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Animal kingdom > Chordates > Flashcards

Chordates Flashcards

1
Q

Summary

5 key features of the Chordates

A
  1. Notochord,
  2. dorsal hollow nerve cord,
  3. pharyngeal slits,
  4. endostyle,
  5. post anal tail
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2
Q

Chordates are Deuterostomes [all previous to this protostomes]
4 points

A
  1. Triploblastic
  2. Radial cleavage
  3. Mesoderm comes from archenteron (=enterocoely)
  4. Blastopore becomes anus
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3
Q

classification

A

Phylum: chordates

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4
Q

Definition of chordates

A
  1. Deuterostomes that have, for at least part of their life cycle:

A notochord (L. chorda = “string”)

A hollow dorsal nerve cord

Pharyngeal slits

An endostyle

A post-anal tail

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5
Q

Notochord [important in function]

6 points

A
  1. A flexible rod of glycoproteins encased in actin
  2. Mesoderm origin
  3. Muscle attachment
  4. Precursor of vertebrae
    In most vertebrates it becomes part of the intervertebral disc
  5. Signalling during development
  6. Can be found in:
    Cephalochordates, larvae of tunicates

Hagfish, lampreys

African lungfish, coelocanth, sturgeons, tadpoles

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6
Q

Hollow Dorsal Nerve Cord

A
  1. Forms from the ectoderm

2. In non-chordates, the nerve cord is solid and ventral

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7
Q

Pharyngeal Slits

A
  1. Openings in pharynx
    Allow water to flow in via the mouth and out of the pharynx
    Filter feeding
Retained as gill slits in jawless fish (7) 
cartilaginous fish (5, occasionally 6-7)  
bony fish (1)
2. Pharyngeal arches become, in vertebrates:
Jaw bone(s)

Hyoid bone

In fish: brachial skeleton (supports gills) and/or pharyngeal jaws

In tetrapods: parts of ear, tonsils, thymus

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8
Q

Endostyle

3 points

A
  1. Organ within the pharynx
    Present in cephalochordates, tunicates, larval lampreys; assists in filter feeding
  2. Secretes mucus
    Food particles adhere to mucus
    Cilia sweep mucus through pharynx into oesophagus
  3. Adapted into thyroid gland
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9
Q

Post-anal tail

4 points

A
  1. Has muscular (and skeletal) components
  2. Notochord and nerve cord extend into the tail
  3. Evolved for propulsion in water
  4. In non-chordates the digestive system runs the full length of the body.
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10
Q

Respiration & Circulation

2 points

A
  1. The primitive chordate respires through diffusion across skin

Pharyngeal slits devoted to feeding not oxygen exchange

  1. Basic circulation of blood

Dorsal system of vessels run from head to tail, paired aortae in front half

Ventral vessels run from tail to head via the liver

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11
Q

Nervous system

A
  1. Dorsal nerve cord protected by the notochord
  2. Slight enlargement at anterior end forms brain
  3. Visual sense organs located in neural tube
    Frontal eye
    Joseph cells in dorsal part
    Hesse organs in ventral part
  4. Oral cirri have sensory cells
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12
Q

Digestion and Excretion

4 points

A
  1. Gather plankton into pharynx
  2. Attaches to mucus produced by endostyle

Cilia push mucus over pharyngeal arches

Once laden with food, mucus pushed into digestive tract

  1. Water passes through pharyngeal slits into atrium and then out via the atriopore / gonopore
  2. The liver is a blind-ending caecum that branches from the gut

Cell lining engulfs food particules

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13
Q

Other Systems
Excretion
4 points

A
  1. Segmented ‘kidneys’ have protonephridia
  2. More like the invertebrate system
  3. Blind-ended
  4. Osmoregulation through partial pressurisation
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14
Q

Other Systems
Reproduction
4 points

A
  1. Segmented gonads
  2. Spawn once a year
  3. External fertilisation
  4. Larvae are planktonic
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15
Q

Phylum Chordata

3 points

A
  1. May be a very old phylum (c. 505 Mya) during the Cambrian explosion
  2. Subphylum: Cephalochordata
  3. Olfactores
    Subphylum Tunicata
    Subphylum Vertebrata
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16
Q

Cephalochordata (subphylum)

3 points

A
  1. Notochord extends into head
  2. Lancelet or amphioxus (AGr amphi = “on both sides” + oxus = “pointed, sharp”)
  3. Spend most of time half-buried in sand, filter feeding
17
Q

Tunicata
(subphylum)
5 points

A
  1. Well-developed heart and circulatory system
  2. Carries oxygen and nutrients dissolved in plasma
  3. Hollow cerebral ganglion and neural gland
  4. Produce cellulose for various functions
  5. Suspension feeders, employing endostyle and pharynx
18
Q

Vertebrata

subphylum

A
  1. L. vertebra = “(spine) joint”
  2. Also called “Craniata” (L. cranium = “skull”)
  3. Hagfish do not have vertebrae
19
Q

Agnatha

3 points

A
  1. Formerly, the living members were put into two classes:

Myxini (hagfishes)

Hyperoartia (lampreys)

  1. Now recognised as single monophyletic group called Cyclostomata
  2. Well-represented in fossil record by other classes such as conodonts and ostracoderms
20
Q

Agnatha
Bodyplan
4 points

A
  1. No jaws
  2. No paired fins or other limbs (in modern forms)
  3. Notochord in both larvae and adults
  4. Seven or more paired gill pouches
21
Q

Agnatha

Respiration

A
  1. Water taken and out of pharynx through gill pores
22
Q

Agnatha
Circulation
4 points

A
  1. Two-chambered heart
    Only has deoxygenated blood
  2. Aorta branches into two to serve gills
  3. Accessory pumps
  4. Blood returns to heart via veins
23
Q

Agnatha
Digestion
4 points

A
  1. No definable stomach
  2. Pharynx subdivided by valve
  3. Prevents food entering the respiratory system
  4. Can eat and breathe at same time
24
Q

Agnatha
excretion
4 points

A
  1. Paired kidneys
  2. Two ureters open into urogenital sinus
  3. Maintain osmotic neutrality with environment
  4. Regulation of ions rather than water
25
Q

Agnatha
Nervous system
4 points

A
  1. Brain and nerve cord
  2. 10 pairs of cranial nerves
  3. Spinal nerves
  4. Autonomic nervous system
26
Q

Agnatha
senses
6 points

A
  1. Olfactory sac
    Single nostril, does not connect to respiratory system
  2. Eyes
  3. Pineal apparatus (‘eye’) [3rd eye]
  4. Integumentary photoreceptors
  5. Ears
  6. Lateral line
27
Q

Agnatha
Reproduction
5 points

A
  1. External fertilisation
  2. Believed to only breed once in their lives
  3. Most species of hagfish are hermaphrodites
  4. Larvae of lampreys = ammocoetes

Filter feeders

Closely resemble
cephalochordates in this form

Undergo metamorphosis

  1. Hagfish don’t have larval stage
28
Q

Agnatha

Ecology : Lampreys

A
  1. Coastal / freshwater
  2. Many species migrate to freshwater to mate
  3. Feed on live prey
    Mostly blood, inject anticoagulants
29
Q

Agnatha
Ecology : Hagfish
4 points

A
  1. Marine
  2. Mostly scavengers
  3. Tie themselves into knots to lever scraps of food off carcasses
  4. Can produce copious amounts of slime

Expands in water – one hagfish can produce 20 litres

30
Q

Tunicata
Ascidiacea (Sea squirts)
4 points

A
  1. Sessile, solitary or colonial
  2. Filter feeders
    Water enters through oral siphon, through pharynx, and out through cloacal siphon
  3. No excretory or respiratory organs
  4. Tunic
    Secreted by epithelial cells
    Often pigmented
31
Q

Tunicata
Appendicularia (salps)
[barrel shaped planktonic tunicate]
6 points

A
  1. Common planktonic organisms, mostly transparent
  2. U-shaped body with trunk and elongated tail
  3. Trunk has all organs and a midventral anus
  4. Tail contains notochord, nerve cord, and 2 muscle bands
  5. Protoandrous (“male-first”) hermaphrodites
  6. House
    Secreted by epithelial glands

Simple temporary structures or more complex in form

Animal kingdom (14 decks)

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