L01_what_is_a_fish11COLOR

L01_what_is_a_fish11COLOR - What is a fish? Fish = one or...

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What is a fish?
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FISH FISHES versus Fish = one or more individuals of a single species Fishes = more than one species, regardless of number of indiv.
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How many are there? Low estimate: 15,000-17,000; High estimate: 40,000 Probably about 25,000 species of fish = 50% of the vertebrate species Most successful vertebrates in aquatic habitats: 41% live in freshwater 58% live in seawater 1% move between fresh and seawater
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What is a fish? 1) Aquatic – except, occasionally: grunion, walking catfish, etc.
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What is a fish? 2) Vertebrates except: hagfishes, lampreys (no vertebral centra) 1) Aquatic – except, occasionally: grunion, walking catfish, etc.
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What is a fish? 3) Cold blooded / poikilotherms except: some fast swimming fishes like tunas are partial homeotherms 2) Vertebrates except: hagfishes, lampreys (no vertebral centra) 1) Aquatic – except, occasionally: grunion, walking catfish, etc. Bluefin tuna, 200 kg - higher temperature than ambient
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What is a fish? 4) Usually median and paired fins for locomotion and steering – except: eels
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What is a fish? 4) Median and paired fins for locomotion and steering. - except: eels 5) Scales – except: many derived fishes of Perciformes • clingfishes, blennies, jacks, etc.
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What is a fish? 4) Median and paired fins for locomotion and steering. - except: eels 5) Scales – except in many derived fishes of Perciformes • blennies, jacks, etc. 6) Gills extras: lungfishes (lungs), mudskippers (facultative skin respiration), other devices
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What is a fish? 7) Simple, one way heart, one pump with two simple chambers – only exception: African lungfish Main pump From body To gills then to the body
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What is a fish? 7) Simple, one way heart, one pump with two simple chambers – only exception: African lungfish 8) Lateral line, “distant touch”, near-field pressure sensor
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So what is a fish? • mostly aquatic vertebrate, • mostly cold-blooded, • usually with appendages developed as fins, • whose chief respiratory organs are usually gills aided by a simple two chambered heart, • and whose body is usually covered with scales and a lateral line. Exceptions give us clues to adaptations that have arisen from selection pressures in the environment
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Why so many exceptions?
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L01_what_is_a_fish11COLOR - What is a fish? Fish = one or...

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