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A second merger, 1.6 billion years ago, added chloroplasts, creating the green plants. [31] Eukaryotic cells were created some 2.2 billion years ago in a process called eukaryogenesis. This is widely agreed to have involved symbiogenesis, in which archaea and bacteria came together to create the first eukaryotic common ancestor.
B lymphocytes are the cells of the immune system that make antibodies to invading pathogens like viruses. They form memory cells that remember the same pathogen for faster antibody production in future infections. In immunology, a memory B cell (MBC) is a type of B lymphocyte that forms part of the adaptive immune system.
Just as a map is a scaled approximation of true geography, a phylogenetic tree is an approximation of the true complete evolutionary relationships. For example, in a full tree of life, the entire clade of animals can be collapsed to a single branch of the tree. However, this is merely a limitation of rendering space.
Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. [1] [2] All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and functioning of organisms. [3] Cell biology is the study of the structural and functional ...
[1] After the inflammatory immune response to danger-associated antigen, some of the antigen-specific T cells and B cells persist in the body and become long-living memory T and B cells. After the second encounter with the same antigen, they recognize the antigen and mount a faster and more robust response.
The centrosome is copied only once per cell cycle, so that each daughter cell inherits one centrosome, containing two structures called centrioles. The centrosome replicates during the S phase of the cell cycle. During the prophase in the process of cell division called mitosis, the centrosomes migrate to opposite poles of the cell. The mitotic ...
Two or more atoms is a molecule, like a dioxide. Many small molecules may combine in a chemical reaction to make up a macromolecule, such as a phospholipid. Multiple macromolecules form a cell, like a club cell. A group of cells functioning together as a tissue, for example, Epithelial tissue. Different tissues make up an organ, like a lung.
Also narrow. A land or water passage that is confined or restricted by its narrow breadth, often a strait or a water gap. nation A stable community of people formed on the basis of a common geographic territory, language, economy, ethnicity, or psychological make-up as manifested in a common culture. national mapping agency A governmental agency which manages, produces, and publishes ...