Search results
Results from the WOW.Com Content Network
From these conclusions about plants and animals, two of the three tenets of cell theory were postulated. 1. All living organisms are composed of one or more cells 2. The cell is the most basic unit of life. Schleiden's theory of free cell formation through crystallization was refuted in the 1850s by Robert Remak, Rudolf Virchow, and Albert ...
In evolutionary biology, the term cellularization (cellularisation) has been used in theories to explain the evolution of cells, for instance in the pre-cell theory, [1] [2] [3] dealing with the evolution of the first cells on this planet, and in the syncytial theory [4] attempting to explain the origin of Metazoa from unicellular organisms.
Light micrograph of a moss's leaf cells at 400X magnification. The following outline is provided as an overview of and topical guide to cell biology: . Cell biology – A branch of biology that includes study of cells regarding their physiological properties, structure, and function; the organelles they contain; interactions with their environment; and their life cycle, division, and death.
The organism used is decided by the experimenter, based on the hypothesis to be tested. Many generations are required for adaptive mutation to occur, and experimental evolution via mutation is carried out in viruses or unicellular organisms with rapid generation times, such as bacteria and asexual clonal yeast.
The cell cycle is a sequence of activities in which cell organelles are duplicated and subsequently separated into daughter cells with precision. There are major events that happen during a cell cycle. The processes that happen in the cell cycle include cell development, replication and segregation of chromosomes.
DNA replication, or the process of duplicating a cell's genome, [2] always happens when a cell divides through mitosis or binary fission. This occurs during the S phase of the cell cycle. In meiosis, the DNA is replicated only once, while the cell divides twice. DNA replication only occurs before meiosis I.
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
Cell fusion is an important cellular process in which several uninucleate cells (cells with a single nucleus) combine to form a multinucleate cell, known as a syncytium. Cell fusion occurs during differentiation of myoblasts , osteoclasts and trophoblasts , during embryogenesis , and morphogenesis . [ 1 ]