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Vertebrate Zoology > Chordates > Flashcards

Chordates Flashcards

1
Q

What are the 4 major characteristics of the chordates?

A

Notochord
Post-anal tail
Dorsal hollow nerve cord
Pharyngeal gill slits

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2
Q

What is a chordate?

A

An animal with a notochord present at any stage of its life cycle

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3
Q

Give 6 defining characteristics of chordates which they share with other taxa.

A

Cephalisation
Segmented and regionally differentiated body plan
Bilateral symmetry
Ventral heart with closed circulation
Ventral blood flow from heart to anterior
Active

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4
Q

What is cephalisation?

A

Development of a brain

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5
Q

What are the 2 basic rules when deducing the course of chrodate evolution?

A

Principle of Maximum Parsimony

Distinguishing homologous from analogous characteristics

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6
Q

What is the Principle of Maximum Parsimony?

A

The simplest explanation that is consistent with the facts

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7
Q

What do analogous characteristics indicate?

A

Convergent evolution

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8
Q

What 7 things can we learn from when deducing the course of vertebrate evolution?

A 
Geology
Palaeontology
Fossils
'Living fossils'
Extant organisms
Anatomy
Comparative (statistical) analysis
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9
Q

Give an example of a living fossil

A

Coelacanth

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10
Q

Where does the coelacanth live?

A

Indian ocean

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11
Q

When were the coelacanths thought to have died out?

A

Over 65 mya

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12
Q

When was the coelacanth first seen alive?

A

1938

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13
Q

What are the 3 candidate ancestors for chordates?

A

Annelids
Echinoderms
Hemichordates

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14
Q

Who suggested annelids as an ancestor for chordates?

A

Semper and Dohrn, 1875

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15
Q

How would the proposed annelid flip-over make annelids a more likely ancestor of chordates?

A

Blood would flow forward ventrally

Relocation of mouth and anus

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16
Q

Why were annelids rejected as a chordate ancestor?

A 
Flip-over unlikely
Solid ventral nerve cord
Complete segmentation
No notochord
No gill slits
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17
Q

What 5 characteristics for annelids share with chordates?

A 
Bilateral symmetry
Segmented
Active
Cephalisation
Longitudinal nerve cord
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18
Q

What hypothesis supports echinoderms being chordate ancestors?

A

GBR hypothesis

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19
Q

What is the GBR hypothesis?

A

Chordates arose from the motile larval stage of marine echinoderms through paedomorphosis

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20
Q

What is paedomorphosis?

A

When the larval stage becomes sexually mature and independent of changes in adult morphology

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21
Q

What are the 3 problems with the GBR hypothesis?

A

Paedomorphosis is doubted
Gutmann’s (1981) ‘Chordates into Echinoderms’ theory
Recent molecular evidence shows only a subset of genes persist from tunicate larvae to adult

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22
Q

How is it suggested chordates evolved from hemichordates?

A

Progressive alteration of an active adult over millions of years

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23
Q

What is the most likely ancestor of the chordates?

A

Hemichordates

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24
Q

What are the 3 chordate sub-phyla?

A

Urochordata
Cephalochordata
Vertebrata

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25
Q

What are urochordata known as?

A

Tunicates (sea squirts)

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26
Q

What stage of a tunicate’s life cycle bears chordate characteristics?

A

Larval stage

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27
Q

How many species of tunicates are there?

A

2000

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28
Q

What kind of habitat do tunicates live in?

A

Marine

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29
Q

Are tunicates sessile or motile?

A

Most are sessile

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30
Q

Are tunicates solitary or colonial?

A

Most are colonial

31
Q

Describe the life cycle of a tunicate

A

Larval stage swims then settles out on a substrate by releasing adhesive substances. Undergoes radical metamorphosis.

32
Q

What does tunicate metamorphosis involve?

A

The nervous system degenerates and is reabsorbed
Loses internal organs, tail and notochord
Remaining organs rotate 90 degrees

33
Q

What chordate characteristic can still be seen in adult unicates?

A

Pharyngeal gill slits

34
Q

How do adult tunicates filter feed?

A

Water enters through incurrent siphon at the top, pharyngeal gill slits filter out food and water passes out excurrent siphon.

35
Q

What are the 3 distinct groups of urochordates?

A

Ascidiacea
Larvacea
Thaliacea

36
Q

Where do Ascidiaceans live?

A

All oceans, all depths

37
Q

Describe the social structure of Ascidiaceans

A

Live in social groupings where each individual has its own incurrent siphon, but share a group excurrent siphon where waste water is passed out

38
Q

Give 4 characteristics of Larvaceans

A

Solitary
Luminescent
Planktonic
Undergo paedomorphosis

39
Q

Where do Thaliaceans live?

A

Mainly tropical and subtropical waters, with some carnivorous species inhabiting abyssal depths

40
Q

What are Cephalochordates known as?

A

Lancelets

41
Q

How many species of cephalochordates are there?

A

29

42
Q

What kind of habitat to cephalochordates live in?

A

Marine, buried in sand

43
Q

True or false: cephalochordates are dioecious

A

True

44
Q

What stage of a cephalochordate’s life cycle bears chordate characteristics?

A

Larval and adult

45
Q

How do cephalochordates get oxygen?

A

Diffusion

46
Q

What type of feeders are cephalochordates?

A

Ciliary-mucous suspension feeders

47
Q

Describe the process of cephalochordate ciliary-mucous suspension feeding

A

Buccal cirri sort food pre-entry by preventing sediments and other large particles from entering the mouth. Water enters the mouth and goes through the pharyngeal gill slits.

48
Q

What unique structure possessed by cephalochordates is a possible precursor to the pituitary gland?

A

Hatscheks Pit

49
Q

What is a Hatscheks Pit?

A

Structure near the mouth and brain which secretes mucus to be transferred to the cirri

50
Q

What is the main function of cephalochordate fins?

A

Storing fat and nutritional reserves for use during reproductive stages and gamete production

51
Q

Which 2 sub-phyla of chordates have atrium and atriopore folds?

A

Urochordates and cephalochordates

52
Q

Describe the cephalochordate circulatory system

A

Dorsal aorta and ventral heart

53
Q

What 2 things do cephalochordates and vertebrates share?

A

Podocytes

Embryonic features

54
Q

What are podocytes?

A

Specialised excretory cells for getting rid of salts etc

55
Q

How long have vertebrates been around?

A

Since the Cambrian, possibly Pre-Cambrian period

56
Q

Give 4 key characteristics of a vertebrate

A

Cranium
Brain
Paired eyes
Vertebral Column

57
Q

What replaces the notochord in vertebral development?

A

Vertebral column, cartilage and bone

58
Q

What are the craniata?

A

A collective group of chordates with craniums, but not necessarily vertebral columns

59
Q

Give an example of a craniate without a vertebral column

A

Hagfish

60
Q

What 2 things is the Hox gene involved in?

A

Development

Morphology

61
Q

What event(s) was important in allowing the diversity of vertebrates and their body plans?

A

Duplication of the Hox gene complex

62
Q

When did the first Hox gene duplication occur?

A

When vertebrates first evolved

63
Q

When did the second Hox gene duplication occur?

A

When animals evolved jaws

64
Q

Advantage of evolving a head

A

Cranium, complex move and feed

65
Q

Advantage of evolving a vertebral column

A

Support

66
Q

Advantage of evolving jaws

A

Life as a predator

67
Q

Advantage of evolving bone

A

Replaces cartilage support

68
Q

Advantage of evolving lungs

A

Breathing in air

69
Q

Advantage of evolving legs

A

Move on land

70
Q

Advantage of evolving amniotic eggs

A

Reproduce without water

71
Q

Advantage of evolving milk

A

Suckling young

72
Q

What did the key evolutionary steps of morphological features allow animals to do?

A

Exploit new ways of life, live in new habitats, use new resources

73
Q

What are the 8 key evolutionary steps in vertebrate history?

A 
Head
Vertebral column
Jaws
Bone
Lungs
Legs
Amniotic egg
Milk
74
Q

Name the 8 extant vertebrate groups

A 
Myxinoidea
Petromyzontia
Chondrichthes / Elasmobranchii
Osteichthyes
Amphibia
Reptilia
Aves
Mammalia

Vertebrate Zoology (4 decks)

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