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Organisms 2 > Lecture 17 > Flashcards

Lecture 17 Flashcards

1
Q

Protochordata, Craniata, Gnathostomata

A

All are within Phylum Chordata

  • Protochordata
  • Do not have a true brain, skull, or vertebral column
  • Craniata (i.e. Vertebrata)
  • Have a skull (cranium) and/or vertebral column
  • Agnatha (Hagfish and Lampreys) only have a skull (no vertebrae)
  • Gnathostomata
  • Craniates with jaws
  • Includes all of Craniata except for Agnatha
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2
Q

Phylogeny of fish!

A

fish itself is any non tetrapod vertebrate

Agnatha
Osteichthyes* (Bony Fishes)
Chondrichthyes

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3
Q

General characteristics to distinguish what is a fish (5)

A
  • Form
  • Locomotion in water
  • Neutral buoyancy and the swim bladder
  • Respiration
  • Osmotic regulation
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4
Q

Form – types of scales for fish

A
  • Placoid scales
  • Ganoid scales
  • Cycloid and Ctenoid scales
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5
Q

Placoid scales

A
  • Small, conical, toothlike structures
  • Typical of chondrichthyes
  • Modified to teeth in sharks
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6
Q

Ganoid scales

A
  • Diamond shaped

* Early bony fishes and living gars

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7
Q

Cycloid and Ctenoid scales

A
  • Arranged in overlapping rows

* Typical of teleost fish

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8
Q

Locomotion in Water for fish

A

Movement achieved through undulation of the posterior end
• Generates thrust (forward motion) and lateral force (sideways motion)
• The lateral force causes fish head to “yaw”, or deviate in the same direction as the tail
• The “yaw” occurs more in more flexible fish
• A less flexible body plan is conducive to speed!!!!!!!!!!!!!!!

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9
Q

Buoyancy in fish

A

Swim bladder = gas-filled organ
Volume adjusted for neutral buoyancy

present in most pelagic (open sea) bony fishes

Not in very deep fish, and most bottom-dwellers

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10
Q

Why don’t Chondricthyes (e.g. sharks) have no swim bladder

A
  • Asymmetrical tail provides lift,

* Large livers with squalene (particularly buoyant lipid)

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11
Q

Respiration for fish

A

Most fish use gills
• Breathe dissolved oxygen (oxygen that is in the water)
• Gills are located in the pharyngeal cavity
• Gills are covered with an operculum in bony fishes
• Increases efficiency of respiration
• Not present in sharks and rays
• Some fish also have lungs ,Capable of breathing air

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12
Q

Gills in fish

A
  • Gill composed of thin filaments covered with an epidermal membrane
  • The membrane is folded repeatedly into plate-like lamellae
  • Enormous surface area
  • Lamellae contain main blood capillaries
  • Water is pumped continuously in the mouth, over the gills and out through the gill slits
  • Gas exchange occurs across thin walls of blood capillaries
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13
Q

Osmotic Regulation in fish

A
  • Maintenance of balance of fluids
  • Freshwater and Marine fish have opposite challenges
  • Freshwater fish are hyperosmotic regulators
  • Marine fish are hypoosmotic regulators
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14
Q

Hyperosmotic Regulators

A

Freshwater fish
• Greater salt concentration in fish than in surrounding water
• Scales and mucous protect the fish, but water can enter across membranes (e.g. gills)
• Water pumped out by kidneys
• Salt-absorbing cells in the gill move salt from water to blood

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15
Q

Hypoosmotic Regulators

A
  • Marine fish
  • Contain a smaller concentration of salt than surrounding water
  • Salt-secretory cells in the gill move salt out of body
  • Salt is voided with feces or excreted by the kidney
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16
Q

Agnatha - Hagfishes caracteristics

A
  • Jawless
  • Entirely marine group
  • Feed on annelids, molluscs, crustaceans, and dead or dying fishes
  • Scavengers and predators (not parasitic)
  • Poorly developed eyes
  • Keenly developed sense of smell and touch
  • Produce slime as a defence mechanism
17
Q

Feeding and movement of hagfish

A

Agnatha
• Hagfish rasps bits of flesh from its prey
• Keratinized plates on tongue • Can itself into knot
• Passes the knot forward along its body until it is pressed securely against the side of its prey (for leverage)

18
Q

Agnatha - Lamprey carcteristics

A
  • Half are parasitic

* They use tooth-like plates of keratin for rasping a hole, through which fluids and tissues are sucked.

19
Q

Chondrichthyes carcteristics

A
  • Cartilaginous fishes (sharks, rays, chimaeras)
  • Cartilaginous skeleton
  • Bone entirely absent
  • Placoid scales
  • No swim bladder
20
Q

Chondrichthyes species

A

Rays: skates, stingrays, electric rays, and manta rays
• Dorsoventrally flattened bodies

Chimaeras (also called ratfishes)
• Closest living relatives are sharks
• Instead of teeth their jaws bear large flat plates

Sharks
• Apex predators – most feed at the top of the
marine food chain
• Some exceptions: e.g. whale shark – largest extant fish species (up to 15 m) – is slow-moving and feeds on plankton
• Spined pigmy shark – 28 cm – feeds on small fishes

21
Q

Sharks body plan

A

• Asymmetrical heterocercal tail
• Vertebral column turns upward and extends into the dorsal lobe of
the tale
• Provides lift as the shark swims
• Must constantly move to avoid sinking (even while sleeping!)

22
Q

Osteichthyes

A

• Bony Fish
• Bone replaces cartilage
• 2 groups
• Ray-finned fishes & Lobe-finned fishes
• Gas-filled pouch branches from esophagus
• In fish that use these pouches primarily for gas exchange, they are
called lungs
• In fishes that use these pouches primarily for buoyancy, they are called swim bladders

23
Q

Gills vs Lungs

A
  • Which evolved first? Probably gills, but lungs also evolved early
  • Ancestor of ray-finned and lobe-finned fishes had gills and lungs

In lobe-finned fishes (and tetrapods) lungs were preserved
• Modern lobe-finned fish also retained gills
• In ray-finned fishes, gills were preserved and lungs were adapted into swim bladder

24
Q

Ray-finned fishes

A
  • Symmetrical homocercal tail allows for greater speed

* Permitted by the swim bladder and improved control of buoyancy

25
Q

Lobe-finned fishes

A
  • Small group
  • 6 species of lungfishes
  • 2 species of coelacanths
  • Ancestor of tetrapods is found within an extinct lineage of this group
  • Lobe fins with a single bone that articulates with rest of body
  • Diphycercal tails
  • Lungs and gills
26
Q

Lungfishes

A
  • Can live out of water for extended periods of time

* E.g. African lungfishes live in streambeds during the dry season. They remain dormant until rain returns.

Organisms 2 (23 decks)

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