Module 3 - Gas Exchange

Question 1

What is something that most gas exchange surfaces have in common?

Answer 1

Thin walls which ensure a short diffusion pathway
Large surface area for efficiency
Organisms maintaining a steep concentration gradient

Question 2

What are the small structures that cover a gill filament do and what is their prupose?

Answer 2

Lamella and they increase the surface area of the gills to increase the rate of diffusion.

Question 3

What other adaptations do lamella have to help increase efficiency?

Answer 3

Lots of capillaries and a thin surface to help maximising the rate of diffusion

Question 4

Describe the counter-current system

Answer 4

The counter-current system shows blood flowing in the opposite direction of the flow of water.

Question 5

Explain the purpose of the counter-current system?

Answer 5

The counter-current system creates a steep concentration gradient between the blood and the water allowing majority of the oxygen in the water to diffuse into the blood

Question 6

How high is the concentration of oxygen when blood enters and leaves the lamella?

Answer 6

Low concentration when it enters the lamella and high concentration when its leaves the lamella

Question 7

What happens in a parallel flow system?

Answer 7

The concentration of oxygen between blood and water

decreases with distance meaning that the diffusion of oxygen into the blood decreases with distance.

Question 8

Why is the counter-current system more efficient than the parallel flow system?

Answer 8

A steep concentration gradient can be maintained unlike the parallel flow system

Question 9

How does air diffuse into insects?

Answer 9

Through spiracles on the surface of the exoskeleton of the insect

Question 10

Explain the simple process of gas exchange in an insect

Answer 10

Air moves into the spiracles of the insect down into the trachea. The trachea branch of into smaller pipes called tracheoles. These are connected to respiring cells. It moves down the concentration gradient.

Question 11

How is CO2 released out of the insects?

Answer 11

CO2 moves down its own concentration gradient out through the trachea and spiracles on the insect.

Question 12

How might a student investigate a section of a structure of the insect?

Answer 12

Add a drop of water onto the slide. Then, using tweezers, place the structure being examined onto the drop of water. Use a coverslip and place upright to the structure and gently lay it flat onto the structure.

Question 13

What cells are the main site of gas exchange in a plant and where are they located?

Answer 13

Mesophyll cells and in the epidermis of the leaf.

Question 14

What part of the mesophyll cells control gas exchange?

Answer 14

The stomata

Question 15

Explain how the stomata is adapted to decrease water loss in the plant?

Answer 15

The stomata is surrounded by guard cells. When a lot of water enters the guard cells, they become turgid which causes the guard cells to open up. When water leaves the guard cells, they become flaccid which causes them to close.

Question 16

What are some adaptions that insects have to help reduce water loss?

Answer 16

Close their spiracles, waterproof/waxy cuticle or tiny hairs around their spiracle which reduces water lost through evaporation as moist air gets trapped there.

Question 17

What are the names of animals that live on land?

Answer 17

Terrestrial animals

Question 18

What are the names of plants that are adapted to live in warm, dry and windy environments?

Answer 18

Xerophytes

Question 19

4 xerophytes adaptations that help reduce water loss

Answer 19

• Stomata sunk in pits that trap moist air, decreasing con gradient between the leaf and air
• A layer of hair on epidermis to trap moist air
• curled leaves with stomata inside
• Reduced number of stomata
• Waxy, waterproof cuticles on leaves and stem

Question 20

What is ventilation?

Answer 20

Consists of inspiration (breathing in) and expiration (breathing out)

Question 21

Describe the process of inspiration

Answer 21

The external intercoastal muscles and the diaphragm contract. This causes the diaphragm to flatten and the ribcage to move upwards and outwards. This then increases the volume of the thoracic cavity. The pressure inside the lungs decreases so air moves don the pressure gradient and into the lungs.

Question 22

Describe the process of expiration

Answer 22

The external intercoastal muscles and the diaphragm relax. This causes the diaphragm to become curved and the ribcage to move downwards and inwards. This then decreases the volume of the thoracic cavity. The pressure inside the lungs increases causing the air to move out of the lungs and out of the trachea

Question 23

What happens during forced expiration

Answer 23

This is when internal intercoastal muscles contract and the external intercoastal muscles contract which pulls the ribcage further down and inwards.

Question 24

What is meant by the term antagonistic?

Answer 24

When muscles work in opposing directions for example intercoastal muscles during forced expiration

Question 25

What adaptations do alveoli have to increase the rate of diffusion?

Answer 25

• Large number of alveoli in lungs which increases surface area
• The epithelial cells that coat the alveoli and the cells that coat the capillaries are one cell thick allowing short diffusion pathway
• They are surrounded by a network of capillaries which increases diffusion rate

Question 26

A summary of how gas is exchanged into blood from alveoli

Answer 26

O2 is passed through the alveolar epithelium and then through the capillary endothelium. The red blood cells are usually flat against the epithelium so o2 can be past as quickly as possible. Co2 will pass out of the capillaries in the same way but in the opposite direction. The blood is now oxygenated.

Question 27

What does the opposing travel of co2 and o2 between the blood and alveoli create?

Answer 27

A steep concentration gradient which increases the rate of diffusion