Species-life, both for man and for animals, consists physically in the fact that man, like animals, lives from inorganic nature; and because man is more universal than animals, so too is the area of inorganic nature from which he lives more universal. Just as plants, animals, stones, air, light, etc., theoretically form a part of human consciousness, partly as objects of science and partly as objects of art his spiritual inorganic nature, his spiritual means of life, which he must first prepare before he can enjoy and digest them so, too, in practice they form a part of human life and human activity. In a physical sense, man lives only from these natural products, whether in the form of nourishment, heating, clothing, shelter, etc. The universality of man manifests itself in practice in that universality which makes the whole of nature his inorganic body, (1) as a direct means of life and (2) as the matter, the object, and the tool of his life activity. Nature is man's inorganic body that is to say, nature insofar as it is not the human body. Man lives from nature i.e., nature is his body and he must maintain a continuing dialogue with it if he is not to die. To say that man's physical and mental life is linked to nature simply means that nature is linked to itself, for man is a part of nature.

Estranged labor not only (1) estranges nature from man and (2) estranges man from himself, from his own function, from his vital activity; because of this, it also estranges man from his species. It turns his species-life into a means for his individual life. Firstly, it estranges species-life and individual life, and, secondly, it turns the latter, in its abstract form, into the purpose of the former, also in its abstract and estranged form.

For in the first place labor, life activity, productive life itself, appears to man only as a means for the satisfaction of a need, the need to preserve physical existence. But productive life is species-life. It is life-producing life. The whole character of a species, its species-character, resides in the nature of its life activity, and free conscious activity constitutes the species-character of man. Life appears only as a means of life.

Marx, Karl. 1844. Estranged labor. In Economic and philosophical manuscripts, written between April and August 1844: First manuscript. https://www.marxists.org/archive/marx/works/1844/epm/1st.htm