3.1.1

Question 1

Why is diffusion enough to supply the needs of single-celled organisms?

Answer 1

Metabolic activity is low, so oxygen demands and carbon dioxide production are relatively low. The SA: V ratio of the organism is larger.

Question 2

What are the characteristics of effective exchange surfaces?

Answer 2

Increased surface area. thin layers, good blood supply, and ventilation to maintain the diffusion gradient

Question 3

Describe the important features of the nasal cavity

Answer 3

• Large SA with good blood supply, which warms the air to body temperature
• Hairy lining, secreting mucus to trap dust and bacteria, which protects the lung tissue from irritation and infection
• Moist surfaces, increasing the humidity of the incoming air, which reduces evaporation from the exchange surfaces

Question 4

Describe the structure of the trachea

Answer 4

The trachea is a wide tube supported by incomplete rings of cartilage, which stop the trachea from collapsing. They are incomplete to allow food to move down the oesophagus. The trachea and the branches are lined with ciliated epithelium

Question 5

Describe ciliated epithelium tissue

Answer 5

Layer of ciliated epithelial cells with goblet cells between and below them.

Question 6

What is the function of the goblet cells?

Answer 6

They secrete mucus onto the lining of the trachea, trapping dust and microorganisms. The cilia beat and move the mucus away from the lungs.

Question 7

What are the bronchi?

Answer 7

The initial branches of the trachea. They are similar in structure to the trachea, but are smaller

Question 8

What are the bronchioles?

Answer 8

Divisions of the bronchi. They have no cartilage, instead the walls contain smooth muscle. The contraction and relaxation of the smooth muscle changes the amount of air reaching the lungs. Bronchioles are lined with a layer of flattened epithelium, making some gas exchange possible

Question 9

What are the alveoli?

Answer 9

Tiny air sacs, which are the main gas exchange surfaces in the body. The alveoli consist of a thin layer of thin, flattened epithelial cells, along with some collagen and elastic fibres, allowing for elastic recoil of the alveoli

Question 10

Describe the main adaptations of the alveoli

Answer 10

Large SA. thin layers, good blood supply, good ventilation

Question 11

What covers the inner surface of the alveoli?

Answer 11

A thin layer of a solution of water, salts, and lung surfactant. The lung surfactant allows the alveoli to remain inflated

Question 12

Describe the process of inspiration

Answer 12

The diaphragm contracts, flattening and lowering. The external intercostal muscles contract, so the ribs move up and out. The thoracic volume increases, so pressure decreases. This causes air to be drawn, to equalise the pressure

Question 13

Is inspiration active or passive?

Answer 13

Active

Question 14

Describe the process of expiration

Answer 14

The diaphragm relaxes so it returns to its dome shape. The external intercostal muscles relax so the ribs move down and in. The thoracic volume decreases, so the pressure increases, so air moves out of the lungs until the pressure equalises.

Question 15

What is tidal volume?

Answer 15

The volume of air that moves into and out of the lungs with each resting breath

Question 16

What is the vital capacity?

Answer 16

The volume of air that can be breathed when the strongest possible exhalation is followed by the deepest possible intake of breath

Question 17

What is the inspiratory reserve volume?

Answer 17

The maximum volume of air you can breathe in over and above a normal inhalation

Question 18

What is the expiratory reserve volume?

Answer 18

The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out

Question 19

What is the residual volume?

Answer 19

The volume of air that remains in the lungs after the strongest possible exhalation

Question 20

What is the total lung capacity?

Answer 20

The sum of vital capacity and residual volume

Question 21

What is the breathing rate?

Answer 21

The number of breaths taken per minute

Question 22

What is the ventilation rate?

Answer 22

The total volume of air inhaled in one minute (tidal volume * breathing rate)

Question 23

What can be used to measure lung volume?

Answer 23

Spirometer, vitalograph, peak flow meter

Question 24

How does gas exchange take place in insects?

Answer 24

Along the thorax and abdomen of most insects, there are small openings called spiracles. Air enters and leaves the system through them, but water is also lost. The spiracles are opened or closed by sphincters. Leading from the spiracles are tracheae. They carry the air into the body. They are held together by chitin. Tracheal fluid is present at the end of the tracheoles, which limits the penetration of air for diffusion

Question 25

Describe gaseous exchange in bony fish

Answer 25

The mouth opens and the floor of the buccal cavity lowers. This lowers the pressure in the buccal cavity, and so water moves into it. The opercular cavity containing the gills expands. The buccal floor raises, so the water moves over the gills. The mouth then closes, and the operculum opens. Then, the volume of the opercular cavity decreases, so water is forced over the gills and out of the operculum. The floor of the buccal cavity is steadily moved up, so the flow of water is maintained.

Question 26

How are bony fish adapted for gaseous exhange?

Answer 26

• The tips of adjacent fill filaments overlap. This increases resistance to flow of water over the gills surfaces, slowing down the movement of water.
• The water and the blood flow in opposite directions, ensuring a countercurrent exchange, maintaining the steep concentration gradient