Variation and Selection: Continuous/Discontinuous Variation, Mutation, Natural Selection and Selective Breeding

1. Which statement correctly describes continuous variation?

A individuals fall into distinct categories with no intermediates
B variation is usually controlled by many genes and affected by environment
C variation is caused only by one gene with two alleles
D examples include blood group and sex

2. Which example shows discontinuous variation?

A height in humans
B body mass in humans
C ABO blood group
D leaf length in one species of plant

3. Which statement correctly compares continuous and discontinuous variation?

A continuous variation has categories; discontinuous variation has a range
B continuous variation is usually polygenic; discontinuous variation is often controlled by one or few genes
C continuous variation is never affected by environment
D discontinuous variation is always caused only by diet

4. Which characteristic is most likely to show continuous variation?

A ability to roll tongue
B flower colour controlled by one gene with two alleles
C human height
D sex in humans

5. A student measures the heights of 200 plants of the same species grown in different light intensities. The results form a normal distribution.
   Which explanation is most likely?

A height is continuous variation affected by genes and environment
B height is discontinuous variation controlled by one allele only
C all plants have identical genotypes and no environmental effect
D light intensity causes mutation in every plant

6. Which graph is most suitable for showing discontinuous variation?

A smooth bell-shaped curve only
B bar chart with separate categories
C line graph showing enzyme rate
D scatter graph with no categories

7. Which graph is most suitable for showing continuous variation?

A bar chart with blood group categories only
B histogram or frequency curve showing a range of values
C pie chart showing male and female only
D table of allele symbols only

8. Which factor is an environmental cause of variation?

A different alleles inherited from parents
B mutation in DNA during gamete formation
C nutrition affecting body mass
D random fusion of gametes

9. Which factor is a genetic cause of variation?

A amount of sunlight reaching a plant
B training affecting muscle size
C inherited alleles from parents
D availability of mineral ions in soil only

10. Which statement about identical twins is correct?

A they have identical genotypes but may show phenotypic differences due to environment
B they have different genotypes but identical phenotypes always
C they cannot show any variation because environment has no effect
D they are formed by fertilisation of two ova by two sperm

11. Which statement about mutation is correct?

A mutation is a change in DNA
B mutation always improves survival
C mutation only occurs in body cells and is never inherited
D mutation is the same as fertilisation

12. Which type of mutation can be passed to offspring?

A mutation in a gamete-forming cell
B mutation in a skin cell only
C mutation in a liver cell only
D mutation in a red blood cell only

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

13. Which statement about mutations is most accurate?

A all mutations are harmful
B all mutations are beneficial
C mutations may be harmful, beneficial or neutral
D mutations always produce a new species immediately

14. Which factor can increase the rate of mutation?

A ionising radiation
B oxygen in alveoli only
C bile salts
D insulin

15. Which example is most likely caused by a mutation?

A increased muscle size due to exercise
B darker skin after sun exposure only
C a new allele arising in a population
D loss of water by sweating

16. A mutation gives some bacteria resistance to an antibiotic. The antibiotic is then used.
    What happens to the frequency of the resistance allele?

A it is likely to increase because resistant bacteria survive and reproduce
B it must decrease because antibiotics destroy mutations first
C it remains unchanged because bacteria cannot reproduce
D it becomes zero because all resistant bacteria are weaker

17. Which statement best describes natural selection?

A organisms change because they need to survive
B individuals with advantageous inherited features are more likely to survive and reproduce
C all individuals in a population have equal chances of reproduction
D acquired features are always passed directly to offspring

18. Which sequence best describes natural selection?

A variation → selection pressure → better adapted individuals survive/reproduce → allele frequency changes
B selection pressure → all individuals mutate → all offspring become identical
C fertilisation → no variation → no competition → extinction impossible
D adaptation → individuals decide to change DNA → genes disappear

19. A population of insects contains green and brown individuals. Birds easily see green insects on tree bark. After many generations, brown insects become more common.
    Which process explains this?

A natural selection
B active transport
C osmosis
D artificial cloning

20. In natural selection, what is meant by “selection pressure”?

A a factor that affects survival and reproduction
B the force of blood in arteries
C the pressure inside xylem vessels only
D the number of chromosomes in a gamete

21. Which condition is necessary for natural selection to occur?

A variation between individuals
B all individuals being genetically identical
C no reproduction
D no competition for resources

22. Which statement about adaptation is correct?

A adaptations are inherited features that increase survival and reproduction in a particular environment
B adaptations appear because organisms consciously try to improve
C adaptations are always useful in every environment
D adaptations are never caused by genes

23. A species of moth has light and dark forms. Pollution darkens tree bark. Dark moths become more common.
    Which explanation is best?

A dark moths are better camouflaged, survive more often and pass on alleles
B light moths choose to become dark during life and pass this change on
C pollution directly changes every light allele into a dark allele
D birds stop eating moths completely

24. Which statement about evolution is correct?

A evolution is change in inherited characteristics of populations over generations
B evolution is a change in one individual during its lifetime
C evolution happens only when all organisms die
D evolution always makes organisms more complex

25. Which result would provide evidence of natural selection?

A allele frequencies changing over generations in response to selection pressure
B every individual in a population having exactly the same genotype
C acquired muscle strength being copied into sperm DNA automatically
D offspring always being identical to parents

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

26. Which statement about selective breeding is correct?

A humans choose parents with desirable characteristics to breed
B organisms choose to mutate into desirable forms
C only wild animals can be selectively bred
D selective breeding always increases genetic variation

27. Which example shows selective breeding?

A breeding cows with high milk yield together
B bacteria becoming resistant after antibiotic use
C darker moths surviving better on dark bark
D weeds dying after herbicide spraying

28. Which feature might be selected in crop plants by selective breeding?

A high yield
B increased malaria transmission
C reduced photosynthesis
D no seed production in all cases

29. Which feature might be selected in farm animals by selective breeding?

A high meat production
B inability to reproduce
C reduced milk yield
D lower disease resistance always

30. Which sequence best describes selective breeding?

A choose parents with desired traits → breed them → select best offspring → repeat over generations
B expose all organisms to disease → wait for random survival → ban reproduction
C allow all organisms to mate randomly → select no offspring
D remove all variation → prevent inheritance

31. Which disadvantage can result from selective breeding?

A reduced genetic variation and increased risk of inherited disorders
B increased biodiversity in every case
C no offspring are produced
D all mutations become beneficial

32. Why can inbreeding be a problem in selective breeding?

A it increases the chance that harmful recessive alleles are expressed
B it prevents any alleles from being inherited
C it always causes chromosomes to disappear
D it makes all offspring different species

33. Which statement correctly compares natural selection and selective breeding?

A natural selection is controlled by humans; selective breeding is controlled by environmental pressures
B natural selection involves environmental selection pressures; selective breeding involves humans choosing parents
C both always produce clones
D neither changes allele frequencies

34. Which statement about antibiotic resistance is correct?

A antibiotics cause bacteria to need resistance, so they deliberately mutate
B resistant bacteria already present may survive and reproduce when antibiotics are used
C antibiotics only affect viruses
D resistant bacteria cannot pass resistance alleles to offspring

35. Which action increases the risk of antibiotic-resistant bacteria spreading?

A completing a full prescribed antibiotic course
B using antibiotics only for bacterial infections
C stopping antibiotics early when symptoms improve
D vaccination reducing bacterial infections

36. A population of bacteria is treated with an antibiotic. A few resistant bacteria survive.
    Why do resistant bacteria become more common after several generations?

A they reproduce and pass resistance to offspring
B they become multicellular animals
C they are converted into viruses
D they stop all DNA replication

37. Which statement about variation in natural selection is correct?

A variation provides material on which selection pressures can act
B variation prevents reproduction in all organisms
C variation is always caused by environment only
D variation cannot be inherited

38. Which example shows variation caused by both genes and environment?

A human blood group
B height in humans
C sex chromosomes XX or XY
D ability to have attached or free earlobes only

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

39. Which statement about discontinuous variation is correct?

A it usually has no intermediates between categories
B it is always shown by a normal distribution curve
C it is always controlled by many genes and environment equally
D it cannot be inherited

40. Which example is discontinuous variation in humans?

A blood group
B height
C body mass
D hand span

41. Which statement about continuous variation is correct?

A it often shows a range of values with many intermediates
B it has only two categories
C it is never measured numerically
D it is controlled by one allele only in all cases

42. A student records the number of students with blood groups A, B, AB and O.
    Why is a bar chart suitable?

A blood group is discontinuous and has separate categories
B blood group is continuous and has infinite values
C blood group is caused only by exercise
D blood group changes daily with diet

43. Which statement about phenotype is correct?

A phenotype is the observable characteristic produced by genotype and sometimes environment
B phenotype is only the allele combination
C phenotype is always unaffected by environment
D phenotype exists only in gametes

44. Which situation shows environmental variation?

A a plant grows taller when given more light and mineral ions
B a child inherits blood group O from parents
C a sperm cell carries an X chromosome
D meiosis produces different gametes

45. Which situation shows inherited variation?

A scars caused by injury
B darker skin due to recent tanning only
C different blood groups due to different alleles
D body mass increasing after overeating

46. Which statement about artificial selection is correct?

A it can produce organisms with traits useful to humans but not necessarily useful in the wild
B it always produces organisms best adapted to natural habitats
C it never changes gene frequencies
D it is the same as random mating

47. A farmer repeatedly breeds only the largest chickens. After many generations, average chicken size increases.
    Which explanation is best?

A alleles linked with larger size become more common in the selected breeding population
B each chicken stretches its body and passes this acquired size to offspring
C all small chickens mutate into large chickens before breeding
D the environment has no role in any body size trait

48. Which statement about a harmful recessive allele in selective breeding is correct?

A it may become more common or expressed if closely related individuals are bred
B it can never be inherited
C it is always removed immediately by choosing large parents
D it changes into a dominant allele when food supply increases

49. Which statement about mutation and natural selection is correct?

A mutation creates new alleles; natural selection can change their frequency
B natural selection creates all mutations because organisms need them
C mutation always gives an advantage and selection always removes it
D mutation and natural selection are identical processes

50. Which statement is correct?

A continuous variation shows a range and is often influenced by many genes and environment
B discontinuous variation always has a smooth bell-shaped distribution
C selective breeding is natural selection without human involvement
D mutation can never affect evolution

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

1. Answer: B
   A is wrong because continuous variation does not have only distinct categories.
   B is correct because continuous variation is usually controlled by many genes and influenced by environmental factors.
   C is wrong because one gene with two alleles usually gives discontinuous variation.
   D is wrong because blood group and sex are examples of discontinuous variation.

2. Answer: C
   A is wrong because height shows continuous variation.
   B is wrong because body mass shows continuous variation.
   C is correct because ABO blood group has distinct categories: A, B, AB and O.
   D is wrong because leaf length usually shows continuous variation.

3. Answer: B
   A is wrong because it reverses the definitions.
   B is correct because continuous variation is often polygenic, while discontinuous variation is often controlled by one or few genes.
   C is wrong because continuous variation can be affected by environment.
   D is wrong because discontinuous variation is mainly genetic, not always caused by diet.

4. Answer: C
   A is wrong because tongue rolling is usually treated as discontinuous variation.
   B is wrong because flower colour controlled by one gene with two alleles is discontinuous.
   C is correct because human height shows a continuous range with many intermediate values.
   D is wrong because sex in humans is discontinuous.

5. Answer: A
   A is correct because plant height is continuous variation affected by both genes and environmental factors such as light intensity.
   B is wrong because height is not a simple discontinuous category.
   C is wrong because different light intensities show environmental effects.
   D is wrong because light intensity does not cause mutation in every plant.

6. Answer: B
   A is wrong because a smooth bell-shaped curve is used for continuous variation.
   B is correct because discontinuous variation has separate categories, so a bar chart is suitable.
   C is wrong because a line graph is not best for separate categories.
   D is wrong because a scatter graph is not the best way to show category frequencies.

7. Answer: B
   A is wrong because blood group categories are discontinuous.
   B is correct because continuous variation is shown well by a histogram or frequency curve.
   C is wrong because male/female categories are discontinuous.
   D is wrong because allele symbols do not show a continuous range.

8. Answer: C
   A is wrong because inherited alleles are a genetic cause.
   B is wrong because mutation is genetic.
   C is correct because nutrition can affect body mass and is an environmental cause of variation.
   D is wrong because random fusion of gametes causes genetic variation.

9. Answer: C
   A is wrong because sunlight is environmental.
   B is wrong because training is environmental.
   C is correct because inherited alleles from parents are a genetic cause of variation.
   D is wrong because mineral ion availability is environmental.

10. Answer: A
    A is correct because identical twins have the same genotype but can develop different phenotypes due to environmental differences.
    B is wrong because identical twins have identical genotypes.
    C is wrong because the environment can affect phenotype.
    D is wrong because identical twins form when one fertilised egg splits, not from two ova and two sperm.

11. Answer: A
    A is correct because mutation is a change in DNA.
    B is wrong because mutations may be harmful, beneficial or neutral.
    C is wrong because mutations in gametes or gamete-forming cells can be inherited.
    D is wrong because mutation is not fertilisation.

12. Answer: A
    A is correct because a mutation in a gamete-forming cell can be passed to offspring.
    B is wrong because a mutation in a skin cell is not usually inherited.
    C is wrong because a mutation in a liver cell is not usually inherited.
    D is wrong because mature red blood cells do not even have nuclei/DNA.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

13. Answer: C
    A is wrong because not all mutations are harmful.
    B is wrong because not all mutations are beneficial.
    C is correct because mutations may be harmful, beneficial or neutral.
    D is wrong because mutations do not always produce a new species immediately.

14. Answer: A
    A is correct because ionising radiation can increase mutation rate.
    B is wrong because oxygen in alveoli is not a major mutagen in this syllabus context.
    C is wrong because bile salts emulsify fats.
    D is wrong because insulin controls blood glucose.

15. Answer: C
    A is wrong because increased muscle size from exercise is environmental/acquired.
    B is wrong because tanning is mainly an environmental response.
    C is correct because a mutation can create a new allele in a population.
    D is wrong because sweating is a homeostatic response.

16. Answer: A
    A is correct because resistant bacteria survive antibiotic treatment and reproduce, increasing the resistance allele frequency.
    B is wrong because antibiotics do not specifically destroy mutations first.
    C is wrong because bacteria reproduce rapidly.
    D is wrong because resistant bacteria are not always weaker.

17. Answer: B
    A is wrong because organisms do not change DNA because they “need” to survive.
    B is correct because individuals with advantageous inherited features are more likely to survive and reproduce.
    C is wrong because survival and reproduction are not equal when selection pressures act.
    D is wrong because acquired features are not automatically inherited.

18. Answer: A
    A is correct because natural selection follows variation → selection pressure → better adapted individuals survive/reproduce → allele frequency changes.
    B is wrong because not all individuals mutate in response to pressure.
    C is wrong because natural selection requires variation and competition.
    D is wrong because individuals do not decide to change DNA.

19. Answer: A
    A is correct because brown insects are better camouflaged, survive bird predation more often and reproduce more.
    B is wrong because active transport is movement against a concentration gradient.
    C is wrong because osmosis is water movement.
    D is wrong because artificial cloning is not occurring.

20. Answer: A
    A is correct because a selection pressure is a factor affecting survival and reproduction.
    B is wrong because blood pressure is not selection pressure in evolution.
    C is wrong because xylem pressure is unrelated.
    D is wrong because chromosome number is not a selection pressure.

21. Answer: A
    A is correct because natural selection requires variation between individuals.
    B is wrong because if all individuals were genetically identical, selection has little variation to act on.
    C is wrong because reproduction is needed for allele frequencies to change.
    D is wrong because competition for resources often creates selection pressure.

22. Answer: A
    A is correct because adaptations are inherited features that increase survival and reproduction in a particular environment.
    B is wrong because organisms do not consciously create adaptations.
    C is wrong because an adaptation useful in one environment may be harmful in another.
    D is wrong because adaptations are often genetic/inherited.

23. Answer: A
    A is correct because dark moths are better camouflaged on dark bark, so they survive and pass on dark-colour alleles.
    B is wrong because acquired colour change during life is not passed on like that.
    C is wrong because pollution does not directly convert every light allele into a dark allele.
    D is wrong because birds still eat moths.

24. Answer: A
    A is correct because evolution is change in inherited characteristics of populations over generations.
    B is wrong because a change in one individual during life is not evolution.
    C is wrong because evolution does not require all organisms to die.
    D is wrong because evolution does not always make organisms more complex.

25. Answer: A
    A is correct because changing allele frequencies over generations due to selection pressure is evidence of natural selection.
    B is wrong because identical genotypes show no variation for selection.
    C is wrong because acquired muscle strength is not automatically copied into sperm DNA.
    D is wrong because offspring are not always identical to parents in sexual reproduction.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

26. Answer: A
    A is correct because selective breeding involves humans choosing parents with desirable characteristics.
    B is wrong because organisms do not choose to mutate.
    C is wrong because crops, farm animals and many other organisms can be selectively bred.
    D is wrong because selective breeding often reduces genetic variation.

27. Answer: A
    A is correct because humans choosing high-yield cows to breed is selective breeding.
    B is wrong because bacterial resistance after antibiotic use is natural selection.
    C is wrong because dark moth survival is natural selection.
    D is wrong because weeds dying after herbicide spraying is selection pressure, not selective breeding.

28. Answer: A
    A is correct because high yield is a desirable crop trait selected by humans.
    B is wrong because malaria transmission is not a crop trait.
    C is wrong because reduced photosynthesis is usually undesirable.
    D is wrong because no seed production in all cases would be harmful for crop reproduction unless specific seedless fruit production is intended.

29. Answer: A
    A is correct because high meat production is a desirable farm animal trait.
    B is wrong because inability to reproduce is not generally selected for breeding animals.
    C is wrong because reduced milk yield is undesirable.
    D is wrong because lower disease resistance is undesirable.

30. Answer: A
    A is correct because selective breeding involves choosing parents, breeding them, selecting the best offspring and repeating.
    B is wrong because that describes survival under disease pressure, not planned breeding.
    C is wrong because random mating and no selection is not selective breeding.
    D is wrong because selective breeding depends on inherited variation.

31. Answer: A
    A is correct because selective breeding can reduce genetic variation and increase inherited disorders.
    B is wrong because biodiversity does not always increase; it may decrease.
    C is wrong because offspring can be produced.
    D is wrong because not all mutations become beneficial.

32. Answer: A
    A is correct because inbreeding increases the chance of harmful recessive alleles being inherited from both parents and expressed.
    B is wrong because alleles are still inherited.
    C is wrong because chromosomes do not simply disappear.
    D is wrong because offspring do not become different species due to inbreeding alone.

33. Answer: B
    A is wrong because it reverses the two processes.
    B is correct because natural selection is driven by environmental selection pressures, while selective breeding is driven by human choice.
    C is wrong because neither necessarily produces clones.
    D is wrong because both can change allele frequencies.

34. Answer: B
    A is wrong because bacteria do not deliberately mutate because they need resistance.
    B is correct because resistant bacteria already present may survive antibiotic use and reproduce.
    C is wrong because antibiotics affect bacteria, not viruses.
    D is wrong because resistant bacteria can pass resistance alleles to offspring.

35. Answer: C
    A is wrong because completing a full course reduces the survival of partially resistant bacteria.
    B is wrong because using antibiotics only for bacterial infections reduces unnecessary selection pressure.
    C is correct because stopping early may leave resistant bacteria alive to reproduce and spread.
    D is wrong because vaccination can reduce bacterial infection and antibiotic use.

36. Answer: A
    A is correct because resistant bacteria reproduce and pass resistance to offspring, making resistance more common.
    B is wrong because bacteria do not become multicellular animals.
    C is wrong because bacteria are not converted into viruses.
    D is wrong because surviving bacteria continue DNA replication and reproduction.

37. Answer: A
    A is correct because variation provides the differences on which selection pressures act.
    B is wrong because variation does not prevent reproduction.
    C is wrong because variation can be genetic or environmental.
    D is wrong because genetic variation can be inherited.

38. Answer: B
    A is wrong because blood group is mainly genetic and discontinuous.
    B is correct because height is affected by both genes and environment such as nutrition.
    C is wrong because XX/XY sex chromosomes are genetic and discontinuous.
    D is wrong because attached/free earlobes are commonly treated as mainly genetic and discontinuous.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

39. Answer: A
    A is correct because discontinuous variation usually has clear categories with no intermediates.
    B is wrong because a normal distribution curve is typical of continuous variation.
    C is wrong because discontinuous variation is often controlled by one or few genes.
    D is wrong because discontinuous variation can be inherited.

40. Answer: A
    A is correct because blood group has separate categories.
    B is wrong because height is continuous.
    C is wrong because body mass is continuous.
    D is wrong because hand span is continuous.

41. Answer: A
    A is correct because continuous variation shows a range of values with many intermediates.
    B is wrong because only two categories would be discontinuous.
    C is wrong because continuous variation is often measured numerically.
    D is wrong because continuous variation is often controlled by many genes.

42. Answer: A
    A is correct because blood group is discontinuous and has separate categories, so a bar chart is suitable.
    B is wrong because blood group is not continuous.
    C is wrong because blood group is genetic, not caused only by exercise.
    D is wrong because blood group does not change daily with diet.

43. Answer: A
    A is correct because phenotype is the observable characteristic produced by genotype and sometimes environment.
    B is wrong because allele combination is genotype.
    C is wrong because phenotype can be affected by environment.
    D is wrong because phenotypes are seen in organisms, not only gametes.

44. Answer: A
    A is correct because light and mineral ions are environmental factors affecting plant growth.
    B is wrong because blood group inheritance is genetic.
    C is wrong because sperm carrying X is genetic.
    D is wrong because meiosis producing different gametes is genetic variation.

45. Answer: C
    A is wrong because scars are acquired/environmental.
    B is wrong because recent tanning is environmental.
    C is correct because blood groups are determined by inherited alleles.
    D is wrong because body mass increase after overeating is environmental.

46. Answer: A
    A is correct because artificial selection can produce traits useful to humans but not necessarily useful in nature.
    B is wrong because selected traits may be harmful in wild conditions.
    C is wrong because artificial selection can change allele frequencies.
    D is wrong because it is not random mating; humans choose breeders.

47. Answer: A
    A is correct because repeatedly breeding the largest chickens increases the frequency of alleles linked with large size.
    B is wrong because stretching is an acquired characteristic and is not passed on genetically.
    C is wrong because small chickens do not all mutate into large chickens before breeding.
    D is wrong because environment can also affect body size, though selection changes inherited factors.

48. Answer: A
    A is correct because breeding closely related individuals can increase homozygosity and expression of harmful recessive alleles.
    B is wrong because harmful recessive alleles can be inherited.
    C is wrong because choosing large parents does not automatically remove all harmful alleles.
    D is wrong because food supply does not turn a recessive allele into a dominant allele.

49. Answer: A
    A is correct because mutation creates new alleles, and natural selection can increase or decrease their frequency.
    B is wrong because natural selection does not create mutations because organisms need them.
    C is wrong because mutations are not always advantageous, and selection does not always remove advantages.
    D is wrong because mutation and natural selection are different processes.

50. Answer: A
    A is correct because continuous variation shows a range and is often influenced by many genes and the environment.
    B is wrong because a smooth bell-shaped distribution is typical of continuous variation, not discontinuous.
    C is wrong because selective breeding involves human choice, while natural selection does not.
    D is wrong because mutations can affect evolution by creating new alleles.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.