Vertebrate Development: Birds

Question 1

Microlecithal

Answer 1

Little yolk

Question 2

Mesolecithal

Answer 2

Moderate yolk

Question 3

Macrolecithal

Answer 3

Large yolk

Question 4

Cleavage

Answer 4

Restricted to a small region at the animal pole of the zygote and produces the blastodisc (cleavage)

Question 5

Blastodisc

Answer 5

Flat disc of cells (cleavage)

Question 6

Blastula Formation

Answer 6

Blastodisc cells form the epiblast and the hypoblast (blastula formation)

Question 7

Epiblast

Answer 7

Dorsal layer (blastula formation)

Question 8

Hypoblast

Answer 8

Ventral layer (blastula formation)

Question 9

Blastocoel

Answer 9

Space between the epiblast and the hypoblast (blastula formation)

Question 10

Gastrulation

Answer 10

1. Some epiblast cells migrate inward through the primitive streak to form endoderm (dorsal surface) and mesoderm (gastrulation)
2. Remaining epiblast cells form ectoderm (ventral surface)

Question 11

Primitive Streak

Answer 11

Groove in the epiblast layer

Question 12

Formation of 3 Embryonic Germ Layers

Answer 12

Ectoderm, mesoderm, and endoderm (gastrulation

Question 13

Neurulation

Answer 13

1. Neural plate ectoderm bends along the dorsal midline and sinks ventrally into the embryo to form the neural groove and the neural folds on either side
2. Neural folds fuse to form the hollow neural tube
3. Neural crest cells separate from the dorsal region of the neural tube
   (neurulation)

Question 14

Central Nervous System Development

Answer 14

Anterior region of the embryo:
1. Neural tube of the head region starts to swell and expand into the brain
2. Neural tube posterior to head gives rise to spinal cord
(post-neurulation)

Question 15

Somatic Hypomere Mesoderm

Answer 15

Hypomere mesoderm closer to ectoderm

Question 16

Splanchnic Hypomere Mesoderm

Answer 16

Hypomere mesoderm closer to endoderm (within the chorioallantoic membrane) and forms allantoic vessels, vitelline vessels, and the heart

Question 17

Coelom

Answer 17

Space between the somatic hypomere mesoderm and the splanchnic hypomere mesoderm (neurulation)

Question 18

Lumen

Answer 18

Space of the digestive tract formed by:
1. Endoderm folds dorsally into the embryo
2. Folds come closer together and fuse to form the lumen of the digestive tract (in chicks)
(neurulation)

Question 19

Extra-Embryonic Membranes

Answer 19

Produced and by the embryo and grow outward from the embryo (amnion, chorion, allantois, and yolk sac)

Question 20

Amniotes

Answer 20

Have amnion, chorion, allantois, and yolk sac (mammals, reptiles, and birds)

Question 21

Anamniotes

Answer 21

Yolk is already in the cells of frogs (fish and amphibians)

Question 22

Amnion

Answer 22

Arise from somatopleure and is a waterproof membrane that surrounds the embryo in a capsule filled with amniotic fluid

Question 23

Advantages of Amnion

Answer 23

• Slows cooling of remaining heat from adult
• Prevents desiccation (drying out)
• Prevents external things from getting in (embryonic fluid has anti-infection properties)
• Cushioning (fluid acts as a shock absorber)
• Buoyancy (prevents collapse under the weight of gravity)

Question 24

Chorion

Answer 24

Arise from somatopleure and fuses with the outer section of the allantois to form the chorioallantoic membrane

Question 25

Chorioallantoic Membrane

Answer 25

Vascular respiratory membrane used to exchange gases with the environment (through the shell) and also transports calcium from the shell to the embryo (located close to the shell) Note: in most mammals, the chorioallantoic membrane (and/or yolk sac, depending on the species) produces the umbilical cord and the embryonic region of the placenta while amnion surrounds the embryo in a fluid-filled capsule

Question 26

Somatopleure

Answer 26

Ectoderm and somatic hypomere mesoderm

Question 27

Yolk Sac

Answer 27

Arise from splanchnopleure, grows ventrally to surround the yolk, and forms the vitelline vessels

Question 28

Vitelline Vessels

Answer 28

Blood vessels that transport nutrients from the yolk to the embryo

Question 29

Allantois

Answer 29

Arise from splanchnopleure and sequesters (hides/isolates) nitrogenous metabolic wastes away from the embryo (stores wastes in a large garbage bag) Note: making and breaking proteins (metabolic activities) produce nitrogenous metabolic wastes (ex. ammonia/NH3)

Question 30

Splanchnopleure

Answer 30

Endoderm and splanchnic hypomere mesoderm