what is a shark? Flashcards

1
Q

how long have sharks been around?

A

sharks date back to the Devonian times

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2
Q

class Chondrichthyes - what happened to the endo skeletons?

A

bones were absent from the cartilaginous endoskeleton

prismatic calcification of surface layers of cartilage matrix

bones in teeth and scales

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3
Q

what is a clade?

A

a defining character

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4
Q

why is shark skin rough to the touch?

A

placoid scales or dermal denticles

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5
Q

what are placoid scales?

A

form in dermis
project through the epidermis to surface

tooth-like structures:
enamel tip
dentin
pulp activity

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6
Q

what is special about the dogfish teeth and scales?

A

homologous structures to the placoid scales

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7
Q

what type of teeth do dogfish have?

A

tooth whorls - spirally arranged clusters of the individuals’ teeth

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8
Q

what are the characteristics of dogfish mouth?

A

the ligamentous band along the jaw

cartilage beneath flesh

developing teeth in the file behind each functional tooth

tooth replacement occurs weekly in young shaks

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9
Q

what is cranial kinesis in sharks?

A

the upper jaw can unhinge and extend, protruding outwards

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10
Q

how does cranial kinesis work?

A

hyostylic jaw suspension

cartilage - firm but movable attachment to the cranium

elastic ligament- allows protrusion of the upper jaw

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11
Q

how do sharks breathe?

A

ram ventilation:
when the shark is moving - water comes in via the mouth - out via the gills
5-gill pairs in most sharks and rays
buccal pumping:
sharks at rest - water in via mouth and spiracles
- out via gills
flap valves - no water in via gills

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12
Q

what is ram ventilation?

A

when the shark is moving - water comes in via the mouth - out via the gills
5-gill pairs in most sharks and rays

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13
Q

what is buccal pumping?

A

sharks at rest - water in via mouth and spiracles
- out via gills
flap valves - no water in via gills

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14
Q

how do filter feeders eat?

A

gill filaments contain gill rakers which

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15
Q

how have filter feeders evolved?

A

they have evolved independently in 3 shark species

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