Some animals, such as poisonous snakes, are dangerous and need special care.

poisonous 是形容词，由名词 poison（毒药）加上后缀 -ous（表示"具有...特性的"）构成，意思是"有毒的"。poisonous snakes 指"毒蛇"，这类蛇的毒液能对人类造成伤害。