American Licensing Laws 题目：   In the early-nineteenth-century United States, the medical profession was largely unregulated. There were several competing schools of medic...

题目：   Peruvian farmers have used guano (dried waste of seabirds) as a plant fertilizer since ancient times, but guano was not exported to Europe until 1840. Guano has mu...

TF阅读真题第827篇The Theory of Geographic Speciation

TF阅读真题第735篇The Role of Fragrance in Plant Pollination

Characteristics of Tropical Rain Forests Almost all the action in a rain forest (not just photosynthesis but also flowering, fruiting, predation, and herbivory) happens high in t...

TF阅读真题第704篇Air-Breathing Fishes

TF阅读真题第822篇Newspapers in the Nineteenth-Century

TF阅读真题第784篇Proto-industrialization in Europe

Mars's Disappearing Atmosphere   For about the first billion years of its life, Mars was probably a watery planet. There are signs of past water in surface features, such as d...

Degradation and Erosion of Soil Land without soil can support only very small primitive plants such as lichens and mosses that can cling onto a rock surface. The rest of the worl...