AS CH2.2 Adaptions for gas exchange (humans)

Question 1

Why do larger organisms have higher oxygen requirements?

Answer 1

They have a greater number of cells

Question 2

What are the advantages and disadvantages of organisms having a larger surface area to volume ratio?

Answer 2

• Advantage: can exchange more gas

- Disadvantage: increased area available for waterloss

Question 3

What are some good features for gas exchange?

Answer 3

• Good blood supply to maintain concentration gradient (not in single celled organisms, insects, or plants)
• Ventilation mechanism to maintain concentration gradient (not in single celled organisms, insects, or worms)

Question 4

What are some general characteristics of a gas exchange surface?

Answer 4

• Large surface area to volume ratio
• Moist to allow gases to dissolve
• Thin to provide a short diffusion distance
• Permeable to gases

Question 5

Name a unicellular organism

Answer 5

Amoeba

Question 6

What features do unicellular organisms have that are good for gas exchange?

Answer 6

• Large surface area to volume ratio
• Materials can be directly exchanged across their thin and permeable cell surface membrane
• Cytoplasm constantly moves, maintaining their concentration gradient

Question 7

What is a disadvantage of larger multicellular organisms in gas exchange?

Answer 7

They have a smaller surface area to volume ration so diffusion across the body surface is decreased

Question 8

Why do highly active animals have higher oxygen requirements?

Answer 8

They have a higher metabolic rate

Question 9

What adaptions do highly active animals have to meet their oxygen requirements?

Answer 9

They have a specialised gas exchange surface with a ventilation mechanism to ensure the concentration gradient is maintained across the respiratory surface

Question 10

How do land animals minimise water loss at their respiratory surface?

Answer 10

They have an internal gas exchange surface called lungs

Question 11

What adaptions do flatworms have for gas exchange?

Answer 11

• Flat body to reduce diffusion distance and to increase overall surface area

Question 12

What adaptions do earthworms have for gas exchange?

Answer 12

• Secretes mucus to maintain most surface
• Well developed capillary network under the skin
• Low metabolic rate to reduce oxygen requirements
• Network of blood vessels and blood containing haemoglobin to transport oxygen

Question 13

What adaptions do amphibians have for gas exchange?

Answer 13

• Moist and permeable skin
• Developed capillary network beneath surface
• Have lungs for when they’re more active

Question 14

What adaptions do reptiles have for gas exchange?

Answer 14

• Internal lungs that have a large surface area

Question 15

What adaptions do birds have for gas exchange?

Answer 15

• Efficient ventilation system

Question 16

Why do birds need an efficient ventilation system?

Answer 16

Flight generates high metabolic rate so they have high oxygen requirements

Question 17

What specialized internal gas exchange surface do fish have?

Answer 17

gills

Question 18

What are fish gills made of

Answer 18

Gill filaments containing gill lamellae which are right angled to the filaments

Question 19

Why do fish need gill filaments and lamellae?

Answer 19

To increase surface area for the exchange of oxygen and CO2

Question 20

What direction does blood and water flow in for cartilaginous fish?

Answer 20

Blood and water flow in the same direction over the gills, they have parallel flow

Question 21

Why is gas exchange only possible on parts of the gill filament surface for cartilaginous fish?

Answer 21

Because equilibrium is reached at the gill filament surface which prevents further diffusion

Question 22

What is the ventilation system for cartilaginous fish?

Answer 22

As the fish swim, their mouth is open so water can pass over the gills

Question 23

In what direction does blood and water flow in for body fish?

Answer 23

Blood and water flow in opposite directions so they have counter-current flow

Question 24

What does the counter-current flow do in bony fish?

Answer 24

Diffusion is maintained along the entire length of the fill filament because there is always a higher concentration of oxygen in water than in the blood it meets

Question 25

What does a counter-current flow result in for bony fish?

Answer 25

Higher oxygen absorption as equilibrium is not reached

Question 26

In body fish, why is there always a higher concentration of oxygen in the water than in the blood the gill filaments meet?

Answer 26

Because bony fish have counter-current flow so the concentration gradient is maintained along the entire length of the gill filament

Question 27

What is the ventilation mechanism for water intake in body fish?

Answer 27

1. Mouth opens 2. Floor of the buccal cavity lowers and water rushes in 3. Opercular valve is closed 4. Volume increases and pressure drops

Question 28

What is the ventilation mechanism for water expulsion in bony fish?

Answer 28

1. Mouth is closed 2. Floor of buccal cavity rises 3. Opercular valve opens and water is forced out over the gills 4. Volume decreases and pressure increases

Question 29

What is more efficient, counter current flow or parallel flow?

Answer 29

Counter current flow is more efficient

Question 30

What is the ventilation mechanism for inspiration (active) in humans?

Answer 30

1. External intercostal muscles contract which pulls the outer pleural membrane outwards 2. Diaphragm contracts (flattens) 3. Pressure is reduced in the pleural cavity, the inner pleural membrane moves outwards 4. Pulls on the surface of the lungs causes alveoli to expand 5. Alveolar pressure decreases below atmospheric pressure so air is drawn in

Question 31

What is the ventilation mechanism for expiration (passive) in humans?

Answer 31

1. External intercostal muscles relax, the outer pleural membrane moves inwards 2. Diaphragm relaxes (moves upwards) 3. Pressure increases in the pleural cavity, the inner pleural membrane move inwards 4. Pushes on the surface of the lungs cases the alveoli to contract 5. Alveolar pressure increases above atmospheric pressure so air is forced out

Question 32

What are the adaptions in the alveoli for gas exchange?

Answer 32

- Large surface area - Thin walls - Surrounded by capillaries so there is a short diffusion distance and good blood supply - Moist lining - Permeable to gases - Collagen and elastic fibres allow expansion and recoiling

Question 33

What carries deoxygenated blood to the alveoli?

Answer 33

Branch of the pulmonary artery

Question 34

What carried oxygenated blood from the alveoli back to the heart?

Answer 34

Pulmonary vein

Question 35

What cells do alveoli have that produces a surfactant?

Answer 35

Surfactant-secreting cells

Question 36

What does the surfactant in the alveoli do?

Answer 36

- lowers the surface tension preventing the alveoli from collapsing and sticking together - Allows gasses to dissolve

Question 37

Why are gills more efficient at extracting oxygen than lungs?

Answer 37

Because water contains less dissolved oxygen inn it than in the air

Question 38

What gas exchange structures do insects have?

Answer 38

- Branched, chitin lined system of tracheae with openings called spiracles - Chitin is arranged into rings, which allow the tracheae to expand and contract drawing air in and out of the insects body - Spiracles lead to branched tracheae, which branch into smaller tubes called tracheoles - Spiracles can open and close for gas exchange and to reduce water loss - Hair covering spiracles also reduce water loss and prevent solid particles from getting in - Tracheole tubes have direct contact with every tissue, supplying oxygen and removing CO2 which is why there is no need to haemoglobin - End if tracheole tubes are filled with fluid to allow gases to dissolve - Muscles in the thorax and abdomen contract and relax causing rhythmical movements that ventilate tracheole tubes, maintaining the concentration gradient - Have an exoskeleton of chitin covered in wax, so it is impermeable to water and gases

Question 39

Why is chitin in an insects body arranged into rings?

Answer 39

It allows the tracheae to expand and contract drawing air in and out of the insects body

Question 40

Why do spiracles on an insects body close?

Answer 40

to reduce water loss

Question 41

Why do insects have hair covering their spiracles?

Answer 41

To reduce water loss and prevent solid particles from getting in

Question 42

Why do insects not need haemoglobin?

Answer 42

Their tracheole tubes have direct contact with every tissue, supplying it with oxygen and removing CO2

Question 43

Why is there fluid at the end of insects tracheole tubes?

Answer 43

To allow gases to dissolve

Question 44

How does an insect maintain the concentration gradient in gas exchange?

Answer 44

Muscles in the thorax and abdomen contract and relax causing rhythmical movements t9 ventilate tracheole tubes