Death, Decay and Decomposition

Question 1

What is decomposition?

Answer 1

The breakdown of organic matter. Nutrients are released from dead plants or animals

Question 2

What does decomposition allow?

Answer 2

Nutrients to be recycled

Question 3

What are the 4 stages of decay and their times?

Answer 3

• Fresh (24 hours)
• Bloat (0-10 days)
• Active Decay (10-20 days)
• Dry Decay (20-365 days)

Question 4

List characteristics of fresh decay

Answer 4

• Skin goes tight and grey
• Cells die
• Muscles relax
• Bladder and bowels empty
• Mortis (A, L, R)

Question 5

What are the 3 mortis?

Answer 5

• Algor (cooling of body at 0.32C per hour from 37C)
• Livor (discolouration due to settling of blood. Skin waxy and purple, lips pale, eyes sink)
• Rigor (stiffening due to chemical changes, lactate)

Question 6

What are the time periods for rigor mortis?

Answer 6

• Begins within 10 hours
• Whole body stiff 12-18 hours
• Stiffness goes after 24 hours

Question 7

List characteristics of bloat decay

Answer 7

• Putrefaction (bacterially induced destruction of soft tissue, gas formation)
• Skin slips and marbles
• Green colouration
• Further destruction due to insects

Question 8

List characteristics of active decay

Answer 8

• Body begins to collapse
• Bloat collapses to leave flattened body
• Large volume of fluids drain from body

Question 9

List characteristics of dry decay

Answer 9

• Remaining flesh deteriorates
• Slow decay due to lack of moisture
• Reduced to hair and bones
• Skeletonisation

Question 10

Name 3 things used to predict post mortem interval

Answer 10

• Stages of decomposition
• Forensic entomology
• Environmental factors

Question 11

What is the life cycle of insects?

Answer 11

• Eggs laid
• Eggs hatch into larvae
• Larvae turn to pupae
• Adult stage

Question 12

List factors impacting insect growth rate

Answer 12

• Temperature
• Oxygen levels
• Food quality
• Season

Question 13

Name the common colonisation sequence

Answer 13

• Flies arrive within hours, attracted to odours
• Carrion beetles arrive within a few days
• Carpet beetles arrive during dry stage

Question 14

How does decomposition occur at first?

Answer 14

• Enzymes break down wall of gut and surrounding tissue
• Cells die and release enzymes
• Tissues broken down