Key Takeaways Key Points. The classification system is constantly changing with the advancement of technology. The most recent classification system includes five kingdoms that are further split into phylum, class, order, family, genus, and species. Microorganisms are assigned a scientific name using binomial nomenclature.Key Terms. DNA fingerprinting: A method of isolating and mapping sequences of a cell’s DNA to identify it.Life on Earth is famous for its diversity.
Throughout the world we can find many millions of different forms of life. Biologic classification helps identify each form according to common properties (similarities) using a set of rules and an estimate as to how closely related it is to a common ancestor (evolutionary relationship) in a way to create an order. By learning to recognize certain patterns and classify them into specific groups, biologists are better able to understand the relationships that exist among a variety of living forms that inhabit the planet. Classification of E.
Coli: Domain: Bacteria, Kingdom: Eubacteria, Phylum: Proteobacteria, Class: Gammaproteobacteria, Order: Enterobacteriales, Family: Enterobacteriaceae, Genus: Escherichia, Species: E. Coli.The first, largest, and most inclusive group under which organisms are classified is called a domain and has three subgroups: bacteria, archae, and eukarya. This first group defines whether an organism is a prokaryote or a eukaryote. The domain was proposed by the microbiologist and physicist Carl Woese in 1978 and is based on identifying similarities in ribosomal RNA sequences of microorganisms.The second largest group is called a kingdom. Five major kingdoms have been described and include prokaryota (e.g.
Archae and bacteria), protoctista (e.g. Protozoa and algae), fungi, plantae, and animalia. A kingdom is further split into phylum or division, class, order, family, genus, and species, which is the smallest group.The science of classifying organisms is called taxonomy and the groups making up the classification hierarchy are called taxa. Taxonomy consists of classifying new organisms or reclassifying existing ones. Microorganisms are scientifically recognized using a binomial nomenclature using two words that refer to the genus and the species.
The names assigned to microorganisms are in Latin. The first letter of the genus name is always capitalized. Classification of microorganisms has been largely aided by studies of fossils and recently by DNA sequencing. Methods of classifications are constantly changing. The most widely employed methods for classifying microbes are morphological characteristics, differential staining, biochemical testing, DNA fingerprinting or DNA base composition, polymerase chain reaction, and DNA chips.
Key Takeaways Key Points. The proposed mechanisms for the origin of life on Earth include endosymbiosis and panspermia. Both are debatable theories. In these two theories, bacteria and extremophile archaea are thought to have initiated an oxygenated atmosphere creating new forms of life. Evolutionary processes over billions of years gave rise to the biodiversity of life on Earth.Key Terms. endosymbiosis: A condition of living within the body or cells of another organism. panspermia: The hypothesis that microorganisms may transmit life from outer space to habitable bodies; or the process of such transmission.Scientific evidence suggests that life began on Earth some 3.5 billion years ago.
Since then, life has evolved into a wide variety of forms, which biologists have classified into a hierarchy of taxa. Some of the oldest cells on Earth are single-cell organisms called archaea and bacteria. Fossil records indicate that mounds of bacteria once covered young Earth. Some began making their own food using carbon dioxide in the atmosphere and energy they harvested from the sun. This process (called photosynthesis) produced enough oxygen to change Earth’s atmosphere.Soon afterward, new oxygen-breathing life forms came onto the scene.
With a population of increasingly diverse bacterial life, the stage was set for more life to form. There is compelling evidence that mitochondria and chloroplasts were once primitive bacterial cells. This evidence is described in the endosymbiotic theory. Symbiosis occurs when two different species benefit from living and working together. When one organism actually lives inside the other it’s called endosymbiosis. The endosymbiotic theory describes how a large host cell and ingested bacteria could easily become dependent on one another for survival, resulting in a permanent relationship.Over millions of years of evolution, mitochondria and chloroplasts have become more specialized and today they cannot live outside the cell. Mitochondria and chloroplasts have striking similarities to bacteria cells.
They have their own DNA, which is separate from the DNA found in the nucleus of the cell. And both organelles use their DNA to produce many proteins and enzymes required for their function. A double membrane surrounding both mitochondria and chloroplasts is further evidence that each was ingested by a primitive host. The two organelles also reproduce like bacteria, replicating their own DNA and directing their own division.Mitochondrial DNA (mtDNA) has a unique pattern of inheritance. It is passed down directly from mother to child, and it accumulates changes much more slowly than other types of DNA.
Because of its unique characteristics, mtDNA has provided important clues about evolutionary history. For example, differences in mtDNA are examined to estimate how closely related one species is to another. Extremophiles: Photosynthetic fossilized cyanobacteria in a billion year old rock formation of Glacier National Park, Montana, USA.Conditions on Earth 4 billion years ago were very different than they are today.
The atmosphere lacked oxygen, and an ozone layer did not yet protect Earth from harmful radiation. Heavy rains, lightning, and volcanic activity were common.
Yet the earliest cells originated in this extreme environment. Extremophiles archaea still thrive in extreme habitats. Astrobiologists are now using archaea to study the origins of life on Earth and other planets.
Because archaea inhabit places previously considered incompatible with life, they may provide clues that will improve our ability to detect extraterrestrial life. Interestingly, current research suggests archaea may be capable of space travel by meteorite. Such an event termed panspermia could have seeded life on Earth or elsewhere.The presence of archaea and bacteria changed Earth dramatically. They helped establish a stable atmosphere and produced oxygen in such quantities that eventually life forms could evolve that needed oxygen.
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The new atmospheric conditions calmed the weather so that the extremes were less severe. Life had created the conditions for new life to be formed. This process is one of the great wonders of nature. Microorganisms in a hot environment: Algae growing in a hot pool in New Zealand.Not every microbe can survive in all habitats, though. Each type of microbe has evolved to live within a narrow range of conditions. Although the vast majority of microbial diversity remains undetermined, it is globally understood that the effects of microorganisms on their environment can be beneficial. The beneficial effects of microbes derive from their metabolic activities in the environment, their associations with plants and animals, and from their use in food production and biotechnological processes.In turn, the environment and the recent temperature anomalies play a crucial role in driving changes to the microbial communities.
For instance, the assemblage of microbes that exists on the surface of seawater is thought to have undergone tremendous change with respect to composition, abundance, diversity, and virulence as a result of climate-driving sea surface warming.For microbiologists, it is critical to study microbial adaptation to different environments and their function in those environments to understand global microbial diversity, ecology, and evolution. They rely on specific physical and chemical factors such as measuring temperature, pH, and salinity within a certain geography to formulate a comparison among microbial communities and the environment different species can tolerate. Researchers collect samples from geographical areas with different environmental conditions and between seasons to determine how dispersal patterns shape microbial communities and understand why organisms live where they do. As such, microbial communities from coastal and open oceans, polar regions, rivers, lakes, soils, atmosphere, and the human body can be tested. These samplings create a starting point to understand how the abundance and composition of microbial communities correlate with climatic perturbations, interact to effect ecosystem processes, and influence human health. Interfering with natural microbial biomass disrupts the balance of nature and the ecosystem and leads to loss of biodiversity.
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