C2- Adaptations for gas exchange

Question 1

Explain how gas exchange occurs in amphibians and how they are well adapted for it.

Answer 1

• They’re skin is moist and permeable.
• It has a well developed capillary network just below the surface.
• Gas exchange takes place through the skin when the animal is active.
• When inactive it takes place through the lungs and skin.

Question 2

How does gas exchange in reptiles compare to that of amphibians?

Answer 2

• Their lungs have more complex internal structures than those of amphibians, increased the surface area for gas exchange.

Question 3

Describe how gas exchange occurs in birds.

Answer 3

• they process large volumes of oxygen as require a lot of energy for flight.
• they do not have a diaphragm, but their ribs and flight muscles ventilate their lungs more efficiently.

Question 4

What are the features of gills?

Answer 4

• one-way current flow of water
• many folds that provide a large surface area that water can flow over and gases can be exchanged
• a large surface area maintained by water flowing through that prevents the gills from collapsing on top of each other

Question 5

What is the space that holds the gills called on cartilaginous fish called?

Answer 5

gill slits

Question 6

What features of the ventilation of cartilaginous fish make their gas exchange less efficient than that of bony fish?

Answer 6

• do not have a mechanism to force water over gills, instead must keep swimming for ventilation to happen.
• parallel flow- blood travels in the same direction as the water travels s diffusion of oxygen over can only occur until they are equal which is at 50% its possible maximum value.
• gas exchange in parallel flow does not occur across the whole lamella, only part of it, until oxygen concentration in the blood and water is equal.

Question 7

What is the flap that covers the gills in bony fish called?

Answer 7

operculum

Question 8

Explain how water is taken in by bony fish.

Answer 8

• the mouth opens
• the operculum closes
• the floor of the mouth is lowered
• the volume inside the mouth cavity increases
• the pressure inside the mouth cavity decreases
• water flows in as the external pressure is higher than the pressure inside of the mouth

Question 9

Explain how water is forced out by bony fish.

Answer 9

• the mouth closes
• the operculum opens
• the floor of the mouth is raised
• the volume inside the mouth cavity decreases
• the pressure inside the mouth cavity increases
• water flows out over the gills because pressure inside the mouth is greater than that of the opercular cavity and outside

Question 10

Describe the structure of gills found in bony fish.

Answer 10

• they have four pairs of gills
• each gill is supported by a gill arch made of bone
• along each gill arch are many thin projections called gill filaments
• on each gill filament there are gas exchange surfaces called gill lamella

Question 11

Why do fish die out of water?

Answer 11

The gills stick together and collapse, decreases surface area so not enough gas exchange can take place.

Question 12

Explain the idea of countercurrent flow.

Answer 12

• This occurs within bony fish.
• Blood and water flow in opposite directions at the gill lamella.
• This maintains the concentration gradient so oxygen can diffuse into the blood along its entire length.

Question 13

How does the removal of carbon dioxide from bony and cartilaginous fish compare.

Answer 13

In bony fish its removal is more efficient as they use a counter-current system.

Question 14

What do gills provide fish with?

Answer 14

• a specialised respiratory surface, rather than using the whole body surface
• a large surface extended by gill filaments and gill lamellae
• an extensive network of blood capillaries, with blood carrying haemoglobin, allowing the efficient diffusion of oxygen into the blood and carbon dioxide out of the blood

Question 15

What is the airtight compartment surrounding the lungs?

Answer 15

the thorax

Question 16

What is the name of the membrane that lines the thorax and cover each lung?

Answer 16

The pleural membranes.

Question 17

What is the feature of the pleural membranes that aid breathing?

Answer 17

Contain pleural fluid that prevents friction between the lungs and the chest cavity as the lungs move.

Question 18

What separates the thorax from the abdomen?

Answer 18

The diaphragm

Question 19

What muscles are between the ribs?

Answer 19

The intercostal muscles

Question 20

Name the four structures of the lungs.

Answer 20

• trachea
• bronchi
• bronchioles
• alveoli

Question 21

Describe what occurs during inspiration/ inhalation to the lungs of mammals.

Answer 21

• external intercostal muscles contract
• the ribs pull upwards and outwards
• the diaphragm muscles contract so it flattens
• both actions increase the thorax volume
• this reduces pressure in the lungs
• atmospheric pressure is now greater than the pressure in the lungs so air is forced into the lungs

Question 22

Describe what occurs during expiration/ exhalation to the lungs of mammals.

Answer 22

• external intercostal muscles relax
• the ribs move downwards and inwards
• the diaphragm muscles relax so it domes up
• both actions decrease the thorax volume
• this increases pressure in the lungs
• atmospheric pressure is now less than the pressure in the lungs so air is forced out of the lungs

Question 23

What feature of the lung’s tissue aids ventilation?

Answer 23

It is elastic so recoils and regains its original shape when not actively expanded. This plays a major part in pushing air out of the lungs.

Question 24

What is the surface of alveoli coated in and why?

Answer 24

• surfactant- an antisticking mixture
• made of moist secretions- contains phospholipid and protein
• low surface tension to prevent the alveoli from collapsing during exhalation due to a low air pressure inside them when this occurs
• it allows gases to dissolve before they diffuse in or out

Question 25

What features of the alveoli allow for efficient gas exchange?

Answer 25

• large surface area relative to the size of the body
• gases dissolve is the surfactant moisture lining the alveoli
• their walls are made of squamous epithelium, one cell thick, so the diffusion pathway is short for gases
• an extensive capillary network surrounds them allowing the diffusion gradient to be maintained

Question 26

Define parallel flow

Answer 26

Blood and water flow in the same direction at the gill lamellae, maintaining the concentration gradient for oxygen to diffuse into the blood only up to the point where its concentration in the blood and water is equal.