Population
A population is a group of individuals of the same species in the same area.
Species
A species is a group of similar organisms that can produce fertile offspring. Population and species are similar, but differ. An example of the difference: the human species inhabits the earth. However, the population of North America is different than the population of Australia. The same goes for animals.
Image Sources:
http://i.telegraph.co.uk/multimedia/archive/01007/england-population_1007441c.jpg
http://upload.wikimedia.org/wikipedia/commons/thumb/e/e3/England_counties_population_(crop).png/300px-England_counties_population_(crop).png
http://www.wildlifearchives.com/images/animals/mammals/manatee-distribution-map.gif
http://www.c21naturecoast.com/content/image/EssickTodd_Manatees_lg.jpg
http://i.telegraph.co.uk/multimedia/archive/01007/england-population_1007441c.jpg
http://upload.wikimedia.org/wikipedia/commons/thumb/e/e3/England_counties_population_(crop).png/300px-England_counties_population_(crop).png
http://www.wildlifearchives.com/images/animals/mammals/manatee-distribution-map.gif
http://www.c21naturecoast.com/content/image/EssickTodd_Manatees_lg.jpg