a* Flashcards
(38 cards)
How does size affect an organism’s surface area to volume (SA:V) ratio?
As the size of an organism increases, its SA:V ratio decreases.
What types of body structures increase an organism’s SA:V ratio?
Thin, flat, folded, or elongated structures increase SA:V ratio.
Why might SA:mass be used instead of SA:V for irregular organisms?
SA:mass is easier, quicker to calculate, and more accurate for irregular shapes.
What is metabolic rate and how is it measured?
Metabolic rate is the energy used by an organism in a given time, often measured by oxygen uptake.
What is the relationship between SA:V ratio and metabolic rate?
Smaller organisms have a higher SA:V, so they lose heat faster and have a higher metabolic rate to maintain body temperature.
How do larger organisms overcome a low SA:V ratio?
They develop adaptations like a thin, long shape or specialised exchange systems (e.g. lungs) with a good blood supply and ventilation.
How is the surface of a single-celled organism adapted for gas exchange?
It has a thin, flat shape with a high SA:V ratio and short diffusion distance.
What are the three main parts of an insect’s tracheal system?
Spiracles (pores), tracheae (large air tubes), and tracheoles (small branches for gas exchange).
How are insect tracheoles adapted for efficient gas exchange?
They are thin-walled, highly branched (large SA), and close to cells for short diffusion distance.
What is the function of abdominal pumping in insects?
It changes pressure in the body, maintaining a concentration gradient for gas exchange.
What adaptation helps insects draw fluid into tracheoles during activity?
Lactate lowers the water potential, drawing fluid into tissues and speeding diffusion through air.
Name three adaptations in insects that reduce water loss.
Thick waxy cuticle, closable spiracles, and hairs around spiracles to reduce water potential gradient.
How are fish gills adapted for gas exchange?
Gills have many thin lamellae with a large surface area, short diffusion distance, and a rich capillary network.
What is counter-current flow in fish gills?
Water and blood flow in opposite directions, maintaining a concentration gradient across the whole gill.
What happens in digestion?
Large, insoluble molecules are hydrolysed into small, soluble ones that can be absorbed.
How is starch digested in mammals?
Amylase hydrolyses starch to maltose, then maltase hydrolyses maltose to glucose.
How are disaccharides digested?
Membrane-bound disaccharidases hydrolyse disaccharides to monosaccharides.
How are lipids digested?
Bile salts emulsify lipids into droplets, lipase hydrolyses them into monoglycerides and fatty acids.
How are proteins digested?
Endopeptidases hydrolyse internal peptide bonds, exopeptidases remove terminal amino acids, dipeptidases hydrolyse dipeptides.
Why are membrane-bound enzymes important?
They hydrolyse molecules at the site of absorption and help maintain concentration gradients.
Describe the absorption pathway of digestion products.
Lumen → epithelial cells of ileum → blood.
How are amino acids and monosaccharides absorbed?
By co-transport with sodium ions and then facilitated diffusion into the blood.
How are lipids absorbed?
Micelles deliver fatty acids and monoglycerides to epithelial cells, which diffuse in, reform triglycerides, and are transported as chylomicrons.
What is the role of red blood cells and haemoglobin?
To transport oxygen via oxyhaemoglobin, which forms at high pO2 and releases oxygen at low pO2.
