Cells<span> are the basic units of life. </span>Cells<span> can exist by themselves, like bacteria, or as part of a larger organism, like our </span>cells<span>. </span>Viruses<span> are non-living infectious particles, much smaller than a </span>cell, and need a living host to reproduce. The genetic material of thecell<span> is DNA, a double stranded helix.</span>
I believe the answer is B. <span>warm air is denser then cold air</span>
False
<span>Marine ecosystems like lakes and oceans have aphotic zones. Aphotic zones refer to the zones in the water where there is little or no sunlight. It is found in bodies of water were depths only receive less than 1% of sunlight penetrations. Bioluminescence is essentially the only light found in this zone and most food comes from dead organisms that sink at the bottom of lakes or oceans. </span>
Answer:
secondary consumer
Explanation:
They are the least because they play a less important role in the ecosystems.
<span>Cytotoxic t-cell subpopulations are specialized to combat intracellular pathogens, whereas helper t-cell subpopulations are specialized to combat extracellular pathogens.
</span>Cytotoxic t-cell are CD8+ cells. Cytotoxic t-cell uses granzymes to <span>kill </span><span>intracellular bacteria, that lives in the cytosol such as viruses. They identify the pathogen forgein peptids that are bounded to MHC-I on the cell surface.
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cd4+ T helper (Th) cells include Th1, Th2, and Th17 cells. They contribute to aliergic reactions and fighting extracellular parasites.
