bivalve - Encyclopedia Britannica
Bivalve, (class Bivalvia), any of more than 15,000 species of clams, oysters, mussels, scallops, and other members of the phylum Mollusca characterized by a shell that is divided from front to back into left and right valves.
Clam | Anatomy, Types, Habitat, Mollusk, Bivalve & Marine Life
2024年10月11日 · One species of abra clam (Abra profundorum), however, has been taken in the Pacific Ocean at a depth of more than 4,800 metres (16,000 feet). Clams typically draw in and expel water for respiration and feeding through two tubes, the siphons, or “neck.”
Bivalve - Gills, Filter Feeding, Mantle | Britannica
While the gills are thought to serve a respiratory function, respiratory demands are low in these mostly inactive animals, and, since the body and mantle are both bathed in water, respiration probably takes place across these surfaces as well.
Respiratory system | Definition, Organs, Function, & Facts
respiratory system, the system in living organisms that takes up oxygen and discharges carbon dioxide in order to satisfy energy requirements. In the living organism, energy is liberated, along with carbon dioxide, through the oxidation of molecules containing carbon.
Respiratory system - Gills, Invertebrates, Breathing | Britannica
Clams possess gills across which water circulates, impelled by the movements of millions of microscopic whips called cilia. In the few forms studied, the extraction of oxygen from the water has been found to be low, on the order of 2 to 10 percent.
The nervous system and organs of sensation - Encyclopedia …
2024年11月11日 · Mollusks possess an open circulatory system in which body fluid is transported largely within sinuses devoid of distinct epithelial walls. The posteriodorsal heart enclosed in a pericardium typically consists of a ventricle and two posterior auricles.
Fish - Gills, Lungs, Swim Bladder | Britannica
2024年11月21日 · Fish - Gills, Lungs, Swim Bladder: Most fishes exchange dissolved oxygen and carbon dioxide in water using gills which lie behind and to the side of the mouth cavity. The circulatory system consists of the heart, arteries, capillaries, and veins. The heart pumps the blood to the gills to be re-oxygenated.
Annelid - Respiratory, Segmented, Setae | Britannica
2024年11月15日 · Annelid - Respiratory, Segmented, Setae: The annelids are considered to have evolved in the sea, perhaps from an ancestral flatworm that evolved through the trochophore larva, the characteristic early stage of polychaetes.
Bivalve - Mollusk, Shell, Filter Feeder | Britannica
Bivalve - Mollusk, Shell, Filter Feeder: The bivalve shell is made of calcium carbonate embedded in an organic matrix secreted by the mantle. It has a simple nervous system; the head is absent. The digestive system comprises a complex stomach and a simple intestine.
Respiratory system - Lungs, Airways, Gills | Britannica
Respiratory system - Lungs, Airways, Gills: Respiratory structures are tailored to the need for oxygen. Minute life-forms, such as protozoans, exchange oxygen and carbon dioxide across their entire surfaces. Multicellular organisms, in which diffusion distances are longer, generally resort to other strategies.