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Non-cellular life, also known as acellular life, is life that exists without a cellular structure for at least part of its life cycle. [1] Historically, most definitions of life postulated that an organism must be composed of one or more cells, [2] but, for some, this is no longer considered necessary, and modern criteria allow for forms of life based on other structural arrangements.
Cell physiology is the biological study of the activities that take place in a cell to keep it alive. The term physiology refers to normal functions in a living organism . [ 1 ] Animal cells , plant cells and microorganism cells show similarities in their functions even though they vary in structure.
Whether or not viruses should be considered as alive is controversial. [ 33 ] [ 34 ] They are most often considered as just gene coding replicators rather than forms of life. [ 35 ] They have been described as "organisms at the edge of life" [ 36 ] because they possess genes , evolve by natural selection, [ 37 ] [ 38 ] and replicate by making ...
Biology is the science of life. It spans multiple levels from biomolecules and cells to organisms and populations. Biology is the scientific study of life. [1] [2] [3] It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field.
The cell is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane; many cells contain organelles, each with a specific function. The term comes from the Latin word cellula meaning 'small room'. Most cells are only visible under a microscope.
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 ...
The mechanism, now ubiquitous in living cells, powers energy conversion in micro-organisms and in the mitochondria of eukaryotes, making it a likely candidate for early life. [ 172 ] [ 173 ] Mitochondria produce adenosine triphosphate (ATP), the energy currency of the cell used to drive cellular processes such as chemical syntheses.
No: No metabolism, so not living, not an organism, say many biologists; [7] but they evolve, their genes collaborating to manipulate the host [18] Unicellular organism: Paramecium: One cell, with organelles e.g. cilia for specific functions: Yes: Inter-cellular (inter-organismal) signalling [22] Swarming protistan: Dictyostelium (cellular slime ...