A Survey of Eukaryotic Cells and Microorganisms

Currently, there are two major competing theories for the endosymbiotic origin of eukaryotic cells. The first theory claims that the eukaryotic cell is a combination of an archaeon with a

Ribosomes then started copy themselves into cell-like structure with a thin membrane and cytoplasm. Eventually, cells starting storing DNA. Lateral transfer diversified the cells genetic makeup. From this community of cells came the three domains, known as bacteria, eukaryotes, and archaea. Bacteria and archaea are together called

Mode of reproduction is asexual in Prokaryotes and both asexual and sexual in Eukaryotes. Extracellular structures present in Prokaryotes with pepidoglycocan. Eukaryotes do not have peptidoglyocan. They have cellulose and chitin. Both are present in plants and fungi.

While there are many different hypotheses to the evolution of eukaryotic organisms, two in particular have very plausible yet different approaches to this complex question. The Margulis hypothesis of the evolution of eukaryotic organisms focuses on the idea of endosymbiosis, which is the close interaction or association between different species with one of those species being inhabited within the other. Margulis hypothesized that free-living bacteria that were capable of energy production and photosynthesis where engulfed by a free-living cell. The cell and the bacteria now inside of it formed a mutualistic and symbiotic relationship with the bacteria providing the cell with the energy and food it needs while remaining protected inside the cell. Through evolutionary time this symbiotic relationship would grow so strong that the two individuals would not be able to function alone and thus the eukaryote would arise. The idea was supported by the fact that mitochondria and chloroplasts both have unique genomes that resemble the single circular chromosomes found within bacteria.

Prokaryotic cells only really refer to bacteria, while eukaryotic cells include animals, plants, protists, and fungi. The prokaryotes do not have a nucleus or any membrane-covered organelles, but eukaryotes do. Instead, the prokaryotes have a nucleoid because they have a smaller, circular DNA genome, whereas eukaryotic

In the beginning, on planet Earth, there were single cells (unicellular organism). Millions of years later the Earth was inhabited by plants, animals, fungi, and algae all multicellular organisms (multiple cells that work together). These new multicellular organisms operate cooperatively to consume energy, survive, and reproduce all astonishing evolution achievements since unicellular organisms. But, How did multicellularity evolve and arise long ago? The origins of multicellularity are one of the most interesting topics and evolutionary innovations in biology. Based on scientific research three chosen hypotheses have been established to solve this question.

Prokaryotes were defined in 1962 by Stanier and van Niel as “anucleate cells, without membrane enclosed organelles of respiration or photosynthesis, divided by fission not mitosis, and used peptidoglycan to strengthen their walls” (Mayr, 1998). This definition and the creation of the prokaryote/eukaryote dichotomy served to highlight the diversity and significance of the single-celled organisms previously labelled ‘Monera’ and relegated to the same kingdom status as the distinct groups of plants animals and fungi (Sapp, 2009; Woese, Kandler and

As we all know there are many theories for the evolution of eukaryotic from prokaryotic, but how the prokaryotics came in existence or the beginning of the evolutionary process from one single cell to a complex structure, no one knows for sure, there are only theories for now. Both evolutionists and creationists use evidence to support their theories, but it is difficult to come up with proofs. No one was present as observer when life began, or when the life transformed from single cell prokaryotics to multi cellular eukaryotics neither model of origins can be reproduced in laboratory experiments.

Any organism whose cells contain a nucleus and other structures endowed with with membranes. Any living organism that isn’t my bacteria or archaea Eukaryotic. Animals, plants, fungi, and protists are eukaryotic. All cells have a nucleus, genetic material, plasma membrane and cytoplasm including cytoskeleton. Cells have other membrane bound internal structures names organelles.

Because eukaryote is not perceptible to the naked eye, we tend to neglect them. As a result of this, eukaryote help to furnish the growth of oxygen in the atmosphere, and take care of the decay of organic materials and nutrient cycling, and 3. Polyphyletic also known as algal evolve through separate endosymbiotic occurrence. As a result, this population is identified on the principle of a similar level of structure, and not on evolutionary origins (Plant and Animal

Prokaryote is a single bacterial cell and they are recognized as the earliest form of life. These cells are not complex cells because they do not have a nucleus,

Figure 1 – The Eukaryotic Cell (AQA GCSE Biology, P.86 – Woodward, C. Houghton, T. 2010)

Their structural similarities are the reasoning behind why one might say that they belong to the prokaryotic domain, being structurally very similar, especially on the first glance. The unique properties will be discussed further later in this essay. SIMILARITIES BETWEEN EUKARYOTES AND ARCHAEA Though structurally, prokaryotic cells seem more similar to archaea than eukaryotic cells, yet when one inspects their DNA, similarities between DNA replication, transcription and translation appear. The DNA polymerase in archaea and eukaryotes are not related to any prokaryotic DNA polymerase, suggesting that these two are of common origin. Other components used in DNA replication are similarly only shared between eukaryotes and archaea (y).

Before eukaryotic cells contained organelles and worked symbiotically as one, life consisted of free-living bacteria. Organelles, such as chloroplasts and mitochondria, that are currently found in eukaryotic cells are theorized to have been separate bacteria before the evolutionary success of the eukaryotic cell. Such idea is proven through the endosymbiotic theory. This concept provides an evolutionary origin for the mitochondrion and chloroplast seen in organisms of today. This theory is held together by DNA evidence found within the organelles themselves. The mitochondrion alone contain its own genome enclosed in the form of circular DNA, as well as their own ribosomes and transfer RNA. Similarly, the chloroplasts have their own genome. When compared to their bacterial ancestors, these DNA sequences resemble that of the respective organelles. The DNA sequences of these genes provide clear evidence to the evolutionary success of the eukaryotic cell.

About 2.1 billion years ago, another organism was formed, Eukaryotes. They probably evolve by a process called endosymbiosis, where one prokaryote pairs and ties with another prokaryote. It formed a single-celled organism with organelles, specifically the mitochondria and plastids, which probably evolved from the parasitic prokaryote. By 1.5 billion years ago, we started seeing multi-cellular eukaryotic organisms in the fossil record. The very first would be the Algae. But it wasn’t until 535 million years ago that the Eukaryotes went berserk, known as the Cambrian