Features of Specialised Exchange Surfaces Flashcards
What are the key features of specialised exchange surfaces?
1/ Large surface area relative to volume - increasing rate of exchange
2/ Very thin - allowing short diffusion distance for rapid transport
3/ Selectively permeable - allowing specific materials to cross
4/ Movement of the environmental medium
5/ Transport system for internal medium
What is the role of selective permeability in exchange surfaces?
It ensures only specific materials can cross the surface
How does a large surface area relative to volume benefit exchange surfaces?
It increases the rate of diffusion by providing more area for substances to cross
Why is the movement of the environmental medium important for exchange?
It maintains a diffusion gradient by constantly supplying fresh substances and removing waste
Why mjust specialised exchange surfaces be very thin?
This is so the diffusion distance is reduced, allowing material to cross quickly
Why do many organisms have a transport system for an internal medium?
To maintain a concentration gradient by transporting substances
What is the formula for diffusion rate?
Diffusion∝ (surfacearea × differenceinconcentration) ÷ length of diffusion path
Why are specialised exchange surfaces often located inside the body?
They are thin and easily damaged or dehydrated, so they need protection
How do organisms with internal exchange surfaces maintain effective exchange?
They have mechanisms to move the external medium over the surface, such as ventilation in mammalian lungs
How do gases enter and leave the tracheal system in insects?
Through tiny pores called spiracles in the body surface
What controls the opening and closing of spiracles?
Valves that can open and close the spiracles
Why do insects keep their spiracles closed most of the time?
To prevent water loss by evaporation
Why do insects periodically open their spiracles?
To allow gas exchange for respiration
Why is the tracheal system an efficient method of gas exchange in insects?
It delivers oxygen directly to cells and maintains a short diffusion pathway for rapid gas exchange
What is a limitation of the tracheal system?
It relies mostly on diffusion, which requires a short diffusion pathwy to be effective
Why are insects small in size?
The length of the diffusion pathway limits the size they can grow to, as diffusion alone cannot support large bodies
