Compare And Contrast The Theory Of Endosymbiosis

Mitochondria are small organelles found in eukaryotic cells which respire aerobically. They are responsible for generating energy from food to ‘power the cell’. They contain their own DNA, reproducing by dividing in 2. As they closely resemble bacteria, it gave the idea that they were derived from bacteria (which were engulfed by ancestors of the eukaryotes we know today). This idea has since been confirmed from further investigations, and it is now widely accepted. (Alberts et al., 2010a)

The mitochondria is an organelle of a cell. It works as it was the digestive system, it’s in charge of obtaining the nutrients, then break them down, and finally, all that work is for maintaining the cell full of energy, so they would be as the power plants of the cell. The mitochondria are in charge of creating 90% of the energy that our bodies need so it can sustain life and support our growth. The mitochondria are small organelles that floats all through the cell. Some cells have many, lots of mitochondria, but others just have none; for example, the muscle cells need a lot of energy, so they contain lots of mitochondria, otherwise, neurons don’t need as much. Depending of the quantity of energy that the cell needs, mitochondria could be created.

7. The theory of endosymbiosis says that mitochondria and plastids used to be small prokaryotes living within larger cells. The prokaryotic ancestors of mitochondria and plastids were bacteria engulfed by a larger cell. Because they both benefited from this situation, the bacteria living inside the cell was passed down from generation to generation. The evidence is that mitochondria reproduce and move independently within the cell.

There were two types of bacteria: sulfur-eating bacteria, and cyanobacteria. Sulfur eaters were the predominate kind of bacteria, but died out when cyanobacteria started photosynthesizing and producing oxygen. Oxygen is lethal to sulfur-eating bacteria. This was called the great oxygenation. The sugars produced by photosynthesis would be the base of the modern food chain. The origin of archaea is unknown. Eukaryotes came into play around 1.5 billion years ago.

A more recent evolutionist of the theory is Lynn Margulis, who is famous through her research career that mainly focused on this concept. It was Biologist Lynn Margulis from Boston University who in 1967 began to tell an older view. She suggested that certain prokaryotes had been overtaken by larger more active species. Instead of being digested inside the host cell some victims continued to thrive and grow. The theory of Endosymbiosis describes the origin of chloroplasts and mitochondria and their double membranes. This concept explains the idea that chloroplasts and mitochondria are the results of years of evolution started by endocytosis of bacteria and blue green algae. Based on this theory, blue green algae and bacteria are not

13. Who is largely responsible for proposing the endosymbiosis theory? 
A. Schimper, Wallin, Margulis
B. Lyon, Margulis, Schimper
C. Schimper, Wallin, Barr
D. Barr, Lyon, Margulis

Bacterial symbionts are predominant among organisms that shape the biological world (Hurst 1993, Wernegreen 2004). Some of the bacterial symbionts that have an inordinate influence on the health and evolution of their hosts are those bacteria that live within their symbiotic hosts, so-called endosymbionts. Bacterial endosymbionts are the focus of current research programs by the National Institutes of Health (Human Microbiome Project, http://www.hmpdacc.org/) and the National Science Foundation (The Symbiosis, Defense, and Self-recognition Program).

Since the beginning of the world there has always been one question in common between people around the planet. The question is: ‘how did we come to existence?’. However, the answer is not always the same because everyone has different believes, but according to science eukaryotes came to existence because we evolved from prokaryotic cells. At the beginning of time, the only inhabitants of earth were microbes. Aerobic cellular respiration and oxygenic photosynthesis both play a big role in our evolution.

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.

The theory of Endosymbiosis originated in the early 1900s by the Russian botanist, Konstantin Mereschkowski.1 The Endosymbiont theory states that organelles of eukaryotic cells came from prokaryotic cells that had been swallowed by them and survived by developing a symbiotic relationship, two different entities working together to benefit each other, by living inside the larger cell. Scientists have conducted extensive research and believe that mitochondria, chloroplasts, flagella, and microtubules have all originated from prokaryotes derived from the theory of Endosymbiosis. Many examples of endosymbiotes can be seen all throughout the world. The most common can be seen as unique bacteria living inside the digestive system of many different

Scientists discovered that chloroplasts and mitochondria contain DNA similar to the DNA of certain bacteria, just as Margulis’s theory had predicted. Upon this data, Margulis extended her book and entitled it Symbiosis in Cell Evolution. Margulis then traveled, presenting and defending her theory, and her theory was becoming well accepted by her peers. “Margulis added that flagella and cilia (appendages and protuberances that many microbes use for motility) originated from spiral bacteria called spirochetes (Markov 10).” The second edition of her book, published in 1993, Margulis suggested that “symbiogenesis is a major factor in evolution, leading to the creation of new species via natural selection (Markov

A single-celled eukaryote or protist can carry chlorophyll (it can be an autotrophic, photosynthetic, "alga"), it can eat other organisms (it can be an organotrophic, "protozoan" "animal"), or it may do both.

Endosymbiosis is the theory that eukaryotic cells were formed when a prokaryotic cell ingested some aerobic bacteria. The first step of the evolution of a eukaryotic cell is the infolding of the cellular membrane. This process takes place when the plasma membrane folds inwards and develops an envelope around a smaller prokaryotic cell. Once the smaller cell is engulfed, it becomes dependent upon its host cell. It relies on the host cell for organic molecules and inorganic compounds. However, the host cell also benefits because it has an increased output of ATP for cellular activities and becomes more productive. This ATP comes from the mitochondrion (the aerobe) that is engulfed.

Prokaryotic Cells All living things are made of cells, and cells are the smallest units that can be alive. Life on Earth is classified into five kingdoms, and they each have their own characteristic kind of cell. However the biggest division is between the cells of the prokaryote kingdom (monera, the bacteria) and those of the other four kingdoms (animals, plants, fungi and protoctista), which are all eukaryotic cells. Prokaryotic cells are smaller and simpler than eukaryotic cells, and do not have a nucleus. Prokaryotic means 'pre-nucleus' and eukaryotic means 'true nucleus'.

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