

greater than that of the rest of the organisms

put together

(D) seasonal fluctuations in weather limit the

number of consumers

(E) second-order consumers require more total energy than first-order consumers do

(A) each link in the food chain of an ecosystem

has less available energy than the previous

link has

43. The energy incorporated into this ecosystem is

most dependent on the

(A) photoperiod

(B) total amount of photosynthesis

(C) predator-prey relationships

(D) length of the food chains

(E) total amount of respiration

(B) total amount of photosynthesis

44. If the lake is assumed to be a typical ecosystem,

the percent of radiant energy from the Sun

reaching the lake that is trapped in photosynthesis is about

(A) 100%

(B) 10%

(C) 1%

(D) 0.1%

(E) 0.01%

(C) 1%

45. With respect to body color, the male parent of

the 112 offspring was most probably

(A) homozygous gray

(B) heterozygous gray

(C) homozygous black

(D) heterozygous black

(E) hemizygous gray

(C) homozygous black

46. Examination revealed that all of the 56 red-eyed

offspring were females and all of the 56 whiteeyed offspring were males. This observation

indicates that

(A) red and white eye colors segregate independently of sex

(B) all of the red-eyed offspring inherited

their eye color from their female parent

(C) all of the red-eyed offspring were homozygous

(D) the gene for eye color is linked to the gene for body color

(E) the gene for red or for white eye color is

carried on the X chromosome

(E) the gene for red or for white eye color is carried on the X chromosome

47. In this experiment, the number of offspring that

exhibit both recessive characters is

(A) 1

(B) 27

(C) 28

(D) 55

(E) 56

(B) 27

48. Carbon dioxide is produced by which of the

following?

I. A mesophyll cell in a flowering plant during

the night

II. A muscle cell in a mammalian heart during

contraction

III. A yeast cell growing under anaerobic

conditions

(A) I only

(B) II only

(C) III only

(D) I and II only

(E) I, II, and III

(E) I, II, and III

49. Which of the following is a function of ATP?

(A) It creates energy.

(B) It transports energy.

(C) It is a building block of proteins.

(D) It stores amino acids.

(E) It gives the cells shape.

(B) It transports energy.

50. Protein synthesis is the main function of which of the following structures?

(A) Nucleus

(B) Ribosome

(C) Chromosome

(D) Mitochondrion

(E) Vacuole

(B) Ribosome

51. The terms "EcoRI," "HaeIII," and "HindIII"

refer to which of the following?

(A) The voltage intensity used to prepare the

electrophoresis medium

(B) The restriction enzymes used

(C) The organisms from which the original

DNA sample was obtained

(D) The types of buffers used to maintain a

constant pH in the preparation as the sample was processed

(E) The types of proteins encoded by each

fragment

(B) The restriction enzymes used

52. The patterns of bands in the different lanes result

from which of the following?

(A) Different voltages applied to different lanes

(B) Different buffers applied to different lanes

(C) Different sizes of fragments in the samples in different lanes

(D) Different terminal configurations of the

fragments, with some having blunt ends

while others have sticky ends

(E) Mutations produced by the electrophoresis

(C) Different sizes of fragments in the samples in different lanes

53. In this gel, the smallest fragments are

(A) at the top of the gel, near the wells

(B) at the bottom of the gel, furthest from

the wells

(C) at the left side of the gel

(D) at the right side of the gel

(E) randomly scattered from top to bottom in

each lane

(B) at the bottom of the gel, furthest from the wells

54. Restriction enzymes cut samples of DNA into

fragments by first

(A) binding to specific sequences of nucleotides

(B) oxidizing the DNA

(C) heating the DNA to its denaturation point

(D) breaking peptide bonds

(E) unwinding the DNA

(A) binding to specific sequences of nucleotides

55. Which of the following is the most probable

explanation for the different numbers of

fragments in the different lanes?

(A) There were more EcoRI cut sites than

HaeIII or HindIII cut sites.

(B) There were more HaeIII cut sites than

EcoRI or HindIII cut sites.

(C) There were more HindIII cut sites than

HaeIII or EcoRI cut sites.

(D) A stronger voltage was applied to the

first lane.

(E) Different buffers were used in the different lanes.

(C) There were more HindIII cut sites than

HaeIII or EcoRI cut sites.

56. Which of the following best explains why a pictorial presentation of the biomass at each

trophic level of an ecosystem is a pyramid?

(A) The loss of iron from an ecosystem

(B) The amount of energy passed from one

trophic level to the next

(C) The number of predators in the ecosystem

(D) The chemical compounds in an ecosystem

are recycled

(E) The average size of the individuals in each

species

(B) The amount of energy passed from one trophic level to the next

The original description of the pathway shown

above is attributed to

(A) Louis Pasteur

(B) James Watson and Francis Crick

(C) Hans Krebs

(D) Robert Hooke

(E) Melvin Calvin and Andrew Benson

(E) Melvin Calvin and Andrew Benson

58. A diet with insufficient iodine will most likely

lead to which of the following symptoms in an

individual?

(A) Bleeding gums

(B) Decreased metabolic rate

(C) Increased body temperature

(D) Increased respiratory rate

(E) Weight loss

(B) Decreased metabolic rate

59. Which of the following structures is correctly paired with its function?

(A) Alveolus . . locomotion

(B) Cilium . . impulse transmission

(C) Sarcomere . . nutrient uptake

(D) Neuron . . gas exchange

(E) Nephron..filtration

(E) Nephron..filtration

60. Based on the information in the table, which of the following substitutions is synonymous?

(A) AGU to AGA

(B) GUU to GCU

(C) UUG to CUG

(D) UGA to GGA

(E) CAA to CCA

(C) UUG to CUG

Excess sewage can lead to the death of aquatic animals in a lake because sewage pollution promotes

(A) mineral starvation

(B) erosion

(C) thermal stratification

(D) oxygen depletion

(E) a temperature decrease

(D) oxygen depletion

The aerobic cellular respiration of glucose is

different from the simple burning of glucose in

that the aerobic respiration of glucose

(A) releases no heat

(B) requires no oxygen

(C) releases more energy

(D) releases hydrocarbons

(E) occurs at a lower temperature

(E) occurs at a lower temperature

A given trait occurs in two alternative types, M and m, in a population at Hardy-Weinberg

equilibrium. If 49 percent of the population has

only type M alleles, what percentage of the

population is expected to be heterozygous for

the trait?

(A) 9%

(B) 14%

(C) 21%

(D) 42%

(E) 51%

(D) 42%

The forelimbs of horses and frogs are considered

to be homologous structures. The best evidence for this homology is that the forelimbs have

(A) a similar appearance in both species

(B) a similar function in both species

(C) a common embryological origin

(D) the same chemical composition

(E) the same number of bones

(C) a common embryological origin

Which of the following types of plant cells is dead at functional maturity?

(A) Phloem companion cell

(B) Xylem vessel element

(C) Root endodermal cell

(D) Stem cortex cell

(E) Mesophyll cell

(B) Xylem vessel element

In a particular plant species, the allele for tall plants is dominant and the allele for dwarfing is

recessive. Which of the following is the expected phenotypic ratio of the offspring from a cross between a heterozygous plant and a dwarf plant?

(A) 1 tall plant : 3 dwarf plants

(B) 1 tall plant : 9 dwarf plants

(C) 1 tall plant : 1 dwarf plant

(D) 3 tall plants : 1 dwarf plant

(E) 9 tall plants : 3 dwarf plants

(C) 1 tall plant : 1 dwarf plant

Which of the following best describes the decomposers in an ecological community?

(A) They are the top predators.

(B) They do not occur in early successional

stages.

(C) They are the main contributors to the gross

primary productivity.

(D) They fix carbon for plant respiration.

(E) They are heterotrophic.

(E) They are heterotrophic.

The nearly universal nature of the genetic code supports the view that

(A) all living organisms on Earth share a

common ancestor

(B) nucleic acids were the first living things

(C) proteins are of secondary importance to living systems

(D) the protein composition of all living organisms is the same

(E) there is redundancy in the genetic code

(A) all living organisms on Earth share a

common ancestor

A katydid is an insect. Its leaf-like appearance is

an example of

(A) cryptic coloration

(B) aposematic coloration

(C) Müllerian mimicry

(D) agonistic behavior

(E) Batesian mimicry

(A) cryptic coloration

A population of mice in Hardy-Weinberg

equilibrium will exhibit which of the following

conditions?

(A) Random mating

(B) Small population size

(C) High mutation rate

(D) Immigration

(E) Sexual selection

(A) Random mating

Which of the following biomes typically has the

greatest annual precipitation?

(A) Temperate deciduous forest

(B) Taiga

(C) Savanna

(D) Tropical rain forest

(E) Prairie

(D) Tropical rain forest

Which part of a flower develops into fruit?

(A) Sepal

(B) Stigma

(C) Anther

(D) Ovary

(E) Filament

(D) Ovary

In a particular mammal, the egg has a haploid

number of 8. How many chromosomes are in

the somatic cells of that organism?

(A) 2

(B) 4

(C) 8

(D) 16

(E) 32

(D) 16

A new organism is found with the following

characteristics.

• A terrestrial lifestyle

• A segmented exoskeleton

• Wings

The new organism is most likely a member of

which of the following phyla?

(A) Cnidaria

(B) Porifera

(C) Chordata

(D) Arthropoda

(E) Echinodermata

Arthropoda

Plants that live in the tundra are likely to have

which of the following adaptations?

(A) Tall, single shoots

(B) Broad, light-colored leaves

(C) Cones that are fire adapted

(D) An association with epiphytes

(E) Shallow root systems

(E) Shallow root systems

When a protein is heated, which of the

following will most likely be disrupted?

(A) The amino acid sequence

(B) The tertiary structure

(C) The carbon backbone

(D) The carboxyl groups

(E) The peptide bonds

(B) The tertiary structure

In some horses, the coat is a mixture of red and

white hairs, called roan. Roan horses have one

white-haired parent and one red-haired parent.

This exhibits which of the following inheritance

patterns?

(A) X-linked recessive

(B) Lateral transmission

(C) Codominance

(D) Hybrid vigor

(E) Autosomal recessive

(C) Codominance

A population of crayfish exhibits wide variation

in body size, which is a heritable trait. A species

of fish that preys on crayfish has been introduced to the population, but the fish can only eat small crayfish. Which of the following is a likely

prediction about the population of crayfish in the presence of the predator?

(A) The crayfish will evolve new antipredator

behaviors.

(B) The crayfish diet will shift to avoid

competition with the fish.

(C) The population will have a smaller average

body size owing to stabilizing selection.

(D) The population will have a larger average

body size owing to directional selection.

(E) The population will experience disruptive

selection, resulting in two distinct size

classes of crayfish.

(D) The population will have a larger average

body size owing to directional selection.

All of the following substances are potentially

major sources of energy for the human body

EXCEPT

(A) starches

(B) sugars

(C) vitamins

(D) proteins

(E) fats

(C) vitamins

Which of the following are producers in an

aquatic food chain?

(A) Crustaceans

(B) Algae

(C) Insects

(D) Fungi

(E) Trout

(B) Algae

Which of the following gives the correct

sequence of events in the synthesis of a protein molecule?

(A) DNA, tRNA, formation of polypeptide, mRNA

(B) Formation of polypeptide, tRNA, mRNA, DNA

(C) tRNA, mRNA, DNA, formation of polypeptide

(D) DNA, mRNA, tRNA, formation of polypeptide

(E) mRNA, formation of polypeptide, DNA, tRNA

(E) mRNA, formation of polypeptide, DNA, tRNA

A species of malaria-carrying mosquito lives in a

forest in which two species of monkeys, A and B,

coexist. Species A is immune to malaria, but

species B is not. The malaria-carrying mosquito

is the chief food for a particular kind of bird in

the forest. If all of these birds are eliminated

suddenly, which of the following would be the

immediate observable consequence?

(A) Increased mortality in monkey species A

(B) Increased mortality in monkey species B

(C) Increased mortality in the malaria-carrying

mosquitoes

(D) Emergence of malaria-resistant strains in monkey species B

(E) Emergence of malaria-sensitive strains in monkey species A

(B) Increased mortality in monkey species B

Evolution in action is seen in the case of the

English peppered moth (Biston betularia). The

proportion of melanic forms in the population,

once increasing in areas of heavy soot pollution,

is now decreasing. The most probable

explanation of this is which of the following?

(A) Differential predation fluctuates randomly.

(B) The birds that ate the dark forms have been

killed off by the pollution.

(C) Mutation and back mutation rates have

changed.

(D) Selection pressure has been reversed because of environmental quality control.

(E) Lepidopterists have collected a

disproportionate number of melanic forms

(D) Selection pressure has been reversed because of environmental quality control.