Unit 4 - Gas Exchange In insect, fish, plants and blood vessels

Question 1

How do insects reduce water loss from spiracle?

Answer 1

• they can close their spiracles with a muscular valve

- they have hairs around the spiracle to increase humidity reducing evaporation

Question 2

Describe the ventilation structure in insects:

Answer 2

• rigid waterproof exoskeleton with holes (spiracles)
• spiracles lead to a network of trachea
• trachea branch into smaller tracheoles
• tracheoles carry air directly to cell cytoplasm

Question 3

What makes up the walls of the tracheoles?

Answer 3

Chitin

Question 4

Smaller insects can just rely on diffusion but what about larger insects?

Answer 4

Ventilate their trachea system

• muscles squeeze the abdomen sucking air in and out of the spiracles
• increasing concentration gradient

Question 5

Describe the structure of fish gills

Answer 5

Gills are a structure made of gill arch’s and gill filaments
The filaments are string like extensions from the gill arch covered in feathery lamellae, which provide a large surface area and have a fresh blood supply

Question 6

What are the opercula?

Answer 6

Flaps that stop the entry of water back across the gills from the sea when the floor of the fishes mouth drops lowering pressure in the buccal cavity

Question 7

Describe inspiration in a fish

Answer 7

1) the mouth of the fish opens
2) the floor of the mouth contracts and opercula muscles contract increasing the volume in the buccal cavity
3) this decreases the pressure in the buccal cavity below outside water pressure, opercula valve closes and water rushes in through the mouth
4) the water flows over the gills from a high pressure to a low pressure

Question 8

Describe expiration in a fish:

Answer 8

1) the mouth closes
2) the mouth and opercula muscles relax decreasing the volume in the buccal cavity
3) this increases pressure in the buccal cavity above the outside pressure so the opercula valves open
4) water flows from a high pressure inside the buccal cavity to a low pressure outside the fish over the gills

Question 9

Describe counter current flow:

Answer 9

• blood flows in the opposite direction to the water, meaning blood always meets water with a higher saturation of O2
  This occurs at the lamellae

Question 10

How are stomata opened?

Answer 10

K+ ions are actively pumped into the guard cells, lowering the water potential so water diffuses in by osmosis, making the guard cells more turgid, the cell wall is thinner on the outside so they bend that way opening the stomata

Question 11

What are lenticels and their role?

Answer 11

• a group of loosely arranged cells with many airspace’s linking the inner tissue of thick trunks to the outside for gas exchange, purpose is the same as stomata

Question 12

How are plants adapted for gas exchange?

Answer 12

• leaves provide large surface area
• spongey mesophyll cells also increase surface area within the leaf
• thin cell walls provide a short diffusion pathway

Question 13

What does the waxy cuticle do?

Answer 13

Prevent water loss and gas exchange from the upper epidermis

Question 14

Why do veins need valves?

Answer 14

Very low blood pressure, so valves stop backlfow

Question 15

Why is the left and right side of the heart separated by the septum?

Answer 15

This keeps oxygenated and deoxygenated blood separate so as much O2 can be carried to the cells as possible

Question 16

What 2 systems make up our double circulatory system?

Answer 16

Pulmonary and systemic

Question 17

What 2 parts of the vena cava combine before returning blood to the heart?

Answer 17

Superior (on top) and inferior vena cava