Lecture 26 Flashcards
The science of identifying, naming, and organizing living organisms into systems of classification
Taxonomy
Why does it matter whether an organism is classified as a protozoan or a fungus?
Because cells are constructed in similar ways, it is likely that all cells have descended from a common ancestral cell, the last common universal ancestor of all life ________ .
LUCA
First two billion years of Earth’s existance, the environment was ______ the atmosphere was comprised of N2, CH4, CO2. So the only life found was anaerobic microbes like methanognes who make methane and other __________ , which use inorganic chemicals like _______, _______ , ______ for energy and use CO2 for Carbon.
atmosphere was anoxic
chemoautotrophs
inorganic chemicals like ammonia, nitrite, iron
________ microorganisms, bacteria that were capable of __________ photosynthesis where light energy is captured and stored as ATP without oxygen production occurred within a __________ years of the formation of earth. What evolved from these microbes _________ years later, and slowly began to oxygenate the atmosphere?
Phototrophic
anoxygenic
within a ~billion years of the formation of earth
cyanobacteria evolved a billion years later
Plants and animals have only existed for how long? What percentage of life on earth’s history was exclusively microbial?
About half a billion years
80%
Recent phylogenetic data does not support the five kingdom system. DNA-based phylogenetic analysis (the study of the evolutionary history of organisms) revealed that the 5 kingdoms do not represent 5 primary evolutionary lines. Instead, cellular life on earth evolved along _______ primary lineages called what? What are these three domains?
three primary lineages called domains:
bacteria and archaea which are exclusively microbial and have no membrane enclosed nucleus
and eukaryotes, which is primarily microbial (unicellular) and includes all the other original five kingdoms except bacteria
Classification between the three domains is based on what?
based on differences in ribosomal RNA (rRNA), the 3 domains also differ in membrane lipid structure, transfer RNA, and sensitivity to antibiotics
What does domain archaea include? Also, where do they live?
prokaryotics that do not have peptidoglycan in their cell walls. They often live in extreme environments and carry out unusual metabolic processes.
Theory that suggests that mitochondria and chloroplasts descended from bacteria that somehow survived endocytosis by another cell, and became incorporated into the cytoplasm. What’s the advantage here? When did this develop? Ex. of a current symbiotic relationship like this?
endosymbiosis
The ability of these bacteria to conduct respiration in host cells that had relied on glycolysis and fermentation would have provided a considerable evolutionary advantage.
1.5-2 billion years ago
Cyanophora paradoxa
Main differences to note between Archaea, Bacteria, and Eukaryotes
Archaea have pseudomeurin in their cell walls instead of peptidoglycan…resembles peptidoglycan in appearance, structure, and function, however, lysozyme is ineffective against these wall types.
The basic components are Nacetylglucosamine and N-acetyltalosaminuronic acid (peptidoglycan has Nacetylmuramic acid instead), which are linked by β-1,3-glycosidic bonds. Lysozyme, a host defense mechanism, is ineffective against organisms with pseudomurein cell walls. Lysozyme can break β-1,4-glycosidic bonds to degrade peptidoglycan; however, pseudomurein has β-1,3-glycosidic bonds, rendering lysozyme useless.
Modern characterization is based on the information carried in the genes i.e. the genome. This genotypic information can also tell us something about the evolution of the organism. In other words phylogenetics. These similarities among organisms are due to relatedness, all are related through evolution. Systematics, or phylogeny, is the study of evolutionary history of organisms., the hierarchy of taxa reflects evolutionary, or phylogenetic relationships. We will talk more about the study of phylogeny and methods of classification in the next lecture. Phylogentic approach
Historically, prokaryotes were classified on the basis of their phenotype (morphology, staining reactions, biochemistry, substrates/products, antigens etc). In other words a phenotypic characterization is based on the information carried in the products of the genes. These classification systems were artificial. Phenotypic approach
