Exam Questions 3.1 exchange surfaces

Question 1

How does carbon dioxide produced in the respiring cells of an insect removed to the air outside of a termite mound? (4 marks)

Answer 1

CO2 diffuses down a concentration gradient out of the respiring cell
carried through body from cell to tracheoles by blood passing out through tracheoles
respiration generates heat
hot gases expand and rise out of the termite mound

Question 2

Why would a fish that lives in burrows and deep sand possibly have evolved external gills? (1 mark)

Answer 2

Oxygen in short supply in lugworm habitat

Question 3

Do bronchioles contain:
1. elastic fibres
2. cartilage
3. goblet cells

Answer 3

1. yes
2. no
3. no

Question 4

Compare and contrast the mechanism of expiration for regular breathing compared with breathing out fully
(6 marks)

Answer 4

regular breathing
passive
diaphragm muscles relax so diaphragm moves up
external intercostal muscles relax so ribs move down and in
thoracic cavity volume decreases

forced expiration
active
requires energy
internal intercostal muscles contract
ribs pulled down hard
abdominal muscles contract forcing diaphragm up

Question 5

why do larger multicellular organisms require specialised exchange surfaces?

Answer 5

smaller SA:V ratio
long diffusion distance

Question 6

explain insect ventilation and its adaptations

Answer 6

muscular movement
volume and pressure change in abdomen and thorax
air movement
large SA:vol means sufficient diffusion

Question 7

explain insect gas exchange and its adaptations

Answer 7

oxygen diffuses along tracheae
diffuses into water (tracheole fluid)
diffuses into surrounding cells
many tracheoles so large SA
spirals of chitin hold trachea open