Chordates

Question 1

What are the 4 major characteristics of the chordates?

Answer 1

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

Question 2

What is a chordate?

Answer 2

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

Question 3

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

Answer 3

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

Question 4

What is cephalisation?

Answer 4

Development of a brain

Question 5

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

Answer 5

Principle of Maximum Parsimony

Distinguishing homologous from analogous characteristics

Question 6

What is the Principle of Maximum Parsimony?

Answer 6

The simplest explanation that is consistent with the facts

Question 7

What do analogous characteristics indicate?

Answer 7

Convergent evolution

Question 8

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

Answer 8

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

Question 9

Give an example of a living fossil

Answer 9

Coelacanth

Question 10

Where does the coelacanth live?

Answer 10

Indian ocean

Question 11

When were the coelacanths thought to have died out?

Answer 11

Over 65 mya

Question 12

When was the coelacanth first seen alive?

Answer 12

1938

Question 13

What are the 3 candidate ancestors for chordates?

Answer 13

Annelids
Echinoderms
Hemichordates

Question 14

Who suggested annelids as an ancestor for chordates?

Answer 14

Semper and Dohrn, 1875

Question 15

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

Answer 15

Blood would flow forward ventrally

Relocation of mouth and anus

Question 16

Why were annelids rejected as a chordate ancestor?

Answer 16

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

Question 17

What 5 characteristics for annelids share with chordates?

Answer 17

Bilateral symmetry
Segmented
Active
Cephalisation
Longitudinal nerve cord

Question 18

What hypothesis supports echinoderms being chordate ancestors?

Answer 18

GBR hypothesis

Question 19

What is the GBR hypothesis?

Answer 19

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

Question 20

What is paedomorphosis?

Answer 20

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

Question 21

What are the 3 problems with the GBR hypothesis?

Answer 21

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

Question 22

How is it suggested chordates evolved from hemichordates?

Answer 22

Progressive alteration of an active adult over millions of years

Question 23

What is the most likely ancestor of the chordates?

Answer 23

Hemichordates

Question 24

What are the 3 chordate sub-phyla?

Answer 24

Urochordata
Cephalochordata
Vertebrata

Question 25

What are urochordata known as?

Answer 25

Tunicates (sea squirts)

Question 26

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

Answer 26

Larval stage

Question 27

How many species of tunicates are there?

Answer 27

2000

Question 28

What kind of habitat do tunicates live in?

Answer 28

Marine

Question 29

Are tunicates sessile or motile?

Answer 29

Most are sessile

Question 30

Are tunicates solitary or colonial?

Answer 30

Most are colonial

Question 31

Describe the life cycle of a tunicate

Answer 31

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

Question 32

What does tunicate metamorphosis involve?

Answer 32

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

Question 33

What chordate characteristic can still be seen in adult unicates?

Answer 33

Pharyngeal gill slits

Question 34

How do adult tunicates filter feed?

Answer 34

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

Question 35

What are the 3 distinct groups of urochordates?

Answer 35

Ascidiacea Larvacea Thaliacea

Question 36

Where do Ascidiaceans live?

Answer 36

All oceans, all depths

Question 37

Describe the social structure of Ascidiaceans

Answer 37

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

Question 38

Give 4 characteristics of Larvaceans

Answer 38

Solitary Luminescent Planktonic Undergo paedomorphosis

Question 39

Where do Thaliaceans live?

Answer 39

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

Question 40

What are Cephalochordates known as?

Answer 40

Lancelets

Question 41

How many species of cephalochordates are there?

Answer 41

29

Question 42

What kind of habitat to cephalochordates live in?

Answer 42

Marine, buried in sand

Question 43

True or false: cephalochordates are dioecious

Answer 43

True

Question 44

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

Answer 44

Larval and adult

Question 45

How do cephalochordates get oxygen?

Answer 45

Diffusion

Question 46

What type of feeders are cephalochordates?

Answer 46

Ciliary-mucous suspension feeders

Question 47

Describe the process of cephalochordate ciliary-mucous suspension feeding

Answer 47

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.

Question 48

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

Answer 48

Hatscheks Pit

Question 49

What is a Hatscheks Pit?

Answer 49

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

Question 50

What is the main function of cephalochordate fins?

Answer 50

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

Question 51

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

Answer 51

Urochordates and cephalochordates

Question 52

Describe the cephalochordate circulatory system

Answer 52

Dorsal aorta and ventral heart

Question 53

What 2 things do cephalochordates and vertebrates share?

Answer 53

Podocytes | Embryonic features

Question 54

What are podocytes?

Answer 54

Specialised excretory cells for getting rid of salts etc

Question 55

How long have vertebrates been around?

Answer 55

Since the Cambrian, possibly Pre-Cambrian period

Question 56

Give 4 key characteristics of a vertebrate

Answer 56

Cranium Brain Paired eyes Vertebral Column

Question 57

What replaces the notochord in vertebral development?

Answer 57

Vertebral column, cartilage and bone

Question 58

What are the craniata?

Answer 58

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

Question 59

Give an example of a craniate without a vertebral column

Answer 59

Hagfish

Question 60

What 2 things is the Hox gene involved in?

Answer 60

Development | Morphology

Question 61

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

Answer 61

Duplication of the Hox gene complex

Question 62

When did the first Hox gene duplication occur?

Answer 62

When vertebrates first evolved

Question 63

When did the second Hox gene duplication occur?

Answer 63

When animals evolved jaws

Question 64

Advantage of evolving a head

Answer 64

Cranium, complex move and feed

Question 65

Advantage of evolving a vertebral column

Answer 65

Support

Question 66

Advantage of evolving jaws

Answer 66

Life as a predator

Question 67

Advantage of evolving bone

Answer 67

Replaces cartilage support

Question 68

Advantage of evolving lungs

Answer 68

Breathing in air

Question 69

Advantage of evolving legs

Answer 69

Move on land

Question 70

Advantage of evolving amniotic eggs

Answer 70

Reproduce without water

Question 71

Advantage of evolving milk

Answer 71

Suckling young

Question 72

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

Answer 72

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

Question 73

What are the 8 key evolutionary steps in vertebrate history?

Answer 73

``` Head Vertebral column Jaws Bone Lungs Legs Amniotic egg Milk ```

Question 74

Name the 8 extant vertebrate groups

Answer 74

``` Myxinoidea Petromyzontia Chondrichthes / Elasmobranchii Osteichthyes Amphibia Reptilia Aves Mammalia ```