Question

Three hormones control the metamorphosis of a caterpillar into a butterfly. Which statement about these hormones is false?
A) Moulting hormone promotes the changes in the epidermis (external skeleton).
B) Prothoracicotropic hormone stimulates the prothoracic gland to release the juvenile hormone.
C) Levels of juvenile hormone control the time at which an insect turns into an adult.
D) Moulting hormone promotes the development of imaginal disks.

Answer 1

Hint: Metamorphosis is the process of abrupt change in the body structure of the animal through cell growth and differentiation. As embryonic development leads to a larval stage with characteristics that are different from the adult organism.

Complete step-by-step answer:
Insects grow by shedding off their exoskeleton which is called moulting. Moulting hormone excites growth and helps form cuticles. It acts on the prothoracic gland that secretes ecdysone i.e., a steroid hormone. Metamorphosis is also controlled by insect hormones. Corpus allatum secretes a juvenile hormone that is present in the brain. Prothoracicotropic hormone, ecdysone, and juvenile hormone play a major role in metamorphosis. Juvenile hormones don’t stay during the last larval stage. So in the adult stage, it is not present. PTH or prothoracicotropic hormone is needed to go from caterpillars to moths. PTH is released by neurosecretory cells in the brain of a larva.
PTH is found in 4 groups on the left and right and two in the middle of the brain so it is also named brain hormone. Moulting hormone is released after its activation and activation is done in the brain only.
Hence the correct answer is option B.

Note: PTH is found in 4 groups on the left and right and two in the middle of the brain so it is also named brain hormone. Moulting hormone is released after its activation and activation is done in the brain only.