Zoology MCQs for NEET — Practice Questions with Answers

Thyroxine, the principal hormone, of thyroid gland, is required for tissue differentiation and metamorphosis (the rapid tranformation from the larval to adult form) in amphibians. Thyroxine triggers a response from the hypothalamus, (probably by a genetic mechanism) followed by the production and release of TSH (Thyroid stimulating hormone), thus metamorphosis begins and tadpoles metamorphose into frogs. Thiourea is an organic compound of carbon, nitrogen, sulphur and hydrogen, with the formula CSN₂H₄ OR (NH₂)₂CS. It is similar to urea. except that oxygen atom is replaced by a sulphur atom.

Fibres and fibroblasts are compactly packed in the dense connective tissues. Orientation of fibres show a regular or irregular pattern and are called dense regular connective tissues. In the dense regular connective tissues, the collagen fibres are present in rows between many parallel bundles of fibres. Tendons, which attach skeletal muscles to bones and ligaments which attach one bone to another are examples of this tissue.

In cockroach, exoskeleton has hardened plates called sclerites that are joined to each other by a thin and flexible articular membrane called as arthrodial membrane.

Head of cockroach is triangular in shape.. It is formed by the fusion of six segments and shows great mobility in all directions due to flexible neck.

Excretion in cockroach is performed by Malpighian tubules. Each tubule is lined by glandular and ciliated cells. They absorb nitrogenous waste products and convert them into uric acid which is excreted out through the hindgut.

A ring of 6-8 blind tubules called hepatic or gastric caecae is present at the junction of foregut and midgut, which secrete digestive juice.

At the junction of midgut and hindgut, a ring of 100-150 yellow coloured thin filamentous- malpighian tubules is present. They help in removal of excretory products from haemolymph.

Spermatheca receives sperms and stores them for fertilisation.

A characteristic mushroom shaped gland is present in the 6th-7th abdominal segments which functions as an accessory reproductive gland.

Excretion is performed by Malpighian tubules. Each tubule is lined by glandular and ciliated cells.