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Echinocyte (from the Greek word echinos, meaning 'hedgehog' or 'sea urchin'), in human biology and medicine, refers to a form of red blood cell that has an abnormal cell membrane characterized by many small, evenly spaced thorny projections. [1] [2] A more common term for these cells is burr cells.
Acanthocyte-like cells may be found in hypothyroidism, after splenectomy, and in myelodysplasia. [12] Acanthocytes should be distinguished from echinocytes, which are also called 'burr cells', which although crenated are dissimilar in that they have multiple, small, projecting spiculations at regular intervals on the cell membrane.
The tree of life or universal tree of life is a metaphor, conceptual model, and research tool used to explore the evolution of life and describe the relationships between organisms, both living and extinct, as described in a famous passage in Charles Darwin's On the Origin of Species (1859). [1]
The initial development of the cell marked the passage from prebiotic chemistry to partitioned units resembling modern cells. The final transition to living entities that fulfill all the definitions of modern cells depended on the ability to evolve effectively by natural selection. This transition has been called the Darwinian transition.
The generally accepted parts of modern cell theory include: All known living things are made up of one or more cells [13] All living cells arise from pre-existing cells by division. The cell is the fundamental unit of structure and function in all living organisms. [14] The activity of an organism depends on the total activity of independent ...
Prokaryotic cells divide by binary fission, while eukaryotic cells usually undergo a process of nuclear division, called mitosis, followed by division of the cell, called cytokinesis. A diploid cell may also undergo meiosis to produce haploid cells, usually four. Haploid cells serve as gametes in multicellular organisms, fusing to form new ...
Halophiles (organisms that thrive in highly salty environments) and hyperthermophiles (organisms that thrive in extremely hot environments) are examples of Archaea. [1] Archaea are relatively small. They range from 0.1 μm to 15 μm diameter and up to 200 μm long, about the size of bacteria and the mitochondria found in
Chronobiology – field of biology that examines periodic (cyclic) phenomena in living organisms and their adaptation to solar- and lunar-related rhythms. Dendrochronology – study of tree rings, using them to date the exact year they were formed in order to analyze atmospheric conditions during different periods in natural history.