Gas Exchange

Question 1

What does ‘burning’ food with oxygen mean?

Answer 1

During cellular respiration, cells use oxygen to break down sugar. Breaking down sugar produces energy that is needed by our body. This is very similar to burning wood in fire.

Question 2

How much oxygen do organisms need for gas exchange?

Answer 2

The more energy the organism requires, the more oxygen it needs to oxidize food. The more oxygen it needs, the faster they must exchange gases.

Question 3

Why do active organisms need a much more efficient gas exchange system compared to less active organisms?

Answer 3

Active organisms require large energy supply and so must have a efficient gas exchange system whereas less active organisms do not need as much energy so their gas exchange system is less efficient.

Question 4

How do plants conduct gas exchange?

Answer 4

They rely solely on direct diffusion since they are sessile and do not need rapid gas exchange.

Question 5

State the factors affecting the rate of gas exchange in plants.

Answer 5

• the area available for diffusion.
  -the distance over which diffusion occurs.
• the concentration gradient across the gas exchange surface
• the speed at which molecules diffuse through the membrane.

Question 6

What are the must haves of a efficient gas exchange system.

Answer 6

• have a large surface area to volume ratio
• be thin
• have mechanisms for maintaining higher concentration gradient
• be permeable to gases.

Question 7

What are some adaptations plants have for gas exchange?

Answer 7

-stomata on the lower surface of the leaves.
-air spaces in the spongy layer of the leaf so that carbon dioxide can diffuse quickly to the photosynthesising palisade layer.
-Thin leaves with broad surfaces for maximising the surface area to volume ratio for faster diffusion of gases .
- lenticels, for gas exchange in woody/herbaceous plants.

Question 8

What are the adaptations animals have for gas exchange.

Answer 8

• The respiratory surfaces are moist to dissolve oxygen and carbon dioxide.
• They have large SA for gas exchange.
  They are extremely thin to allow gases to pass through them more quickly.

Question 9

What are some examples of cnidarians?

Answer 9

Hydra, jellyfish, sea anemones, corals.

Question 10

How to cnidarians conduct gas exchange?

Answer 10

They rely on simple direct diffusion to exchange oxygen and carbon dioxide between cells and the surrounding water.

Question 11

Why don’t cnidarians need complex gas exchange systems like larger animals?

Answer 11

Because they are inactive thus the demand for oxygen is less.

Question 12

What is one condition that needs to be satisfied in order for diffusion to occur in annelids and how is that condition achieved?

Answer 12

It is important for the skin of the annelid to be moist. It is kept moist through physiological processes such as secretion of moistening fluid by the mucus glands and by behavioural processes such as living in damp areas, avoiding sunlight and feeding at night.

Question 13

Explain how annelids carry out gas exchange. ( explain the process)

Answer 13

The worms blood absorbs oxygen through the moist skin and carries it to the body cells and takes carbon dioxide away from the cells and that diffuses through the moist skin.

Question 13

Explain how annelids carry out gas exchange. ( explain the process)

Answer 13

The worms blood absorbs oxygen through the moist skin and carries it to the body cells and takes carbon dioxide away from the cells and that diffuses through the moist skin.

Question 14

Explain how desiccation takes place in annelids.

Answer 14

When the surface of the worms skin dries out and oxygen diffuses through it, the worm would suffocate and die.

Question 15

How do worms avoid desiccation?

Answer 15

They mostly burrow into the soil to avoid desiccation due to over exposure to light and air.

Question 16

Why cannot insects survive gas exchange through their skin?

Answer 16

-they live above the ground hence cannot keep their skin moist.
- they are so active that diffusion through their outer surface alone cannot provide enough oxygen to their body cells.

Question 17

what are spiracles?

Answer 17

Are external openings found on the underside of insects for gas exchange.

Question 18

Explain how gas exchange occurs in Insects?

Answer 18

Air enters through the spiracles into the thorax. The air moves into the trachea and branches out into trachioles. These trachioles are connected to body cells. Oxygen reaches the body cells through the trachioles and CO2 diffuses out of the body similarly.

Question 19

What are some ways insects are adapted for water conservation?

Answer 19

• partially close their spiracles when not active.
• trachioles are thin and kept moist at all times, allowing faster diffusion between the gases in trachioles and the body cells.
• larger, flying insects sometimes pump their abdomen in and out to aid the movement of air into their spiracles.

Question 20

How is the tracheal system suitable for insects?

Answer 20

They are quite small thus the gases do not have to diffuse too far to reach the body cells.

Question 21

Why is the tracheal system not a suitable gas exchange system for larger animals?

Answer 21

The body volume of larger animals is too great to be supplied by this kind of system since they need oxygen actively pumped into their body cells.

Question 22

What are adaptations needed in vertebrates for effective gas exchange.

Answer 22

respiratory surface:
- to be well supplied with blood capillaries
-be thin and moist at all times
- have a larger surface area.

Question 23

Difference between fish and tadpoles in terms of gills.

Answer 23

Fish have internal gills whereas tadpoles have external gills.

Question 24

Why is gas exchange with water much more difficult than air?

Answer 24

Because water contains less oxygen than air and also it is denser than air, which makes it harder to pump over the respiratory surface.

Question 25

What are some adaptations fish have to obtain oxygen from the water.

Answer 25

• they constantly pump fresh water over their gills using a muscular pharynx.
• Tiny ridges called lamellae on folds called gill filaments greatly increasing gill surface area for GA.
• Have gill raker’s which trap any bits of food.
• gills are packed with blood capillaries.

Question 26

Explain the ‘counter current flow’.

Answer 26

Is when the direction of blood flow in the gills is in the opposite direction to the flow of water on the gills. This counter current flow maximises the concentration gradient thus maximising the diffusion of O2 from the water into the blood and CO2 from the blood into the water.

Question 27

How do fish die out of the water?

Answer 27

Out of the water, the fish gill filaments stick together greatly reducing surface area for gas exchange. The gills quickly dry up and then no longer are able to dissolve gases for exchange.

Question 28

What type of environment do toads and other amphibians live in?

Answer 28

They often hide under the rocks or logs until it rains or until after the sun sets.

Question 29

What are some adaptations owned by birds, mammals and reptiles, for efficient gas exchange?

Answer 29

• alveoli in the lungs have thin, moist surfaces.
  -the alveoli creates a large surface area for gas exchange
• their lungs are extremely well supplied with blood capillaries.