7.4 GE in Other Organisms

Question 1

Do insects have a tough or soft exoskeleton

Answer 1

Have a tough exoskeleton so little GE can happen.

Don’t have blood pigments to carry oxygen.

Question 2

What are spiracles

Answer 2

Along the thorax and abdomen, most insects have small openings known as SPIRACLES.

Question 3

What causes the spiracles to open?

Answer 3

O2 demand increases or carbon dioxide builds up

Question 4

What are sphincters

Answer 4

Air enters through these spiracles but they also lose water, so many have developed SPHINCTERS to open and close the spiracles.

Question 5

What is the tracheae

Answer 5

Leading away from the spiracles is the TRACHEAE; these are the largest tubes of the insect GE system, up to 1mm in diameter and carry air into body.

Question 6

What is the tracheae lined with

Answer 6

Lined with spirals of CHITIN, which keep them open if the body is bent or pressed against. (relatively impermeable to gases).

Question 7

What does the tracheae lead into

Answer 7

Tracheae branch into TRACHEOLES, narrower tubes with a diameter of 06-0.8.

Question 8

Where are tracheoles found?

Answer 8

They’re spread throughout the tissues between whole cells because they’re very thin and elongated. Because they’re permeable to gases, most gas exchange happens in the tracheoles.

Question 9

How does GE occur in insects through diffusion?

Answer 9

air travels along the tracheae and tracheoles reaching all the tissues; the vast number of tracheoles give a large SA. There is tracheal fluid at the ends of the tracheoles which limits the penetration of air for diffusion.

When lactic acid builds up water moves out of osmosis, it opens up more surface area for diffusion.

Question 10

What other methods are there for GE in organisms with higher energy demands?

Answer 10

1. collapsing of air sacs which act as air reservoirs - to increase amount of air moving through GE system; usually inflated/deflated by ventilating movements of ABDOMEN & THORAX
2. mechanical ventilation of the tracheal system - air is actively pumped into the GE system by the THORAX & ABDOMEN; these movements change the volume of the body and pressure of the tracheae/tracheoles.

Question 11

What limitations are there with animals that get their oxygen from water?

Answer 11

1. water is 100x more viscous (thick)
2. 1000x denser than air
3. much lower oxygen count
   Therefore, fish have evolved a different respiratory system

Question 12

Why do fish need gills

Answer 12

because of their SA:V ratio, simple diffusion wouldn’t be enough, and their activity means they have a higher oxygen demand

Question 13

What type of system do fish have in their circulatory system

Answer 13

There is a counter-current system where the water runs in one direction over the gill; they take O2 from the water.

Question 14

How are gills adapted to be he main organ in the GE system

Answer 14

Good blood supply, thin layers, large SA,

Question 15

What are the gills covered by in bony fish

Answer 15

operculum (bony flap), contained in the gill cavity

Question 16

How do fish keep the flow of water in one direction

Answer 16

by opening their mouth and operculum

Question 17

What is the process of maintaining water flow over gills?

Answer 17

1. Lower mouth to open buccal cavity (increasing volume)
2. pressure therefore drops in the cavity and water comes in
3. opercular valve is shut and opercular cavity, containing gills, expands (lowering pressure again)
4. floor of buccal cavity rises so pressure increases, forcing water to the back, over the gills
5. mouth closes, operculum opens and opercular cavity sides move inwards
6. all of this increases pressure, forcing water over gills and out of operculum.

Question 18

How are gills adapted for efficient gas exchange

Answer 18

thin surfaces, rich blood supply, large area for diffusion (general)

(advanced):
Tips of adjacent gill filaments overlap; increases resistance to flow of water over gill surfaces and slows movement of water
—-> more time for GE to happen
water moving over gill and blood in gill filaments flow in different directions (COUNTER-CURRENT SYSTEM)
—-> 80% of oxygen can be taken from the water with a counter current exchange system, compared to only 50% in a parallel system, as a result of CC systems maintaining steep concentration gradients