Eukarya Domain

The Earth is 4.6 billion years old, and microbial life is considered to have first appeared between 3.8 and 3.9 billion years ago; in fact, microbial life accounted for 80% of Earth’s history. Microbial life is still the most common kind of life on the planet. The total number of microbial cells on Earth is estimated to be on the order of 2.5×1030 cells, making it the largest fraction of biomass on the planet.

Phylogeny is the study of the evolutionary relationships between species. The Three Domain System, suggested by Woese and others, is a phylogenetic evolutionary model based on differences in nucleotide sequences in ribosomal RNAs (rRNA), as well as cell membrane lipid structure and antibiotic susceptibility. Comparing the structure of rRNA is very useful. Because rRNA molecules perform the same function throughout nature, their structure does not change much over time. As a result, rRNA nucleotide sequence similarities and differences are a reliable indicator of how related or unrelated different cells and species are.

The origins of prokaryotic and eukaryotic cells are the subject of numerous theories. Because all cells are similar in nature, it is commonly assumed that they all descended from a single ancestor cell known as the last universal common ancestor (LUCA). These LUCAs subsequently differentiated into three distinct cell types, each representing a distinct domain. The Archaea, Bacteria, and Eukarya are the three domains.

Phylogenetic Tree of Life

             Various fusion hypotheses have recently started to dominate the literature. One theory posits that the eukaryotic genome became diploid or 2N after the union of two haploid or 1N prokaryotic cells.

Domains

PVC stands for Planctomycetes, Verrucomicrobia, and Chlamydiae, and refers to the three members of the superphylum. Members of the PVC, while belonging to the Bacteria domain, exhibit characteristics of the Archaea and Eukarya domains.

Similar to eukaryotic cells, some of these bacteria have cell compartmentalization, in which membranes surround areas of the cell core, such as clusters of ribosomes or DNA. Some, like eukaryotes, divide by budding or include sterols in their membranes. Some, like eukaryotes and archaea, lack peptidoglycan. These bacteria are thought to be an intermediary step between an ancestor that emerged from a bacterium (domain Bacteria) and an archael-eukaryotic ancestor before the domains Archaea and Eukarya split.

The Current System

As scientists get a better understanding of species, classification systems evolve. Researchers now have a whole new approach of examining organism-to-organism connections because to genetic sequencing.

The current Three Domain System categorises species based on structural differences in ribosomal RNA (rRNA). Ribosomal RNA is a ribosomal molecular building block.

Organisms are divided into three realms and six kingdoms using this method. Domain names are

• Archaea
• Bacteria
• Eukarya

The kingdoms are:

1. Archaebacteria
2. Eubacteria
3. Protista
4. Fungi
5. Plantae
6. Animalia

Archaea Domain

Single-celled creatures are found in the Archaea domain. Genes in Archaea are comparable to those in bacteria and eukaryotes. They were initially mistaken for bacteria due to their resemblance to bacteria in appearance.

Archaea, Prokaryotic animals with a membrane-bound nucleus, such as bacteria. They also lack internal cell organelles, and many of them are the same size as bacteria and have a similar structure. Archaea reproduce by binary fission, have one circular chromosome, and move around the environment with flagella, just like bacteria.

In terms of cell wall composition, archaea differ from bacteria, and in terms of membrane composition and rRNA type, archaea differ from both bacteria and eukaryotes. These distinctions are significant enough to warrant the creation of a separate category for archaea.

Bacteria Domain

The Bacteria Domain is where bacteria are categorised. Because some of these organisms are harmful and can cause disease, they are generally feared.

Bacteria, on the other hand, are necessary for life because some are found in the human microbiome. These bacteria have important roles in our bodies, including helping us digest and absorb nutrients from our diet. Bacteria that live on the skin help to activate the immune system and prevent harmful microorganisms from invading the area.

Bacteria are also vital for the global ecosystem’s nutrient recycling because they are major decomposers.

Bacteria have a distinct cell wall composition as well as a distinct rRNA type. They are divided into five major groups:

• Proteobacteria: E.coli, Salmonella, Heliobacter pylori, and Vibrio bacteria are all members of this phylum.
• Cyanobacteria: Photosynthesis is possible for these microorganisms. Because of their colour, they are sometimes known as blue-green algae.
• Firmicutes: Clostridium, Bacillus, and mycoplasmas are examples of gram-positive bacteria (bacteria without cell walls.)
• Chlamydiae: These parasitic bacteria reproduce within the cells of their hosts. Chlamydia trachomatis (which causes chlamydia STD) and Chlamydophila pneumonia are two organisms (that cause pneumonia.)
• Spirochetes: The twisting action of these corkscrew-shaped bacteria is remarkable. Borrelia burgdorferi (which causes Lyme disease) and Treponema pallidum are two examples (cause syphilis.)

Eukarya Domain

Eukaryotes or organisms with a membrane-bound nucleus are included in the Eukarya domain.

This domain is further subdivided into the kingdoms

• Protista
• Fungi
• Plantae
• Animalia

Eukaryotes have a different rRNA than bacteria and archaea. Plants and fungi have cell walls that are distinct from bacteria in composition. Antibacterial antibiotics are often resistant to eukaryotic cells.

Protists, fungi, plants, and animals are all members of this domain. Algae, amoeba, fungi, moulds, yeast, ferns, mosses, blooming plants, sponges, insects, and mammals are just a few examples.

Comparison of Classification Systems

The classification systems for creatures evolve as discoveries are discovered. Only two kingdoms were acknowledged in the early systems (plant and animal.) The existing Three Domain System is the finest organising system we have at the moment, but if new knowledge becomes available, a new system for classifying organisms may be established in the future.

Here’s how the Five Kingdom System compares to the Six Kingdoms Three Domain System:

Five kingdom system:

• Monera
• Protista
• Fungi
• Plantae
• Animalia

Conclusion

The page contains all of the critical information that a student needs to know about the Eukarya Domain.

1. The evolutionary links between organisms are referred to as phylogeny.
2. 2. Organisms are classified into one of three domains based on differences in ribosomal RNA (rRNA) nucleotide sequences, cell membrane lipid structure, and antibiotic sensitivity.
3. The Archaea, Bacteria, and Eukarya are the three domains.
4. 4. Archaea and Bacteria classify species with prokaryotic cells, while Eukarya classifies organisms with eukaryotic cells.
5. Horizontal gene transfer, or the transfer of DNA to an organism that is not its progeny, is how bacteria transfer genes to other microbes.