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Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. According to modern evolutionary biology, all living beings could be descendants of a unique ancestor commonly referred to as the last universal common ancestor (LUCA) of all life on Earth. [1] [2] [3] [4]
The remaining elements found in living things are primarily metals that play a role in determining protein structure. Examples include iron, essential to hemoglobin; and magnesium, essential to chlorophyll. Some elements are essential only to certain taxonomic groups of organisms, particularly the prokaryotes.
The polar bear was given its common name by Thomas Pennant in A Synopsis of Quadrupeds (1771). It was known as the "white bear" in Europe between the 13th and 18th centuries, as well as "ice bear", "sea bear" and "Greenland bear". The Norse referred to it as isbjørn ' ice bear ' and hvitebjørn ' white bear '. The bear is called nanook by the ...
The chirality of DNA, RNA, and amino acids is conserved across all known life. As there is no functional advantage to right- or left-handed molecular chirality, the simplest hypothesis is that the choice was made randomly by early organisms and passed on to all extant life through common descent.
Graphic representation of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. CHNOPS and CHON are mnemonic acronyms for the most common elements in living organisms. . "CHON" stands for carbon, hydrogen, oxygen, and nitrogen, which together make up more than 95 percent of the mass of biological system
Parasitism is a relationship between species, where one organism, the parasite, lives on or in another organism, the host, causing it some harm, and is adapted structurally to this way of life. [20] The parasite either feeds on the host, or, in the case of intestinal parasites, consumes some of its food.
Lipids (oleaginous) are chiefly fatty acid esters, and are the basic building blocks of biological membranes. Another biological role is energy storage (e.g., triglycerides). Most lipids consist of a polar or hydrophilic head (typically glycerol) and one to three non polar or hydrophobic fatty acid tails, and therefore they are amphiphilic.
Ursus is a genus in the family Ursidae that includes the widely distributed brown bear, [3] the polar bear, [4] the American black bear, and the Asian black bear. The name is derived from the Latin ursus, meaning bear. [5] [6]