Secondary Endosymbiosis

The leaves of a plant are the main photosynthetic organs and are involved in gas exchange and water transportation throughout a plant (Evans et al, 17). A leaf typically consists of an upper and lower epidermis, the mesophyll cells, veins, guard cells and stomata. The mesophyll cells contains spongey cells which have large gaps between each cell to allow oxygen and carbon dioxide circulation. The mesophyll cells contain palisade cells, which are located beneath the upper epidermis. The palisade cells contain many chloroplasts, which are green organelles. Located in the internal layers of chloroplasts is the pigment chlorophyll which is involved in trapping the light energy in photosynthesis (Evans et al, 17).

When life arose on Earth about 4 billion years ago, the first types of cells to evolve were prokaryotic cells. For approximately 2 billion years, prokaryotic-type cells were the only form of life on Earth. The oldest known sedimentary rocks found in Greenland are about 3.8 billion years old. The oldest known fossils are prokaryotic cells, 3.5 billion years in age, found in Western Australia and South Africa. The nature of these fossils, and the chemical composition of the rocks in which they are found, indicates that these first cells made use of simple chemical reactions to produce energy for their metabolism and growth. Eukaryotic cells evolved into being between 1.5 and 2 billion years ago. Eukaryotic cells appear to have arisen from prokaryotic cells, specifically out of the archaea. Indeed, there are many similarities in molecular biology of contemporary archaea and eukaryotes. However, the origin of the eukaryotic organelles, specifically chloroplasts and mitochondria, is explained by evolutionary associations between primitive nucleated cells and certain respiratory and photosynthetic bacteria, which led to the development of these organelles and the associated explosion of eukaryotic diversity. Today Prokaryotes

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

Microbes are necessary for life to exist. "Without microbes, decomposition cannot take place" (Chivukula, 2015). Photosynthesis and decomposition are vital to the ecosystem to ensure that life can exist, and both use microbial activity to provide energy and nutrients. Photosynthesis must take place to convert light into chemical energy for organic material. Decomposition uses microbial activity to breakdown

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.

Wischusen, William, Jolissaint, Ann, Reiland, Jane, and Pomarico, Steven. 2012. Biology 1208/1209: Biological Laboratories for Science Majors. Hayden McNeil, Plymouth,

Prior to the development of DNA technology and the sequencing of organismal genomes, Charles Darwin suggested that the “tree” of life can be traced back to a single root (Koonin and Wolf, 2012). While Darwin’s theory was primitive, it laid the groundwork for the phylogenetic trees that are currently studied in science classrooms around the world. The three-domain tree, containing Eukarya, Archea, and Bacteria, soon became too simplistic due to the realization that some bacteria possessed the ability to exchange genetic information by horizontal gene transfer (Koonin and Wolf, 2012).

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)

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.

The experiment focused on the fact that certain organisms are affected by light and will move depending on whether or not light is present. There were four organisms that were placed in a tray that was half lit and half dark. Euglena is a photosynthetic organism that uses light as a vital part of its existence. Euglena showed a significant preference for the light side over the dark side (X2 = 529, p<0.01) (Table 5). Phototaxis is an organism’s movement as a result of light (Urry et al. 2014). If an organism is attracted to light it is an example of positive phototaxis

Prokaryotes are ubiquitous, successfully adapting to diverse environments as well as developing symbiotic relationships with host organisms (Lengeler, Drews, & Schlegel, 1999). Prokaryotes may have both autotrophic and heterotrophic characteristics. A cyanobacteria is photosynthetic, commonly called blue-green algae, and may produce toxins (Crayton, 1993). Bacteria are most commonly associated in the general

Microscopic  organisms  known  as  cyanobacteria are  interesting  for  the  following  reasons: [SELECT  ALL  THAT  APPLY] Select  one  or  more: A.  Oxygen  produced  by  their  photosynthesis is  thought  to  be  responsible  for  the  "great oxygenation  event"  about  2.3  billion  years ago.   B.  The  methane  they  produce  is  a greenhouse  gas  that  could  have  helped warm  the  early  Earth,  helping  to  resolve  the Early-­faint-­Sun  paradox. C.  The  chloroplasts  that  carry  out photosynthesis  in  green  plants  are evolutionary  descendents  of  early cyanobacteria.   D.  They  are  known  to  be  the  earliest  forms of  life  on  Earth.

In order for growth to occur microorganisms need to obtain energy. One of those ways is by either the use of oxygen or not using oxygen. Microorganisms that require oxygen are obligate aerobes. It is essential for

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

The trophozoite of N fowleri consists of an amoeba surrounded by a two-layer membrane. The cytoplasm contains free and bound ribosomes, as well as membrane-bound organelles. A smooth endoplasmic reticulum, a Golgi-like structure, mitochondria, vacuoles, and nucleus-containing nuclear envelope are present. Microfilaments create a supportive cytoskeleton. The N fowleri flagellate is pear-shaped. The cytoplasm has fewer vacuoles, and the components of a flagellar apparatus (flagellum, basal body, rootlet) are present. The spherical cyst is enclosed in a mucous-sealed porous cell wall. The cytoplasm contains enlarged mitochondria and the nucleolus is less pronounced.