Origin of vertebrates Flashcards

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)

A
  • verterbrates
  • cephalochordates
  • urochordates
  • hemichordates
  • echinoderms
  • xenoterbellids
25
Q

ambulacraria: comprised of (3)

A
  • from deuterostomes
  • hemichordates
  • echinoderm
  • xenoterbellid
26
Q

ambulacraria: hemichordates eg.

A
  • pterobranchs

- acorn worms

27
Q

ambulacraria: hemichordates general features

A
  • 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
Q

ambulacraria: echinoderm general features and eg.

A
  • larval characteristics fit
  • extant species no pharyngeal slits, fossil evidence some did
  • larvae bilaterally symmetrical and ancient adult echinoderms

eg. starfish

29
Q

ambulacraria: xenoterbellid general features and eg.

A
  • worm-like, only 2 species

- recently added, due to molecular analysis is related to hemichordate and echinoderm

30
Q

chordates: comprised of

A
  • from deuterostomes
  • cephalochordates
  • urochordates
  • vertebrates
31
Q

chordates: cephalochordates general features and eg.

A
  • aka lancelets and eg. amphixious

- sml fish-like capable of swimming, majority buried in marine sediments

32
Q

chordates: urochordates general features and eg.

A
  • incl. acidians and sea squirts
  • sedentary filter feeders
  • brief free-swimming larval phase
  • larval phase places them in chordata
33
Q

chordate characteristics: list (5)

A
  • notochord
  • muscular, postanal tail
  • pharyngeal slits
  • endostyle
  • brain, dorsal nn. cord

MUST be apparent at some point of lifecycle (eg. tunicates- larval stage)

34
Q

chordate characteristics: notochord

A
  • 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
Q

chordate characteristics: muscular postanal tail

A
  • stiffened notochord w mm. provided motility for early chordates
  • evolved propulsion in water
  • many fish expanded to incl caudal tail= increase propulsion
36
Q

chordate characteristics: pharyngeal slits

A
  • 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
Q

chordate characteristics: endostyle

A
  • mucus centre: help w transport of food items to gut
  • present in protochordates and lamprey larvae
  • sequesters iodine
  • later becomes thyroid gland
38
Q

chordate characteristics: dorsal nn cord

A
  • 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
Q

list basals and eg.

A
  • cephalochordates (lancelets)

- urochordates (tunicates)

40
Q

urochordata: features

A
  • marine, filter feeders (sedentary)
  • 2000 extant species
  • larvae have chordate characteristics
  • acidians
41
Q

urochordata: eg.

A
  • acidians
  • sea squirts
  • cunjevoi
  • sea pork
42
Q

urochordata: filter system

A
  • 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
Q

urochordata: chordate characterstics

A
  • found in only free swimming larvae (100 free living species)
  • notochord, dorsal nn chord, postanal tail
44
Q

Garstang hypothesis:

A
  • 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
Q

cephalochordata: features

A
  • small eel-like animals
  • 30 species
  • most species burrow in sediment as adults
  • share lot of characteristics w ascidians (urochordates) esp feeding apparatus
46
Q

cephalochordata: eg.

A
  • lancelet

- amphioxus

47
Q

cephalochordata: shared characteristics w vert

A
  • notochord
  • dorsal tubular nn chord
  • postanal tail
  • segmented mm blocks along flanks
  • similar circulatory sys
48
Q

cephalochordata: characteristic differences

A
  • 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
Q

vertebrata/ craniata: general features

A
  • 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
Q

vertebrata/ craniata: embryonic features

A
  • duplication Hox genes
  • appearance of neural crest cells, placodes
  • multiplication of microRNAs
51
Q

conservation of dev genes: controlled by

A
  • HOX gene complex
  • cell dev and differentiation
  • innovation arrived from duplication of entire HOX gene complex
52
Q

conservation of dev genes: 1 copy

A
  • urochordates

- cephalochordates

53
Q

conservation of dev genes: 2 copies

54
Q

conservation of dev genes: 4 copies

A
  • gnathostomes (all jawed vert)
55
Q

conservation of dev genes: 8+ copies

A
  • teleosts

- reason for domination of teleost fishes today

56
Q

neural crest: features

A
  • 4th germ layer
  • ## responsible for novel vert structures esp around head
57
Q

placodes: features

A
  • 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
Q

microRNA: features

A
  • 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
Q

brains: general features and eg. amphioxus

A
  • 3 principal areas: fore/mid/hindbrain
  • less well dev brain, lack genes to form forebrain
  • gene expression largely responsible for evolutionary innovations