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Under the pre-cell theory (Kandler 1994ff) [6] [7] [8], based on the Iron-Sulfur world hypothesis (metabolism-first scenario), [9] primordial metabolism led to the early diversification of life through the evolution of a multiphenotypical population of pre-cells, defined by Kandler as metabolizing, replicating loose entities exhibiting many of ...
One partner of this symbiosis is proposed to be a bacterial cell, and the other an archaeal cell. It is postulated that this symbiotic partnership progressed via the cellular fusion of the partners to generate a chimeric or hybrid cell with a membrane bound internal structure that was the forerunner of the nucleus.
The fact that the lines remain parallel with the time axis illustrates the unchanging appearance of each of the fossil species depicted on the graph. During each species' existence new species appear at random intervals, each also lasting many hundreds of thousands of years before disappearing without a change in appearance.
All organisms are adapted to their environment to a greater or lesser extent. If the abiotic and biotic factors within a habitat are capable of supporting a particular species in one geographic area, then one might assume that the same species would be found in a similar habitat in a similar geographic area, e.g. in Africa and South America ...
The genome-wide amount of recombination is directly controlled by the number of chromosomes, with one crossover per chromosome or per chromosome arm, depending on the species. [ 31 ] Changes in chromosome number can play a key role in speciation , as differing chromosome numbers can serve as a barrier to reproduction in hybrids.
A protocell is a pre-cell in abiogenesis, and was a contained system consisting of simple biologically relevant molecules like ribozymes, and encapsulated in a simple membrane structure – isolating the entity from the environment and other individuals – thought to consist of simple fatty acids, mineral structures, or rock-pore structures.
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 cells. [15] Energy flow (metabolism and biochemistry) occurs ...
A multipotent cell is one that can differentiate into multiple different, but closely related cell types. [6] Oligopotent cells are more restricted than multipotent, but can still differentiate into a few closely related cell types. [6] Finally, unipotent cells can differentiate into only one cell type, but are capable of self-renewal. [6]