Eukaryotes have a nucleus and organelles, while prokaryotes do not. Eukaryotic cells are larger and more complex, with various organelles that perform specific functions. Eukaryotes include plants, animals, fungi, and some microorganisms. They have surface features for locomotion and protection, and some organelles are ancestors of prokaryotes. Eukaryotes evolved between 2.1 and 1.6 billion years ago, with the earliest fossils dating back 1.2 billion years.
A eukaryote is a type of cell (or unicellular organism) that possesses a nucleus and membrane-bound organelles, in contrast to prokaryotes (bacteria and archaea) which do not. Eukaryote means in Greek “good/true nut/hazel” referring to the nucleus, while “prokaryote” means “before nut/hazel”. Eukaryotic cells tend to be larger (about an order of magnitude) and much more complex than prokaryotic cells.
All plants, animals, fungi and many microorganisms are eukaryotes. Eukaryotic cells have numerous organelles or cellular subunits with designated roles. These include mitochondria (which feed the cell), endoplasmic reticulum (synthesizes important biomolecules), Golgi apparatus (processes and packages biomolecules), lysosomes (which break down dead or foreign material), centrioles (which mediate cell division), chloroplasts (found in plants), and a strong cytoskeleton. These organelles all float in the cytoplasm, a sticky, semi-transparent fluid that serves as the cell’s “blood.”
Additionally, eukaryotic cells may have a number of surface features used for locomotion or protection that are not found in prokaryotes. Examples include a flagellum, such as those found in human sperm, and a cell wall, found in plants. Fungal cells have a chitin cell wall, the same material used by insects for their exoskeletons. Fungi such as fungi don’t feel hard to the touch because the thickness of their chitin walls are much less than the chitin exoskeletons of insects and other arthopods.
Eukaryotes have the potential for much greater complexity and diversity than prokaryotic cells. Some organelles in eukaryotic cells are actually ancestors of prokaryotes, which once had a symbiotic relationship with the eukaryote but have since been absorbed by it. Examples include mitochondria and chloroplasts. Mitochondria even have their own DNA, which over evolutionary time has slowly been transferred to the better protected nucleus.
Eukaryotes are newer to life on Earth than prokaryotes. While prokaryotes evolved 3.4-2.7 billion years ago, eukaryotes evolved between 2.1 and 1.6 billion years ago, although some evidence points to a possible origin of 2.7 billion years ago. The earliest fossils of eukaryotes date back 1.2 billion years, in the form of red algae, a type of seaweed.
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