Bird anatomy Birds have a four-chambered heart, in common with mammals, and some reptiles (mainly the crocodilia). This adaptation allows for an efficient nutrient and oxygen transport throughout the body, providing birds with energy to fly and maintain high levels of activity. A ruby-throated hummingbird's heart beats up to 1200 times per minute (about 20 beats per second). Many birds possess a muscular pouch along the esophagus called a crop. The crop functions to both soften food and regulate its flow through the system by storing it temporarily. The size and shape of the crop is quite variable among the birds. Members
Names for the human species "Gaian") is frequently used, as it were naming humanity by its planet of origin. Incidentally, this situation parallels the naming motive of ancient terms for humanity, including "human" ("homo", "humanus") itself, derived from a word for "earth" to contrast humans as earth-bound with celestial beings (i.e. deities) in mythology. Names for the human species The common name of the human species in English is historically "man" (from Germanic), often replaced by the Latinate "human" (since the 16th century). In addition to the generally accepted taxonomic name "Homo sapiens" (Latin: "sapient man", Linnaeus 1758), other Latin-based names for the human species