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The evolution of biological complexity is one important outcome of the process of evolution. [1] Evolution has produced some remarkably complex organisms – although the actual level of complexity is very hard to define or measure accurately in biology, with properties such as gene content, the number of cell types or morphology all proposed as possible metrics.
A multicellular organism is an organism that consists of more than one cell, unlike unicellular organisms. [1] All species of animals , land plants and most fungi are multicellular, as are many algae , whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium .
A species complex typically forms a monophyletic group that has diversified rather recently, as is shown by the short branches between the species A–E (blue box) in this phylogenetic tree. Species forming a complex have typically diverged very recently from each other, which sometimes allows the retracing of the process of speciation .
Unicellular organisms can move in order to find food or escape predators. Common mechanisms of motion include flagella and cilia. In multicellular organisms, cells can move during processes such as wound healing, the immune response and cancer metastasis. For example, in wound healing in animals, white blood cells move to the wound site to kill ...
Differentiation happens multiple times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover.
A biological system is a complex network which connects several biologically relevant entities. Biological organization spans several scales and are determined based different structures depending on what the system is. [1] Examples of biological systems at the macro scale are populations of organisms.
LUCA likely inhabited an anaerobic hydrothermal vent setting in a geochemically active environment. It was evidently already a complex organism, and must have had precursors; it was not the first living thing. [10] [204] The physiology of LUCA has been in dispute. [205] [206] [207] Previous research identified 60 proteins common to all life. [208]
Evolution is an inevitable result of imperfectly copying, self-replicating organisms reproducing over billions of years under the selective pressure of the environment. The outcome of evolution is not a perfectly designed organism. The end products of natural selection are organisms that are adapted to their present environments.