diagnostic features of chordates

Question 1

what are the five main chordate diagnostic features?

Answer 1

notochord, pharyngeal slits, post anal tail, dorsal hollow nerve cord, and endostyle

Question 2

what is the notochord?

Answer 2

a rod that provides support, moves without shortening, and allows for movement - it runs anterior to posterior

Question 3

what is the dorsal hollow nerve cord’s purpose?

Answer 3

it develops into the CNS - connected to longitudinal muscles - runs from anterior to posterior

Question 4

what is the pharyngeal gill slits? purpose?

Answer 4

openings that match with the infoldings of the skin, aid in respiration

Question 5

what is the post anal tail? purpose?

Answer 5

extension to the notochord that extends down to the posterior end - helps with locomotion and navigation

Question 6

what is the endostyle? purpose? purpose of cilia?

Answer 6

mucus secreting structure. it is glandular in nature, with a longitudinal groove located ventrally on the floor of the pharynx. the mucus collects food particles that have been filtered from water by cilia. the cilia line the inner wall off the pharynx and move particles to the posterior end of the digestive tract

• Anatomy
	○ Glandular ventral pharyngeal groove 
• Function 
	○ Filter feeding - cilia pass food to digestive tract 
• Homologous structure in vertebrates = thyroid gland

Question 7

what is the thyroid glad analogous to? is it more or less developed?

Answer 7

the endostyle. less developed organisms have an endostyle - thyroid is more advances

Question 8

how are chordates classified?

Answer 8

phylum chordata

subphylums: urochordata, zephalochordata, and vertebrata

Question 9

what are subphylum urochordata known as? why?

Answer 9

tunicates - have “tunics” as they contain cellulose

Question 10

what are tunicates? two classes

Answer 10

• Small marine invertebrates !!!!!
	• Approx. 3000 extant species 
	• Two classes: 
		○ Class Ascidiacea 
		○ Class Appendicularia

Question 11

describe class ascidiacea

Answer 11

• Most are sessile, filter-feeders as adults - a derived character
• Brief free swimming larva
Adults retain gill slits and endostyle

Question 12

describe class appendicularia (Larvacea)

Answer 12

• Approx. 100 living species
• Have a mobile adult that resemble larvae (no metamorphosis)
•
Many represent paedomorphosis - child form

Question 13

what two paths can lead to paedomorphosis in larvacea?

Answer 13

○ Via neoteny - retention of larval characteristics past the time of reproductive maturity
○ Via progenesis - accelerated development of reproductive organs relative to somatic tissue

Question 14

what do neoteny and progenesis result from?

Answer 14

• Both neoteny and progenesis result from heterochrony:
• Changes in timing of events during development
• Two components:
○ The onset/offset (process)
○ The rate
• e.g. brain and head growth in primates:
○ In a chimp-occurs in fetus until birth
○ In humans: it is extended several years after birth

Question 15

what are cephalochordata known as? describe them

Answer 15

lancelets 
	• Marine invertebrates 
	• Approx. 27 extant species 
	• Small (<5 cm), most benthic in sandy bottoms 
Adults exhibit all 5 chordate features

Question 16

what group is sisters with vertebrata? phylogeny in lecture 1 notes

Answer 16

• Morphologically similar to vertebrates, but molecular analyses now places tunicates as the sister group of vertebrates

Question 17

what are subphylum vertebrata known as? why?

Answer 17

craniata
• More than 67,000 extant species
• Most have a cartilaginous or bony vertebrae
• All have a cartilaginous or bony cranium partially or fully enclosing the brain

Question 18

list the 6 general vertebrate characteristics

Answer 18

1. Have the five chordate characteristics
   
   2. Segmented muscles (myomeres- W shaped)
   3. Endoskeleton of cartilage and or bone
   4. Cranium and vertebrae
   5. Ventral heart with closed circulation
   6. Tripartite brain

Question 19

what are the ten organ systems?

Answer 19

a. Integumentary
b. Skeletal
c. Muscular
d. Digestive
e. Circulatory
f. Respiratory
g. Reproductive
h. Excretory
i. Nervous
j. Endocrine

Question 20

what is special about segmented muscles?

Answer 20

2. Segmented muscles (myomeres- W shaped)

○ Substantial modification in terrestrial forms

Question 21

what is special about endoskeleton in vertebrates?

Answer 21

3. Endoskeleton of cartilage and or bone
   ○ Living tissue; growth without molting
   ○ Bone is unique to vertebrates

Question 22

what is special about the cranium and vertebrae?

Answer 22

4. Cranium and vertebrae
   ○ Vertebrae arise from connective tissue sheaths
   ○ Surrounds the notochord and dorsal nerve cord

Question 23

what is special about the vertebrate heart?

Answer 23

5. Ventral heart with closed circulation
   ○ Closed circulation
   ○ Dorsal (posterior flow) and ventral (anterior flow)
   ○ Blood vessels

Question 24

what is special about the vertebrate brain?

Answer 24

6. Tripartite brain
   ○ An extension of the dorsal, hollow nerve cord
   ○ Constrictions form 3 distinct regions with 5 vesicles
   ○ Fore-, mid-, and hindbrain
   ○ Modified in various groups
   ○ Evolved before vertebrae