CoachA population is all the individuals of one species living in one place — the pond’s frogs, the wood’s beeches. Reproduction adds to it; deaths and departures subtract; the environment sets the ceiling.
Examples
Example 55.7 (Two springs at the pond)
Spring 1, mild and wet: high water, early insects — thousands of eggs, hundreds of froglets, the population climbs. Spring 2, a drought: the pond shrinks to a puddle, tadpoles crowd, oxygen falls (Proposition 48.3), herons feast on the concentrated shoal — a handful of froglets. Same frogs, same mechanism, two verdicts: the environment countersigns every generation.