Q.Give an example for each of the following a. A viviparous animal
b. A fish possessing a poison sting
c. A fish possessing an electric organ
d. An organ, which regulates buoyancy
e. Animal, which exhibits alternation of generation
f. Oviparous animal with mammary gland

a. A viviparous animal — Panthera tigris (tiger), a placental mammal.

b. A fish with a poison sting — Trygon (sting ray).

c. A fish with an electric organ — Torpedo (electric ray).

d. An organ that regulates buoyancy — the air bladder (found in Osteichthyes).

e. An animal exhibiting alternation of generation — Obelia (metagenesis). …

Each category has a clearly named example within the classification of the animal kingdom.

• a. A viviparous animal: placental mammals such as Panthera tigris (tiger) give birth to live young.
• b. A fish possessing a poison sting: Trygon, the sting ray, among the cartilaginous fishes, carries a poison sting.
• c. A fish possessing an electric organ: Torpedo, the electric ray, also among the cartilaginous fishes, possesses electric organs.
• d. An organ that regulates buoyancy: the air bladder, present in Osteichthyes (bony fishes), lets these fish control their buoyancy, unlike Chondrichthyes, which lack it. …

Method: Mnemonic sentence chaining by contrast pairs

Rather than recalling six unrelated examples, group them into contrasting THEMES first (a reproduction theme, a "special organ" theme, a life-cycle theme) and build one short mnemonic sentence per theme, since organising by theme is easier to hold in memory than one flat list of six.

Theme 1 — reproduction extremes: "A tiger gives birth to live cubs, while a platypus, oddly, lays eggs." This single contrasting sentence covers two of the six blanks at once: a viviparous animal (tiger) and an oviparous mammal with mammary glands (platypus) — and the CONTRAST between them (live birth vs egg-laying, both within warm-blooded animals) makes both easier to recall together than separately.

Theme 2 — unusual fish organs: "A sting ray (Trygon) stings, an electric ray (Torpedo) shocks." Both are cartilaginous fishes with a specialised defensive/offensive organ, and pairing them by "both are rays with a special weapon" links the two facts (poison sting fish; electric-organ fish) into one easy-to-hold image. …