Specialised Exhcange Systems

Question 1

How are gases exchanged in multicellular organisms?

Why is this possible?

Answer 1

They have specialised exchange surfaces. (like alveoli)
This is because large animals have a small surface area:volume ratio.
They have high energy demands and require more oxygen.

Question 2

What properties make an exchange surface good for efficient exchange?

Answer 2

1) A large surface area
2) Thin
3) A good blood supply and/or ventilation

Question 3

Give an example of an exchange surface with a large surface area?

Answer 3

Root hair cell

Question 4

Give an example of an exchange surface with thin walls?

Answer 4

Alveoli

Question 5

Give an example of an exchange surface with a good blood supply?

Answer 5

Gills/alveoli

Question 6

Give an example of an exchange surface with good ventilation?

Answer 6

Alveoli

Question 7

How are gases exchanged in single celled organisms?

Why is this possible?

Answer 7

Gases diffuse directly into or out of the cell by diffusion across the cell surface membrane.
It is possible because of short/thin distances and high surface area:volume ratios.

Question 8

How do you dissect fish gills (step by step)?

Answer 8

1) Place the fish in a dissecting tray
2) Push back the operculum and use scissors to remove the gills
3) Cut each gill arch through
4) Finally draw the gill and label it

Question 9

How do you dissect an insect (step by step)?

Answer 9

Use a big insect that has been killed humanely fairly recently.

1) Fix the insect to a dissecting board
2) Cut and remove a piece of exoskeleton from along the length of the abdomen
3) Fill the abdomen with saline solution using a syringe
4) Silvery grey tubes appear- these are tracheae
5) Mount the tracheae on a wet mount microscope slide to view under a light microscope.

Question 10

What are the 4 main dissecting tools used to carry out dissections?

Answer 10

Scalpel
Dissecting scissors
Tweezers/forceps
Dissecting pins