E. O. Wilson in the context of "Orthogenesis"

Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson characterised parasites' way of feeding as "predators that eat prey in units of less than one". Parasites include single-celled protozoans such as the agents of malaria, sleeping sickness, and amoebic dysentery; animals such as hookworms, lice, mosquitoes, and vampire bats; fungi such as honey fungus and the agents of ringworm; and plants such as mistletoe, dodder, and the broomrapes.

There are six major parasitic strategies of exploitation of animal hosts, namely parasitic castration, directly transmitted parasitism (by contact), trophically-transmitted parasitism (by being eaten), vector-transmitted parasitism, parasitoidism, and micropredation. One major axis of classification concerns invasiveness: an endoparasite lives inside the host's body; an ectoparasite lives outside, on the host's surface.

The biophilia hypothesis (also called BET) suggests that humans possess an innate tendency to seek connections with nature and other forms of life. Edward O. Wilson introduced and popularized the hypothesis in his book, Biophilia (1984). He defines biophilia as the "innate tendency to focus on life and lifelike processes". He argued that "to explore and affiliate with life is a deep and complicated process in mental development. To an extent still undervalued in philosophy and religion, our existence depends on this propensity, our spirit is woven from it, hope rises on its currents". Wilson saw modern biology as converging with biophilia: "Modern biology has produced a genuinely new way of looking at the world that is incidentally congenial to the inner direction of biophilia. In other words, instinct is in this rare instance aligned with reason. . . . to the degree that we come to understand other organisms, we will place a greater value on them, and on ourselves".

Eusociality (Greek εὖ eu 'good' and social) is the highest level of organization of sociality. It is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generations within a colony of adults, and a division of labor into reproductive and non-reproductive groups. The division of labor creates specialized behavioral groups within an animal society, sometimes called castes. Eusociality is distinguished from all other social systems because individuals of at least one caste usually lose the ability to perform behaviors characteristic of individuals in another caste. Eusocial colonies can be viewed as superorganisms.

Eusociality has evolved among the insects, crustaceans, trematoda and mammals. It is most widespread in the Hymenoptera (ants, bees, and wasps) and in Isoptera (termites). A colony has caste differences: queens and reproductive males take the roles of the sole reproducers, while soldiers and workers work together to create and maintain a living situation favorable for the brood. Queens produce multiple queen pheromones to create and maintain the eusocial state in their colonies; they may also eat eggs laid by other females or exert dominance by fighting. There are two eusocial rodents: the naked mole-rat and the Damaraland mole-rat. Some shrimps, such as Synalpheus regalis, are eusocial. E. O. Wilson and others have claimed that humans have evolved a weak form of eusociality. It has been suggested that the colonial and epiphytic staghorn fern, too, may make use of a primitively eusocial division of labor.