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VERTEBRATE EVOL > Origin of vertebrates > Flashcards

Origin of vertebrates Flashcards

(59 cards)

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1
Q

big gap btw:

A

rise of deteurostome and first appearance of chordates

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2
Q

earliest chordate fossils:

A

530mya

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3
Q

clues found about precursors to chordates by:

A
  • comparing basal modern chordates w sister taxa
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4
Q

current understanding of life: MBNDCAmOl

A 
Metazoa
Bilateria
Nephrozoa
Deuterostomia
Chordata
Ambulacraria
Olfactores
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5
Q

metazoa:

A

multicellular animals

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6
Q

bilateria:

A

bilateral symmetry at some point of life cycle

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7
Q

nephrozoa (or coelomta):

A

incl. deuterostomes and protostomes

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8
Q

deuterostomes:

A

chordates and ambulacraria

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9
Q

common features: metazoans

A
  • whip-like tails on sperm
  • embryo forms hollow ball of cells (blastula)
  • sex cells formed in special organs
  • collegen is structural protein
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10
Q

common features: animals more complicated than sponges (and eg.)

A
  • 2 distinct cell layers: endo/ectoderm

- eg. cnidarians like jellyfish and coral have these 2 layers

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11
Q

common features: bilataria

A
  • developed 3rd middle layer: mesoderm which forms body mm
  • bilaterally symmetrical, gut open at both ends
  • head at one end (w mouth)
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12
Q

common features: coelom

A
  • inner body cavity

- those w coelom part of Coelomata

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13
Q

coelom divides into:

A
  • protostomes

- deuterostomes

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14
Q

key differences btw protostomes and deuterostomes seen in:

A

early dev

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15
Q

body plan: first stages and diff btw protostomes and deuterostomes

A
  • fertilisation egg -> zygote
  • zygote divides via cleavage into smaller cells (blastomeres)
  • bilateral animals have 2 types of cleavage:

spiral: protostomes
radial: deuterostomes

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16
Q

body plan: protostomes cleavage features

A
  • spiral cleavage
  • cells divide to give quartet
  • tightly packed
  • mosaic dev
  • offset cells
  • highly predetermined cells, damage = defective organism
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17
Q

body plan: deuterostomes cleavage features

A
  • radial cleavage
  • symmetrical cleaving planes, aligned cells
  • tiered cells
  • regulative dev
  • daughter cells omnipotent (determination occurs later in dev)
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18
Q

protostomes: eg

A
  • mollusc
  • annelids
  • arthropods
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19
Q

deuterostomes: eg

A
  • echinoderms
  • hemichordates
  • chordates
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20
Q

body plan: coelum formation protostomes

A
  • mesoderm forms band of tissue around blastophore, migrates inward and splits into 2
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21
Q

body plan: coelum formation deuterostomes

A
  • mesoderm forms as pocket from gut which pinches off eventually
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22
Q

body plan: blastophore protostomes

A
  • eventually becomes mouth and pushes through to future anus
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23
Q

body plan: blastophore deuterostomes

A
  • eventually becomes anus to meet mouth
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24
Q

deuterostomes: comprised of (6)

Study These Flashcards
A
  • verterbrates
  • cephalochordates
  • urochordates
  • hemichordates
  • echinoderms
  • xenoterbellids
25
ambulacraria: comprised of (3)
- from deuterostomes - hemichordates - echinoderm - xenoterbellid
26
ambulacraria: hemichordates eg.
- pterobranchs | - acorn worms
27
ambulacraria: hemichordates general features
- fern-like wormy creatures - burrow into sediment/ float in water column to settle in new places - was thought sis group to chordates, pharyngeal slits and endostyle (all deurostomes have these features)
28
ambulacraria: echinoderm general features and eg.
- larval characteristics fit - extant species no pharyngeal slits, fossil evidence some did - larvae bilaterally symmetrical and ancient adult echinoderms eg. starfish
29
ambulacraria: xenoterbellid general features and eg.
- worm-like, only 2 species | - recently added, due to molecular analysis is related to hemichordate and echinoderm
30
chordates: comprised of
- from deuterostomes - cephalochordates - urochordates - vertebrates
31
chordates: cephalochordates general features and eg.
- aka lancelets and eg. amphixious | - sml fish-like capable of swimming, majority buried in marine sediments
32
chordates: urochordates general features and eg.
- incl. acidians and sea squirts - sedentary filter feeders - brief free-swimming larval phase - larval phase places them in chordata
33
chordate characteristics: list (5)
- notochord - muscular, postanal tail - pharyngeal slits - endostyle - brain, dorsal nn. cord MUST be apparent at some point of lifecycle (eg. tunicates- larval stage)
34
chordate characteristics: notochord
- rod like - flexible, stiff: hydrostatic organ - extends length of body - first structure of endoskeleton to appear in embryo - reduced to cartilaginous disks (nucleus pulposus) in organisms w vertebrate
35
chordate characteristics: muscular postanal tail
- stiffened notochord w mm. provided motility for early chordates - evolved propulsion in water - many fish expanded to incl caudal tail= increase propulsion
36
chordate characteristics: pharyngeal slits
- pharynx digestive tract immediately post to mouth - pharynx pierces at dev stage - role in suspension feeding for primitive chordates (pharyngeal basket) - helped in respiration ie. fish gills -> structures of pharyngeal slits and arches become ear, neck, jaw parts
37
chordate characteristics: endostyle
- mucus centre: help w transport of food items to gut - present in protochordates and lamprey larvae - sequesters iodine - later becomes thyroid gland
38
chordate characteristics: dorsal nn cord
- beginning of CNS, formed through invagination of ectoderm - dorsal to digestive tract - hollow - ant end (bulges) extends from brain - passes through neural arches of vert in vertebrates - brain highly dev and protected by cranium
39
list basals and eg.
- cephalochordates (lancelets) | - urochordates (tunicates)
40
urochordata: features
- marine, filter feeders (sedentary) - 2000 extant species - larvae have chordate characteristics - acidians
41
urochordata: eg.
- acidians - sea squirts - cunjevoi - sea pork
42
urochordata: filter system
- siphon water - suck thorugh incurrent siphon - food filtered in basket-like pharynx (in atrium) - water passes out excurrent siphone - food particles trapped pass into oesophagus, digested in stomach and waste passes out anus
43
urochordata: chordate characterstics
- found in only free swimming larvae (100 free living species) - notochord, dorsal nn chord, postanal tail
44
Garstang hypothesis:
- ancestral vert derived from larvae sedentary adult stage - we now think ascidian sedentary adult stage is derived character and ancestral chordate most likely free-swimming filter feeder
45
cephalochordata: features
- small eel-like animals - 30 species - most species burrow in sediment as adults - share lot of characteristics w ascidians (urochordates) esp feeding apparatus
46
cephalochordata: eg.
- lancelet | - amphioxus
47
cephalochordata: shared characteristics w vert
- notochord - dorsal tubular nn chord - postanal tail - segmented mm blocks along flanks - similar circulatory sys
48
cephalochordata: characteristic differences
- asymmetrical dev - nn chord does not enlarge into brain - notochord elongated for burrowing - pharyngeal slits not as gills -> filter feed - atrium assoc w filter feeding - mm layered as myomeres (like fish)
49
vertebrata/ craniata: general features
- protects nn cord - early in dev replaces notochord completely (IVD only remnants) - defined skull to protect well dev brain - obvious head w lots sensory sys
50
vertebrata/ craniata: embryonic features
- duplication Hox genes - appearance of neural crest cells, placodes - multiplication of microRNAs
51
conservation of dev genes: controlled by
- HOX gene complex - cell dev and differentiation - innovation arrived from duplication of entire HOX gene complex
52
conservation of dev genes: 1 copy
- urochordates | - cephalochordates
53
conservation of dev genes: 2 copies
- agnathans
54
conservation of dev genes: 4 copies
- gnathostomes (all jawed vert)
55
conservation of dev genes: 8+ copies
- teleosts | - reason for domination of teleost fishes today
56
neural crest: features
- 4th germ layer - responsible for novel vert structures esp around head -
57
placodes: features
- similar to neural crest cells, diff og - also migrate out give rise to complex sensory organs (nose, eyes, inner ear) - lateral line and cranial nn
58
microRNA: features
- regulate synthesis of proteins - chordates have 2 new microRNA - vert share further 3 - all vert share additional 41 - each vert lineage has evolved set of microRNA
59
brains: general features and eg. amphioxus
- 3 principal areas: fore/mid/hindbrain - less well dev brain, lack genes to form forebrain - gene expression largely responsible for evolutionary innovations

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