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Devolution, de-evolution, or backward evolution (not to be confused with dysgenics) is the notion that species can revert to supposedly more primitive forms over time. The concept relates to the idea that evolution has a divine purpose and is thus progressive (orthogenesis), for example that feet might be better than hooves, or lungs than gills.
In cell biology, a biological pathway is a series of interactions among molecules in a cell that leads to a certain product or a change in the cell. Such a pathway can trigger the assembly of new molecules, such as a fat or protein. Pathways can also turn genes on and off, or spur a cell to move. [1]
[3] Gould argues that the definition of Evolution to professional biologists is "adaptation to changing environments", not progress, and that the composition of life on the planet is rather a "copiously branching bush, continually pruned by the grim reaper of extinction, not a ladder of predictable progress."
12. “It’s hard to be clear about who you are when you are carrying around a bunch of baggage from the past.” - Angelina Jolie 13. “We would do ourselves a tremendous favor by letting go of ...
Passive versus active trends in complexity. Organisms at the beginning are red. Numbers are shown by height with time moving up in a series. If evolution possessed an active trend toward complexity (orthogenesis), as was widely believed in the 19th century, [12] then we would expect to see an active trend of increase over time in the most common value of complexity among organisms.
Introgression is an important source of genetic variation in natural populations and may contribute to adaptation and even adaptive radiation. [7] It can occur across hybrid zones due to chance, selection or hybrid zone movement. [8]
Evolution is the change in the heritable characteristics of biological populations over successive generations. [1] [2] It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. [3]
Cell migration is a central process in the development and maintenance of multicellular organisms.Tissue formation during embryonic development, wound healing and immune responses all require the orchestrated movement of cells in particular directions to specific locations.