The Exoskeleton And Metamorphis

Question 1

What do you say the cuticle is when it’s brown in colour?

Answer 1

Sclerotized

Question 2

What is the exoskeleton made of?

Answer 2

Chitin, which is linked to a protein matrix giving tensile strength

Question 3

Give an example of a ‘rubber-like’ cuticle and when it might be used

Answer 3

Resilin: it is like a mechanical spring when bent so is good after a large fluid intake (arthrodial membrane)

Question 4

When does size gain occur in an insect?

Answer 4

At the moult

Question 5

Give the four layers of cuticle secreted by the epidermal cells

Answer 5

Endocuticle
Exocuticle
Epicuticle
Wax layer

Question 6

Give the stages of the moult cycle:

Answer 6

1. Apolysis (cuticle still present but not attached)
2. New epicuticle forms
3. New exocuticle forms
4. Ecdysis (cuticle is moulted)
   = Expansion

Question 7

What are holometabolous insects?

Answer 7

Endopterygotes where they have immature stages called larvae and have a pupal stage

Question 8

What are hemimetabolous insects?

Answer 8

Extopterygote where they have immature stages called nymphs e.g locusts

Question 9

What are ametabolous insects?

Answer 9

Apterygotes where they undergo gradual or no metamorphosis e.g silverfish

Question 10

What part of the cuticle is sclerotized?

Answer 10

The exocuticle

Question 11

What are the two hormones that determine whether an insect develops a larval, pupal or adult cuticle?

Answer 11

Juvenile hormone

Ecdysteroid

Question 12

What hormone does an adult not have?

Answer 12

Juvenile hormone

Question 13

What does the ecdysis triggering hormone cause the insect to do?

Answer 13

Causes the insect to perform a stereotyped behaviour to shed the old cuticle

Question 14

Give the order of the 5 hormones that control ecdysis

Answer 14

PTTH: triggers ecdysteroid synthesis 
Ecdysteroid 
Juvenile hormone 
Ecdysis triggering hormone 
Eclosion hormone 
=ECDYSIS