Biodiversity 5: Fish Flashcards

1
Q

What were the ancient jawless fish called?

A

Ostracoderms ‘shell-skinned’

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2
Q

Describe the Ostracoderms

A

Dominated 450-375 mil years ago
Went extinct ~150 mil years ago, outcompeted by jawed fish
Heavily armoured
Covered with bony plates and scales surfaced in dentine and enamel (Protection)
Plates around mouth probably acted as a scoop for shovelling food into mouth
Early forms lacked pectoral fins = probably poor swimmers

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3
Q

Give 2 species that are modern jawless fish

A

Hagfish and Lampreys

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4
Q

Describe modern jawless fish

A

Eel-like
No armour
Skeleton cartilaginous
Protective slime production
Lack paired fins and jaws

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5
Q

Describe hagfish

A

Many are scavengers that feed on dead animals
Enter body through opening and eat from inside out
Only vertebrate that are isotonic with seawater

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6
Q

Describe lampreys

A

Predators/parasites of fish
Adults may be freshwater/marine
Larvae (ammocoetes) are eel shaped suspension feeders that live in send
Go through metamorphosis
Cartilaginous ‘vertebral column’

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7
Q

What are jawed vertebrates called?

A

Gnathostoma

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8
Q

Describe the Gnathostoma

A

Jaws
2 pairs of appendages = active roles
Developed into:
Fish: pectoral & pelvic fins
Mammals: Forelimbs & hindlimbs

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9
Q

Describe the evolution of jaws

A

Hinged to work up/down unlike invertebrates
Arose from modification of skeletal rods that support the pharyngeal slits
= Shows evolution as a remodelling process, rather than a creative one

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10
Q

What are ancient jawed fish called?

A

Placoderms ‘plate skinned’

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11
Q

Describe the placoderms

A

Silurian to the end of the Devonian period
All extinct
Large group of predators
Heavily armoured, some with cleaver like plates for biting prey

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12
Q

What are the two types of modern jawed fish called?

A

Cartilaginous Fish
Bony fish

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13
Q

What are the 2 groups of cartilaginous fish

A

sharks & rays
Ratfish & chimaeras

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14
Q

Describe the features of cartilaginous fish

A
  • Flexible endoskeleton of cartilage (not bone!)
  • Cartilaginous skeleton is a derived trait → new to that group (didn’t belong to an ancestor)
  • Many are covered in small tooth-like placoid scales
  • Some have acute senses adapted to predatory lifestyle
  • Heterocercal tail (upper lobe bigger than lower lobe) and wing-like pectoral fins provide lift because body is negatively buoyant (heavy and no swim bladder)
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15
Q

Describe the acute senses some cartilaginous fish have evolved

A

Sharp vision, not colour
Nostrils with smell receptors
Lateral line system (row of microscopic organs) for detecting pressure changes
Electroreceptive organs in the head detect electric fields

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16
Q

Describe the tail and fins of cartilaginous fish

A

Heterocercal tail (upper lobe bigger than lower lobe) and wing-like pectoral fins provide lift because body is negatively buoyant (heavy and no swim bladder)

17
Q

What is the endoskeleton of bony fish made from?

A

Calcium phosphate

18
Q

What is the skin of bony fish like?

A

Flattened bony scales

19
Q

What system do bony fish use to detect pressure changes?

A

Lateral line system

20
Q

Describe the gas-sac organ in bony fish

A

→ either swim bladder or sometimes a lung
Hydrostatic organ for buoyancy
May act as an oxygen reservoir during periods of stagnation/ drought
= Don’t have to keep swimming to stay up in the water column
= Suggests bony fish derived from a murky freshwater ancestor

21
Q

Describe the gills in bony fish

A

Gills covered by an operculum, with pharyngeal muscles
Acts like bellows to keep water flowing across gills (even while fish isn’t moving)

22
Q

What type of fertilisation do most bony fish use?

A

External

23
Q

What are the 3 classes of bony fish?

A

Lobe-finned fish
Lungfish
Ray-finned fish

24
Q

What shape do all fish have? Describe it.

A

Fusiform means tapered at both ends
→ reduces drag for efficient movement in the water

(other marine organisms have convergently evolved this shape e.g penguins, seals, squid)

25
Q

Describe lobe-finned fish

A

Muscular pectoral and pelvic fins supported by extensions of the skeleton
Large bottom dwellers that may have walked on the sea bed
Coelacanth → only living species

26
Q

Describe lung-fish

A

Were dominant predators in the shallow waters of the Devonian
Have lungs and nostrils
Breathe air
Adaptation, allowing them to survive in stagnant ponds and swamps

27
Q

Describe ray-finned fish

A

Reduced scaled for increased mobility
Fins free from being wings, adapted as brakes (pectoral) or rudders (pelvic)
Homocercal tail allows better maneuverability
Evolved more efficient jaw
Maxilla now free and articulated

28
Q

What is another name for bony fish?

A

teleosts

29
Q

What are the Lake Malawi Cichlids an example of?

A

Example of great diversity and adaptive radiation

30
Q

Describe the case study of the Lake Malawi Cichlids

A

Relatively small as a body of water (when compared to the oceans)
Been isolated for 2 mil years
= 450 species of Cichlid have evolved to fill many niches in the lake
Consequence of both natural and sexual selection