Â­Mesoamericans began writing during the mid-Pre-classic period. The Mayans were the first to keep any sort of historical record, and the beginnings of the calendar were born. The Mayans used stelae, or stone monuments, to carve their civil events, calendars and astronomy knowledge. They also inscribed their religious beliefs and mythology on pottery.
The nucleus is a membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction. It is commonly the most prominent organelle in the cell. The nucleus is surrounded by a structure called the nuclear envelope.
Animal cell nucleus is a membrane bound organelle. It is surrounded by double membrane. The nucleus communicates with the surrounding cell cytoplasm through the nuclear pores. The DNA in the nucleus is responsible for the hereditary characteristics and protein synthesis.ucleus a double-membrane bound cell organelle present in eukaryotic cells. The nucleus constitutes most of the genetic material of the cell-the DNA. The nucleus maintains the integrity of the genes which regulate the gene expression, in-turn regulating the activities of the cell.