Synopsis
▫ Life’s diversity is a testament to the ease and versatility of evolutionary adaptation.
Biological Classification
▫ In extensively cataloging species by physical characteristics, Carl Linnaeus is considered the father of biological taxonomy. More recent efforts are grounded in genetic research.
▫ 8 major biological taxonomic ranks are generally recognized: life, domain, kingdom, phylum, class, order, family, genus, and species. Organisms are scientifically termed by genus and species.
▫ Zoology and botany organizations have their own schemas, including subdivisions, such as tribe. Thus, binomial nomenclature (naming species) is mired by lack of consensus. Numerous naming inconsistencies exist between different biology organizations.
▫ In 1977, Carl Woese proposed 3 domains: archaea, bacteria, and eukaryote – a categorization which is generally accepted. More recent evidence shows that eukaryotes descended from archaea. Moreover, viruses have been universally and inscrutably ignored as life forms. Hence, the proper domains of life are: viruses, archaea, and bacteria. A eukaryote is an archaeon hosting a bacterial endosymbiont.
Microbes
▫ Microbes are microscopic life: comprising a diverse variety of unicellular and multicellular organisms, including viruses, bacteria, archaea, fungi, protists, microscope plants (green algae), and animals, such as plankton and planarian. Though most microbes are prokaryotes, many are eukaryotes, including amoeba.
▫ Microbes are by far the most abundant life on Earth, and among the most diverse.
Many microbes can tolerate conditions that larger species can▫ not, tolerating thermal and/or chemical adversity. Microbes may even be space travelers.
▫ Microbes are eminently sociable. Biofilms are a common cooperative association among a species population.
▫ Quorum-sensing – decision-making among decentralized groups coordinating their behavior – is ubiquitous with biofilms. Quorum-sensing also used with social animals, including eusocial insects and schools of fish.
▫ Many microbes have an intimate symbiotic relationship with other living beings, either beneficial, commensal, or pathogenic. Relationships vary between a microbe and its host, by species or even by individual population.
Viruses
▫ Viruses evolved into undisputed masters of genetic manipulation and genomic architecture. Viruses invented DNA and passed it on to other early life.
Viruses are almost miraculously devious. They’re just bundles of protein and nucleic acid, and they’re able to get into cells and run the show. ~ American virologist Eric Freed
▫ Viruses infect all other life forms. They hijack the cellular machinery of their host to replicate.
▫ A worldwide community, and a major player in the global ecosystem, viruses are the most abundant and diverse life. They are everywhere other life exists: in the air, soil, water, and sea.
▫ During infection, viruses recognize specific host cell molecules. A virus may be patient in activating itself.
▫ Viruses kill only because they have not evolutionarily matured to know better. Learning to infect and run cellular machinery without terminating the host is a fine art. Some ancient viruses, such as herpes, infect without grievously harming its host. Other viruses benefit their hosts.
▫ Some viruses manipulate host behavior to improve their chances of spreading through a population. Herpes, for instance, make their hosts more sexually receptive.
Bacteria
▫ Along with archaea and viruses, bacteria had Earth to themselves for 3 billion years; plenty of time to diversify and settle into every possible niche, which they have.
▫ Bacteria come in a considerable diversity of shapes and sizes, with various means for locomotion.
▫ Bacteria have self-awareness. Bacteria communicate among themselves and operate as a community.
▫ Bacteria rapidly adapt by selectively incorporating found or shared genetic material (horizontal gene transfer).
Multicellular Life
▫ The advantage of multicellular organisms is specialization: differentiated cells that perform different tasks. Specialization requires coordination. Coordination involves communication, and, except for plants, cells moving about.
▫ Every complex organism is a cellular colony, living symbiotically with microbes as a symbiorg. All plants and animals comprise a community: a host living in concert with a microbiome. The quality of the microbiome determines the health of its host’s life.
Fungi
▫ There are over a million different fungi, both microscopic and macroscopic.
▫ Single-celled fungi that live solitary lives are yeast, while colonial unicellular fungi are molds.
▫ Fungi are both hardy and prolific. They are one of the most abundant soil microbes.
▫ All fungi are heterotrophic. Most are saprovores; others, pathogens. A few are predatory. Some fungi are mutualists with plants and animals.
▫ Macroscopic fungi, such as mushrooms, are typically terrestrial. Only a few are aquatic.
▫ A lichen is a composite collaboration of fungus and photosynthetic microbes. Lichens are long-lived, slow growers. This permits patience in their competition with plants for access to sunlight.
