Time of death and decompositionEdexcel A-Level Biology A: Flashcards
Card 1 of 130 of 13 known
Question
What is the post-mortem interval?
Tap or press Space to reveal
Tap card or press Space to flip
See all 13 cards
- What is the post-mortem interval?
- The time that has passed since death.
- How does a body cool after death?
- It loses heat towards its surroundings because metabolism has stopped; cooling is faster in water or with a large surface area and slower with insulation.
- Over what time is body temperature useful for estimating time of death?
- About the first 24 hours.
- Why does rigor mortis occur?
- ATP is no longer made, so myosin heads cannot detach from actin and the muscles stay contracted.
- When is rigor mortis complete and when does it pass off?
- About 12 hours after death; after about 24 to 36 hours as muscle proteins break down.
- What is succession on a body?
- The predictable order in which different organisms colonise it as its condition changes.
- Name the stages of decomposition.
- Fresh, bloat, active decay, advanced decay and dry remains.
- Why do blowflies arrive first?
- They detect the chemicals released by early decomposition and lay eggs within hours.
- What does the age of the oldest larvae show?
- A minimum time since death.
- Why is the site temperature needed in forensic entomology?
- The rate of larval development is controlled by enzymes and depends on temperature.
- What is a saprotroph?
- An organism that feeds on dead organic matter by secreting enzymes and absorbing the products.
- How do saprotrophs release carbon dioxide?
- They respire the soluble products of digestion.
- How is carbon from a dead body recycled?
- Respiration releases carbon dioxide; plants take it up in photosynthesis, returning carbon to food chains.
Exam questions on Time of death and decomposition
- A body is found in a room in a house at 10:00. The room temperature is 18 °C. The rectal temperature of the body is 31.0 °C. The pathologist records that rigor mortis is present in the muscles of the jaw, neck and arms but not yet in the legs. For this question, assume that the body temperature was 37.0 °C at death and that the body has cooled at a constant 1.5 °C per hour.Calculate the time that has passed between death and the discovery of the body. Show your working.2 marks
- A body is found in woodland in June. Blowfly larvae are present and the largest are 14 mm long. No pupae are present. Laboratory data show that at 18 °C, the mean temperature recorded at the site, blowfly eggs laid on a body hatch after about 1 day and the larvae reach 14 mm in length 5 days after the eggs were laid.Estimate the minimum time since death and explain your answer.2 marks
- At a forensic research facility, a team observes a human donor body left on the surface of woodland soil in summer. Decomposition passes through stages: fresh (0–3 days), bloat (4–7 days), active decay (8–15 days), advanced decay (16–30 days) and dry remains (over 30 days). Blowflies are the first insects to arrive, followed in turn by flesh flies, then carrion beetles during active decay, and finally hide beetles and mites on the dry remains.Explain how the stage of succession on a body found in similar woodland could be used to estimate the time of death.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).