If the numbers of a species begin to decline dramatically, the species becomes known as an "endangered" species. When the numbers decline so far that the species no longer exists, the species is known to be "extinct."
Sexual Frustration.
The human body begins to decline at an old age or it can decline due to the lack of nutrition.
Factories begin because of the working conditions.
The decline of any population will perturb the ecological balance. If the number of one particular species declines, then any species that preys on it will lose some of its food supply and so its population may decline as well. A species in parasitic or symbiotic relationship is also likely to decline. On the other hand, any species which lives in competition - for food or other resources - would face less competition and so its numbers are likely to increase.
Between 2000b.c.and 1500b.c.
Poachers hunting this endangered species has made the number of their population decline.
the 1970s
Between 2000b.c.and 1500b.c.
Smaller natural habitat, more human encroachment, and less food are the three main causes for the decline of the frog species.
A species at risk of extinction due to a drastic decline in population or habitat destruction.
Immigration numbers did not decline.
The set of numbers that begin with the number 1 is Natural Numbers.