Answer to Question 1
Increasing the concentration of greenhouse gases like carbon dioxide strengthens the greenhouse effect. As the surface of the Earth is warmed by radiation from the Sun, it emits heat energy. Greenhouse gases absorb this heat energy before it can pass through the atmosphere and back into space, raising the temperature of the atmosphere. When greenhouse gas concentrations increase, so does the temperature of the atmosphere and at the surface.
Answer to Question 2
Several thousand species are in transit every day in the ballast water of tankers and other ships. Juvenile forms of marine organisms can easily hitch rides across otherwise insurmountable oceanic barriers and set up housekeeping at distant shores. These foreign organisms-called introduced species or exotic species-sometimes outcompete native species and reduce biological diversity in their new habitats. New marine diseases can also be introduced in this way. Even canals and fishery enhancement projects can introduce potentially destabilizing new species.
Sites of mtDNA mutations in certain human diseases
Stable isotopes of carbon
The Distribution of Water on Earth
Human embryo shortly after fertilization in the laboratory
A colorized image of human chromosomes
Partial pressures (in mm Hg) for oxygen (red boxes) and carbon dioxide (blue boxes) in the atmospher