Gas Exchange in fish, insects, plants

Question 1

What substances do you need to exchange with the environment?

Answer 1

1. oxygen
2. waste (CO2, urea)
3. heat (so temperature remains constant)
4. water (for water regulation)

Question 2

How are large organisms adapted for gas exchange?

Answer 2

1. They don’t have enough surface area in order to diffuse through their surface as not enough oxygen will be supplied in time.
2. They increase surface area by:
   * having additional absorbing areas
   * adapting their shape
   * having transport systems to keep the distance of diffusion to a minimum

Question 3

How are small organisms adapted for gas exchange?

Answer 3

they have a high surface area to volume ratio so they get their oxygen through their bodies’ surface via simple diffusion

Question 4

What determines the amount of oxygen an organism needs?

Answer 4

1. amount of living cells
2. rate they need to respire

Question 5

What makes a good exchange surface?

Answer 5

1. thin so their is a short diffusion pathway
2. large surface area to volume ratio
3. partially permeable so particles can pass without obstructions
4. has an environment of internal and environmental medium
5. moist as substances dissolve in solutions mechanisms to maintain diffusion gradient

Question 6

What problems do land animals face?

Answer 6

The cells need to be exposed to air in order for oxygen to diffuse into the organisms. However they’re also made of a high percentage of water so when they are exposed to air, the water molecules evaporate, causing the cells to dehydrate.

Question 7

What problems do flatworms (and tubular or thin organisms) face?

Answer 7

They are flat (tubular/thin) so they lack specialized exchange systems

Question 8

How do flatworms face their problems?

Answer 8

They use their outer surface for gas exchange by diffusion as their cells are localized near the equator so gas can exchanged cell by cell

Question 9

How do earthworms face large organism problems?

Answer 9

1. their thin walled blood vessels (capillaries located around the body) act as specialized exchange surfaces
2. they also respire through their surface
3. they live in damp environments and are covered in slime in order to reduce water loss from being exposed to air

Question 10

What problems do insects face?

Answer 10

They are usually terrestrial so water evaporates easily from their body, which causes them to become dehydrated

Question 11

How do insects face these problems?

Answer 11

1. They reduce water loss by:
   . they have rigid coverings with waterproof cuticles
   . they have a small surface area to volume ratio
2. They have a tracheoles that supplies air to every tissue

Question 12

How to measure the surface area of a leaf?

Answer 12

1. draw around the leaf of a graph
2. count the squares
3. then multiply by 2

Question 13

How do scientists ensure they make a valid comparison between leaves from different species?

Answer 13

They use fully grown leaves

Question 14

What is the relationship between size and surface area to volume ratio of organisms?

Answer 14

As size increases ratio of surface area to volume decreases

Question 15

What is the relationship between metabolic rate and surface area to volume ratio of organisms?

Answer 15

As size increases ratio of surface area to volume decreases

Question 16

why oxygen uptake is a measure of metabolic rate in organisms?

Answer 16

Oxygen is used in respiration which is a metabolic process

Question 17

How do plants exchange gases?

Answer 17

Their gas exchange surface is the surface of mesophyll cells that are in contact with the air

Question 18

What problems do plants face?

Answer 18

Losing water through gas exchange (evaporation) from the wet cell walls and lost through transpiration

Question 19

What adaptations do plants have?

Answer 19

1. the mesophyll cells (their gas exchange surface) is surrounded by air spaces which creates a large surface area for diffusion
2. the stomata opens and closes to control the amount of water loss

Question 20

How does the stomata open and close?

Answer 20

It’s surrounded by guard cells that open and close:
They open by absorbing water (through osmosis), causing it to become turgid and the inner walls to resist expansion and become curved
They close by losing water (through osmosis), causing it to become flaccid and collapses

Question 21

What does the stomata respond to?

Answer 21

1. high humidity
2. low temperature
3. wind

Question 22

What do plants do when it’s dark?

Answer 22

They don’t photosynthesize, thy just diffuse

Question 23

How do plants limit their water loss while still allowing gas exchange?

Answer 23

The stomata (regulated by guard cells) close to prevent water loss but opens to let oxygen in

Question 24

How are (Xerophyte) plants adapted to minimize water loss?

Answer 24

They have:
1. thick waxy cuticles
2. sunken stoma
3. hairs on their leaves
4. folded/curved leaves
5. small leaves/spines
6. stoma on their lower leaf
7. sheading leaves in cold/dry climates
8. stomatal hairs
9. succulent leaves/stems
10. extensive roots

Question 25

What are examples of plants with thick waxy cuticle?

Answer 25

most dicots

Question 26

What are examples of plants with small levs/spines?

Answer 26

1. plants with conifer needles
2. cacti with spines

Question 27

What issues do fish have when exchanging gases?

Answer 27

they have an impermiable membrane so gases can’t diffuse through skin

Question 28

How are fishes adapted for gas exchange?

Answer 28

they has specialised structures (gills) that perform gas exchange instead of their surface

Question 29

Describe the structure of a gill.

Answer 29

• in bony fish there are 4 gills
• gills are supported by an arch
• lamellae are on the gills
• gills are made up of gill filaments

lamellae participate in gas exchange

Question 30

Describe counter-current direction.

Answer 30

• blood and water flow across the lamellae in opposite diractions
• ensures that a steep diffusion gradient is maintained
• this means that a max amount of oxygen diffuses into deoxygenated blood

Question 31

Why can’t fish survive long out of water?

Answer 31

• the water flow separates the gill filaments
• this prevents them from sticking together which reduces their SA:V which reduces the amount of oxygen that can diffuse into the blood

Question 32

Describe the process of ventillation in fish?

Answer 32

• fish lowers the floor of buccal cavity (opens mouth), allowing water to flow in
• floor of buccal cavity rises (mouth closes) which increases the pressure
• pressure change between the mouth cavity and opercular cavity, forces water of gill fillaments
• operculum acts as a valve and pump and lets water out and pumps it in

Question 33

Why does ventillation in fishes occur?

Answer 33

to maintain a continuous unidirectional flow