The green house effect occurs when carbon dioxide and water vapor form an invisible blanket around the globe that allows the sun's light to enter, but traps the heat. Green house effect is a process that warms the Earth's surface. When the sun's energy reaches the Earth's atmosphere, some of it is reflected back to the space and the rest is absorbed and re-radiated by greenhouse gases.
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One method I know of is comparing a sample of the rock to other samples which the scientist already knows the age of. I forgot what this method is called but I know it's used by lazy scientists that use other scientist findings like the age of a rock to compare to their own work
Codominance.
Codominance occurs when, for example, a Dominant Blue color gene for a leaf crosses with a Dominant White color gene for a leaf. The genotype would be BW. This would result in, for example, a blue and white spotted leaf color. INCOMPLETE dominance occurs when both dominant alleles blend together, resulting in, eg, a pale blue color resulting from the blue and white colors mixing.