Context: Dinosaurs are a diverse group of animals of the clade Dinosauria that first appeared during the Triassic. Although the exact origin and timing of the evolution of dinosaurs is the subject of active research, the current scientific consensus places their origin between 231 and 243 million years ago. They became the dominant terrestrial vertebrates after the TriassicJurassic extinction event 201 million years ago. Their dominance continued through the Jurassic and Cretaceous periods and ended when the CretaceousPaleogene extinction event led to the extinction of most dinosaur groups 66 million years ago., The ostrich or common ostrich ("Struthio camelus") is either one or two species of large flightless birds native to Africa, the only living member(s) of the genus "Struthio", which is in the ratite family. In 2014, the Somali ostrich ("Struthio molybdophanes") was recognized as a distinct species., An apex predator, also known as an alpha predator or apical predator, is a predator residing at the top of a food chain upon which no other creatures prey. Apex predators are usually defined in terms of trophic dynamics, meaning that apex-predator species occupy the highest trophic level or levels and play a crucial role in maintaining the health of their ecosystems. One study of marine food webs defined apex predators as greater than trophic level four. The apex predator concept is commonly applied in wildlife management, conservation and ecotourism., Flightless birds are birds that through evolution lost the ability to fly. There are over 60 extant species including the well known ratites (ostrich, emu, cassowary, rhea and kiwi) and penguins. The smallest flightless bird is the Inaccessible Island rail (length 12.5 cm, weight 34.7 g). The largest (both heaviest and tallest) flightless bird, which is also the largest living bird, is the ostrich (2.7 m, 156 kg). Ostriches are farmed for their decorative feathers, meat and their skins, which are used to make leather. , Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds (avian-dinosaurs) that were the largest species of apex predators in South America during the Cenozoic era; their temporal range covers from 62 to 1.8 million years (Ma) ago., The bee hummingbird, zunzuncito or Helena hummingbird ("Mellisuga helenae") is a species of hummingbird., The superclass Tetrapoda (Ancient Greek s tetrapods, "four-footed"), or the tetrapods , comprises the first four-limbed vertebrates and their descendants, including the living and extinct amphibians, birds, mammals, reptiles and some ancient, exclusively aquatic creatures such as the Acanthostega. Tetrapods evolved from the lobe-finned fishes around 390 million years ago in the middle Devonian Period, with modern tetrapod groups having appeared by the late Devonian, 367.5 million years ago. The specific aquatic ancestors of the tetrapods, and the process by which land colonization occurred, remain unclear, and are areas of active research and debate among palaeontologists at present., A passerine is any bird of the order Passeriformes, which includes more than half of all bird species. A notable feature of passerines compared to other orders of Aves is the arrangement of their toes, three pointing forward and one back, which facilitates perching. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders, with over 5,000 identified species. It has roughly twice as many species as the largest of the mammal orders, the Rodentia. It contains more than 110 families, the second-most of any order of tetrapods (after Squamata, the scaled reptiles).
The passerines contain several groups of brood parasites such as the viduas, cuckoo-finches, and the cowbirds. Most passerines are omnivorous, while the shrikes are carnivorous., The heart is a muscular organ in humans and other animals, which pumps blood through the blood vessels of the circulatory system. Blood provides the body with oxygen and nutrients, as well as assists in the removal of metabolic wastes. The heart is located between the lungs, in the middle compartment of the chest.
In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria; and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the "right heart" and their left counterparts as the "left heart". Fish in contrast have two chambers, an atrium and a ventricle, while reptiles have three chambers. In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow. The heart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall of the heart is made up of three layers: epicardium, myocardium, and endocardium.
The heart pumps blood with a rhythm determined by a group of pacemaking cells in the sinoatrial node. These generate a current that causes contraction of the heart, traveling through the atrioventricular node and along the conduction system of the heart. The heart receives blood low in oxygen from the systemic circulation, which enters the right atrium from the superior and inferior venae cavae and passes to the right ventricle. From here it is pumped into the pulmonary circulation, through the lungs where it receives oxygen and gives off carbon dioxide. Oxygenated blood then returns to the left atrium, passes through the left ventricle and is pumped out through the aorta to the systemic circulationwhere the oxygen is used and metabolized to carbon dioxide. The heart beats at a resting rate close to 72 beats per minute. Exercise temporarily increases the rate, but lowers resting heart rate in the long term, and is good for heart health.
Cardiovascular diseases (CVD) are the most common cause of death globally as of 2008, accounting for 30% of deaths. Of these more than three quarters are a result of coronary artery disease and stroke. Risk factors include: smoking, being overweight, little exercise, high cholesterol, high blood pressure, and poorly controlled diabetes, among others. Cardiovascular diseases frequently have no symptoms or may cause chest pain or shortness of breath. Diagnosis of heart disease is often done by the taking of a medical history, listening to the heart-sounds with a stethoscope, ECG, and ultrasound. Specialists who focus on diseases of the heart are called cardiologists, although many specialties of medicine may be involved in treatment., A songbird is a bird belonging to the clade Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as a scientific or vernacular name is Oscines, from Latin "oscen", "a songbird". This group contains some 4,000 species found all over the world, in which the vocal organ typically is developed in such a way as to produce a diverse and elaborate bird song., A clade (from , "klados", "branch") is a group of organisms that consists of a common ancestor and all its lineal descendants, and represents a single "branch" on the "tree of life"., Kelenken guillermoi was a species of giant flightless predatory birds of the extinct family Phorusrhacidae , or `` terror birds '' . K. guillermoi lived in the Langhian stage of the Miocene , some 15 million years ago , in Argentina along with Argentavis . With a skull 28 inches ( 71 cm ) long ( including its 18 inch , 45.7 cm beak ) , it had the largest head of any known bird . It is the largest species of phorusrhacid . The tarsometatarsus was about 45 cm long ., Hummingbirds are birds from the Americas that constitute the family Trochilidae. They are among the smallest of birds, most species measuring . Indeed, the smallest extant bird species is a hummingbird, the 5-cm bee hummingbird weighing less than a U.S. penny (2.5 g)., Vertebrates comprise all species of animals within the subphylum Vertebrata (chordates with backbones). Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 64,000 species described. Vertebrates include the jawless fish and the jawed vertebrates, which include the cartilaginous fish (sharks and rays) and the bony fish. , In biology, a species (abbreviated sp., with the plural form species abbreviated spp.) is the basic unit of biological classification and a taxonomic rank. A species is often defined as the largest group of organisms in which two individuals can produce fertile offspring, typically by sexual reproduction. While this definition is often adequate, looked at more closely it is often problematic. For example, in a species complex, the boundaries between closely related species become unclear or disappear altogether. Other ways of defining species include similarity of DNA, morphology, or ecological niche. The presence of locally adaptive traits may further subdivide species into infraspecific taxa such as subspecies., Birds (Aves), also known as avian dinosaurs, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton. Birds live worldwide and range in size from the bee hummingbird to the ostrich. They rank as the class of tetrapods with the most living species, at approximately ten thousand, with more than half of these being passerines, sometimes known as perching birds or, less accurately, as songbirds., Feathers are epidermal growths that form the distinctive outer covering, or plumage, on birds. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They are among the characteristics that distinguish the extant birds from other living groups., Subject: kelenken, Relation: taxon_rank, Options: (A) branch (B) family (C) form (D) genus (E) group (F) order (G) phylum (H) species (I) subphylum (J) superclass
Output: genus