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Animal Diversity > 12. Chordates > Flashcards

12. Chordates Flashcards

1
Q

What is the notochord and myomeres and why are they important in chordates? 4

A
  1. Notochord and myomeres 2. rigid rod along body 3. transforms into vertebrae in vertebrates - we have a notochord at embryonic stage that transforms into a spinal column 4. works with muscles to allow lateral undulations for swimming
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2
Q

What is the dorsal nerve cord and why is it important in chordates? 3

A
  1. dorsal relative to gut 2. opposed to invertebrates in which the nerve cord is ventral 3.often brain at anterior end of nerve cord
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3
Q

What is the importnace of pharyngeal gills and the endostyle in chordates?4

A
  1. breath in through mouth and water passes out over gills 2. in combination with endostyle used to filter feed 3.Cilia in openings move food towards the endostyle 4. transformation to gill arches and thyroid in higher vertebrates
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4
Q

What are cepalochordates? 5

A
  1. Small filter feeding marine animals 2. Also known as lancelets, amphioxus, Branchiostoma 3. Simple morphology seen as ‘archetypal chordate’ 4. Alive today - live at shores. 5. only a few inches big
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5
Q

What are the urochordates? 6

A
  1. Diverse group of marine invertebrates
  2. Also known as tunicates or sea squirts
  3. Filter feed in roughly the same way, mostly using siphons
  4. Tunicate larvae look like our early stages
  5. metamorphosis from chordate-like larva to sessile adult form involves digesting own brain
  6. Thaliaceans are pelagic, colonial with some asexula repro
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6
Q

What are the two groups of vertebrates? 2

A
  1. jawless/cyclostomata/agantha
  2. jawed/gnathostomata
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7
Q

What are the differenced between chordate and vertebrate anatomy? 10

A

Vertebrates have extra specialisation related to senses, locomotion and physiology,

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8
Q

What is special about vertebrate development? 10

A
  1. Neural crest, a migratory multipotent cell population, forms many structures that are specific to vertebrates
  2. Peripheral nervous system -Parts of the brain

3-Sensory capsules

4-Endocrine glands

  1. Parts of head and face
  2. Pigment cells -Parts of circulatory system
  3. Teeth and jaws
  4. Branchial skeleton
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9
Q

What is special about vertebrate genes? 6

A
  1. Have Hox genes - related to development pattern of body
  2. Amphioxus had one set
  3. duplication event, leading to hypothetical jawless vertebrate ancestor
  4. thought to be key reason for diversification and success of vertebratesw
  5. may be a safe back up in case a gene mutates, allowing for more experiementation
  6. the a second duplication event (4 sets) gave rise to modern vertebrates eg. mice
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10
Q

What are lampreys (lawless vertebrates)? 6

A
  1. Formal name for group: Petromyzontida
  2. Eel-like (anguilliform) morphology - convergent
  3. Parasitic freshwater-marine lifecycle - breed in freshwater
  4. Semelparity (single breeding event)
  5. No bone or jaws, just cartilages
  6. suck blood of fish
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11
Q

Decribe lamprey anatomy. 6

A
  1. Oral sucker with keratinous teeth
  2. Sucking velum apparatus
  3. Dorsal nasohypophysial opening - like a nostril on top of head
  4. 7 gill pouches with branchial cartilage
  5. Brain, cranium and sensory organs that are homologous with ours
  6. Arcualia (vertebrae) - cartilaginous and sit on nerve cord
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12
Q

Describe lamprey development. 5

A
  1. Larval stage: ammocoete
  2. Infaunal filter feeder
  3. Blind and lacks oral sucker
  4. Anatomically similar to cephalochordates
  5. Metamorphosis to adult stage
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13
Q

Describe the hagfish (jawless vertebrates). 6

A
  1. Formal name for group: Myxinoidea
  2. Eel-like (anguilliform) morphology
  3. Blind deep marine scavenger/predator
  4. Unique gelatinous slime and twisting escape - slime bands secrete mucus that expands quickly and forms knot that moves along body
  5. No bone or jaws, just cartilages
  6. Burrow into carcasses and eat their way out
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14
Q

Decribe hagfish anatomy. 6

A
  1. Tentacles and rasping keratinous teeth
  2. Velum and tongue apparatus
  3. Anterior single nasal opening
  4. Multiple gill pouches (5-16 pairs)
  5. Simple brain and sense organs - no cranium
  6. No vertebrae
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15
Q

Describe hagfish development. 4

A
  1. Very little know about hagfish
  2. Eggs hard to grow in a lab environment
  3. Discovery of neural crest in 2007
  4. Reconstruction of craniofacial development in 2013
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16
Q

Describe the anatomy of jawed vertebrates. 6

A
  1. Pectoral and pelvic fins, homologous with arms and legs
  2. Bone and dentine
  3. Hinged jaws
  4. Paired nostrils
  5. Ribs and ventral vertebrae
  6. Internal gill arches
17
Q

What groups are included in the jawed vertebrates? 4

A
  1. cartilaginous fish
  2. boney fish
  3. lobe finned fish
  4. tetrapods
18
Q

What is the traditional view of chordate phylogeny? 4

A

This is based on morphology and some genetics

19
Q

What is the modern view of chordate phylogeny?

A
  1. This is absed on whole genome analysis
  2. Suggests that in some cases there has been a loss of characteristics and genome simplification
20
Q

What is the traditional view of vertebrate phylogeny?

A
  1. This is based on the apparenty degeneracy of hagfish - but they are not vertebreates
21
Q

What is the view of vertebrate phylogeny based on morphology and physiology?

A
22
Q

What is the modern view of vertebrate morphology, based on benetic and microRNA analysis?

A
23
Q

What can we learn from cyclostome fossils? 9

A
  1. Soft-bodied so few of them
  2. We have one hagfish
  3. There are some cambrian fossils that may be chordate relatives
  4. Pikaia has possible sigmoidal myomeres, dorsal fin, notochord? But looks like annelid. Morris and Caron 2012
  5. Metaspriggina has notochord, post anal tail, paired eyes, gill bars? Moris and Caron 2014
  6. Myllokunmingia has paired eyes, nasal sacs, arcualia, gill pouches and dorsal fin, clearly fishy, Shu et al. 2013
  7. Yunnanozoan has possible pharynx and endostyle and disputed muscles, looks like nothing alive but seems to have gill slits
  8. Cathaymyrus has some muscle bands and gill slits? Shu et al, 2006
  9. there many interpretations of the phylogeny of these and no consenus
24
Q

What are the limitations of studying soft-bodied fossils? 9

A
  1. Taphonomy- study of fossilisation
  2. Decay and preservation can alter the appearance of fossilised beings
  3. A lot of information may be lost so can’t just compare anatomy to that of living beings
  4. decaying organisms may lose syanamorphies and appear more primitive
  5. Cathaymyrus only has decay resistant characters and looks rotten: Potentially any chordate
  6. Cartliage decays early, nerves are more robust
  7. Haikouichthys has some decay prone vertebrate characters but no skull: True stem-vertebrate
  8. If there was a skull, we would usually expect to see it
  9. some fossils cast aside as cannot be useful

Animal Diversity (13 decks)

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