7.1 Exchange Surfaces And SA:Vol

Question 1

Describe single celled organisms

Answer 1

Surrounded by the environment
So diffusion is sufficient
As it supplies all of what they need to get in and out

Question 2

Describe multicellular organisms

Answer 2

Not all cells are surrounded by the environment
Diffusion is not sufficient
So specialised exchange surfaces are needed

Question 3

Give examples of a specialised exchange surface

Answer 3

Small intestine
Alveoli in the lungs
Root hairs of plants

Question 4

What makes the perfect exchange surface

Answer 4

Good blood supply, maintains the concentration gradient
Short diffusion distance
Large surface area

Question 5

Describe the function and use of the nasal cavity

Answer 5

Large surface area and good blood supply so air is warmed
Hairy lining secretes mucus and traps dust and microorganisms
Moist surfaces which increase humidity reducing evaporation from exchange surfaces

Question 6

Describe the function and use of the trachea

Answer 6

Incomplete rings of cartilage to allow food to pass down the oesophagus
Smooth muscle to allow control of the trachea
Lined with collated epithelia and goblet cells
Also found elastic fibres

Question 7

Describe the function and use of the bronchi

Answer 7

TraOchea divides into two bronchi as it enters the lungs
Consists of cartilage smooth muscle ciliates epithelium and elastic fibres however the cartilage occurs in more irregular patterns

Question 8

Describe the use and function of the bronchioles,.a

Answer 8

The bronchi divide further into bronchioles
They consist of smooth muscle, elastic fibres and ciliated epithelium
The smooth muscle in them allows for them to expand and contract based on demand for air I when more air is needed they widen, asthma . Is the reaction to harmless substances
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Question 9

Describe the function and use of the alveoli

Answer 9

They are found deep in the lungs and are the surface of gaseous exchange
The tissue is air spaces divided up by thin walls
Elastic tissue provides strength and flexibility when breathing
Elastic fibres stretch and recoil during exhalation to force air out
Lung surfactant prevents the alveoli from collapsing

Question 10

Why do insects need specialised exchange surfaces

Answer 10

Exoskeleton made of chitin which gaseous exchange cannot occur through
No blood pigment for carrying oxygen
But still need to deliver oxygen und remove carbon dioxide

Question 11

How does gaseous exchange occurs in insects?

Answer 11

Holes in the abdomen, in the chitin called spiracles.

Spiracles lead to trachea which are lined with spirals of chitin

Then the trachea lead to tracheoles which are narrower tubes and directly into tissues

Question 12

Why do fish need gas exchange to be specialised?

Answer 12

. Oxygen contentin water is a lot lower than in air

Therefore fish have to pass large volumes of water over the gills to get the same volumes of oxygen as what land mammals do.

Question 13

How do fish get oxygen out of the water? Including bony and cartilaginous

Answer 13

Fish have internal gills which water continually flows over.
. The water has oxygen dissolved in it

Bony fish: have a ventilation mechanism

Cartilaginous fish: need to keep moving, or sit in flowing water

Question 14

Describe the structure of the gill

Answer 14

-Fish keep their mouths open whilst swimming to allow water to flow over the gills

• the operculum is a bony flap covering the gills
• the bony gill arch supports the gill filaments
• blood vessels carryoxygenated blood away from the gills and deoxygenated blood to the gills
• gill filaments are in stacks, and the blood flows through the labella

Question 15

Explain how fish ventilate

Answer 15

1. When they open their mouth they lower the buccal cavity floor which increases the volume of the mouth whilst decreasing pressure
2. Water flows in and the mouth closes rising pressure in the buccal cavity
3. Water flows from the buccal cavity and into the gill cavity over the gills
4. Once passes over the gills the water exits through the operculum
   S. This is then close and buccal cavity floor is lowered to repeat the process again.

Question 16

How do fish get - maximum oxygen absorption?

Answer 16

Fish use countercurrent flow

Blood and water flow over gill labella in opposite directions.

Blood that is already loaded in oxygen meets water that has the maximum amount of oxygen. So some oxygen moves into blood from water

Blood that has little to no oxygen meets water that has lost of it’s most oxygen so some oxygen moves into the blood.