BIOL113 L32

What are the evolutionary consequences of the need for oxygen uptake?

Selection favors efficiency, especially where energy requirements (and therefore oxygen requirements) are higher.

What are the differences between air and water in relation to gas exchange?

Air has a higher oxygen concentration and is less viscous.

What is the composition of air at sea level in terms of molar proportions and partial pressure?

Oxygen: 20% (20 kPa), Nitrogen: 76% (76 kPa), Water vapour: 3% (3 kPa), Argon: 1% (1 kPa), CO2: 0.03% (0.03 kPa).

What is the oxygen content in air at 20°C?

260.0 mg/L.

What is the oxygen content in fresh water at 10°C?

11.3 mg/L.

What is the oxygen content in sea water at 20°C?;

7.4 mg/L.

What is the rate of diffusion of oxygen equation?

Rate of diffusion of oxygen = Ko2 . A . ΔP/d.

How much greater is Ko2 in air compared to water?

About 300,000 times greater.

What are the advantages of air as a respiratory medium?

High oxygen content, low density and viscosity, high diffusion constant for oxygen, and ease of getting O2 from the air.

Why would a rabbit have trouble breathing when moved to a meadow high on a mountainside?

The partial pressure of oxygen in the air at high elevations is lower than at sea level.

What are the gas exchange mechanisms in air?

A. Cutaneous diffusion, B. Tracheal systems (circulatory system not involved), C. Lungs (always involve circulatory system).

Which animal uses cutaneous diffusion with a circulatory system for gas exchange?

Anguilla australis, NZ short-finned eel migrating over land.

Why are gills inefficient in air?

Because of clumping of the filaments.

How does oxygen uptake from the skin improve?

Because of the higher oxygen content of air.

Why is gas exchange by cutaneous diffusion more efficient on land than in water?

Because air has a higher O2 concentration than water.

Which gas exchange mechanism does not involve a circulatory system?

Tracheal systems.

What are tracheoles?

Sites of gas exchange in the tracheal system.

Where is air taken to supply the mitochondria?

Right up to the cells, through the tracheal system.

What is the difference between cutaneous diffusion and tracheal systems in terms of the circulatory system?

Tracheal systems do not involve the circulatory system, while cutaneous diffusion may or may not involve it.

What are the different mechanisms for lungs?

diffusion lungs, tidally ventilated and unidirectionally ventilated

describe what is meant by ‘tidally ventilated’ lungs

Tidally ventilated lungs refer to a respiratory system where air flows in and out of the lungs in a bidirectional (tidal) manner, similar to the movement of tides. This is characteristic of the respiratory system in mammals, including humans.

What is used as a lung in land snails and the NZ veined slug?

Mantle cavity.

what is buccal pumping?

Amphibians use a unique mechanism called buccal pumping to move air into and out of their lungs. This involves the throat muscles creating positive pressure to push air into the lungs, rather than relying on a diaphragm as in mammals.

what type of respiratory system do amphibians use?

tidally ventilated lungs where air flows in and out of the lungs through the same pathways in a bidirectional manner

What happens when the amphibian lowers the floor of its mouth during inhalation?

it draws air into the buccal cavity (mouth).

What action does the amphibian take after closing its mouth during inhalation?

The amphibian raises the floor of the buccal cavity, forcing the air into the lungs.

How does the amphibian compress its lungs during exhalation?

The amphibian relaxes its throat muscles and contracts its body muscles to compress the lungs.

Through which openings is the air expelled from the buccal cavity during exhalation?

The air is expelled through the nostrils or mouth.

What allows amphibians to absorb oxygen and release carbon dioxide directly through their skin?

they have permeable skin that allows them to absorb oxygen and release carbon dioxide directly through their skin.

When is cutaneous respiration particularly important for amphibians?

when amphibians are underwater or in moist environments.

How many terminal bronchioles are produced through repeated branching in mammalian lungs?

About 8 million (2^23) bronchioles

What is the surface area of the alveoli in mammalian lungs?

70 m^2, which is equivalent to the size of 1 badminton court.

Approximately how many alveoli are present in mammalian lungs?

About 300 million.

How are mammalian lungs inflated?

Through negative pressure.

how is negative pressure created?

Diaphragm and intercostal muscle contraction expands the chest cavity and reduces the pressure inside the lungs compared to the outside air pressure. Because the pressure inside the lungs is now lower than the outside air pressure, air flows into the lungs.

What is the gas exchange mechanism in mammalian lungs?

Lungs, which always involve the circulatory system.

What are the structures in bird lungs that allow for efficient gas exchange?

Air tubes (parabronchi).

What is the function of anterior air sacs in bird lungs?

to create unidirectional flow of air across the lung

What is the function of posterior air sacs in bird lungs?

To store air and aid in the exhalation of air from the lungs.

Which of the following respiratory systems is not closely associated with a blood supply?

the tracheal system of an insect

What are some terrestrial solutions for efficiency of oxygen uptake?;

Increase surface area for gas exchange (lungs). Bring respiratory medium (air) directly to cells (tracheal in insects). Increased partial pressure of O2 (active ventilation, cross-current exchange). Improved efficiency of ventilation (tidal & unidirectional)

What are the advantages of air as a respiratory medium over water?

Air has a much higher O2 concentration than water, it is less viscous and has a higher rate of diffusion of O2

Why can terrestrial animals using diffusion be bigger than aquatic ones?

Oxygen concentration is much higher in air, making diffusion more efficient in air.

Why do terrestrial animals need a circulatory system?

without a circulatory system, animals would be limited to being 1mm thick as lots oxygen needs to diffuse through a lot of internal water.

What are the components of the circulatory system in an earthworm?

Dorsal vessel, ventral vessel, and accessory pumping vessels.

Why does oxygen uptake from the skin improve in air?

Because of the higher oxygen content of air.

Why do we see tracheal systems in animals that breathe air, but not in those that live in water?

Because the rate of diffusion of oxygen through air is 300,000 times faster in air than water