Australia Has More Kangaroos Than People

Cats, like most birds, fish, reptiles, and amphibians, possess a nictitating membrane — a translucent third eyelid that moves horizontally across the eye from the inner corner. Normally hidden in healthy, alert cats, it becomes visible when a cat is drowsy, ill, or under stress. Humans lost this structure through evolution.

Chameleons are not actually great at camouflage — their resting color already blends with their surroundings. Rapid color changes serve primarily as social signals: males flash bright colors during courtship or to threaten rivals, dark tones indicate fear or submission, and bright hues signal excitement. A 2014 study by Stuart-Fox confirmed communication as the primary function.

A crocodile's tongue is fused to the floor of its mouth along its entire length by a thick membrane, leaving no free portion to protrude. This differs from most other reptiles such as lizards and snakes. Crocodiles catch prey using their jaws, which exert a bite force of up to 16,460 Newtons — the strongest recorded in the animal kingdom.

Sea stars (Asteroidea) have no brain — instead, a nerve ring coordinates their movements. Rather than blood, they use a water vascular system: seawater filtered through their bodies delivers nutrients and operates thousands of tube feet used for locomotion and feeding. Each arm can regenerate an entirely new body.