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Early theory that held that some organisms originated from nonliving material.
Tendency of an organism to suit its environment; one of the major points of Charles Darwin's theory of evolution by natural selection : organisms adapt to their environment. Those organisms best adapted will have a greater chance of surviving and passing their genes on to the next generation.
3. Big bang theory
A model for the evolution of the universe that holds that all matter and energy in the universe were concentrated in one point, which suddenly exploded. Subsequently, matter condensed to form atoms, elements, and eventually galaxies and stars.
The theory that life always arises from previously existing life, and never from things which are not alive (as would be the case for the theory of spontaneous generation).
5. Biogenetic law (recapitulation theory, "ontogeny recapitulates phylogeny")
The theory that " ontogeny recapitulates phylogeny ," which means that one can trace the evolutionary development of a species by studying the development of an individual embryo or young of that species. The theory is still used, especially in paleontology , but has been found to not be strictly true when applied to problems in biology .
6. Cell theory
The theory that all cells come from previously existing cells, and that cells are the most fundamental structural units of all living things.
7. Cell theory
One of the four (or five) unifying concepts in biology. The cell theory states that all living things are composed of at least one cell and that the cell is the fundamental unit of function in all organisms. Corollaries: the chemical composition of all cells is fundamentally alike; all cells arise from preexisting cells through cell division.
8. Chemiosmotic theory (chemiosmotic hypothesis, chemiosmosis)
The theory that the synthesis of ATP (an energy source made and used by the organism) within mitochondria and chloroplast s occurs by way of a proton gradient which forms when electron s are passed through their inner membranes. When protons are then passed through the inner membrane in the opposite direction, energy is released and used to make ATP.
9. Chromosome theory of inheritance
Holds that chromosomes are the cellular components that physically contain genes ; proposed in 1903 by Walter Sutton and Theodore Boveri.
10. Clonal selection
A theory that each B or T lymphocyte , when stimulated by antigen , divides to form a clone of itself.