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MBIO228 > Vertebrate origins > Flashcards

Vertebrate origins Flashcards

1
Q

What is a chordate?

A
  • Dorsal, hollow nerve cord
  • Notochord
  • Pharyngeal slits
  • post anal tail
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2
Q

What is a vertebrate?

A
  • Vertebrae
  • Neural crest cells (origin of vertebrate skeletal tissue)
  • Dermal bone

-Often: paired appendages, cephalisation, skull, closed circulation, red blood cells

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3
Q

What are the subphylums of Chordata?

A
  1. Urochordata
  2. Craniata
  3. Cephalochordata
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4
Q

What are craniates?

A

Chordates w/ cephalisation and bone/cartilage.

Especially vertebrates, but may lack vertebrae

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5
Q

How many vertebrates are there?

A

55,000 known living species

-27,000 tetrapods (0.5k marine)
- 28,000 fishes (16k marine)

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6
Q

What is cartilage?

A
  • Tough, semitransparent, elastic, flexible
  • Glycoprotein strengthened by collagen
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7
Q

What can mineralised skeleton be?

A
  • External (dermal) bone
  • Internal, derived from cartilage precursors (endochondral)
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8
Q

Why is bone important?

A

-Solid support for attachment of muscles
- Fast, efficient locomotion – avoid predators and catch prey
-Storehouse of chemicals (e.g. phosphates) for metbolism
- protection

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9
Q

What are examples of early vertebrate-like finds?

A
  • Conodonta (superclass) - 475 mya
  • Myllokunmingia & kin – 525 mya
  • Cephalochordates (e.g. pikaia) – 525 mya
  • Urochordates - 540 mya
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10
Q

What are the Ostracoderms?

A

Dominant fishes in the silurian

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11
Q

What are features of the Ostracoderms?

A
  • Bony shields over head + thorax
  • Often small, but some large (>1m)
  • Bony – still no jaws
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12
Q

What are some vertebrate innovations of the Ostracoderms?

A
  • Cellular bone
  • Dentine-like tissue
  • Paired limbs
  • Intricate sensory line systems
  • Complex eye muscles
  • Inner ear with 2 semi-circular canals
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13
Q

How many extinct superclasses are in Ostracoderms?

A

5

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14
Q

What are the extinct superclasses of Ostracoderms?

A
  • conodonta
  • Pteraspidomorphi
  • Anaspida
  • Thelodonti
  • Osteostracomorphi
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15
Q

What are features of the superclass Pteraspidomorphi? X

A
  • 10-20cm, but some up to 1.5m
  • Benthic filter feeders
  • Evolved reduced armour, narrower head shield, lateral projections
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16
Q

What are features of the superclass Anaspida? X

A
  • <15cm, fusiform, compressed
  • Benthic parasitic/ detrital feeders: marine –> freshwater
  • Overlapping tuberculate scales
  • Fin-like projections + muscles + internal skeleton –> manoeuvrability
17
Q

What are features of the superclass Thelodonti? X

A

– 10-20cm, fusiform, depressed, large head, horizontal mouth
- Hypoceral tail, dorsal + anal fins: benthic
– Forktail form - supra-benthic!
– Covered with characteristic scales or denticles ( like sharks)
- Stomach
– Lateral line

18
Q

What are features of the superclass Osteostracomorphi? X

A
  • Abundant and diverse
  • Large, anterior, bony shield with eye, nose & pineal openings
    – Ossification of endoskeleton
    – Epicercal tail, body form and paired fins creates lift
    – complex brain
19
Q

How many living superclasses are in Ostracoderms?

A

2

20
Q

What are the living superclasses of Ostracoderms?

A
  • Myxinomorphi
    – Petromyzontomorphi
21
Q

How many species and classes are in the superclass Myxinomorphi?

A

70 living species in 1 class: Myxini

22
Q

What are the preferred conditions of Myxinomorphi?

A
  • Temperate/cold temperate oceans, below 30m
  • Restricted to seawater: isosmotic!
23
Q

What are the features of Myxinomorphi?

A
  • Sister group to vertebrates: lack even primitive vertebrae
  • No true eyes
  • Mud-burrowing species extremely hypoxia tolerant
  • Predators of benthic inverts and scavengers (burrow into prey)
  • 70-200 pairs of slime glands: exude mucous and thread cells
24
Q

How many species and classes are in the superclass Petromyzontomorphi?

A

38 living species in one class: Petromyzontida

25
Q

What are the preferred conditions of Petromyzontida?

A
  • Freshwater species: may be parasitic
  • Anadromous species: all are parasitic
    – migrate to upper streams for spawning
26
Q

What are features of Petromyzontomorphi?

A
  • Functional eyes
  • Cerebellum
  • Separate ventral & dorsal roots of the spinal nerves (a vertebrate feature)
  • Olfactory and respiratory pathways are separated
27
Q

What is an example of a Hagfish?

A

Myxine glutinosa

28
Q

What is an example of a Lamprey?

A

Petromyzon marinus

29
Q

What are similarities between Hagfishes and Lampreys?

A
  • Eel-like, scale-less, jawless forms
    – Produce pathogen-specific defensive substances: “variable lymphocyte receptors” (vs. antibody proteins in gnathosomes)
  • Tongue posses keratinous, replaceable teeth
    – No stomach
30
Q

What are differences between Hagfishes and Lampreys?

A
  • Hagfishes produce mucus
    – FINS – H: continuous caudal, L: 1 or 2 dorsal, caudal
    – Mouth – H: terminal, L: Sub-terminal
    – Gill-openings – H: 1-16, L:7
    – Reproduction – H: repeat spawning, direct dev. from egg – L: terminal spawning, larval ammocoetes
    – Tongue – H: biting & tearing, L: rasping & sucking
31
Q
A

MBIO228 (7 decks)

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