specific character descriptions

Question 1

dorsal hollow nerve chord (what is it, location, gives rise to…)

Answer 1

hollow, fluid filled structure dorsal to the digestive tract

arises from the neural tube (which is from neural plate ectoderm)

forms the central nervous system (brain [anterior] and spinal chord in vertebrates)

Question 2

what is the dorsal hollow nerve chord made of

Answer 2

neurons and glial cells

Question 3

neurons

Answer 3

specialized cells that send and receive electrical impulses

generate action potential, to rapidly send an impulse down an elongated process (AXON) to send a chemical signal (NEUROTRANSMITTER) to other cells

Question 4

notochord in protostomes vs deuterostomes

Answer 4

protostomes don’t have notochord’s, and the nerve chord is located VENTRAL to the digestive tract

deuterostomes have notochords btwn the nerve chord and digestive tract
** nerve chord DORSAL to digestive tract AND notochord

Question 5

what embryonic germ layer is the notochord from

Answer 5

mesoderm

Question 6

the notochord

Answer 6

location:

structure: slender rod w/ core of cells and fluid surrounded by a tough fibrous sheath

function: STRUCTURAL SUPPORT, can bend side to send helping w/ lateral undulation for locomotion, but cannot be axially compressed

AND signals ectodermal cells around it to differentiate into neural plate ectoderm/fold into neural tube

origin: mesoderm

gives rise to: functionally replaced by the vertebral column during development

Question 7

notochord involvement in neural tube formation

Answer 7

signals ectoderm cells around it to differentiate into neural plate ectoderm, and fold in to form the neural tube

Question 8

pharyngeal slits

Answer 8

a series of openings in the walls of the pharynx

in many terrestrial vertebrates, closed before the embryo is born or hatched

synapomorphy for DEUTEROSTOMES

pharynx arrises from endoderm

in fish, water passes in through the mouth and out through pharyngeal slits and over gills

Question 9

endostyle

Answer 9

origin: the ventral side of the pharynx therefore endoderm

location: ventral side of the pharynx

structure: groove filled w/ gladular tissue

function: produces mucus and processes iodine

homologous to thyroid gland of vertebrates

synapomorphy for chordates

Question 10

post-anal tail

Answer 10

structure: posterior elongation of the body extending beyond the anus

generally the notochord extends into it, and it’s primarily composed of myomeres (therefore very muscular)

Question 11

myomeres

Answer 11

segmented blocks of skeletal muscle separated by layers of connective tissue (myosepta)

arranged in series from anterior to posterior

Question 12

what is different about the notochord and dorsal hollow nerve chord?

Answer 12

function: noto provides structural support, nerve is used for rapid communication of signals within the body

origin: noto from mesoderm, nerve from neural plate ectoderm

fate: noto is functionally replaced by vertebrae in many verts, nerve forms brain and spinal chord in adult vertebrates

Question 13

vertebral column

Answer 13

series of separate bones or cartilage blocks along the central axis of the body

Question 14

cranium

Answer 14

made of cartilage and/or bone

arises from neural crest cells and mesenchymal mesoderm

Question 15

muscular pharyngeal pump

Answer 15

replaced the cilia used to pump water in the common ancestor of chordates

expands the chamber of the pharynx via skeletal muscles which pull on the skeletal structures supporting the pharynx. This also involves the opening and closing of various valves

Question 16

cilia pump vs muscular pharyngeal pump

Answer 16

muscular is far more efficient, as cilia only pump water on the surface.

this works for smaller animals, but muscular pharyngeal pump is able to moge greater volumes of water for larger organisms

Question 17

benefits of paired pectoral and pelvic fins/jaws on lifestyle

Answer 17

large effect on diet, giving gnathostomes acces to a wide variety of food sources

• hard to catch
• larger
• herbivory
• more nutrient rich prey

fins specifically help with stability and control in movement (steering and direction)

Question 18

gas bladder

Answer 18

in many actinopterygii acts as a swim bladder providing neutral buoyancy, and in many teleostomi acts as lungs in gas exchange