Question: The first vertebrates appeared over 500 million years ago (Mya), during the Cambrian period, and may have resembled the modern hagfish in form. Sharks appeared about 450 Mya, amphibians about 400 Mya, reptiles about 350 Mya, and mammals about 200 Mya. Each species has an equally long evolutionary history, but the brains of modern hagfishes, lampreys, sharks, amphibians, reptiles, and mammals show a gradient of size and complexity that roughly follows the evolutionary sequence. All of these brains contain the same set of basic anatomical components, but many are rudimentary in the hagfish, whereas in mammals the foremost part (the telencephalon) is greatly elaborated and expanded.
Is there an answer to this question: During which scientific period did vertebrates appear?

Answer: Cambrian period


Question: Writing in 1998 Kurt Jonassohn and Karin Björnson stated that the CPPCG was a legal instrument resulting from a diplomatic compromise. As such the wording of the treaty is not intended to be a definition suitable as a research tool, and although it is used for this purpose, as it has an international legal credibility that others lack, other definitions have also been postulated. Jonassohn and Björnson go on to say that none of these alternative definitions have gained widespread support for various reasons.
Is there an answer to this question: What does the definition possess that others lack?

Answer: unanswerable


Question: Distinguishing motifs of Islamic architecture have always been ordered repetition, radiating structures, and rhythmic, metric patterns. In this respect, fractal geometry has been a key utility, especially for mosques and palaces. Other features employed as motifs include columns, piers and arches, organized and interwoven with alternating sequences of niches and colonnettes. The role of domes in Islamic architecture has been considerable. Its usage spans centuries, first appearing in 691 with the construction of the Dome of the Rock mosque, and recurring even up until the 17th century with the Taj Mahal. And as late as the 19th century, Islamic domes had been incorporated into European architecture.
Is there an answer to this question: When did domes first appear in the architecture of the Muslim World?

Answer: 691


Question: The most familiar, and historically the oldest, types of glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. The term glass, in popular usage, is often used to refer only to this type of material, which is familiar from use as window glass and in glass bottles. Of the many silica-based glasses that exist, ordinary glazing and container glass is formed from a specific type called soda-lime glass, composed of approximately 75% silicon dioxide (SiO2), sodium oxide (Na2O) from sodium carbonate (Na2CO3), calcium oxide, also called lime (CaO), and several minor additives. A very clear and durable quartz glass can be made from pure silica, but the high melting point and very narrow glass transition of quartz make glassblowing and hot working difficult. In glasses like soda lime, the compounds added to quartz are used to lower the melting temperature and improve workability, at a cost in the toughness, thermal stability, and optical transmittance.
Is there an answer to this question: What is sand mostly made of?

Answer:
silica