SSC
The transformation of a larva into an adult through drastic changes in body form is called:
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Answer: Option B — Metamorphosis
Detailed Solution
Metamorphosis (from the Greek words "meta", meaning "change", and "morphe", meaning "form") is a biological process in which an animal undergoes a dramatic change in its body structure and form after hatching or birth, as it develops from a larva into an adult. The larva often looks very different from the adult and may live in a different habitat and eat different food. This reduces competition between the young and adults.
Metamorphosis is controlled by hormones:
In frogs and other amphibians, it is controlled by thyroxine, a hormone produced by the thyroid gland, which needs iodine. If a tadpole lacks iodine or thyroxine, it fails to change into a frog; if extra thyroxine is given, it changes early into a tiny frog.
In insects, it is controlled by the moulting hormone ecdysone and by the juvenile hormone.
Examples:
Frog: egg, tadpole (larva, lives in water, breathes through gills, has a tail), and then adult frog (lives on land and water, breathes through lungs and skin, no tail). During metamorphosis, the tail is absorbed, legs develop, and the gills are replaced by lungs.
Complete metamorphosis (holometabolous insects): four stages: egg, larva, pupa and adult. Examples include butterflies and moths (caterpillar larva), houseflies (maggot larva), mosquitoes (wriggler larva), beetles, bees and the silk moth (Bombyx mori), whose pupa is enclosed in a cocoon of silk.
Incomplete metamorphosis (hemimetabolous insects): three stages: egg, nymph and adult. The nymph looks like a small adult without wings. Examples include cockroaches, grasshoppers, locusts, dragonflies and termites.
Humans and most mammals show direct development, in which the young look like small adults, without metamorphosis.
Why not the other options?
- ✗Metagenesis is the alternation of asexual and sexual generations (Obelia).
- ✗Moulting is the shedding of the outer skin or exoskeleton, as in insects and snakes.
- ✗Differentiation is the process by which cells become specialised.
Quick tip
Remember: Metamorphosis = larva to adult (frog: controlled by thyroxine, needs iodine); complete = egg, larva, pupa, adult (butterfly, mosquito, silk moth); incomplete = egg, nymph, adult (cockroach, grasshopper).
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Reproduction in Plants & Animals — Preparation
This question tests your understanding of Reproduction in Plants & Animals, a key topic in the General Knowledge section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
This topic covers reproduction: asexual methods such as fission, budding, fragmentation and vegetative propagation, sexual reproduction in flowering plants including pollination and fertilisation, and the human reproductive system. Questions often ask which method of reproduction an organism uses (binary fission in amoeba and budding in yeast and hydra), which agent pollinates which flower, and what each part of a flower does. Know the difference between self-pollination and cross-pollination, and the role of the ovary and ovule in forming fruit and seed. Practise the reproduction questions below, written in the style of the general awareness sections of exams such as SSC, banking, railways, CUET GAT, MAH CET and CLAT. Each question comes with a detailed explanation that adds related facts, so every question helps you revise more than one point.