The factors that most directly affect blood flow are blood pressure, blood volume, resistance and activity level.
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There are all sorts of ways to reconstruct the history of life on Earth. Pinning down when specific events occurred is often tricky, though. For this, biologists depend mainly on dating the rocks in which fossils are found, and by looking at the “molecular clocks” in the DNA of living organisms.
There are problems with each of these methods. The fossil record is like a movie with most of the frames cut out. Because it is so incomplete, it can be difficult to establish exactly when particular evolutionary changes happened.
Modern genetics allows scientists to measure how different species are from each other at a molecular level, and thus to estimate how much time has passed since a single lineage split into different species. Confounding factors rack up for species that are very distantly related, making the earlier dates more uncertain.
These difficulties mean that the dates in the timeline should be taken as approximate. As a general rule, they become more uncertain the further back along the geological timescale we look. Dates that are very uncertain are marked with a question mark.
Answer:
Glomerular Hydrostatic pressure
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Explanation:
The basic function of the kidney is the formation of urine for elimination through the urinary excretory system. Two different processes determine this formation: the filtration of fluid through the glomerular capillaries into Bowman's space and the modification of the volume and composition of the glomerular filtrate in the renal tubules. The fluid passes from the glomerular capillaries to Bowman's capsule due to the existence of a pressure gradient between these two areas. This process is favored by two structural characteristics that make renal corpuscles particularly effective filtration membranes: glomerular capillaries have a much higher number of pores than other capillaries, and the efferent arteriole has a smaller diameter than the afferent arteriole, causing greater resistance to outflow of blood flow from the glomerulus and increasing glomerular hydrostatic pressure. Increased glomerular hydrostatic pressure (due to increased blood flow through the glomerulus) increases filtration, while increases in Bowman's hydrostatic pressure or urinary space (which remains constant, unless there is disease at that level, usually due to fibrosis) and plasma P. oncotic (determined by proteins, which tend to "drag" plasma into the glomerulus) decrease filtering. Resulting in a filtering pressure of 10 mmHg.
Answer:
Natural selection, the keystone of evolution, can switch direction in a matter of months, a novel experiment on lizards reveals.
Answer:
An organism's DNA affects how it looks, how it behaves, and its physiology. So a change in an organism's DNA can cause changes in all aspects of its life. Mutations are essential to evolution; they are the raw material of genetic variation. Without mutation, evolution could not occur.
Explanation:
