The ESG Biology Hypertextbook Eukaryotic cells are much more complicated than prokaryotic cells. The eukaryote has a differentiated nucleus enclosed in a nuclear membrane. It usually has two whole copies of the genome, so in computer terms the eukaryotic cell has a backup copy of all of its programs. Outside of its nucleus, the eukaryotic cell has an array of complex subunits that are essential to it. These two subunits enable eukaryotic cells to conduct respiration and photosynthesis, respectively.
Eukaryotic cells are able to constitute multicelled animals and plants.
Apparently eukaryotes are able to evolve much more rapidly than prokaryotes. If life has existed on Earth for almost four billion years, the consensus is that eukaryotes first appeared just after the halfway point, maybe 1.7 billion years ago. Returning to the computer analogy, the relationship between prokaryotes and eukaryotes is like the relationship between handheld calculators and desktop personal computers. Both kinds of cells come in a broad range of sizes, but eukaryotes are, on average, about ten times bigger, so the relative physical sizes suit the metaphor. Like prokaryotes, handheld calculators come in a wide variety, each with a narrow special purpose.