?
Answer:
An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel.
In California there are two plates - the Pacific Plate and the North American Plate. The Pacific Plate consists of most of the Pacific Ocean floor and the California Coast line. The North American Plate comprises most the North American Continent and parts of the Atlantic Ocean floor. The primary boundary between these two plates is the San Andreas Fault. The San Andreas Fault is more than 650 miles long and extends to depths of at least 10 miles. Many other smaller faults like the Hayward (Northern California) and the San Jacinto (Southern California) branch from and join the San Andreas Fault Zone.
The Pacific Plate grinds northwestward past the North American Plate at a rate of about two inches per year. Parts of the San Andreas Fault system adapt to this movement by constant "creep" resulting in many tiny shocks and a few moderate earth tremors. In other areas where creep is NOT constant, strain can build up for hundreds of years, producing great earthquakes when it finally releases.
a cell wall
B.
a plasma membrane
C.
genetic material
D.
cytoplasm
A border that exists outside the plasma membrane or cell membrane is the cell wall. It only exists in plant cells and is composed of cellulose. In a cell of an animal, it is absent. Thus, option A is correct.
Plant cells have a cell wall that surrounds their plasma membrane and offers tensile strength as well as defense against osmotic and mechanical stress.
Additionally, it enables the development of turgor pressure, or the pressure of the contents of the cell against the cellwall.
Animals lack cell walls, but most other eukaryotes, such as algae, fungus, and plants, as well as most prokaryotes, do (except few bacteria).
Serving as pressure channels, they prevent the cell from over expanding when water enters, which is one of their main roles.
Therefore, cell wall is not present in all organism.
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