Gas exchange in animals ( Component 3 )

Question 1

What do adaptations for gas exchange allow ?

Answer 1

allow an increase in body size and metabolic rate.

Question 2

What is the total oxygen requirement of an organism proportional to ?

Answer 2

organism’s total volume

Question 3

What is the rate of absorption of oxygen proportional to ?

Answer 3

the organisms surface area

Question 4

What happens to the SA:V ratio as the organism’s size increases ?

Answer 4

Ratio decreases

Question 5

Where does gas exchange in small organisms occur ?

Answer 5

Across their general body surface

Question 6

How does SA : V ratio affect transport of molecules ?

Answer 6

The lower SA:V ratio
The further the distance molecules must travel to reach all parts of the organism.
Diffusion alone is not sufficient in organisms with low SA:V ratios

Question 7

Why do larger organisms require mass transport and specialised gas exchange surfaces ?

Answer 7

Small SA:V ratio
Diffusion is insufficient to provide all cells with oxygen and remove carbon dioxide.
Large organisms are more active than small organisms.

Question 8

Describe the gas exchange mechanism in Amoeba

Answer 8

Unicellular organism with large SA:V ratio
Cell membrane provides short distance for diffusion
Simple diffusion across cell surface membrane is sufficient to meet demands of respiratory processes.
Gaseous diffusion through the cell membrane is fast enough to meet its oxygen demands

Question 9

Describe the gas exchange mechanism in flatworms

Answer 9

Multicellular organisms with a high SA:V ratio
Flat structure provides large SA and short diffusion pathway - reduces diffusion distance
Simple diffusion is sufficient enough to meet demands of respiratory processes.
Rely on their external surface for gas exchange.

Question 10

Describe the gas exchange mechanism in earthworms

Answer 10

Cylindrical, multicellular organisms with a relatively small SA:V ratio
Slow moving and low metabolic rate so require little oxygen
Rely on external surface for gas exchange
Require ventilation system - Circulatory system transports oxygen to tissues and removes carbon dioxide, maintain steep concentration gradient.

Question 11

In what type of animals and why are ventilating mechanisms required ?

Answer 11

large active animals with high metabolic rates to maintain gradients across respiratory surfaces

Question 12

Name 6 features of an efficient gas exchange surface

Answer 12

Large SA - more contact with air for gas exchange
Thin - Short diffusion distance
Moist - allows gases to dissolve to cross membrane
Permeable - allows gases to pass through respiratory surface
Good blood supply - maintains steep diffusion conc gradient
Ventilating mechanism

Question 13

What is ventilation ?

Answer 13

The movement of fresh air into a space and stale air out of a space to maintain a steep concentration gradient of oxygen and carbon dioxide.

Question 14

Name the organ of gaseous exchange in fish ?

Answer 14

Gills

Question 15

What do gills have to allow for efficient diffusion and oxygen carriage ?

Answer 15

Gills have an extensive network of blood capillaries to allow efficient diffusion and haemoglobin for oxygen carriage.

Question 16

What do gills provide that aids in carbon dioxide exchange ?

Answer 16

A specialised respiratory surface, rather than using whole body surface
A large SA extended by the gill filaments and gill lamellae
An extensive network of blood capillaries, with blood carrying haemoglobin, allowing efficient diffusion of oxygen into the blood and CO2 out

Question 17

What are gill filaments ?

Answer 17

Main site of gaseous exchange in fish, over which water flows
Gill filaments overlap to increase resistance to flowing water - slowing it down and maximising gaseous exchange
Found in large stacks, called gill plates - contain gill lamellae which provide a large SA and good blood supply for exchange.

Question 18

Why does water need to be forced over the gill filaments by pressure differences ?

Answer 18

maintains a continuous, unidirectional flow of water.
Water is a dense medium with a low oxygen content; therefore, to increase efficiency.

Question 19

Bony fish properties

Answer 19

Larger and more active. Their needs are supplied by a specialised area, the gills, with a large surface extended by gill filaments.

Question 20

Explain the process of ventilation in bony fish

Answer 20

Buccal cavity volume increases and pressure decreases to enable water flow in
Contraction of buccal cavity forces water across gills
Pressure in gill cavity increases, opening the operculum
Water leaves

Question 21

Ventilation in fish - inhalation and exhalation

Answer 21

Inhalation :
Mouth opens - operculum closes - floor of buccal cavity is lowered - volume of buccal cavity increases and pressure decreases - water flows into mouth as external pressure is higher than pressure inside mouth.
Exhalation
Mouth closes - operculum opens floor of buccal cavity is raised - volume of buccal cavity decreases and pressure increases - water flows out over gills because pressure in mouth cavity is higher than outside

Question 22

How is a steep diffusion gradient maintained across the entire gas exchange surface in bony fish ?

Answer 22

Due to counter current flow

Question 23

What is counter current flow ?

Answer 23

Blood and water flow in opposite directions along the gill plate.
Blood is always meeting water with a high % oxygen saturation
Therefore, there is a diffusion gradient maintained across the width of the whole of the gill plate
Blood leaves about 95% saturated with oxygen

Question 24

What type of flow is seen in cartilaginous fish ?

Answer 24

Parallel flow

Question 25

What is parallel flow ?

Answer 25

Water and blood flow in same direction At start of gill plate, the deoxygenated blood is meeting oxygenated water ; there is a steep concentration gradient between the two areas so oxygen diffuses into the blood. However halfway across the gill plate the % saturation of oxygen in the blood and the water reaches equilibrium and so the blood leaving the gill plate is about 50% saturated.

Question 26

Counter current flow vs Parallel flow

Answer 26

Counter current : bony fish more efficient diffusion gradient maintained higher rate of diffusion Parallel : cartilaginous fish less efficient diffusion gradient not maintained lower rate of diffusion

Question 27

Name and describe the main features of an insect's tracheal ( respiratory ) system

Answer 27

Spiracles : small, external openings along the thorax and abdomen through which air enters, and air and water leave the gaseous exchange system. Tracheae : large lined air tubes extending through all body tissues, supported by rings of chitin to prevent collapse. Tracheoles : smaller branches dividing of the tracheae

Question 28

What is the main site of gas exchange in insects ?

Answer 28

Tracheoles

Question 29

Describe the adaptations of an insect tracheal system to a terrestrial environment.

Answer 29

Spiracles can be open or closed to regulate diffusion and conserve water Bodily contractions speed up the movement of air through the spiracles, aiding ventilation Highly branched tracheoles provide large SA Impermeable cuticle reduces water loss by evaporation Internal tracheal system and hairs in spiracles reduce water loss

Question 30

How is air moved into and out of insects ( ventilation mechanism )

Answer 30

Air is moved by contraction and relaxation of muscles in the abdomen which change the size of the abdomen and cause pressure changes.

Question 31

Describe inspiration and expiration in insects

Answer 31

Inspiration Expansion of abdomen - opens the thorax spiracles ( through which air enters ) - and closes the abdominal spiracles Expiration : Compression of abdomen - closes the thorax spiracles - opens the abdominal spiracles ( through which air is expelled )

Question 32

Compare the gas exchange surface of an active and inactive amphibipian ( eg frog )

Answer 32

Active has simple internal lungs Inactive uses its moist skin as a respiratory surface

Question 33

What do amphibians have ?

Answer 33

a larval form (tadpole) which develops in water and undergoes metamorphosis into the adult form.

Question 34

How are mammals adapted for gas exchange ?

Answer 34

Alveoli provide large SA and thin diffusion pathway, maximising the volume of oxygen absorbed in one breath. They have a large supply of deoxygenated blood to maintain a steep concentration gradient.

Question 35

Describe the structure and function of the larynx

Answer 35

A hollow, tubular structure located at the top of the trachea involved in breathing and phonation

Question 36

Describe the structure and function of the trachea in the mammalian gas exchange system

Answer 36

Primary airway, carries air from nasal cavity to chest Wide tube supported by C shaped cartilage to keep the air passage open during pressure changes Lined by ciliated epithelial cells which move mucus ( produced by goblet cells ) towards the back of the throat to be swallowed. This prevents lung infections.

Question 37

Describe the structure of bronchi

Answer 37

Divisions of the trachea that lead to the lungs Narrower than the trachea Supported by rings of cartilage and lined by ciliated epithelial cells and goblet cells.

Question 38

Describe the structure and function of the bronchioles

Answer 38

Many small divisions of the bronchi that allow the passage of air into the alveoli Contain smooth muscle to restrict air flow to the lungs but do not have cartilage. Lined with a thin layer of ciliated epithelial cells

Question 39

What is the primary gaseous exchange surface in humans ?

Answer 39

Alveoli

Question 40

Describe the alveoli in the mammalian gas exchange system

Answer 40

Mini air sacs, lined with epithelial cells Walls one cell thick Network of capillaries - good blood supply - maintain steep diffusion gradient 300 million in each lung

Question 41

What are pleural membranes ?

Answer 41

Thin, moist layers of tissue surrounding the pleural cavity that reduce friction between the lungs and the inner chest wall.

Question 42

What is the pleural cavity ?

Answer 42

The space between the pleural membranes of the lungs and the inner chest wall

Question 43

Describe ventilation in humans

Answer 43

The movement of fresh air into the lungs and stale air out of the lungs via inspiration and expiration Via negative pressure breathing

Question 44

What are internal intercostal muscles ?

Answer 44

A set of muscles found between the ribs on the inside that are involved in forced exhalation

Question 45

What are external intercostal muscles ?

Answer 45

A set of muscles found between the ribs on the outside that are involved in forced and quiet inhalation

Question 46

Explain the process of inspiration and the changes that occur throughout the thorax.

Answer 46

External intercostal muscles contract This raises the ribcage Diaphragm contracts, so turns into flattened shape. The outer pleural membrane is pulled out This reduces pressure in the pleural cavity and the inner pleural membrane moves outward This pulls on the lungs and causes the alveoli to expand Alveolar pressure decreases to below atmospheric pressure and air is drawn into the lungs Volume of air in thorax and lungs increase.

Question 47

What is surfactant ?

Answer 47

It is a fluid lining on the surface of the alveoli that reduces the surface tension and prevents alveoli collapsing during exhalation.

Question 48

Why do terrestrial vertebrates have lungs ?

Answer 48

They have adapted for exchange with air, a less dense medium, instead of water

Question 49

What do internal lungs do ?

Answer 49

Minimise loss of water and heat