IBBiologyHLExam QuestionsContinuity & ChangeNatural Selection

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First teaching 2023

First exams 2025

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Natural Selection (HL IB Biology)

Exam Questions

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Natural Selection

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Natural Selection

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11 mark

What is the definition of the term 'gene pool'? 

  • All of the genes that exist within a population

  • All of the genes and their different alleles that exist within a species

  • The different alleles that exist for one gene within a species

  • All of the genes and their different alleles that exist within a single population

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21 mark

An example of a trait that evolved by natural selection is body size in fish, which has declined with warming ocean temperatures. 

State the type of selection that this change represents. 

  • Allopatric

  • Directional

  • Disruptive

  • Stabilizing

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3
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Which process does not generate heritable variation in a population?

  • Mutation

  • Mitosis

  • Metaphase I of meiosis

  • Fertilisation

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4
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Which of the following statements correctly explains the process of natural selection?

I. Some species produce small numbers of young and provide higher levels of parental care

II. Advantageous alleles increase an individual's chance of surviving and reproducing

III. Individuals that change to suit their environment pass their alleles on to offspring

IV. Advantageous alleles increase in frequency in the population

  • I and II only

  • I, II, III, and IV

  • II, III, and IV only

  • II and IV only

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11 mark

A game farm in South Africa has a population of about 5 000 large antelope called Kudu. Kudu bulls have large, spiralled horns which draw the attention of trophy hunters that frequently visit the game farm.

The antelope are all kept in a large, fenced-off area consisting of open grassland habitat.

Could this be considered an example of a stable gene pool?

  • No, since there will be a selective pressure to increase the allele frequency for antelope with large horns

  • No, since there will be a selective pressure for antelope with smaller horns

  • Yes, it is a large population of antelope with an equal chance to mate with each other

  • Yes, it is a large population located in a habitat that enables random matings between antelope of different phenotypes

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21 mark

Which of the following applies to the process of evolution by natural selection?

  1. Changes in the phenotype of organisms in a population
  2. Selection pressures favouring certain alleles within a population
  3. Individuals with a certain genetic makeup will not pass on their genes
  4. Changes in the allele frequencies within a population over time

  • II only

  • I, II and III

  • II and IV only

  • I, II, III and IV

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31 mark

What would be the most accurate description of the following graphs?q4_10-3_gene_pools_speciation_ib_biology_hl_mcq

 

I

II

III
A

Stabilising selection as giraffes with longer necks are selected for

Directional selection as larger and smaller turtles are selected for

Disruptive selection as cacti with a medium spine density are selected for
B

Directional selection as giraffes with longer necks are selected for

Disruptive selection as larger and smaller turtles are selected for

Stabilising selection as cacti with a medium spine density are selected for
C

Stabilising selection as giraffes with medium neck lengths are selected for

Disruptive selection as larger and smaller turtles are selected against

Directional selection as cacti with medium spine density are selected for
D

Directional selection as giraffes with medium neck lengths are selected for

Stabilising selection as larger and smaller turtles are selected against

Disruptive selection as cacti with medium spine density are selected for

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    41 mark

    Which of the following examples would be a useful application of comparing allele frequencies between populations?

    1. Estimating the number of individuals in a population that may be susceptible to certain diseases
    2. Studying the evolutionary history of populations within a specific species
    3. Investigating the effect of environmental factors on the phenotype within different populations

    • I only

    • III only

    • I and II only

    • I and III only

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    51 mark

    Which of the following processes generate genetic variation?

    1. Random assortment
    2. Mitosis
    3. DNA replication
    4. Random fertilisation

    • I and III only

    • I and IV only

    • I, III, and IV only

    • I, II, III, and IV

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    61 mark

    Which of the following must occur for natural selection to take place?

    • Sexual reproduction.

    • Genetic variation.

    • The presence of predators.

    • Advantageous characteristics.

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    71 mark

    Research was carried out on beak size in the island-living finch species Geospiza fortis. G. fortis feeds on seeds, which are plentiful, small, and soft in the years when the weather is normal, but which become larger and tougher in drought years. Some of the research results are shown in the graph below.

    dOlrvi6g_3

    Which of the following statements explains the results in the graph?

    • Finches adapt to drought years by developing larger beaks, passing on the characteristic to their offspring, and leading to an increase in average beak size.

    • Average finch beak size increases during years of drought and decreases during wet years.

    • Average beak size increased from 9.5 mm in 1976 to 9.9 mm in 1977, before slowly decreasing to 9.7 mm by 1979.

    • Finches with larger beaks have an advantage when competing for food in drought years, and are therefore more likely to survive and pass on their alleles, leading to an increase in average beak size.

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    11 mark

    In a population of fruit flies, Drosophila melanogaster, there are several alleles that code for eye colour. 

    In one particular population there are four alleles, red, white, cherry and apricot. 

    The table below shows the allele frequencies of each of the alleles in this population. 

    Some of the data is missing. 

    Allele type Frequency
    red 0.44
    white 0.25
    cherry  
    apricot 0.18

    Which of the following statements is a correct conclusion that can be made from this data? 

    • The red eye colour allele is dominant to the rest of the eye colour alleles

    • The apricot eye colour allele is the least common allele in the population

    • Most of the fruit flies in this population show the red eye phenotype

    • The phenotype frequencies are totally unknown

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    21 mark

    Which of the following does not describe the process of natural selection? 

    • A species of antelope where the population has stronger muscles after the individuals with weak muscles are eaten by predators

    • When a bacteria is exposed to a new type of antibiotic the exposure causes the bacteria to become resistant

    • Sharks adapting to store more oxygen in their blood because the sharks with less oxygen were more likely to die

    • Dark peppered moths increasing in number during the industrial revolution in response to increased predation of the light colour moths

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    31 mark

    The three graphs below show how the allele frequencies of two alleles in three different populations changed over several generations. 10-3_q3h

    Which of the graphs show changes in allele frequency that suggest that evolution is taking place?

    • II. only

    • II. and III. only

    • III. only

    • I., II. and III. 

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    4
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    In adult humans, the ability to digest the lactose sugar in milk depends on the presence of an allele known as -13910*T. Individuals with this allele continue to produce the enzyme lactase into adulthood; this is known as lactase persistence. Individuals without this allele are not able to produce lactase after infancy and cannot digest lactose as adults. The table below shows the frequency of the -13910*T allele in European Neolithic hunter-gatherers who lived around 5 000 years ago and in modern Europeans.

      European Neolithic hunter-gatherers  Modern Europeans
    Frequency of -13910*T allele 0.03 (+/- 0.11) 0.74 (+/- 0.06)

    Which of the following can be concluded from the table?

    • There is no significant difference in the frequency of the -13910*T allele between Neolithic hunter-gatherers and modern day humans in Europe

    • Lactase persistence gave a survival advantage to humans at some stage between Neolithic and modern-day times

    • Lactase persistence gave a survival advantage to European Neolithic hunter-gatherers

    • Adult European Neolithic hunter-gatherers did not consume milk

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