Gen 1:20-23 "And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven. 21 And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good. 22 And God blessed them, saying, Be fruitful, and multiply, and fill the waters in the seas, and let fowl multiply in the earth. 23 And the evening and the morning were the fifth day."

On the fourth day God made and placed the sun, moon and stars in the firmament of heaven. We know this to be the outer space area because that is where the planets are located. That passage didn’t say anything about that area being closed, but life is not able to exist there unless it takes along a life support system. The birds cannot fly there because the higher one goes the thinner the atmosphere becomes - they can’t breathe. In the sense of not being able to sustain life, the outer space area, the second heaven, is closed to natural life.

On the fifth day God created fowl that may fly above the earth in the OPEN firmament of heaven. This firmament is open as opposed to closed because life can exist within it. The word ‘firmament’ is defined as ‘expanse’, and the word ‘heaven’ is shamayim, which is the same word as we saw in Gen. 1:1, a duel term. This is the first heaven and it is accessible to natural life.

In vs. 21 God CREATES. Back on the third day God called forth plant life - he did not create it. Here in the fifth day God is creating again, first fish then birds. This is not evolutionary: the birds did not evolve out of the fish. There are four kinds of life: fish, fowl, animal, man. Each is distinct and separate from the others, and each class of life will have blood different from the others.

In vs. 22 - God blessed them and told them to multiply. Although it’s not stated, we see again the principle of life with seed in it. God will not again create fish and fowl, they were created able to reproduce themselves after their own kind. Again, it’s after their own kind - no cross breeding.