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The anatomy of fish is often shaped by the physical characteristics of water, the medium in which fish live. Water is much denser than fish, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always ...
Many species live most of their lives as single cells or are filamentous, while others form colonies made up from long chains of cells, or are highly differentiated macroscopic seaweeds. Red algae , a (disputed) phylum contains about 7,000 recognised species, [ 50 ] mostly multicellular and including many notable seaweeds.
In fish, the divisions of the small intestine are not clear, and the terms anterior or proximal intestine may be used instead of duodenum. [21] The small intestine is found in all teleosts, although its form and length vary enormously between species. In teleosts, it is relatively short, typically around one and a half times the length of the ...
A fish (pl.: fish or fishes) is an aquatic, anamniotic, gill-bearing vertebrate animal with swimming fins and a hard skull, but lacking limbs with digits.Fish can be grouped into the more basal jawless fish and the more common jawed fish, the latter including all living cartilaginous and bony fish, as well as the extinct placoderms and acanthodians.
Many species live most of their lives as single cells or are filamentous, while others form colonies made up from long chains of cells, or are highly differentiated macroscopic seaweeds. Red algae , a (disputed) phylum contains about 7,000 recognised species, [ 146 ] mostly multicellular and including many notable seaweeds.
Myocytes ("muscle cells") conduct signals and cause parts of the animal to contract. "Grey cells" act as sponges' equivalent of an immune system. Archaeocytes (or amoebocytes) are amoeba-like cells that are totipotent, in other words, each is capable of transformation into any other type of cell. They also have important roles in feeding and in ...
Some protists accomplish this using contractile vacuoles, while freshwater fish excrete excess water via the kidney. [4] Although most aquatic organisms have a limited ability to regulate their osmotic balance and therefore can only live within a narrow range of salinity, diadromous fish have the ability to migrate between fresh and saline ...
Osteichthyes (/ ˌ ɒ s t iː ˈ ɪ k θ iː z / ost-ee-IK-theez; from Ancient Greek ὀστέον (ostéon) 'bone' and ἰχθύς (ikhthús) 'fish'), [2] also known as osteichthyans or commonly referred to as the bony fish, is a diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue.