This is a period of bacteria, algae, and fungi. Amoebas are living examples of protozoans. These evolved during the expansion of the eukaryotes. Metazoans - multicellular animals that possess more than one kind of cell and have their cells organized into tissues and organs. These organisms started evolving about 900 million years ago.
Modern examples are jellyfish, flat worms, and annelid worms.
Rocks of about this age contain the first calcium carbonate shell bearing fossils. Invasion of the lands - Vascular plants have tubes and vessels that convey fluids from one part of the plant to another. Psilophytes - the first vasular plants are found in the middle Silurian. These plants evolved in the Devonian. Jawless fish appear in the Upper Cambrian.