100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Previously searched by you
Previously searched by you
logo
Edexcel Biology A (Salters-Nuffield): Topic 6 IIF (Infection, Immunity and Forensics) summary £4.09
Add to cart
Quickly navigate to
Preview
  2.  
  3. PEARSON (PEARSON)
  4.  
  5. Biology A Salters-Nuffield
  6.  
  7. Topic 6 : Infection, Immunity and Forensics

Summary

Edexcel Biology A (Salters-Nuffield): Topic 6 IIF (Infection, Immunity and Forensics) summary
 0 purchase

This is a summary of every learning objective (6.1-6.15) for Topic 6 IIF, on the Edexcel Biology A (Salters-Nuffield) specification. I have arranged my notes answering each objective, and have given definitions, core practical information, and equations, based from the textbook. These notes inc...

[Show more]

Preview 2 out of 12  pages

Document information

  • January 4, 2023
  • 12
  • 2021/2022
  • Summary

Subjects

Written for

All documents for this subject (1)

Seller

avatar-seller
issy078

Reviews received

Content preview

BIOLOGY SPECIFICATION NOTES
Edexcel Biology Salters-Nuffield A AS/A-Level

Key:
Definitions are in turquoise
Core practicals are in orange
Equations are in green

Topic 6: Infection, immunity and forensics (IIF)

6.1 Understand how to determine the time of death of a mammal by examining the extent of
decomposition, stage of succession, forensic entomology, body temperature and degree of
muscle contraction. p.79

As soon as a person dies, a series of physical and chemical changes start to take place.
These occur in a known order due to the timing of a death which can be used to estimate
the time of death.
Body temperature
- Lasts from 30-60 minutes, but is useful within first 24 hours
- Normal body temperature is between 36.2 - 37.6 C
- Core body temperature measured through rectum or
abdominal stab
- Long thermometer or electronic temperature probe used
- Cooling of the body follows sigmoid curve
- Not very accurate as other factors must be taken into
account. These include: body size and fat (insulation), body
position, clothing, air movement, humidity, and temperature of
surroundings, which encompasses the environment.
- A body immersed in water cools faster than in air, water better conductor of heat

Rigor mortis
- Complete is seen at 6-9 hours after death
- Rigor mortis is the stiffening of muscles. Rigor mortis eventually passes and muscles
are relaxed again when the muscle tissue breaks down. This is because:
- After death, muscles are starved of oxygen and oxygen-dependent reactions stop
- Anaerobic respiration in cells, lactic acid produced
- pH of cells falls, inhibits enzymes and stops respiration
- ATP for muscle contraction no longer produced, bonds between muscle proteins are
fixed
- Proteins can’t move to shorten the muscle, so muscles and joints are fixed
- The stages of rigor mortis can be divided up into four as well.
- < 3 hours: Warm, not stiff
- 3-8 hours: Warm, stiff
- 8-36 hours: Cold, stiff
- 36-48 hours: Cold, not stiff

, Decomposition
- Between 36-72 hours after death
- First is autolysis, where the body’s enzymes (from digestive tract and lysosomes)
break down cells
- Bacteria from gut and lungs invade tissues, releasing enzymes that aid
decomposition
- Loss of oxygen favours growth of anaerobic bacteria
- First sign of decomposition is putrefaction, green discoloration of skin in abdomen
- Spreads across body, darkening
- After about a week, gas or liquid blisters appear
- Body smells and becomes bloated due to methane, CO2, ammonia and hydrogen
forming
- Fluid from putrefaction drains away, soft tissues shrink and decay rate is reduced
- Temperature and injuries slow or speed up this process. A high temperature can
actually denature enzymes.

Forensic entomology and stage of succession can also be used to help detect the time since
death.

Forensic entomology involves the study of insects to help determine when the body died.
The temperature, air, ground, and maggot mass are measured, and as the stages of maggot
development are clearly defined, can be used to determine the death. Some maggots may
be killed, to retain the age they are when they are found, and some are left to grow, so their
development is completed and the species can be identified. It generally takes insects one
day to lay their eggs. If the length of time for an egg to form and pupate is subtracted from
the date of pupation, the date the eggs were laid can be worked out.

The different species found on the body can also be used. There is a predictable sequence
of organisms that feed on the body. For example:

1. Bluebottles, house fly
2. Flesh flies
3. Beetle larvae, moths
4. Cheese skipper

6.2 Know the role of microorganisms in the decomposition of organic matter and the
recycling of carbon. p.85

- There are other microorganisms involved in the decomposition of the body
- Bacteria from the gut invade the tissues after death
- Other bacteria and fungi from surrounding colonate
- These microorganisms are called decomposers
- The body is a great source of energy
- Organic carbohydrates, proteins, fats and nucleic acids are used as a food
source
- Energy is released through aerobic and anaerobic respiration
- Energy allows decomposers to grow more rapidly

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through credit card for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller issy078. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for £4.09. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

66391 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy revision notes and other study material for 15 years now

Start selling
£4.09
  • (0)
Add to cart
Added