Earth's ClimateUsually in geography, latitude and longitude are equally important because you need both to specify a location. The patterns of Earth's climates and habitats depend on exposure to sunlight, which varies with latitude, not longitude. So you don't have to worry about longitude for biogeography, only latitude.
Distribution PatternsWhen talking about plate tectonics, keep in mind that "theory" here is used in the same sense of the Big Bang Theory (no, not the show staring Sheldon)—scientists are sure of the explanation, but the scientific method itself doesn't produce laws, just theories that can be refined over time. Laws are more fundamental and can be applied to many of science-y things. Think gravity.
Current Patterns of Diversity on EarthWhen we talk about species area curves, it is common to think that more species = better. While species diversity is important, ecosystems can still be highly productive with fewer species. There is nothing inherently bad about having fewer species.
Island BiogeographyExtinction from islands does not mean the species goes extinct globally. Extinction here just means there are no individuals of that species left on the island in question. If only one individual of a species arrived on an island, then the species will be extinct from the island after that individual dies—unless, of course, more individuals of the same species immigrate to the island.