The wind is just strong enough to move the sand grains which were sorted by size by the wind. Heavier grains were left in place where as smaller grains were carried away. These grains kept moving till they were concentrated in one place usually up a hill. The grains climb the flat slope on the windward side and then fall off the steep side. The dunes may migrate slowly as this process continues, the grains at the upwind side climb the dune with the help of the wind and then fall down the downwind side.<span>
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Oceanic crust has been forming on Earth for over 4 billion years, all of the sea floor older than <span>about 200 million years. </span>
Answer:
Un nucleótido esta formado por una molécula de azúcar (ribosa en el ARN o desoxirribosa en el ADN) unido a un grupo de fosfato y a una base nitrogenada.
Explanation:
ADN, ARN son polímeros formados por largas cadenas de nucleótidos.
Las bases utilizadas en el ADN son: adenina, citosina, guanina y timina
En ARN, la base uracilo y ocupa el lugar de la timina.
The choices are:
<span>A. Matrix protein
B. Hemagglutinin
C. An ion channel
D. Neuraminidase
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The right answer is B. Hemaglutinin
Explanation:
Haemagglutinins are triangular rods. They allow the attachment of Influenzaviruses on the target cells of the respiratory tree. In the presence of red blood cells, a haemagglutination (liquid medium) is obtained.
<u>About the other components of Influenza virus:</u>Neuraminidase is a mushroom-shaped spike composed of a tetramer consisting of 4 subunits of a single glycoprotein. At 37 ° C, the neuraminidase destroys the bonds (virus - cells) and thus allows the release of neoformed virions in the external environment: it is elution.
The membrane protein M and the protein subunits of the nucleocapsid are antigenic and are the basis of the classification of Influenzavirus types A, B and C. They induce the synthesis of non-protective antibodies fixing the complement.
Answer:
A source from which organisms generally take elements is called exchange pool (option B).
Explanation:
Options for this question are:
- <em>Food web.</em>
- <em>Exchange pool.</em>
- <em>Reservoir.</em>
- <em>Biotic community.</em>
The term exchange pool is related to the biogeochemical cycles that exist in nature, referring to the source from which elements present in the environment become part of living organisms.
<u>Exchange pools are the biotic components</u> -like animals and plants- of an ecosystem, which determine the passage of elements between living beings. An element can remain as a reservoir (abiotic) in the soil, and then be incorporated into the exchange pool.
