Systema Naturae. Digital Paintings

The animals were arranged on a scale from man (with blood, 2 legs, rational soul) down through the live-bearing tetrapods (with blood, 4 legs, sensitive soul) and other groups such as crustaceans (no blood, many legs, sensitive soul) down to spontaneously-generating creatures like sponges (no blood, no legs, vegetable soul).

Humans make use of animal species, such as for food, for materials, as pets, and as working animals including for transport.

Although humans are part of nature, human activity is often understood as a separate category from other natural phenomena.

Operant conditioning is a form of learning in which an individual's behavior is modified by its consequences. The use of punishment is controversial with both the humaneness and effectiveness questioned by many behaviourists.

A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal or a laboratory animal. Popular perceptions of intimate relationships are strongly influenced by movies and television.

The movement of a tree includes the flow of the juices through the veins of the tree, the breathing of the leaves, the roots sucking the water, the never-ending activities between the tree and earth and air, and the growth of the tree.

The increased focused communication between two twins may isolate them from the social environment surrounding them. In fiction and mythology, a doppelgänger is often portrayed as a ghostly or paranormal phenomenon and usually seen as a harbinger of bad luck.

Flies tend to fly in a straight line then make a rapid change in direction before continuing on a different straight path. For visual course control, flies' optic flow field is analyzed by a set of motion-sensitive neurons.