Ibn Ezra gives a philosophical answer. Just as the tabernacle needs every one of its sections and parts or else it will be deficient, so is God’s world “one”. Every one of the Divine creations, so lovingly and carefully listed at the beginning of the Book of Genesis, is an indispensable feature of the whole.
If the world had birds but not bees, if it had men but not mountains, plants but not people, the overall structure of Creation would be defective. For the universe to function properly, everything has to be there and to work in mutual co-operation.
An example of how the total structure must work in harmony is found in one of the most common of daily b’rachot, the blessing said after going to the toilet. It praises God who made the intricate human body with such care that “it is revealed and known before the Throne of Your glory” that if one orifice is closed when it should be open, or vice-versa, the human being would be unable to function and he/she would be “unable to stand before God”.
There is an important academic analysis of this b’rachah (which seems to date from at least as early as the Mishnaic period) written by the great legal scholar, Professor David Daube, who points out that “nothing like it seems to exist in any other religion”. He argues that making normal bodily functions part of the pattern of the Jewish way of thinking illustrates a conception of spirituality that exalts both the this-worldly and the other-worldly.