Gas exchange

Question 1

What is the issue with in marine environment?

Answer 1

• Oxygen concentration is 40 times lower than in air
• Oxygen concentration is variable and affected by temperature and salinity (the higher temp or salinity the lower the dissolved oxygen)

-Water more dense so 
more effort (energy) 
needed to move it 
through the body and
 separate inlet and 
outlet opening is needed

Question 2

Why is more energy needed?

Answer 2

More dense water also is harder to moe through. (so more respiration so more oxygen needed)

Question 3

What do smaller organisms have?

Answer 3

a Large surface area : volume ratio, so diffusion of respiratory gases is sufficient across the body surface

• have a permeable body surface
• Less need for adaptations to increase gas exchange

Question 4

What do larger organisms have?

Answer 4

a small surface area : volume ratio, so diffusion of respiratory gases is too slow

-most have an impermeable body surface (restricting gas exchange)

-need adaptations to increase gas exchange:
	Ex:
-gills
-lungs
-flattened bodies

-need transport system for carrying respiratory gases

Question 5

What does good gas exchange surface have?

Answer 5

• large surface area
• thin (short diffusion distance)
• permeable surface
• moist
• good blood supply (carries gas away quickly, maintaining the concentration difference)
• usually good ventilation (pumping mechanism-like lungs)

Question 6

What is the distance like in larger organisms?

Answer 6

the distances are too great and diffusion alone is too slow so a transport system is required, as some cells are too far from the external environment to receive sufficient raw materials by diffusion alone

Question 7

What do large organisms need?

Answer 7

an internal mass transport systems for efficient delivery of oxygen/glucose to all cells/tissues

Question 8

Why do large organisms have a large surface area?

Answer 8

for diffusion of respiratory gases

Question 9

What respiratory pigments do larger organisms have?

Answer 9

hemoglobin and hemocyanin

Question 10

What do the respiratory pigments help with?

Answer 10

• High affinity for oxygen

- Assist in the uptake of oxygen from environment

Question 11

What is hemocyanin?

Answer 11

is a complex oxygen carrier protein. It is found in the blue blood of some molluscs (e.g. octopus) and arthropods (e.g. crab).

Question 12

What do coral polyps have?

Answer 12

• Have a large surface area

- Only 2 layers of cells (diploblastic) so a thin distance for diffusion

Question 13

Where does gas exchange occur in coral polyps?

Answer 13

Gas exchange also occurs across the surface of their gastrovascular cavity (water enters cavity so diffusion can occur from both sides)

Question 14

Explain gas exchange in coral polyps

Answer 14

• Surface area increased by tentacles
• Body protrudes out of skeleton into water for maximum exposure
• The have a low oxygen demand as they are relatively small (few cells) and sedentary (less active)
• Can use tentacles to create water currents to move more oxygenated water around the polyp
• Corals can pump oxygenated fluids between polyps

Question 15

What do grouper have?

Answer 15

• larger and more active animals so need more oxygen
• Pumping requires energy also
• use gills with a large surface extended by

-gill filaments with lamellae (ie: highly folded)
gills are held by bony arches, and have filaments with small projections called lamellae (at 90o)

• allows fish to ventilate without swimming forward
• Can increase rate of pumping with increased activity

Question 16

What is pumped ventilation?

Answer 16

mouth cavity (buccal/oral cavity) and the chamber at the side (operculum cavity) help to increase ventilation over gills (like a pump) creating an almost constant flow of water

Question 17

Explain the steps of pumped ventilation

Answer 17

• Mouth opens
• Floor of buccal/oral cavity lowers
• These all increases the volume inside the buccal/oral cavity, thus lowering pressure below outside
• Water is drawn in to buccal cavity (down pressure gradient)
• The operculum closes (as water tries to flow back across the gills)
• The mouth closes
• The buccal/oral floor rises and the pressure increases
• Water is forced over the gills pushing open the operculum (high to low pressure)

Question 18

What is ram ventilation?

Answer 18

Some fish (ex: Tuna) swim continuously with their mouth open to maintain a constant flow of water over gills (they cannot stop swimming)

Question 19

What happens in ram ventilation?

Answer 19

• constant flow of water maintains the concentration gradient for absorbing oxygen
• as the fish swims faster, more water will flow over the gills automatically increasing gas exchange

Question 20

What can some species do in ram ventilation?

Answer 20

can change from pumped to ram ventilation as their swimming speed increases to between 0.5 – 0.8 m/sec

Question 21

What does the change from pumped to ram ventilation do?

Answer 21

reduces energy cost of maintaining opercular pumping at higher swimming speed

Question 22

Whart do bony fish use?

Answer 22

gills with a large surface extended by gill filaments with lamellae

Question 23

What is each gill composed of?

Answer 23

many filaments that are each covered in many lamellae to increase surface area.

Question 24

What does lamellae contian?

Answer 24

blood capillaries, which have blood flowing in the opposite direction to the water

Question 25

What do lamellae ensure?

Answer 25

ensure that the diffusion distance between the blood, in the lamellae, and the water is small

Question 26

What does counter current flow allow?

Answer 26

allows continuous diffusion of oxygen into the blood as there is always a concentration gradient across the gill plate even when the blood is very saturated with oxygen

Question 27

How many pairs of gills do sharks have?

Answer 27

5-7 pairs of gill slits located on the sides of their heads and have no gill covers

Question 28

How do sharks allow the continuous water flow?

Answer 28

• swimming,
• standing still in a current,

-fanning water across the gills with its fins
(this is done by the nurse shark).