Dissecting gas exchange systems

• What is the purpose of dissecting gas exchange systems?

  To understand how different organisms are adapted for efficient gas exchange
• What is expected of students regarding dissections in their AS or A level Biology?


  Students are expected to carry out at least one dissection
• What types of systems can students dissect for their biology coursework?

  A gas exchange system or a mass transport system
• Why is it important to know how to carry out dissections safely and ethically?

  To ensure the well-being of the organisms and the safety of the students
• What should students do to record their observations during dissections?


  Record observations using labelled diagrams
• What is the first step in dissecting lungs?

  Wear a lab coat to protect yourself from mess
• What should you ensure about your dissecting tools before starting a lung dissection?

  They should be clean, sharp, and free from rust
• What should you do with the lungs before starting the dissection?

  Lay them on a cutting board provided by your teacher
• How can you inflate the lungs during dissection?

  Attach a piece of rubber tubing to the trachea and pump air into the lungs
• Why should you never blow into the trachea during lung dissection?

  You could end up sucking air from inside the lungs into your mouth
• What should you do to prevent bacteria from being released into the room during lung dissection?

  Place the lungs in a plastic bag before starting
• What can you examine after inflating the lungs?

  The different tissue types in the lungs
• What supports the trachea in the lungs?

  Shaped rings of cartilage
• How should you cut the trachea to open it up?

  Cut along the gap in the C-shaped rings
• What should you expect to feel when cutting a piece of lung?

  It will feel spongy because of the air trapped in the alveoli
• Why is it important to wash your hands after a dissection?

  To prevent food poisoning from bacteria
• What should you do before removing the gills from a bony fish?

  Wear an apron or lab coat
• Where are the gills located on a fish?


  On either side of the fish's head
• What protects the gills on a fish?

  A bony flap called an operculum
• How do you remove the gills from a bony fish?

  Push back the operculum and carefully cut the gills from the gill arches
• What should you see when you look closely at the gills?

  You should be able to see the gill lamellae
• Which insects are usually best for dissection?

  Grasshoppers or cockroaches
• What must be done to the insect before dissection?

  The insect must be humanely killed fairly recently
• How do you hold the insect in place during dissection?

  Use dissecting pins through its legs to hold it in place
• What do you need to do to examine the tracheae of an insect?

  Carefully cut and remove a piece of exoskeleton
• What should you fill the insect's abdomen with to see the tracheae?

  Saline solution
• Why do the tracheae appear silver or grey under the microscope?

  Because they are filled with air
• What is the purpose of the rings of chitin in the tracheae?

  They provide support
• What are some ethical issues involved in dissecting animals?

  Some argue it is morally wrong to kill animals for dissection
• What concerns exist regarding the treatment of animals used for dissection?

  They may not be raised in a humane way and could suffer
• What should be ensured if insects are raised in school for dissection?

  They should be looked after properly and killed humanely
• Why is it important for dissection tools to be sharp?

  Sharp tools cut better and are safer to use
• How should gills be removed from a bony fish?

  Carefully cut each gill arch through the bone at the top and bottom
• Why might the tracheae of a preserved grasshopper appear dark grey instead of silver under the microscope?

  Preservation may cause changes in the appearance of the tracheae
• Why does a piece of lung float in water?

  Because it is filled with air
• What is one safety precaution to take when carrying out dissections?


  Ensure that dissection tools are clean and sharp
• What are the steps to dissect the gaseous exchange systems of animals?

  1. Wear appropriate protective clothing (lab coat).
  2. Use clean, sharp tools.
  3. Lay the specimen on a cutting board.
  4. Inflate the lungs or examine the gills as appropriate.
  5. Record observations with labelled diagrams.
• What are the ethical considerations when dissecting animals?

  • Morality of killing animals for dissection
  • Humane treatment of animals used
  • Proper care for animals raised for dissection
• What are the main components of the gas exchange systems in animals?

  • Lungs (with trachea and bronchi)
  • Gills (in bony fish)
  • Tracheae (in insects)