Animal physiology

Question 1

Why are insects today so much smaller than they used to be?

Answer 1

Fossil record gigantism due to historical atmosphere having higher oxygen concentration so insects (invertebrates so no lungs) were able to grow larger and maintain optimal gas diffusion. Current levels of oxygen mean that insects are thus limited in size (smaller diffusion pathway)

Question 2

insects that go through gradual metamorphosis are called?

Answer 2

hemimetabolous

Question 3

insects that go through complete metamorphosis are called?

Answer 3

holometabolous

Question 4

describe the hormonal stages that hemimetabolous insects go through

Answer 4

Egg, young nymph, later nymph, adult

Question 5

describe the hormonal stages that holometabolous insects go through

Answer 5

Egg, larvae, pupa, adult

Question 6

Name the 3 insect hormones responsible for undergoing metamorphosis

Answer 6

PTTH, Ecdysone in its active form (20E) and Juvenile hormone (JH)

Question 7

How does the Juvenile hormone affect molting in hemimetabolous insects?

Answer 7

maintains young insect characteristics so when 20E triggers molting and JH levels are high the larvae will molt into a larger larvae or nymph. When JH low the adult develops.

Question 8

what is the role of Juvenile hormone in adult insects?

Answer 8

egg/sperm production, pheromone production

Question 9

In what order are PTTH and Ecdysone secreted and what are their functions in metamorphosis?

Answer 9

PTTH secreted in the brain, stimulating secretion of Ecdysone from the prothoracic gland which is converted to E20 form and stimulates further enzyme secretion for the molting process.