Answer:
the cup like opening becomes the mouth in placental mammals, including humans.
The ability of a cell or a body to fight against the infection is called immunity. The T cell and B cell helps the body to fight against the infection.
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What are T cells?</h3>
T cell is also called as T lymphocyte, it is also a important part of immune system. T cell originate in the bone marrow and mature into the thymus.
There are three types of T cells:
- T helper cell
- T killer cells
- T cytotoxic cells.
Helper T cells secrete chemical messengers called cytokines. Regulatory T cells helps to control immune reactions. They are released into blood streams.
Therefore, The ability of a cell or a body to fight against the infection is called immunity. The T cell and B cell helps the body to fight against the infection.
To learn more about T cells, refer to the link:
brainly.com/question/1434048
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Answer:
Similarities: both are chemical messengers, both can have (but don't necessarily have) similar structures (made from amino acids), both can be produced by the central nervous system (hypothalamus produces some hormones), certain molecules can act as both hormones and neurotransmitters (example: norepinephrine).
Differences: neurotransmitters are released by neurons across a synaptic gap, have very short distances to travel, and act very quickly on the neighboring cell. Hormones are released by glands and often have to travel longer distances, which means that they are slower-acting. Also, hormones are typically used for regulation (negative feedback) while neurotransmitters are used for stimulation of a neighboring cell.
Explanation:
Answer: D. A river separates members of a squirrel population that used to occupy the same geographical area.
Explanation:
Allopathic Speciation occurs when a geographic barrier (river, mountain, or canyon) separates members of a population
Hope this helps!
