Royal jelly, a thick, milky substance secreted by young nurse honeybees to feed a bee colonyâs larvae, most notably the queen larvae, is a rich source of nutrients, as well as acetycholine, a neurotransmitter that plays a critical role in cognitive function.
The origin of the eukaryotic cell is a milestone in the evolution of life, since eukaryotes include all complex cells and almost all multicellular organisms. The timing of this series of events is hard to determine; Knoll (2006) suggests they developed approximately 1.6â2.1 billion years ago.
The first microscopic eukaryotes appeared about 1.4 billion years ago. Life-forms with soft parts, such as jellyfish and worms, developed in profusion, albeit locally, toward the end of the Precambrian about 650 million years ago, and it is estimated that this corresponds to an oxygen level of 0.1 PAL.