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Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It results in hemostasis , the cessation of blood loss from a damaged vessel, followed by repair.
Small blood clots—say, dime- or nickel-sized on your heaviest flow days—may appear during menstruation and that’s not uncommon, especially if you feel fine otherwise and you’re not ...
It is a theory of biological evolution that seeks to explain aspects of organisms' anatomy and behavior by reference to the way that their life histories—including their reproductive development and behaviors, post-reproductive behaviors, and lifespan (length of time alive)—have been shaped by natural selection.
Hemostasis can be achieved in various other ways if the body cannot do it naturally (or needs help) during surgery or medical treatment. When the body is under shock and stress, hemostasis is harder to achieve. Though natural hemostasis is most desired, having other means of achieving this is vital for survival in many emergency settings.
Evolution provides the field of biology with a solid scientific base. The significance of evolutionary theory is summarised by Theodosius Dobzhansky as "nothing in biology makes sense except in the light of evolution." [78] [79] Nevertheless, the theory of evolution is not static. There is much discussion within the scientific community ...
During this period he used the time he could spare from his other scientific work to slowly refine his ideas and, aware of the intense controversy around transmutation, amass evidence to support them. In September 1854 he began full-time work on writing his book on natural selection. [82] [94] [95]
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
Regardless of the timing of the isthmus closer, biologists can study the species on the Pacific and Caribbean sides in, what has been called, "one of the greatest natural experiments in evolution." [ 244 ] Studies of snapping shrimp in the genus Alpheus have provided direct evidence of allopatric speciation events, [ 246 ] and contributed to ...