Gas Exchange

Question 1

What 5 features speed up the rate of gas exchange?

Answer 1

1. Moist
2. Large surface area : volume ratio
3. Thin layer so short diffusion pathway
4. Permeable membrane so gasses diffuse easily
5. Maintenance of concentration gradient

Question 2

What are the 3 unicellular/small multicellular organisms with adapted gas exchange?

Answer 2

1. Amoeba
2. Flatworm
3. Earthworm

Question 3

How is amoeba adapted, how does it deliver oxygen, what is its habitat, and what are other adaptions?

Answer 3

Adaption: pseudopodia
Oxygen delivery: simple diffusion
Habitat: fresh water ponds with low oxygen concentration, dissolved oxygen dissolved through cell membrane
Other: short diffusion pathway

Question 4

How are flatworms adapted, how do they deliver oxygen, what is their habitat, and what are other adaptions?

Answer 4

Adaption: very thin and flat
Method: simple diffusion
Habitat: mostly aquatic (fresh or salt water) where dissolved oxygen diffuses across cell membrane (large, more active flatworms have basic gills)
Other: short diffusion pathway

Question 5

How are earthworms adapted, how do they deliver oxygen and what is their habitat?

Answer 5

Adaption: elongated
Method: diffusion across moist skin with a closed circulation and haemoglobin to carry oxygen to each cell.
Habitat: damp areas, so oxygen dissolves and diffuses across body surface

Question 6

Why do multicellular organisms have a different oxygen requirement and what are examples of terrestrial animals and their gas exchange surface?

Answer 6

As the have a small surface area : volume ratio and a high metabolism, they require more oxygen.
Terrestrial organisms include:
Amphibians (both), reptiles and birds

Question 7

What are amphibians gas exchange surface?

Answer 7

Surface: As a larvae they have gills and as an adult after metamorphosis they use moist skin or lungs when active

Question 8

What are reptiles gas exchange surface?

Answer 8

Reptiles lungs have an in-out bellow-like arrangement.
Ribs project from vertebrae to a) provide strength and protection and b) for ventilation
Also have more complex lungs with in growth of tissue that increases SA
Features:
Movement of ribs aid in ventilation of lungs and they have no diaphragm

Question 9

What are birds gas exchange surface and what are features of it?

Answer 9

Birds breathe into their rear air sacs, and air moves through lung into front air sacs, then it is expelled.
It is ventilated by the ribs as there is no diaphragm.
Blood that picks up O2 flows in opposing direction to air in counter current exchange which is very efficient for releasing energy in flight.
When bird breathes in any air that remains from last breathe is sucked into air sac so lungs always filled with fresh air