生态学

生 = 牛 + 一 : Mnemonic symbol: a cradle.

Sherlock Holmes (sh) comforts a crying baby bull (牛) in a cradle (生) in front of the engine ((e)ng1) and plays him a tune on a flute (一).

态 = 太 + 心 : The empress dowager (太) asks Tecumseh (t) about his attitude (态) towards her in the airplane's bathroom (ai4). Tecumseh isn't sure himself and samples his hearts (心) on a scale from 1 to 10 with one bin per integer. After N is large enough, he sees that his attitude forms a Gaussian distribution (态) with a mean of 6.

学 = 小 + 冖 + 子 : Xu Xian wants to study scienceology and learn more about daisies. Just inside the elevator's kitchen, he put some daisies into a prize cup and covered them with a cooking top. He wants to study the growth rate of the daisies depending on the pH of the water in the prize cup.