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