Prokaryotic cells don’t possess a membrane-bound nucleus—instead of chromosomal deoxyribonucleic acid (DNA), they have circular DNA structures called plasmids. They are more primitive than eukaryotic cells, and they are generally thought to be simpler in structure. Organisms made of prokaryotic cells, including bacteria and cyanobacteria, are called prokaryotes, and they are the most numerous creatures on earth. The word prokaryotic comes from combining the Greek words "pro," which means “before,” and "karyose," which means “grain." In this context, “grain” is meant to refer to the nucleus of a cell, so prokaryote literally means “before a nucleus," and it’s generally intended to describe the prokaryote's primitive nature compared to the more evolved eukaryotic organisms like animals and plants.
A prokaryote has a cell wall and a membrane that both serves to give it a shape and allow for the exchange of materials with the outside world. The cell will absorb food and gases through the barriers and release waste products the same way. Inside the cell, there is a protein substance called cytoplasm, which the cell uses to metabolize materials. Attached to the cell wall is the plasmid DNA structure, which is in direct contact with the cytoplasm. Some prokaryotic cells can exchange plasmids and, thereby, share DNA with each other, which allows them to evolve rapidly when adapting to things like antibiotics.
In general, prokaryote reproduction works in a simpler manner than the reproductive methods of eukaryotic organisms. The process is a kind of cell division called binary fission, and it is basically a self-replication procedure. In theory, the end result is two identical prokaryotic cells, and that’s generally how it works out, but because bacteria mutate at a higher rate than other organisms, differences do occur occasionally. The prokaryotic reproductive method has the end result that nearly all the organisms in a given group will have almost identical DNA, which is one of the characteristics that separates them from eukaryotes.
The organisms with prokaryotic cells, which primarily include members of the monera kingdom, are generally thought to be vitally important to the overall functionality of earth's ecosystem. When people think of bacteria, they often think of illness, and it’s generally true that certain bacteria can be very dangerous, but they are also necessary for human survival. For example, there are several bacteria that help the digestive system work properly. Bacteria are also largely responsible for the decomposition of organic matter, which returns the nutrients of dead living things to the soil. Without this function, the planet's soil would be unhealthy, which could theoretically result in a total ecological collapse.