gas exchange - insects, fish, plants

Question 1

what is on the surface of an insect?

Answer 1

Have an exoskeleton - used for protection and to prevent water loss

Question 2

What does an insects tracheal system consist of?

Answer 2

• spiracle
• trachea
• tracheoles
• tissues

Question 3

How do insects limit water loss?

Answer 3

1. Small SA: vol ratio in which water can evaporate from
2. Waterproof exoskeleton
3. Spiracle which can open and close to reduce water loss

Question 4

What are spriracles?

Answer 4

• round opening along abdomen
• where oxygen and carbon dioxide enter and leave, attached to trachea

Question 5

what are tracheoles?

Answer 5

• extend throughout tissues, deliver oxygen to respiring cells, branch off from trachea

Question 6

What are the three ways insects can move gases?

Answer 6

1. Gas exchange by diffusion
2. Air sac pushes air to tissues
3. Lactic acid creates air pressure

Question 7

gas exchange by diffusion - insects

Answer 7

• cells use up oxygen in respiration and produce carbon dioxide, maintains a concentration gradient

Question 8

Air sac

Answer 8

Insects contract and relax abdominal muscles
Air pushed to tissues by pressure
Creates concentration gradient

Question 9

Lactic acid

Answer 9

Lactic acid produced by tissues in aerobic respiration
Lowers the water potential of the cell
Water moves from tracheoles to cell by osmosis
Air from atmosphere drawn in as tracheoles volume decreases

Question 10

How are insects adapted for diffusion?

Answer 10

1. Lots of tracheoles which are branched - large surface area
2. Tracheoles are thin and are embedded in muscle - short diffusion pathway
3. Oxygen is used up in tissues by respiration - maintains concentration gradient
4. Air sac - creates concentration gradient by contract muscles and pushing air to tissues
5. Lactic acid - lowers water potential, air moves in from atmosphere as tracheoles volume decreases

Question 11

What is fish’s gas exchange structure?

Answer 11

• layers of gills on both sides of head
• made up of stacks of gill filaments
• each gill filament is covered in gill lamellae = large surface area

Question 12

What are fish’s gas exchange adaptations?

Answer 12

1. Many gill filaments covered in gill lamellae = large surface area
2. Thin gill lamellae = short diffusion pathway
3. Good blood supply and countercurrent flow = maintains concentration gradient

Question 13

What is counter current flow?

Answer 13

• blood and water move in opposite directions
• oxygen diffuses from water to blood

Question 14

Benefit of countercurrent flow?

Answer 14

• concentration gradient maintained across entire length of gill lamellae
• diffusion all the way along
• more efficient

Question 15

What is concurrent flow + disadvantages?

Answer 15

• blood and water move in the same direction, parallel
• concentration gradient only half way along gill lamellae
• initial large concentration gradient
• no concentration gradient = no diffusion