For both plants and animals it is the species. But there are subspecies in animals and cultivars in plants.
The United States
Mammals limbs look different from species to species. Limbs are prehensile or jointed appendages and include arms (from the shoulder down) and legs (from the hip down).
Around 1,000.
To maintain their species. Any species that lost reproductive ability would eventually die out.
The order of the Monotremata contains the fewest species, with only five extant species. These species include the platypus and four species of echidnas.
The US has fewer mammals. Mexico is considered a "mega-diverse" country and as such forms part of a select group of nations that possess the greatest number and diversity of animals and plants, being home of nearly 10-12% of global species diversity. Mexico ranks third in mammal biodiversity in the world with 535 species, behind Indonesia (667) and Brazil (578).
Biosphere contains the fewest number of species compared to community and population.
I would guess the country with the most native mammal species is Madagascar.
population
Anarctica
which central American country has the fewest climate zones
Population
The Vatican City has the fewest people, with a population of around 800 residents.
The "Maldives" has the fewest people in Asia. The population is 360,000.
Chad has the fewest paved roads in Sahel.
Oman