In 1953, Stanley Miller and Harold Urey built a model of Earth's early atmosphere by mixing gases that were thought to have been there. They

exposed the gases to an electric current to simulate lightning. The liquid that

condensed during the experiment contained amino acids.

What was the significance of their results?

There results pointed out that it was possible for organic molecules to be produced  under some reducing conditions which are similar to the primitive earth.Specifically they deduced that volcanic eruption occurring  simultaneously with the lightning may have been responsible for the production of large quantities of some biological molecules on the early earth.

However, objection was raised to the claim that, NH3 and CH4 used in the experiment were the most  abundant gases of  primitive earth.  Inert Nitrogen and Carbon were the  prevalent gases of the early earth,nullifying  the authentication of the experiment.Thus their experiment was wrong.

1. is geographic distribution

2 is increasing complexity

3 is transitional forms

the wetland preservation movement began in the u.s. in earnest with the clean water act (cwa) of 1972. although not specifically written to protect wetlands, the cwa is comprised of a series of regulations designed to prevent pollutants from contaminating u.s. waters.