Exchange- Gas Exchange

Question 1

How is being thin beneficial in gas exchange surfaces?

Answer 1

This provides a short diffusion pathway across the gas exchange surface

Question 2

What increases the rate of diffusion?

Answer 2

• Large surface area
• Thin
• Steep concentration gradient

Question 3

How do single-celled organisms absorb and release gases?

Answer 3

By diffusion through their outer surface

Question 4

Why don’t single-celled organisms need a gas exchange system?

Answer 4

They have a large surface area, a thin surface and a short diffusion pathway

Question 5

Why do fish have special adaptations for gas exchange?

Answer 5

There’s a lower concentration gradient of oxygen in water than in air

Question 6

How does oxygen get to the gills in fish?

Answer 6

Water enters the fish through the mouth and passes through the gills

Question 7

What is the structure of the gills?

Answer 7

Made of lots of thin plates called gill filaments which are covered in tiny structures called lamellae

Question 8

How is the surface area increased in gills?

Answer 8

Filament increase surface area and lamellae increase it more

Question 9

How do gill lamellae speed up diffusion?

Answer 9

They have lots of blood capillaries and a thin surface area of cells

Question 10

What is the counter-current system?

Answer 10

Blood flows through the lamellae in one direction and water flows over in the other direction

Question 11

Why is counter-current flow important?

Answer 11

Maintains a large concentration gradient between the water and the blood

Question 12

Where is concentration of oxygen higher?

Answer 12

In the water than in the blood so as much oxygen as possible diffuses from the water into the blood

Question 13

What are tracheae?

Answer 13

Microscopic air-filled pipes that insects use for gas exchange

Question 14

How does air move into the tracheae?

Answer 14

Through pores on the surface called spiracles

Question 15

What way does oxygen travel in insects?

Answer 15

Down the concentration gradient towards the cells

Question 16

What does the tracheae branch into?

Answer 16

Smaller tracheoles which have thin, permeable walls and go to individual cells which means that oxygen diffuses directly into the respiring cells as the insect’s circulatory system doesn’t transport oxygen

Question 17

What way does carbon dioxide travel in insects?

Answer 17

Moves down its concentration gradient towards the spiracles to be released into the atmosphere

Question 18

How do insects move air in and out of the spiracles?

Answer 18

By using rhythmic abdominal movements

Question 19

Where do dicotyledonous plants exchange gases?

Answer 19

At the surface of the mesophyll cells

Question 20

Why do plants need to exchange gases?

Answer 20

They need carbon dioxide for photosynthesis (produces oxygen as a waste product) and they need oxygen for respiration (produces carbon dioxide as a waste product)

Question 21

How are mesophyll cells in the leaf well adapted?

Answer 21

Have a large surface area

Question 22

How do gases move to the mesophyll cells (that are inside the leaf)?

Answer 22

Gases move in and out through pores in the epidermis called stomata

Question 23

What do guard cells do?

Answer 23

Control the opening and closing of stomata

Question 24

What can the stomata do to allow gas exchange and control water loss?

Answer 24

• Open to allow exchange of gases

- Close if plant is losing too much water

Question 25

What is the conflict between gas exchange and water loss?

Answer 25

Features that make an efficient gas exchange system also increase water loss

Question 26

How do insects minimise water loss?

Answer 26

Close their spiracles

Question 27

How do insects reduce evaporation?

Answer 27

They have a waterproof, waxy cuticle all of the body and tiny hairs around their spiracles

Question 28

When are plants’ stomata usually open?

Answer 28

During the day to allow gaseous exchange

Question 29

What opens the stomatal pore?

Answer 29

Water enters the guard cells to make them turgid

Question 30

What happens if the plant gets to dehydrated?

Answer 30

The guard cells lose water and become flaccid which closes the pore

Question 31

What are xerophytes?

Answer 31

Plants that are specially adapted for life in warm, dry or windy habitats where water loss is a problem

Question 32

How is sunken stomata in xerophytes a good adaptation?

Answer 32

Reduces the concentration gradient of water between the leaf and the air which reduces the amount of water diffusing out of the leaf and evaporating away

Question 33

How is a layer of hairs on the epidermis in xerophytes a good adaptation?

Answer 33

Traps moist air round the stomata

Question 34

How is curled leaves with the stomata inside in xerophytes a good adaptation?

Answer 34

Protects them from wind as windy conditions increase the rate of diffusion and evaporation

Question 35

How is a reduced number of stomata in xerophytes a good adaptation?

Answer 35

So that there are fewer places for water to escape

Question 36

How is waxy waterproof cuticles on leaves and stems in xerophytes a good adaptation?

Answer 36

Reduce evaporation