Answer: Infection occurs when the host is exposed to pathogens. virus uses the cell's metabolism, and replicates itself while destroying the cell or changing the cell's genetic makeup.
Explanation:
- A virus is a miniscule pocket of protein that contains genetic material.
- Viruses pose a considerable challenge to the body’s immune system because they hide inside cells.
- This makes it difficult for antibodies to reach them. Some special immune system cells, called T-lymphocytes, can recognise and kill cells containing viruses, since the surface of infected cells is changed when the virus begins to multiply.
- Many viruses, when released from infected cells, will be effectively knocked out by antibodies that have been produced in response to infection or previous immunisation.
- Antibiotics are useless against viral infections. So antiviral drugs work differently to antibiotics, by interfering with the viral enzymes instead.
Hence virus are the pathogen that use the cell's metabolism. And replicate itself while destroying the cell or changing the cell's genetic makeup. viruses are so simple that they use their host cells to perform their activities for them
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I think thats because small animals have small body that can hide in a safe place. Like example if small animals hide go down to the earth, and the meteorite hit the earth, they will safe down to the ground.
Not like larger animals, they can only hide up he surface and when the meteorites came, they died.
Also some small animals such as cockroaches have ability to adapt to changes.
Answer:
blood can still return via the deep veins
Explanation:
The venous system at the leg is known for its complexity and highly branched nature. The superficial and deep veins, both branches and connects with each other at different points along their length
