Gastrulation

Question 1

What is gastrulation?

Answer 1

Gastrulation rearranges the cells of a blastula into a three-layered embryo called a gastrula.

Question 2

o A Gastrula has a _____ gut.

o. The three layers produced by gastrulation are called ____ ____ layers.

Answer 2

primitive

embryonic germ

Question 3

The three embryonic germ layers are: (3)

Answer 3

o The ectoderm forms the outer layer.
o The endoderm lines the digestive tract.
o The mesoderm partly fills the space between the endoderm and ectoderm.

Question 4

What does the blastula consist of?

Answer 4

The blastula consists of a single layer of cells surrounding the blastocoel.

Question 5

What does the process of gastrulation consist of in sea urchins? (5)

Answer 5

o Mesenchyme cells migrate from the vegetal pole into the blastocoel.
o The vegetal plate forms from the remaining cells on the vegetal pole and buckles inward.
o The endoderm cells form an invagination.
o The newly formed cavity is called the archenteron.
o This opens through the blastopore, which will become the anus.

Question 6

What does the process of gastrulation consist of in frogs? (7)

Answer 6

1. The frog blastula is many cell layers thick.
2. Cells of the dorsal lip originate in the gray crescent.
3. Cells below the dorsal lip invaginate to create the archenteron.
4. Cells continue to move from the embryo surface into the embryo by involution until the blastocoel disappears.
5. These cells become the endoderm and mesoderm.
6. The blastopore encircles a yolk plug when gastrulation is complete.
7. The surface of the embryo is now the ectoderm, the innermost layer is endoderm, and the middle layer is mesoderm.

Question 7

o Cleavage forms a small cap called a blastoderm instead of a ____.
o Blastoderm forms on top of the ___ mass.
o The upper layer of the blastoderm is called the _____.
o The lower layer is the ____.

Answer 7

blastula
yolk
epiblast
hypoblast

Question 8

What does the process of gastrulation consist of in chicks? (7)

Answer 8

1. The epiblast moves toward the midline of the blastoderm and then into the embryo toward the yolk.
2. Cell movements result in a pile-up of cells and in the formation of the primitive streak.
3. Primitive streak- is the thickened midline in the blastoderm.
4. The migration of cells gives rise to the endoderm, mesoderm, and ectoderm.
5. The epiblast cells continue to migrate and sort- a process called convergent extension.
6. This lengthens and narrows the primitive streak.
7. The hypoblast cells are displaced to form the sac that surrounds the yolk and the stalk that connects the yolk to the embryo.

Question 9

The embryo develops from the _____ and the _____ forms the extra embryonic membranes.

Answer 9

epiblast

hypoblast