Lesson 6.1.1

6.1.1 Time of death, decomposition and forensic entomology Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 6

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 6.1.1, Time of death, decomposition and forensic entomology: 20 multiple choice questions for the Pearson Edexcel Biology A (Salters-Nuffield) (9BI0), Unit 6: Immunity, Infection and Forensics, written with Revision Ninja.

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The 20 questions

  1. Which factor is used to estimate the time of death of a mammal from decomposition?

    • The number of teeth lost from the jaw, which falls at a fixed rate after death
    • The colour of the hair, which changes at a fixed rate after death in all mammals
    • The stage of decomposition, reached at a known rate under given conditions
    • The number of red blood cells remaining in the body's veins at the time of death

  2. Forensic entomology uses insects to estimate time of death mainly by:

    • Testing insects for the presence of the deceased person's blood group antigens
    • Measuring the total mass of insects found in the soil beneath the body at the scene
    • Identifying the species and developmental stage of insects colonising the body
    • Counting the number of flies that are seen flying near the body during the day

  3. What is meant by succession in the context of forensic investigation of a body?

    • The orderly sequence of muscle contractions that occurs immediately after death
    • The gradual replacement of the body's proteins with inorganic minerals from the soil
    • The predictable sequence of different organisms that colonise and feed on the body over time
    • The series of blood tests performed by a pathologist during a post-mortem examination

  4. Body temperature is used as a time-of-death indicator because:

    • Body temperature falls to exactly the air temperature within five minutes of death in every case
    • Body temperature rises only when decomposition bacteria are absent from the body surface
    • The body warms up after death and reaches a fixed maximum temperature after exactly 24 hours
    • The body cools after death at a broadly predictable rate

  5. Muscle contraction after death, known as rigor mortis, is used in estimating time of death because:

    • It is caused by the blood clotting in the veins and cannot change once it has begun
    • It develops and then passes off in a fairly predictable sequence over the hours after death
    • It starts only after the body has been buried for at least a week and never before
    • It makes muscles grow larger after death, so their size can be measured with callipers

  6. A forensic scientist finds fly larvae on a body. Why is the larval stage important for estimating time since death?

    • Larvae only grow when the body has been moved, so they cannot indicate time since death
    • Larvae develop through predictable stages at known temperatures
    • Larvae are always the same age on a body, regardless of temperature or the amount of time passed
    • Larvae appear on the body at exactly the same time as death in all cases, so their presence confirms it

  7. Which of these would make a body decompose more quickly, all else being equal?

    • A dry, sealed environment, since moisture is needed for insects to lay eggs on a body
    • A body buried deep in dry sand, since oxygen is removed from the tissues by the soil
    • A colder environment, since low temperatures speed up the activity of decomposing bacteria
    • A warmer environment, since higher temperatures speed up microbial and insect activity

  8. Why must forensic scientists consider environmental conditions when estimating time of death?

    • Temperature, humidity and access to insects all change the rate of decomposition and so affect the estimate
    • Environmental conditions only affect the colour of the body, which is irrelevant to time estimates
    • Environmental conditions are irrelevant because decomposition rates are the same in every location
    • Environmental conditions only matter if the body has been moved to a laboratory after death

  9. Which group of organisms is primarily responsible for decomposition of a body after the first stages?

    • Viruses that dissolve the cell walls of the tissues and release water
    • Mammals that scavenge the body, which consume the entire carcass within a single day
    • Bacteria and fungi, which break down tissues and release nutrients and carbon dioxide
    • Plants that grow through the soil and absorb the proteins released by the body

  10. A body is found with a late-stage insect succession and mature larvae. What does this suggest?

    • The body has been dead for a longer period than a body with only early-stage colonisers
    • The body was frozen throughout, so insect development has not taken place at all
    • The body has been dead for only a few minutes, since insects arrive instantly after death
    • The body was moved from a different species, so the insects are not relevant to the estimate

  11. Why is the estimate of time since death usually given as a range rather than a single exact time?

    • Several factors such as temperature and insect activity vary and introduce uncertainty into the estimate
    • Because bodies decompose at random, so no pattern can ever be observed in any evidence
    • Because the law requires a range to be given, and single times are never accepted by courts
    • Because the time of death can only be found by testing blood, which always gives a range

  12. Which evidence is most useful when a body has been dead for more than several days?

    • Body temperature alone, since it stays the same for as long as the body is exposed
    • The presence of blood on the clothes, which indicates the time of death precisely
    • Muscle contraction alone, since rigor mortis continues for the whole period after death
    • Insect succession and larval development

  13. Which statement best evaluates the use of forensic entomology in time-of-death estimates?

    • It is a valuable method, but it depends on accurate temperature records and identification of the insect species involved
    • It is useless in every case, because insects never arrive on a body until it has been buried
    • It is always accurate to the nearest hour, since insects never vary in their rate of development
    • It is only valid for mammals found in deserts, so it cannot be applied in any other environment

  14. A body is at ambient temperature 15 C and cooling is estimated at 1.5 C per hour from an initial 37 C. Approximately how long has the body been dead if its temperature is 25 C? Assume a linear cooling rate.

    • About 4 hours, since (37 - 25)/3 = 4 with the rate doubled for the first hour
    • About 8 hours, since (37 - 25)/1.5 = 8
    • About 12 hours, since (37 - 25) x 1.5 = 18 and the time is taken as 18 minus 6
    • About 2 hours, since 25 minus 15 gives 10 and 10 divided by 1.5 gives about 7

  15. Which statement is most accurate about the use of decomposition stages in forensic science?

    • Stages cannot be used at all, because decomposition is a random process with no pattern
    • Stages provide broad estimates
    • Stages only apply to human bodies, and can never be used for animal remains in a forensic setting
    • Stages provide exact times, because every body passes through each stage at the same rate

  16. Which stage of decomposition is characterised by bloating caused by gases produced by bacterial activity?

    • Skeletal stage, when only the bones remain after the soft tissues have decomposed completely
    • Putrefaction, when bacterial activity produces gases that cause the body to swell
    • Dry stage, when the soft tissues have been removed and the skin has become leathery
    • Fresh stage, when the body is cool and rigor mortis has not yet begun to set in

  17. Why are blowfly larvae often used as evidence in forensic cases?

    • They produce enzymes that break down the body's proteins at a fixed rate in all conditions
    • They indicate the cause of death directly, through toxins that they produce in the tissues
    • They are only found on bodies that have been buried underground for several weeks
    • They arrive quickly after death and their development follows a predictable, temperature-dependent timeline

  18. A larva grows from 1 mm to 9 mm in 40 hours at a constant temperature. What is its average growth rate?

    • 0.025 mm per hour, since 1/40 = 0.025 and the growth is measured from zero
    • 5 mm per hour, since the total length of 9 mm is divided by a time of about 2 hours
    • 0.2 mm per hour, since (9 - 1)/40 = 0.2
    • 0.4 mm per hour, since 9 mm divided by 40 hours plus the initial length gives 0.4

  19. The post-mortem interval is best defined as:

    • The time elapsed since death, which forensic methods aim to estimate
    • The period between the start of rigor mortis and the complete disappearance of muscle stiffness
    • The interval between two successive post-mortem examinations carried out on the same body
    • The time taken for an insect to complete its whole life cycle from egg to adult

  20. Why might a forensic scientist combine several methods rather than rely on one?

    • Combining methods removes the need to consider environmental conditions such as temperature
    • Each method has its own uncertainties
    • Single methods are not admissible in court, so several must always be used in every case
    • Combining methods always produces one exact time, so no range or uncertainty is ever reported

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