18.5 Small-Scale and Large-Scale adaptations to Low Oxygen Environments

Question 1

How have some bacteria evolved to live in low to zero oxygen environments?

Answer 1

By using nitrate ions, sulfur ions or carbon dioxide as final electron acceptor for anaerobic respiration

Question 2

Where are methanogens found? What are they?

Answer 2

In digestive system of ruminants.

They’re a type of bacteria.

Question 3

What do methanogens do?

Answer 3

Digest cellulose from grass cell walls into products that can be further digested and absorbed by the ruminant

Question 4

What is the final electron acceptor in the respiratory pathway of methanogens? What is produced from this?

Answer 4

CO2

Water and methane

Question 5

What are the 3 types of adaptations marine mammals have to survive when there’s no oxygen?

Answer 5

1. Biochemical adaptations
2. Physiological adaptations
3. Physical adaptations

Question 6

What biochemical adaptation in terms of concentrations do marine mammals have to deal with periods of little oxygen?

Answer 6

Higher concentrations of haemoglobin and myoglobin in muscles vs land mammals
• This maximises oxygen stores, delaying onset of anaerobic respiration

Question 7

What biochemical adaptation in terms of lactate do marine mammals have to deal with periods of little oxygen?

Answer 7

Whales have higher tolerance to lactic acid than humans, so can respire anaerobically for longer without tissue damage

Question 8

What biochemical adaptation in terms of carbon dioxide do marine mammals have to deal with periods of little oxygen?

Answer 8

Whales have higher tolerance of high CO2 levels - they have effective blood buffers which prevent spikes in pH

Question 9

What are the 3 biochemical adaptations marine mammals have to deal with periods of little oxygen?

Answer 9

1. Increased concentration of myoglobin and haemoglobin
2. Higher tolerance of lactic acid
3. Higher tolerance of high CO2 levels

Question 10

What physiological adaptation do marine mammals have in terms of circulatory systems to deal with periods of little oxygen?

Answer 10

A modified circulatory system - when marine mammals dive, they show peripheral vasoconstriction, so blood is focused to the brain, muscles and heart.

Question 11

What happens to a marine mammal’s heart as it dives? What is the benefit of this?

Answer 11

Heart slows by 85%, bradycardia, reducing energy demand of heart muscle

Question 12

In terms of gas exchange, what physiological adaptation do mammals have to deal with periods of low oxygen?

Answer 12

Whales exchange 80-95% of air in the lungs in 1 breath, whereas it’s 15% in humans

Question 13

State the 2 physical adaptations marine mammals have to deal with periods of low oxygen.

Answer 13

1. Streamlining

2. Fin-shaped limbs

Question 14

How does streamlining act as a physical adaptation for marine mammals in periods of low oxygen?

Answer 14

Streamlining reduces drag due to friction from water whilst swimming, so reduces energy demand during dive

Question 15

How do fin-shaped limbs act as a physical adaptation in marine mammals during periods of low oxygen?

Answer 15

Fin-shaped limbs maximise efficient use of energy in propulsion