SA:V Ratio and Exchange surfaces

Question 1

How do unicellular organisms get oxygen into the cell?

Answer 1

Unicellular organisms exchange substances through diffusion.
It’s got a large enough surface area to volume ratio to do so

Question 2

What are large organism’s surface area to volume ratio like?

Answer 2

Large organisms have a small surface area to volume ratio.
They haven’t got a big enough surface area to provide for a big volume

Question 3

How is a larger surface area to volume ratio useful for organisms?

Answer 3

If an organism has a large surface area to volume ratio, the more efficient diffusion will be.

Question 4

How is a larger surface area to volume ratio useful for organisms?

Answer 4

If an organism has a large surface area to volume ratio, the more efficient diffusion will be.

Question 5

Explain how surface area to volume ratio works.
Using an example of a hippo vs a mouse.

Answer 5

• A hippo has a larger volume than a mouse.
  This means its surface area to volume ratio is smaller as the surface area is not large enough to provide for such a big organism.
• A mouse has a smaller volume.
  This means it has a larger surface area to volume ratio as substances can reach the organelles a lot quicker.

Question 6

What are the adaptations of a root hair cell?

Answer 6

• Large surface area to move mineral ions by active transport/ diffusion and water by osmosis.
• Contains lots of mitochondria for movement of minerals using energy.

Question 7

What are the adaptations of the alveoli?

Answer 7

• Folded structure: bigger surface area to volume ratio.
• Good blood supply: mantains concentration gradient (capilaries)
• Thin wall, decrease diffusion distance

Question 8

What are the adaptations of the small intestine ?

Answer 8

• Folded structure: Large surface area to volume ratio (covered in microvilli)
• Good blood supply
• Thin wall, decrease diffusion distance.
• Very long - increase the time for absorption…

Question 9

Give 3 adaptations of the gills in fish.

Answer 9

• Gill fillaments give folded structure/ Fillaments covered in lamellae : Large surface area.
• Gill fillaments have good blood supply (from lamellae)
  -Gill fillaments have thin wall to decrease diffusion pathway.

Question 10

How do animals sort the problem of having a small surface area to volume ratio?

Answer 10

• Having special structures for gas ecchange.
• Having a tranpsort system

Question 11

What is the meaning of a large surface area to volume ratio?

Answer 11

It means that a large area is folded to fit into a small space(volume).

Question 12

State the name of the gas exchange surface in fish.

Answer 12

• Gills

Question 13

Explain the adaptation of the gill fillaments.

Answer 13

• Large surface area to increase the rate of diffusion.

Question 14

What are gill fillaments covered in?

Answer 14

• Gill fillaments are covered in lamellae.

Question 15

How is the water that leaves the fish different to the water that enters?

Answer 15

• Water that leaves has more CO₂ from fish respiring.
• Less oxygen

Question 16

What are gill fillaments?

Answer 16

• Gill fillaments are thin plates that form the gills.

Question 17

What is an exchange surface?

Answer 17

• A part of an organism where substances are exchanged with the envrionment.

Question 18

Explain how substances diffuse in a leaf (for photosynthesis….)

Answer 18

• CO₂ and water vapour diffuses into stomata
• O₂ diffuse out stomata

Question 19

How does water diffuse out of a leaf?

Answer 19

• It evaporates
• Escapes by diffusion

Question 20

Why do spongy mesophyll cells have an irregular structure?

Answer 20

• Leads to air gaps –> gas can travel

Question 21

What cells are transparent to allow light to reach the palisade cells?

Answer 21

• Upper epidermal cells

Question 22

What covers the epidermis of the leaf?

Answer 22

A waxy cuticle layer

Question 23

Why does the epidermis have a waxy cuticle?

Answer 23

• So H₂0 doesn’t evaporate.

Question 24

What 4 things increase the effectiveness of an exchange surface?

Answer 24

• Large surface area
• Thin membrane
• Good blood supply
• Being ventilated (for gas exchange)

Question 25

Give 3 adaptations of a leaf that increase the rate of diffusion.

Answer 25

• Thin: decrease diffusion distance
• Flattened shape (large surface area)
• Stomata allow movement of gases in and out air spaces: steep gradient.

Question 26

What 3 substances move in and out of leaves?

Answer 26

-CO₂
- O₂
- Water vapour

Question 27

Give the pathway of CO₂ in a leaf.

Answer 27

• Atmosphere
• stomata
• air spaces
• Palisade cells
• Chloroplasts

Question 28

Explain how gases diffuse in gills.

Answer 28

• Water enters fish
• Oxygen diffuses from water to blood
• CO₂ diffuses from blood to water
  Water = higher concentration CO₂ + lower concentration of O₂

Question 29

Why is it useful that the blood flows through the lamellae in a different direction to the water?

Answer 29

• This mantains a steep concentration gradient.

Question 30

Explain why a good supply of an “external medium “ is good for exchange.

Answer 30

• Mantains strong gradient as food or air etc is being replaced.

Question 31

What 2 factors give something a large surface area?

Answer 31

• Shape
• Number of it
  Eg. villi has a folded structure/ has many microvilli

Question 32

How does the alveoli having a good blood supply mantain the concentration gradient of oxygen and carbon dioxide?

Answer 32

• Blood is constantly being replaced.
• More carbon dioxide coming
• Less oxygen in the blood.
• Increased rate of diffusion of both gases.

Question 33

Q.)

Why are root hairs useful to plants? (2 marks)

Answer 33

• Provide large surface area
• More mineral ions and water are moved into cell and absorbed.