Title: On the Origin of Species.
Question: What did Darwin use to illustrate the way that original species change and adapt into new ones?

Title: Ottoman Empire.
Question: What system deemed non-Muslims subjects of the empire but unbound by Muslim law?

Title: Railway electrification system.
Question: When was the first trail of RhB system tested?

Title: Mammal.
Question:
Why is it necessary for smaller animals to have an insulative covering?