A - Viruses cannot survive outside of a host whereas bacteria can.
Answer:
Mutations leading to the better attachement of virus to the host cell would allow the virus to spread the infection and leave more progeny. The reproductive fitness of mutant viruses would allow the mutation to spread.
Explanation:
1. The organisms with same resource requirement compete with each other. Viruses are not living things but once inside the host cell, they behave like living things. Rapid multiplication of virus overpopulate the host cells.
2. Genetic variations are added to the viral progeny by random errors during replication of the viral genome. These random variations may impart beneficial trait, harmful feature or remain neutral. If a random mutation in the SARS-CoV2 virus allows it to adhere better to the cells of the respiratory system, the virus would be better able to infect these cells to spread the infection. Once inside the host cells, the mutant virus would leave more progeny. On the other hand, the wild type virus that lack this mutation would have lesser chances of entering the host cells and may or may not replicate.
3. The progeny of the mutant virus would compete better with the non mutant ones due to the presence of same mutation.
4. Differential reproduction and more progeny of the mutant virus would spread the mutation among the virus.
Lava flows are typically finer grained (i. e. the rock is made up of smaller mineral grains) than intrusive igneous rocks because the extrusive magma cools quickly so the mineral grains do not have time to grow.
When lava comes out of a volcano and solidifies into extrusive igneous rock, the rock cools very quickly. Crystals inside solid volcanic rocks are small because they do not have much time to form until the rock cools all the way, which stops the crystal growth. Magma, called lava when molten rock erupts on the surface, cools and solidifies almost instantly when it is exposed to the relatively cool temperature of the atmosphere. Quick cooling means that mineral crystals don't have much time to grow, so these rocks have a very fine-grained or even glassy texture.
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Answer:
Bound complement components, especially bound C3b and its inactive fragments, are recognized by specific complement receptors on phagocytic cells