The great elements of material creation, namely earth, water, fire, air and ether, all enter into the body of all manifested entities—the seas, mountains, aquatics, plants, reptiles, birds, beasts, human beings, demigods and everyone materially manifested—and at the same time such elements are differently situated. In the developed stage of consciousness, the human being can study both physiological and physical science, but the basic principles of such sciences are nothing but the material elements and nothing more. The body of the human being and the body of the mountain, as also the bodies of the demigods, including Brahmā, are all of the same ingredients—earth, water, etc.—and at the same time the elements are beyond the body.
(Srimad Bhagavatam-----2:9:35-----purport).

The human being is more passionate than the animals, and thus the sex life of the human being is more irregular. The animals have their due time for sexual intercourse, but the human being has no regular time for such activities. The human being is endowed with a higher, advanced stage of consciousness for getting relief from the existence of material miseries, but due to his ignorance he thinks that his higher consciousness is meant for advancing in the material comforts of life. Thus his intelligence is misused in the animal propensities—eating, sleeping, defending and mating—instead of spiritual realization.
(Srimad Bhagavatam-----3:10:26-----purport).

In the phenomenal manifestation there are three stages: the stage of consciousness, the stage of semiconsciousness in dreaming, and the stage of unconsciousness. But Your Lordship is transcendental to all these different material stages of existence. You exist, therefore, in a fourth dimension, and Your appearance and disappearance do not depend on anything beyond Yourself. You are the supreme cause of everything, but of You there is no cause. You Yourself cause Your own appearance and disappearance. Despite Your transcendental position, my Lord, in order to show Your six opulences and advertise Your transcendental qualities, You have appeared in Your different incarnations—fish, tortoise, boar, Nṛsiṁha, Keśava and others—by Your personal manifestation; and You have appeared as different living entities by Your separated manifestations. By Your internal potency You appear as the different incarnations of Viṣṇu, and by Your external potency You appear as the phenomenal world.
(Krsna Book).

Within the body there are five different departments of existence, known as anna-maya, prāṇa-maya, mano-maya, vijñāna-maya and, at last, ānanda-maya. In the beginning of life, every living entity is food conscious. A child or an animal is satisfied only by getting nice food. This stage of consciousness, in which the goal is to eat sumptuously, is called anna-maya. Anna means “food.” After this one lives in the consciousness of being alive. If one can continue his life without being attacked or destroyed, one thinks himself happy. This stage is called prāṇa-maya, or consciousness of one’s existence. After this stage, when one is situated on the mental platform, his consciousness is called mano-maya. The materialistic civilization is primarily situated in these three stages, anna-maya, prāṇa-maya and mano-maya. The first concern of civilized persons is economic development, the next concern is defense against being annihilated, and the next consciousness is mental speculation, the philosophical approach to the values of life.
(Krsna Book).

Persons who act in this way become progressively detached from matter and attached to Lord Kṛṣṇa's devotional service. Thus they are able to purify the mirror of their hearts, extinguish the forest fire of material existence, and become situated in their original, spiritual position. They exist at a level of realization far above the impersonal realization of the Absolute, for they are free from the contamination of vainly trying to merge with the Supreme and usurping His Absolute position. They never fall from this stage of consciousness.
(Renunciation through Wisdom).