Question

the northern cardinals (cardinalis cardinalis) living on opposite shores of lake champlain; the american bison (bison bison) and grey wolves (canis lupus) currently living in yellowstone national park; the group of american bison (bison bison) currently living in yellowstone national park; all of the whales currently living in the atlantic ocean off cape cod, massachusetts; a group of calliope hummingbirds (selasphorus calliope) and a group of rufous hummingbirds (selasphorus rufus) living in the same new hampshire woods; all of the rainbow trout (oncorhynchus mykissaha) that have ever lived in lake erie; population; not a population; cant tell

Explanation:

A population is defined as a group of individuals of the same species living in the same geographic area at the same time. We categorize each item based on this definition:

1. Northern cardinals on opposite Lake Champlain shores: Same species, same general geographic region (Lake Champlain system), counts as a population.
2. American bison + grey wolves in Yellowstone: Two different species, so not a single population.
3. American bison in Yellowstone: Same species, same defined area, counts as a population.
4. All whales off Cape Cod: "Whales" includes multiple different species, so not a single population.
5. Calliope + rufous hummingbirds in NH woods: Two different hummingbird species, so not a single population.
6. All rainbow trout ever in Lake Erie: Same species, same geographic area (Lake Erie; the time frame includes all past individuals, which still fits the broader definition of a historical population of the species in that location).

Answer:

Population:

• the northern cardinals (Cardinalis cardinalis) living on opposite shores of Lake Champlain
• the group of American bison (Bison bison) currently living in Yellowstone National Park
• all of the rainbow trout (Oncorhynchus mykiss) that have ever lived in Lake Erie

NOT a population:

• the American bison (Bison bison) and grey wolves (Canis lupus) currently living in Yellowstone National Park
• all of the whales currently living in the Atlantic Ocean off Cape Cod, Massachusetts
• a group of calliope hummingbirds (Selasphorus calliope) and a group of rufous hummingbirds (Selasphorus rufus) living in the same New Hampshire woods

Can't tell:

(No items fall into this category)