Genesis 1:11-13

God already knew He was going to create man, He also knew man would fall and corrupt the earth and His creation would be degenerative. Because of this, he developed many plants which would not survive the earths changes, but with a variety of plants needs, this made varieties that would survive all the earth would be going through. The same holds true for animals, since the tree's and foliage were going to grow very rapidly in this new earth which had an atmosphere similar to a green house, he needed large animals that would be able to consume and keep in control the vegetation so it would not choke out all other life itself, but we'll get to that when he creates the animals.

Without Gods word, the earth lies barren, without God's presence holding things together, the universe would be one instantaneous explosion of splitting atoms, with positive and negative charges neutralizing each other, and there would be nothing left of the physical universe. Now with gods word, the barren earth springs forth with life, fed by the power of Gods pure light, a light that would provide eternal growth and eternal life, the same life and light for us to see in the new Heaven and New Earth, when we dwell in the presence of the Lord forever.

The day closes with, and the evening and the morning were the third day. how do you interpret that? Is a day 1,000 years? is it 100 million years? I interpret it as it is written, the evening, (the setting of the sun, or in this case the light) and the morning were the third day. I don't believe interpretation is needed here, it is God's word, and I don't perceive God to be a liar, therefore if God gives us the enclosing elements of morning and evening, it is a day just as a day it to you and I.