Unit 3 - Suface Area To Volume Ratio And Gas Exchange. Flashcards
The larger the organism…?
The smaller the SA:Vol
Why do single celled organisms not need special adaptations to increase the rate of diffusion?
They have a large enough surface area to volume ratio to meet their gas exchange needs by diffusion across their surface.
Why do multicellular organisms develop specialised gas exchange systems?
Larger organisms have a smaller S.A.:Vol so the cannot rely on diffusion across their surface alone to supply sufficient amounts of oxygen to all their cells.
How do multicellular organisms maintain body temp?
They have a high metabolic rate (rate of respiration and other chemical reactions in cells) which releases heat energy.
What is ficks law?
Diffusion rate is proportional to (surface area x difference in concentration) divided by diffusion distance.
What dilemma do insects face?
The need for gas exchange versus the need to conserve water.
To limit water loss insects may have?
1) Waterproof covering over their body surfaces. This is usually a rigid outer skeleton (exoskeleton) covered with a waterproof cuticle.
2) Small surface area to volume ratio to minimise the area over which water is lost.
Parts of the gas exchange system in insects?
Movement of oxygen through the insect?
1) Oxygen enters the insect through spiracles and into the trachea. Spiracle closes.
2) Oxygen diffuses through the trachea into the tracheoles down a concentration gradient.
3) Oxygen is delivered directly to the tissues to be used for aerobic respiration.
How does oxygen diffuse throughout insects?
1) Tissues aerobically respire using oxygen, which reduces the concentration of oxygen at the tissue.
2) Oxygen diffuses from an area of high concentration in the trachea to low concentration at the tissue.
3) This lowers the oxygen concentration in the trachea so oxygen diffuses into the tracheas from outside the insect via the spiracles.
How does CO2 diffuse throughout the insect?
1) Aerobic respiration produces carbon dioxide, increasing the concentration at the tissue.
2) Carbon dioxide diffuses from an area of high concentration at the tissue to the low concentration traction in the tracheae.
3) Carbon dioxide moves from high concentration in tracheae to low concentration outside the insect via the spriacles.
How does ventilation occur in insects?
Movement of the insects muscles creates a mass movement of air in and out the tracheae, thus speeding up the gaseous exchange.
Why do insects have a larger surface area?
-many small/narrow tracheoles.
Why do insects have a greater concentration gradient?
-aerobic respiration in tissues removed O2 and produced CO2
-so O2 diffuses in + CO2 diffuses out = diffusion gradient.
-rhythmic abdominal pumping
-ventilation
-air sacs (not all insects) can store O2
What decreases insects diffusion distance?
-Tracheoles are next to cells in tissue.
-Tracheole walls = 1 squamous epithelial cell thick.
Role of the gills?
They are the organ by which gases are exchanged between the fish and the water. Gulls enable fish to absorb oxygen and expel carbon dioxide.
How does water move in and out of the mouth through the gills in fish?
1) The mouth opens which increases the volume and so decreases the pressure inside the mouth.
2) Water moves into the mouth down pressure gradient.
3) The mouth then shuts, decreasing the volume and so increasing the pressure.
4) Water is forced over gills, down pressure gradient.
