Eukaryotic vs Prokaryotic
All the organisms are either prokaryotic or eukaryotic, i.e. all the animals, plants, bacteria, fungus, protozoa… etc fall into either of those categories. Therefore, understanding the differences between prokaryotic and eukaryotic organisms is very important. This article discusses the major differences between these two.
“Pro” means before, and “karyone” means case in Greek, giving the rise to the term prokaryote. The best example to introduce the prokaryotes is the bacteria. Prokaryotic organisms are more often unicellular and vary rarely multi-cellular. There is no defined nucleus in prokaryotic organisms, and in addition, they do not have organelles with membranes. However, they have small ribosomes in the cytoplasm. They have a nucleoid with strands of irregular DNA complex in the cytoplasm. There is only one loop of chromosomal DNA in the nucleoid. However, they have a primitive cyctoskeleton for the maintenance of the shape of cell. The surface-area-to-volume ratio is very high in prokaryotes that results a high metabolic rate, which leads to an increased growth rate. Therefore, the generation time of prokaryotes is very short. They are able to form aggregate communities, called colonies that suggest social bonding among prokaryotic organisms. Biofilms are prime examples for their social living, and scientists believe that antibiotic resistance is higher in biofilms. Prokaryotic shapes are mainly of four known as Coccus, Bacillus, Spirocheate, and Vibrio. They reproduce via asexual means such as binary fission and budding. However, gene exchange takes place through bacterial conjugation. People could never stop studying the prokaryotes, as it is almost impossible to measure the diversity at any scale.
Eukaryotic organisms have organized cells with membrane-bound organelles with defined nuclei. All the plants, animals, fungus… etc are eukaryotic organisms. They have large ribosomes in the cytoplasm and mitochondria, and chloroplast ribisomes are smaller. The nuclear envelope is the most defining character of all in the eukaryotic organisms. Genome of the eukaryotes is a tightly bound and organized complex of chromosomes inside the nuclear envelope. Eukaryotics include both simple and complex organisms. Their reproduction could be either sexual or asexual. The sexual reproduction is present only among eukaryotes and that involves the important step of meiosis in cell division. Simply, meiosis is the division of DNA of a diploid cell (two sets of identical chromosomes in the nucleus) of one parent into a haploid cell (only one set of chromosomes). The resulted haploid cell will meet another haploid from the other parent and form a new line of chromosomes in the resulting generation. That means the sexual reproduction has allowed the gene exchange to create new traits as adaptations for the changing world. However, the diversity of eukaryotic organisms is very low; e.g. in human body there are ten times more prokaryotes than body cells according to Zimmer (2010).
Differences Between Prokaryotic and Eukaryotic Organisms
|Prokaryotic organisms||Eukaryotic organisms|
|No defined nucleus, but a nucleoid without an envelope||Defined nucleus with a nuclear envelope|
|Membrane-bound organelles are absent||Organelles are membrane-bound|
|Ribosomes are smaller||Ribosomes are smaller, contain both large and small ribosomes|
|Genome is an irregular complex of DNA with only one loop of stable chromosomes||Genome is a tightly-packed and organized complex of chromosomes|
|Shorter generation time||Longer generation time|
|Smaller in the cell size||Larger cell size|
|Very high taxonomic diversity||Taxonomic diversity is low compared to prokaryotes|
|Reproduction takes place only via asexual fission and budding||Both sexual and asexual reproduction takes place|