Gaseous exchange in animals

Question 1

What are the 5 features of gas exchange surfaces

Answer 1

• Large surface area to volume ratio
• Permeable
• Thin (shorter diffusion pathway)
• Moist
• High concentration gradient

Question 2

How is a unicellular organism adapted for gas exchange?

Answer 2

Are one cell thick and very small, so simple diffusion provides enough oxygen for the cell.

Question 3

How are marine flatworms organisms adapted for gas exchange?

Answer 3

• Organism is flattened and has folds which increases surface area.
• Very thin, no cell is far from the surface so simple diffusion provides enough Oxygen.

Question 4

How are earthworms adapted for gas exchange?

Answer 4

• Earthworms are elongated
• Has Haemoglobin and a circulatory system which carries oxygenated blood to cells deep in the body

Question 5

How are amphibians adapted for gas exchange?

Answer 5

• Larvae are aquatic so have gills
• Adult uses moist skin as a respiratory surface during rest, and uses lungs during activity

Question 6

How are reptiles adapted for gas exchange?

Answer 6

• Have lungs with an in and out bellows-like arrangement
• They have in-growth of tissue to increases surface area

Question 7

How are birds adapted for gas exchange?

Answer 7

• Birds have lungs with air sacs attached
• When the bird breathes in the last breath gets sucked into air sacs, so the lungs are always filled with fresh air.

Question 8

Describe the pathway of air in humans.

Answer 8

Nasal cavity/mouth -> trachea -> bronchi -> bronchioles -> alveoli -> capillary

Question 9

What is the function of the cilia and the goblet cells?

Answer 9

Goblet cells secrete mucus, which traps particles (e.g dust, bacteria.) The cilia then wafts the mucus up the airway.

Question 10

What is the function of cartilage in the trachea and the bronchi?

Answer 10

Cartilage C-rings support the trachea and bronchi to prevent them from collapsing during inhalation.

Question 11

How are the alveoli adapted for gas exchange?

Answer 11

• Walls are one cell thick
• Network of capillaries maintains a concentration gradient
• Moist
• Many alveoli means a high total surface area

Question 12

What is the function of surfactant?

Answer 12

Fluid that covers the surface of the alveoli which prevents them from collapsing when breathing out. Surfactant reduces the surface tension of water.

Question 13

Describe what happens to the lungs during inhalation

ref to Intercostal muscles, diaphragm, vol and pressure of lungs.

Answer 13

• External intercoastal muscles contract which pulls the ribcage upwards and out. - The diaphragm contracts and is pulled into a flattened shape.
• So the volume of the lungs has increased and the pressure has decreased so air is pulled inwards.

Question 14

Describe what happens to the lungs during relaxed exhalation

ref to Intercostal muscles, diaphragm, vol and pressure of lungs.

Answer 14

• External intercostal mucles relax, ribcage falls under its own weight.
• Diaphragm relaxes and gut pressure pushes it back into dome shape.
• There is elastic recoil of lung tissue.
• The volume of the lungs has decreased so the pressure has increased so air is forced outwards.

Question 15

Descibe what happens to the lungs during forced exhalation

Answer 15

• Internal intercoastal muscles contract and pull the ribcage down and in
• Abdominal muscle contracts which pushes the diaphragm upwards.
• So the volume of the lungs decrease and pressure increases so air is forced out.

Question 16

Describe the pathway of air in insects.

Answer 16

Spiracles -> tracheae -> tracheoles -> muscle cells

Question 17

How do large insects ventilate their lungs?

Answer 17

The abdomen expands and the thoracic spiracles open. Air enters through the thoracic spiracles. The abdomen contracts and forces air out of the open abdominal spiracles.

Question 18

How are gills adapted for gas exchange?

Answer 18

• Gills have many folds which provides a large surface area.
• Thin layer of cells separate blood from water so short diffusion pathway.
• Good blood supply.

Question 19

Describe the structure of a gill?

Answer 19

• Gill arch -> bony structure to support gill filaments and gill rakers
• Gill rakers -> filters water
• Gill filaments -> provides a large surface area and short diffusion path.
• Gill plates -> site of gas exchange

Question 20

Describe how a fish inhales.

Answer 20

• Mouth opens
• The operculum closes
• The floor of the mouth cavity is lowered
• The volume of the mouth cavity increases and pressure decreases.
• Water flows in.

Question 21

What is countercurrent exchange?

Answer 21

Blood in the capillaries flows in the opposite direction to the water.