4- SA:V ratio

Question 1

what does higher SA:V ratio mean?

Answer 1

• faster diffusion: a high SA:V ratio provides a larger surface area for molecules to pass through relative to the volume they must travel, enabling faster diffusion of substances
• efficient nutrient and waste exchange: a higher SA:V ratio allows cells to more efficiently absorb nutrients from their environment and eliminate waste products
• heat regulation: for thermoregulation a larger SA:V ratio allows for quicker heat loss, which can be beneficial for smaller organisms to prevent overheating

Question 2

SA:V ratio in smaller organisms

Answer 2

single-celled organisms have a high SA:V ratio, they don’t need specialised transport systems as substances can enter and leave the cell via diffusion

Question 3

SA:V ratio in larger organisms

Answer 3

• as organisms increase in size, their SA:V ratio decreases, making it harder for them to exchange materials with their surroundings
• greater diffusion distance
• higher metabolic rate: this demands more efficient exchange of materials
• smaller SA:V ratio: this necessitates more specialised systems for material exchange

Question 4

characteristics of an efficient mass transport system:

Answer 4

• vessels: structures that carry the transport medium
• directional movement: ensures efficient and targeted transport of substances
• transport medium: carries substances throughout the organism
• maintenance of speed: ensures timely and efficient transport

Question 5

features of an efficient gas exchange surface

Answer 5

• large surface area: allows for the high volume of exchange required by the organism
• thin structure: ensures short diffusion paths, facilitating quicker exchange
• steel concentration gradient: encourages diffusion from areas of high concentration to areas of low concentration
• abundance of protein carriers and ion channels: facilitates transport of specific molecules
• presence of mitochondria: provides ATP for active transport
• permeability to respiratory gases: allows gases to pass through
• moist environment: facilitates dissolving and diffusion of gases