False
crossing over occurs in prophase 1 of meiosis 1. The significance of this crossing over is to ensure cell differentiation. If this occurred in prophase two it means the cells in meiosis 1 will be identical.
The list that is composed of substances that are widely used for many years without apparent ill effects is the GRAS. GRAS is an abbreviation for generally recognized as safe; it is an American food and drug adminstration designation where chemical or substance added to food is considered safe by experts, and therefore, it is exempted from the usual federal food, drug, and cosmetic Act.
67 million years ago in the form of phyollths (small sllica flecks in grass that make it difficult to digest)
