Exchange surfaces- Insect and Fish gas exchange Flashcards
Define the term exoskeleton
An external skeleton of some organisms- made of chitin and is waterproofed to reduce water loss.
Define the term spiracle
Small openings along the thorax and abdomen of an insect that open and close to control the amount of air moving in and out of the gas exchange system.
Define the term trachea
The main airway, supported by incomplete rings of cartilage, which carries warm moist air down form the nasal cavity into the chest.
Define the term tracheoles
A small pipe that branches of a trachea in insects and is used for gas exchange.
Define the term tracheal fluid
Fluid found at the ends of the tracheoles in insects that helps control the surface area available for gas exchange and water loss.
Outline the structure of the insect gas exchange system and describe the way oxygen reaches the body cells.
- Air moves into the tracheae through pores on the surface called spiracles.
- O2 travels down the conc gradient towards the cells.
- CO2 from the cells moves down its own conc gradient towards the spiracles to be released into atomsphere.
- The tracheae branch off into smaller tracheoles which have thin permeable walls and go to individual cells.- they also contain fluid which oxygen dissolves in
- The oxygen then diffuses from this fluid into body cells- CO2 diffuses in the opposite direction.
Explain why insects will tend to keep spiracles closed when oxygen demands are very low.
Spiracles can be opened and closed by sphincters- the spiracle sphincters are kept close as much as possible to minimise water loss.
Describe the adaptations of the insect gas exchange system that make it an efficient exchange surface.
- The tracheoles provide a large SA for gas exchange
2. The tubes are thin- allows the tracheoles to go close to cells- minimise diffusion distance
Describe how activity changes the volume of tracheal fluid in the tracheoles, and explain the value of this occurring.
- When oxygen demands builds up- Lactic acid builds up in the tissues- results in water moving out of the tracheoles (tracheal fluid) by osmosis- exposes more SA for gaseous exchange.
Describe two adaptations that insects with very high energy demands have to increase the efficiency of their gas exchange system.
- Mechanical ventilation of the tracheal system- air is actively pumped into the system by muscular pumping movements of the thorax and/or abdomen. These movements change the volume of the body- changes the pressure in tracheae and tracheoles- air is drawn into or forced out of them as pressure changes.
- Collabsible enlarged tracheae or air sacs which act as resevoirs- these are used to increase the amount of air moved through the gas exchange system- usually they are inflated or deflated by the ventilating movements of the thorax and abdomen.
Describe the advantages of, and challenges faced by, gas exchange systems operating in water rather than air.
Advantages:
1. Water loss isn’t an issue
2. Water provides structural support which air doesn’t
Disadvantages:
1. Much lower oxygen concentration- lower conc. gradient- more difficult to obtain sufficient O2
2. Water is more viscous and dense than air.
Define the term opperculum
The bony flap covering the gills of bony fish. Part of the mechanism that maintains a constant flow of water over the gas exchange surfaces.
Define the term buccal cavity
The space behind the mouth in a fish.
Define the term opercular valve
The flap that allows the oppeculum to be moves outwards whilst keeping it closed
Define the term gill arch
The bony structure that supports the gill filaments,