7- Exchange surfaces in animals

Question 1

What are the 5 characteristics needed for a sufficient exchange system?

Answer 1

• large SA
• maintenance of conc gradient; circulation
• maintenance of conc gradient; ventilation
  -short diffusion distance
• moistness

Question 2

How are mammals adapted to have a large SA?

Answer 2

• vast amount of alveoli (where gas exchange takes place) at end of each terminal bronchiole

Question 3

How are mammals adapted ti maintain their concentration gradient (circulation)?

Answer 3

• good blood supply
• capillaries (where exchange from blood occurs) around alveoli continuously deliver low oxygen/high carbon dioxide and remove high oxygen/low carbon dioxide from around the alveoli

Question 4

How are mammals adapted to maintain their conc gradient (ventilation)?

Answer 4

inhalation:
-rib muscles contract, ribs go up and out
- diaphragm contracts and flattens
Both actions increase the volume of the thorax, reducing the pressure so air enters delivering more oxygen rich/low carbon dioxide into alveoli
- Reverse occurs when exhale, diaphragm relaxes and is dome-shaped

Question 5

How are mammals adapted to having a short diffusion distance?

Answer 5

• Walls of alveoli are one cell thick (squamous epithelial cells
• The capillary network is extensive

Question 6

How are mammals adapted to providing a moist environment during exchange?

Answer 6

• Goblet cells secrete mucus for gases to dissolve
• Suffactants are also produced to prevent collapsing of the alveoli (prevents them sticking together e.g like a balloon)

Question 7

How are fish adapted to having a large SA for exchange?

Answer 7

• large number of filaments; thin plates which are covered in structures called lamellae

Question 8

How are fish adapted to maintain their conc gradient (circulation)?

Answer 8

counter-current arrangement of blood capillaries and wanter direction across gills
- blood in gills goes in opposite direction to water
- necessary that water always has a higher oxygen concentration than the blood across the WHOLE distance of the gills
- Without it a conc gradient wouldn’t be maintained across the entire length off the gills (to do with diffusion, both sides have to be at opposites e.g at start 02 from water is high conc and blood is lower)

Question 9

How are fish adapted to maintain their conc gradient?

Answer 9

• closure of the operculum and lowering the buccal cavity floor increases the volume of the buccal acitivty
• water enters via the mouth, bringing oxygen rich/low co2 into the mouth.
• By closing the mouth and raising the buccal floor, pressure in the buccal cavity increases
• low 02/higher conc co2 water forced through the gills slits as passes the operculum on the way.

Question 10

How are fish adapted to have a short diffusion distance for exchange?

Answer 10

Capillary network within the lamellae of gill filaments

Question 11

why dont fish have an adaption for moistness in exchange?

Answer 11

NOT RELEVANT AS LIVE IN AN AQUEOUS ENVIORONMENT