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OCR A Level Biology:復習筆記1.2.3 Practical: Dissection of Gas Exchange Surfaces in Fish & Insects

Category: A-level課程, 國際課程, 教材筆記, 福利干貨 Date: 2022年11月16日下午2:56

Practical: Dissection of Gas Exchange Surfaces in Fish & Insects

The safe use of instruments for the dissection of an animal or plant organ

Dissections are a?vital part?of scientific research
They allow for the?internal structures?of?organisms?and?organs?to be examined so that theories can be made about how they?function
- For example, dissections can be performed on?fish?to expose and study their?gills?(the gas exchange surface in fish) or on?insects?to expose and study their?spiracles, tracheae and tracheoles?(the gas exchange system in insects)
There are?ethical concerns?surrounding dissections
- People worry about how the animals for dissections are?raised?and?killed
- It goes against the?religious beliefs?of some individuals
The biological specimen used for dissection should be from a?reputable source?and should be?disposed of in the correct manner
If multiple specimens are being dissected then they should be taken from individual organisms of the same species and roughly the same age
Safety is a priority?when conducting dissection experiments with sharp tools like scalpels and scissors
The method below outlines some precautions that should be taken in the interest of safety

Apparatus

Scissors
Scalpel
Tweezers / Forceps
Dissection board
Paper towels
Biological specimen
Pins
Gloves
Goggles

Method

A lab coat, gloves and eye protection should be worn
- This is done to?avoid contamination?with biological material (which could cause an allergic reaction)
Place the specimen on the dissecting board
Use the tools to access the desired structure
- When using the scalpel?cut away from your body?and keep your?fingers far from the blade?to reduce the chance of cutting yourself
- Scissors can be used for cutting large sections of tissue (cuts do not need to be precise)
- A scalpel enables finer, more precise cutting and needs to be sharp to ensure this
Use pins to move the other sections of the specimen aside to leave the desired structure exposed

Limitations

It can be hard to see some of the smaller, finer structures within organs
The specimens do not reflect how the tissue would look in a living organism
If only a single specimen is dissected then anomalies found within that specimen may be ignored or glossed over
Dissection instruments (scissors and scalpel) should be sharp to give good clean cuts with as little damage as possible -?blunt instruments are dangerous?(as more force is required to cut) and will not give precise cuts making internal structures harder to distinguish

Exam Tip

You may be asked to suggest a method of dissection for a particular organ. Make sure you?name the specific tools?(e.g. scissors and forceps) that should be used in order to get the marks.

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