7.4 Ventilation and Gas Exchange in Other Organisms Flashcards
What are the adaptations fish have to get enough oxygen from water?
Each gill is made of filaments with give a big surface area for exchange of gases. The gill filaments are covered in lots of tiny structures called gill lamellae ( gill plates ) which increases the surface area even more.
The gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion.
The tips of adjacent gill filaments overlap. This increases the resistance to the flow of water over the gill surfaces and slows down the movement of the water. As a result there is more time for gaseous exchange to take place.
The water moving over the hills and the blood in the gill filaments flow in different directions. This is called a counter - current system. It maintains a large concentration gradient between the water and the blood. The concentration of oxygen in the water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the blood.
Describe how fish gills are ventilated
The fish opens its mouth which lowers the floor of the buccal cavity. The volume of the buccal cavity increases so pressure decreases. Water enters the cavity.
The fish closes its mouth which raises the floor of the buccal cavity. The volume inside the cavity decreases, the pressure increases, and water is forced out of the cavity across the gill filaments.
Each gill is covered by an operculum which protects the gill. The increase in pressure forces the operculum in each side of the head to open, allowing water to leave the gills.
How do you dissect, examine and draw fish gills?
Wear a lab coat and gloves
Place chosen fish in a dissection tray or on a cutting board
Push back the operculum (using tweezers or a mounted needle ) and use scissors to remove the gills. Cut each gill arch through the bone at the top and bottom.
Finish by drawing and labelling
How does gas exchange occur in insects?
Air moves into their tracheae through pores on the insects surface called spiracles.
Oxygen travels down the concentration gradient towards the cells. Carbon dioxide from the cells moves down its own concentration gradient towards the spiracles to be released into the atmosphere
Tracheae branch off into smaller tracheoles which have thin, permeable walls and go into individual cells. The tracheoles also contain tracheal fluid, which oxygen dissolves in.
Th oxygen then diffuses from this fluid into body cells. Carbon dioxide diffuses in the opposite direction.
What are the alternative methods insects with higher energy demand use to increase the level of gaseous exchange?
Mechanical ventilation of the tracheal system
Collapsible enlarged tracheae or air sacs
Describe how mechanical ventilation of the tracheal system increases gaseous exchange?
Air is actively pumped into the system by muscular pumping movements of the thorax and / or the abdomen.
This changes the volume of the body and this changes the pressure in the tracheae and tracheoles.
Air is drawn into the tracheae and tracheoles, or forced out, as the pressure changes.
Describe how collapsible enlarged tracheae or air sacs helps to increase gaseous exchange levels
They are used to increase the amount of air moved through the gas exchange system.
They are usually inflated and deflated by the ventilating movements of the thorax and abdomen.
How can you dissect the gaseous exchange systems in insects?
Fix the insect to a dissecting board. Use dissecting pins to hold the legs in place.
To examine the tracheae, cut and remove a piece of exoskeleton from along the length of the insects abdomen.
Use a syringe to fill the abdomen with saline solution. A network of very thin tubes should be visible - these are the tracheae. They look silver as they’re filled with air.
What is the best way to examine tracheae?
Use a light microscope and a wet mount slide.
The tracheae will appear silver / grey.
Rings of chitin in the walls of the tracheae should be visible - these are there for support.
