1C - Development(2)

Question 1

Basic structure of chordate NS

Answer 1

hollow tube dorsal to notochord

Question 2

True or False: The nerve cord is dorsal in chordates

Answer 2

True

Question 3

In inveterbrates, where is the neural cord?

Answer 3

Ventral, and its solid

Question 4

Differences in nerve cord; vertebrates and invertebrates

Answer 4

• Vertebrates: Dorsal, hollow nerve cord

- Invertebrates: Ventral, solid nerve cord

Question 5

Myelin, who has it?

Answer 5

Vertebrates only

Question 6

What happens when you rotate annelids (earthworms)? Earthworms are invertebrates

Answer 6

Nerve cord is ventral, but if you rotate 180 degrees, then the nerve cord is dorsal (just like chordates)

Question 7

Geoffroy Saint-Hilaire proposed Inversion Theory. What is it?

Answer 7

• Common ancestry of invertebrates flipped itself around.
• Converted dorsal surface into ventral surface
• Swim on its back, nerve cord changed from being ventral in location to dorsal in location

Question 8

What evidence proved the Inversion Theory?

Answer 8

Homebox genes

Question 9

What are Homebox genes?

Answer 9

Series of genes expressed primarily in embryo

Question 10

Features of homebox genes?

Answer 10

1) . Front to back order
2) . Expressed heavily in neural tissue precursors
3) . Expressed in adjacent tissue –> like vertebral column

Question 11

What do hindbrain zones correspond to?

Answer 11

• Reflect basic segmentation pattern of vertebrae brain

- Anatomical markers

Question 12

Where are homebox genes expressed?

Answer 12

Dorsal in embryo

Question 13

Fruitfly vs Mouse homebox genes

Answer 13

-Mouse:
Homebox genes expressed dorsally

-Fruitfly:
Homebox genes expressed ventrally

Question 14

What are the 3 layers of tissue present in all chordates?

Answer 14

1) . Ectoderm (outside)
2) . Mesoderm (inside)
3) .Endoderm (middle)

Question 15

What does ectoderm give rise to?

Answer 15

outer most layer of skin, epidermis, glands

Question 16

What does endoderm give rise to?

Answer 16

lining of gut, liver, pancreas

Question 17

What does mesoderm give rise to?

Answer 17

bones, musculature

Question 18

What layer of skin gives rise to CNS/PNS (Nervous system) ?

Answer 18

Ectoderm

Question 19

What is the blastula?

Answer 19

-Hollow ball of cells

Question 20

3 properties of blastula

Answer 20

• Has empty cavity inside it
• Cells form a single layer
• Cells undifferentiated

Question 21

What is the process that converts blastula to gastrula? (converts a single layer blastula to a 3-cell layer)?

Answer 21

Gastrulation

Question 22

What has not formed in early stage of blastula?

Answer 22

Primordium of gut

Question 23

Does gastrulation occur the same way in all animals? why or why not?

Answer 23

No, because shape of gastrula is different

Question 24

Blastula of amphioxus

Answer 24

• Hollow inside
• Cavity inside blastula is called blastocele
• Simple
• Single-cell layer
• Dorsally (no yolk)
• Ventrally (yes yolk)

Question 25

Blastula of frog/amphibian

Answer 25

- Couple cells thick - 2 layers are differentiated so basically 1 layer - More yolk ventrally

Question 26

Blastula of reptile/bird

Answer 26

- Large amount of yolk - Does not divide - Below blastocele in cellular disk

Question 27

What is the cavity inside of the gastrula that is the precursor to the gut?

Answer 27

Gastrocele

Question 28

In chordates, what does the blastopore become?

Answer 28

Anus, while mouth forms secondarily

Question 29

In invertebrates, what does the blastopore become?

Answer 29

Mouth, while anus forms secondarily

Question 30

Gastrulation in amphioxus

Answer 30

- short cube cells outside - large columnar cells inside - Outermost layer --> ectoderm - Innermost layer --> endoderm and mesoderm

Question 31

Does the blastopore open into the gastrocele?

Answer 31

Yes

Question 32

Gastrulation in frog

Answer 32

-Yolk stops cells from moving, cannot change shape

Question 33

Does in-rolling occur dorsally first, then involuation laterally?

Answer 33

Yes

Question 34

-Dorsal lip of blastopore:

Answer 34

- dorsally located - first point at which rolling occurs - Cells from outside of embryo start at this point and move inward - 1st tissue that involvues to give rise to notochord

Question 35

What derives notochord?

Answer 35

Mesoderm

Question 36

Fate map

Answer 36

- Tissue that rolls in at different times/places gives rise to different structures in embryo - Fate Map maps different locations on outside where cells end up after gastrulation occurs (what adult structures will form)

Question 37

T/F: There is 1 opening into gastrocele, which is the blastopore, and forms the anus first and mouth secondarily

Answer 37

True

Question 38

Does endoderm line gastrocele?

Answer 38

Yes

Question 39

T/F: Humans evolve from animals that have a lot of yolk

Answer 39

True