Srila Prabhupada - Vedic Teachings

Regarding your question about why we do not eat meat and yet we eat plant life, the answer is that we do everything as Krishna recommends. Everything we eat is first offered to Lord Krishna, and because Krishna does not eat meat, therefore we also do not eat meat. The fruits, grains, and vegetables which we offer to the Lord are not caused any suffering by our offering them to Krishna. Rather they are greatly benefited because to be offered for the pleasure of the Lord will grant for the living entity within the plant body certain liberation in the near future. Everything that we do in Krishna Consciousness is ultimately beneficial to all living creatures because we are working under the recommendations of the Lord Himself who is the well-wisher of all His part and parcel children. (From Srila Prabhupada's letter to: Ann Clifford — Los Angeles 2 August, 1969)          

  Puṣṭa Kṛṣṇa: Sometimes people ask, Prabhupāda, that if one falls down into lower species of life like plants or animals, how then do they come again to the human form of life? Prabhupāda: Yes. That is nature's way. Give them again chance to develop. From trees they become flies. That is the beginning of movement. Then from flies to birds, birds to beast, and beast to animal, er, human being. This is great chastisement. You cannot move even. Suffer torrents of rain, cyclone, scorching heat, pinching cold. Stand up for hundreds and thousands of years. Then, when the punishment is finished, then he becomes moving. If there is scorching heat he can move to some shelter. But he cannot move. They do not study all this science, why there are so many varieties of life, of different grades. Wherefrom they are coming? Puṣṭa Kṛṣṇa: The living entity, then, in the tree is actually conscious of its condition of life. Prabhupāda: Eh? Puṣṭa Kṛṣṇa: The living entity inside the tree i...