SA: volume ratio, plants, insects, and fish

Question 1

What type of SA: volume ratios do a large vs small organism have?

Answer 1

large- small SA: volume ratio, small- large SA: volume ratio

Question 2

What are the features of a gas exchange surface?

Answer 2

large surface area- faster rate of diffusion
very thin- shorter diffusion distance
maintained concentration gradient- such as from a good blood supply to allow for faster diffusion

Question 3

How do single-celled organisms do gas exchange?

Answer 3

no need for a specialised gas exchange system as substances can diffuse directly into or out of the cell-surface membrane due to high SA: volume ratio

Question 4

What adaptions do single-celled organisms have for their gas exchange?

Answer 4

large surface area, thin surface/membrane, short diffusion pathway

Question 5

What are dicotyledonous plants?

Answer 5

seed has 2 leaves

Question 6

Where do plants exchange gases?

Answer 6

stomata - maintains a concentration gradient

Question 7

Describe and explain how a leaf is adapted for efficient gas exchange

Answer 7

stomata- allow gases in and out
shorter diffusion distance- leaves are very thin
air spaces between the spongey mesophyll to allow move easier
palisade mesophyll- lots of chloroplasts for photosynthesis

Question 8

Why do insects have an exoskeleton?

Answer 8

made of hard fibrous material/ chitin for protection and a lipid layer to prevent water loss

Question 9

What do insects have instead of lungs?

Answer 9

a tracheal system made up of trachea, tracheoles, and spiracles)

Question 10

What are the adaptions of a xerophyte?

Answer 10

waxy, waterproof cuticles on leaves so evaporation is reduced

hairy leaves so trap moist air

curled leaf so reduced surface area and trap humid air

reduced number of stomata so few places for water to escape

Question 11

How do insects prevent waterloss?

Answer 11

small SA: volume ratio where water can evaporate from

waterproof exoskeleton

spiracles (where gases enter and water can evaporate from) can open and close

Question 12

What are spiracles?

Answer 12

round, valve like openings that run along the abdomen of an insect, and the trachea attach to these openings. where O2 and CO2 enter and leave from

Question 13

What are the trachea?

Answer 13

a network of internal tubes that have rings within them to strengthen them and stop them from collapsing so gases can move in and out

Question 14

What are tracheoles?

Answer 14

smaller tubes that branch off the trachea, they extend throughout all the tissues in the insect to deliver oxygen to all respiring cells

Question 15

What are the three ways of moving gases in the tracheal system?

Answer 15

1- by diffusion, as when cells respire they use up oxygen and produce carbon dioxide which creates a concentration gradient from the tracheoles to the atmosphere

2- mass transport, where the insects contracts and relaxes their abdominal muscles to move gases on mass

3- when the insect is in flight the muscle cells start to respire anaerobically to produce lactate, which lowers the water potential of the cells, so water moves into the cells by osmosis. this decreases volume in the tracheoles and as a result more air is drawn in

Question 16

How is an insect adapted for efficient gas exchange?

Answer 16

large number of fine tracheoles which increases surface area

walls of tracheoles are thin and there is a short distance between the spiracles and tracheoles which means there is a short diffusion pathway

body can be moved by muscles to move air which maintains the diffusion gradient for oxygen used and carbon dioxide produced

Question 17

Why do fish need specialised structures to ensure needs for oxygen can be met?

Answer 17

because there is around 30x less oxygen in water than in air, and is even worse when water warms up

Question 18

How many layers of gills are there on each side of the head?

Answer 18

4 layers

Question 19

What are the gills made up of and what do they compose of?

Answer 19

gill filaments, and they have many lamellae

Question 20

What are lamellae made of and what do they do?

Answer 20

the many lamellae made from a single layer of flattened cells on the many gill filaments creates a larger surface area for diffusion. they also have a large number of capillaries so there is a short diffusion pathway

Question 21

How is the concentration gradient maintained in fish?

Answer 21

via the countercurrent flow mechanism- in the gills the blood and the water flow in opposite directions as this ensures that equilibrium of the diffusion of oxygen into the blood from water is never reached. hence the diffusion gradient is maintained along the whole length of the lamellae membrane

Question 22

How is the countercurrent flow better than if the blood and water were to flow next to each other?

Answer 22

with the countercurrent flow, about 80% of the oxygen available is absorbed, whereas if they were parallel the gradient would only be maintained across part of the lamellae membrane, and only 50% of the oxygen available would be absorbed

Question 23

Why might fish who are more active/swim faster have gills with a greater surface area?

Answer 23

larger surface area equals a faster rate of diffusion, so more oxygen is delivered to respiring tissues for aerobic respiration and the production of ATP

Question 24

Explain 3 ways in which an insect’s tracheal system is adapted for efficient gas exchange