whats an environmental selective pressure?

Answer 1

The name is almost self explanatory. It is a type of selective pressure imposed by the environment.

Wikipedia correctly states:
"Under selection, individuals with advantageous or "adaptive" traits tend to be more successful than their peers reproductively--meaning they [are more likely to] contribute more offspring to the succeeding generation than others do."

So, environmental selective pressure is conditions that are applied by the environment that may cause change or stabilize conditions.

To cause change there must be a change in the environment, so for example if the environment got colder then individuals which are better suited for cold have an advantage against others in their environment. This is called disruptive selective pressure.

Stabilizing environmental selective pressure occurs when ever there isn't disruptive selective pressure. So if there is no change to the environment then the individuals which are best adapted to the current conditions will have the advantage.

Answer 2

A selection pressure imposed by the environment. Contrast it with sexual selection, which is imposed by members of your own species, or metabolic selection pressures imposed by your own body.

Answer 3

It is a kind of Darwinian "noblesse oblige"... when something just happens just to you just to extinct your kind - or to make you a very special piece of a ecological web.