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BI2131: Animal Diversity and Adaptation > Vertebrate Evolution > Flashcards

Vertebrate Evolution Flashcards

1
Q

What are the 3 groups of chordates?

A

Vertebrata, Cephalochordata and Urochordata.

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2
Q

What 5 anatomical structures must be possessed at some point in the life cycle of a chordate?

A

1) Notochord.
2) Tubular dorsal nerve tube.
3) Pharyngeal slits.
4) Endostyle/Thyroid glands.
5) Postanal tail.

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3
Q

What is the notochord?

A

A rod-like flexible structure found dorsally along the longitudinal axis of the body.

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4
Q

What anatomical feature was the precursor to the backbone?

A

The notochord.

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5
Q

Describe the location of the notochord.

A

Between the digestive tract and the nerve cord.

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6
Q

Describe the structure of the notochord.

A

A core of fluid-filled cells encased in a stiff, fibrous connective tissue sheath.

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7
Q

What is the function of the notochord?

A

It provides support whilst remaining flexible and allows swimming motion through lateral pressure against surrounding substrate.

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8
Q

What feature of the backbone is a remnant of the notochord?

A

The gelatinous material of the disks between vertebrates.

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9
Q

What is the dorsal tubular nerve cord?

A

A hollow cord dorsal to the notochord.

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10
Q

What does the dorsal tubular nerve cord develop from?

A

Dorsal ectodermal cells that form an invagination and sink inward.

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11
Q

Describe the structure of the dorsal tubular nerve cord.

A

A fluid-filled tube of nerve tissue running the length of the animal.

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12
Q

Describe the location of the dorsal tubular nerve cord.

A

Dorsal to the notochord and running the length of the animal.

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13
Q

What does the dorsal tubular nerve cord develop into in chordates?

A

The CNS.

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14
Q

How does the nerve cord of non-chordates differ to the nerve cord of chordates?

A

Non-chordate nerve cords are solid and are usually ventrally located.

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15
Q

What are pharyngeal slits?

A

Filter-feeding organs that resemble a series of slits.

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16
Q

Describe the location of pharyngeal slits.

A

Caudal to the mouth.

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17
Q

How have pharyngeal slits evolved in fish?

A

They have become modified to contain filaments for gas exchange (gills) and are supported by gill arches.

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18
Q

When are pharyngeal slits present in terrestrial chordates?

A

Only in embryonic development.

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19
Q

What is an endostyle?

A

A groove in the pharyngeal floor of protochordates that secretes mucus.

20
Q

What is the function of the endostyle?

A

To secrete mucus which traps small food.

21
Q

What organ is derived from the endostyle? What additional activity links the 2 organs?

A

The thyroid gland is derived from the endostyle as both organs have iodine-concentrating activity.

22
Q

What is a postanal tail?

A

An extension of the spinal cord that extends beyond the anus.

23
Q

What are myotomes?

A

Blocks of muscle surrounding the notochord and nerve cord.

24
Q

What is the function of the postanal tail in aquatic chordates?

A

To provide propulsion.

25
Q

How are chordates classified?

A 
Urochordata = tail chordates.
Cephalochordata = head chordates.
Vertebrata = backbone chordates.
26
Q

What are urochordates commonly referred to as?

A

Tunicates, sea squirts, salps and larvaceans.

27
Q

At what life stage(s) do urochordates show the 5 anatomical structures found in chordates?

A

As larvae.

28
Q

How do urochordate larvae and adults differ?

A

Larvae are mobile whilst adults are sessile. Adults can be both solitary or colonial. Larvae are just solitary.

29
Q

What occurs during urochordate metamorphosis?

A

Larvae settle head first on hard substrates. The tail, notochord, muscle segments and nerve cord disappear.

30
Q

How do adult urochordates feed?

A

They are filter feeders that draw in water through an incurrent siphon. Plankton is trapped in a mucus sheet and cilia direct food-laden mucus to the stomach.

31
Q

How many species are there in cephalochordata?

A

25

32
Q

Where are cephalochordates found?

A

Exclusively in marine environments.

33
Q

From which sub-phyla of the chordates did vertebrates evolve from?

A

Branchiostoma (lancelets) - a group within the sub-phyla cephalochordata.

34
Q

How do cephalochordates feed?

A

They are filter feeders.

35
Q

At what life stage(s) do cephalochordates show the 5 anatomical structures found in chordates?

A

Throughout their entire life.

36
Q

What features do cephalochordates lack, meaning they are not vertebrates?

A

Very small + poorly developed brain.
Poorly developed sense organs.
Notochord is not replaced by vertebrae.

37
Q

What features class a chordate as a vertebrate?

A

Neural crest.
Pronounced cephalisation.
Vertebral column.
Closed circulatory system.

38
Q

What is the clade Craniata? What are some example craniates?

A

A clade of chordate animals with a bone or cartilage skull. Examples include hagfish (non-vertebrate craniate) and lampreys (vertebrate craniate).

39
Q

How do craniates differ to vertebrates?

A

Both possess a neural crest and pronounced cephalisation but craniates lack a vertebral column and closed circulatory system.

40
Q

What are vertebrates in relation to craniates?

A

Craniates with a backbone.

41
Q

Describe the anatomical features of lampreys.

A

Ectoparasitic blood-suckers as adults (filter feeders as young).
Circular adhesive disk + rasping tongue.
No gill arches - gills contained in 7 muscular pouches.

42
Q

From what organ are jaws derived in vertebrates?

A

Gill supporting structures. All modern vertebrates except lampreys have jaws.

43
Q

How did the evolution of jaws and fins benefit fish?

A

Jaws + teeth allowed the exploitation of food supplies unavailable to jawless fish. Fins + tail enabled accurate maneuvering.

44
Q

What group includes the jawless vertebrate fish?

A

Agnatha

45
Q

What group includes the jawed vertebrates?

A

Gnathostomata

BI2131: Animal Diversity and Adaptation (19 decks)

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