In the beginning it was night and the land was created, so was the plant life in the ocean and on the land. As it led later into night the fish and other aquatic beings came to be. As the first light of dawn came the birds and insects of the lad were created. As dawn grew animals that could traverse both land and sea were born. Dawn hits and humans with other land animals were created. As the day came humans grew and populated the earth.
The symbolic nature of the story is that the earth and all life grew as the day came to be, the life that grew corresponded with where they lived. The sea life was grown in the night as the life on land was born closer to the day.
In the story the darkness symbolized the man and woman who created all the life. It could also symbolize the early life forms and their connection to the land.
The light symbolizes the start of new life and the finalized creation of the world.
The story might really represent birth. It starts in the dark and as life is created finally it is brought to light and is born.