Most breeds of dog are at most a few hundred years old, having been artificially selected for particular morphologies and behaviors by people for specific functional roles. Through this selective breeding, the dog has developed into hundreds of varied breeds, and shows more behavioral and morphological variation than any other land mammal. For example, height measured to the withers ranges from 15.2 centimetres (6.0 in) in the Chihuahua to about 76 cm (30 in) in the Irish Wolfhound; color varies from white through grays (usually called "blue") to black, and browns from light (tan) to dark ("red" or "chocolate") in a wide variation of patterns; coats can be short or long, coarse-haired to wool-like, straight, curly, or smooth. It is common for most breeds to shed this coat.
The majority of dog breeds have only been around for how long?
a few hundred years

In 1695, the Scottish Parliament granted a charter to the Company of Scotland, which established a settlement in 1698 on the isthmus of Panama. Besieged by neighbouring Spanish colonists of New Granada, and afflicted by malaria, the colony was abandoned two years later. The Darien scheme was a financial disaster for Scotland—a quarter of Scottish capital was lost in the enterprise—and ended Scottish hopes of establishing its own overseas empire. The episode also had major political consequences, persuading the governments of both England and Scotland of the merits of a union of countries, rather than just crowns. This occurred in 1707 with the Treaty of Union, establishing the Kingdom of Great Britain.
When was the Treaty of Union?
1707

Upon exposure, the amount of light energy that reaches the film determines the effect upon the emulsion. If the brightness of the light is multiplied by a factor and the exposure of the film decreased by the same factor by varying the camera's shutter speed and aperture, so that the energy received is the same, the film will be developed to the same density. This rule is called reciprocity. The systems for determining the sensitivity for an emulsion are possible because reciprocity holds. In practice, reciprocity works reasonably well for normal photographic films for the range of exposures between 1/1000 second to 1/2 second. However, this relationship breaks down outside these limits, a phenomenon known as reciprocity failure.
What determines the effect on the emulsion after exposure?
the amount of light energy that reaches the film