Answer:
When we say that a trait has been "selected for", this means that. individuals with that trait reproduce more than individuals without that trait.Explanation:
I'm pretty sure it's A.<span>Evaporation decreases salinity, and heavy polar air increases atmospheric pressure.</span>
The immune system is spread throughout the body and involves many types of cells, organs, proteins, and tissues. Crucially, it can distinguish our tissue from foreign tissue — self from non-self. Dead and faulty cells are also recognized and cleared away by the immune system.
If the immune system encounters a pathogen, for instance, a bacterium, virus, or parasite, it mounts a so-called immune response. Later, we will explain how this works, but first, we will introduce some of the main characters in the immune system.
