Estimating populations can be a difficult and challenging task for many biologists - yet they have to try their best to conduct accurate estimates. What would some of the challenges by for the following populations:

a. Whales that migrate along the western coasts of North and South America< >

b. Algae that live in water bodies receiving excess fertilizers in runoff from cropland< >

c. Caribou that inhabit an Arctic tundra environment< >

d. Amphibians that live in marshes< >

e. Grizzly bear populations in the Rocky Mountains. < >