Question 1

Which result did Hans Spemann get when he bisected a salamander zygote, isolating the gray crescent in one of the two resulting cells?

Accepted Answer

When Hans Spemann bisected a salamander zygote and isolated the gray crescent in one of the resulting cells, the half with the gray crescent developed into a complete embryo, while the other half formed a belly piece. This experiment demonstrated the concept of embryonic induction, where one group of cells can influence the development of neighboring cells to form different tissues and structures. Spemann's experiment was a crucial step in understanding the process of embryonic development, and he was awarded the Nobel Prize in Physiology or Medicine in 1935.

Question 2

Which feature characterizes the chick gastrula?

Accepted Answer

The chick gastrula is characterized by the presence of a blastocoel located between the epiblast and the hypoblast, which are two layers of cells in the early embryo. This feature is crucial for the development of the chick embryo.

Question 3

Refer to the figure showing some of the manipulations carried out by Spemann on developing amphibians.  Experiment 2 resulted in

Accepted Answer

Experiment 2 involved transplanting the gray crescent from one embryo to the opposite side of another embryo. The side with the gray crescent typically develops into the dorsal side while the opposite side develops into the ventral side. Therefore, in Experiment 2, one side of the embryo lacked a gray crescent while the other side had two gray crescents. This resulted in one normal embryo developing from the side with the gray crescent and one clump of undifferentiated cells from the side lacking gray crescent.

Question 4

Which feature is characteristic of birds' but not placental mammals' embryonic development?

Accepted Answer

The answer of Which feature is characteristic of birds' but...

Question 5

Epiboly

Accepted Answer

Epiboly refers to the movement where cells of the animal hemisphere spread and thin over the embryo's surface, as seen in frog gastrulation. It does not involve convergent extension (A), rolling inward to form an inner layer (B), cells moving apart (C), or bending inward (E).

Question 6

Many signaling molecules found in the frog organizer have also been found in the chick embryo's

Accepted Answer

The Hensen's node in the chick embryo is similar to the dorsal lip of the blastopore found in the frog embryo, and it is the region where the organizer forms. Many signaling molecules found in the frog organizer have also been found in the Hensen's node, suggesting a similar role in axis formation.

Answer: A
 The primitive neural tube is the precursor to the central nervous system and it forms from the ectoderm. Many signaling molecules found in the frog organizer, such as BMP and noggin, are crucial for neural tube formation in both frogs and chicks.

Question 7

Which feature characterizes β-catenin's role in amphibian embryos?

Accepted Answer

β-catenin's overexpression in a particular region of the blastula induces a second axis of embryo formation. This is known as the Wnt signaling pathway and it plays a critical role in the establishment of the embryonic axes. In amphibian embryos, β-catenin is responsible for organizing the dorsal axis.

Question 8

Which result did Hans Spemann and Hilde Mangold get when they transplanted the dorsal lip of the blastopore of an early amphibian gastrula to the belly region of another early gastrula?

Accepted Answer

Hans Spemann and Hilde Mangold observed that when they transplanted the dorsal lip of the blastopore of an early amphibian gastrula to the belly region of another early gastrula, a secondary embryo formed belly-to-belly with the first embryo. This experiment demonstrated the concept of embryonic induction, where one group of cells can direct the fate of nearby cells. This experiment played a significant role in the development of our understanding of early embryonic development.

Question 9

Initiation of nervous system development in amphibians occurs when organizer cells

Accepted Answer

Organizer cells in amphibians secrete chordin and noggin, which block the action of BMP (bone morphogenetic protein) molecules that would otherwise direct ectodermal cells to become epidermis. This results in the formation of a neural plate, which will give rise to the nervous system.

Question 10

Working with salamander embryos, which result did Hans Spemann get when he transplanted a piece of an early gastrula that would normally form epidermis of skin to the region of another early gastrula that would normally form neural tissue?

Accepted Answer

When Hans Spemann transplanted a piece of an early gastrula that would normally form epidermis of skin to the region of another early gastrula that would normally form neural tissue, he found that the transplanted tissue formed neural tissue. This experiment demonstrated the concept of embryonic induction, where one group of cells can influence the development of another group of cells in the embryo.

Question 11

Refer to the figure showing some of the manipulations carried out by Spemann on developing amphibians.  Experiment 1 resulted in

Accepted Answer

The answer of Refer to the figure showing some of...

Question 12

The _______ is the primary embryonic organizer in amphibians.

Accepted Answer

The dorsal lip of the blastopore is a region on the surface of the amphibian embryo where cells invaginate and ingress to form the mesoderm layer. It is also known as the Spemann-Mangold organizer after the scientists who first discovered its importance in embryonic development. The dorsal lip of the blastopore plays a crucial role in pattern formation and axis determination in amphibians, and is considered the primary embryonic organizer.

Question 13

Which animals have a blastodisc?

Accepted Answer

Reptiles, along with birds and some fish, have a blastodisc, which is a small disc of cells on top of the yolk where the embryo develops.

Question 14

_______ is the process by which surface cells roll over the lip of the blastopore and move into the blastocoel during amphibian gastrulation.

Accepted Answer

Involution is the process during amphibian gastrulation where surface cells roll over the edge of the blastopore and move inward into the blastocoel, contributing to the formation of the germ layers.

Question 15

In the chick embryo, which structure functions as the blastopore?

Accepted Answer

In chick embryo, the primitive groove serves as the blastopore which is the opening of the archenteron, the future digestive cavity.

Question 16

Working with salamander embryos, Hans Spemann transplanted a piece of a late gastrula that would normally form epidermis of the skin to the region of another late gastrula that would normally form neural tissue.Which result did he get?

Accepted Answer

The transplanted tissue formed epidermis because, at the late gastrula stage, the fate of the cells is already determined, and they will develop into their predetermined tissue type regardless of their new location.

Question 17

Which statement about the organizer of amphibians is true?

Accepted Answer

The organizer cells in amphibians are located in the dorsal lip of the blastopore, which is a depression in the early embryo that will later form the anus in most species. These cells produce signaling molecules that help pattern the developing embryo.

Question 18

Which structure in birds and mammals is the equivalent of the dorsal lip of the amphibian blastopore?

Accepted Answer

Hensen's node is the functional equivalent of the dorsal lip of the amphibian blastopore in birds and mammals. It forms during gastrulation and is responsible for inducing the formation of the nervous system and other dorsal structures. Choices A, C, D, and E do not correspond to the dorsal lip of the amphibian blastopore.

Question 19

As gastrulation begins, the cells of the chick embryo are organized as a

Accepted Answer

The blastodisc is the embryonic disk of cells on top of the yolk in avian embryos. As gastrulation begins, these cells will undergo complex movements to form the three primary germ layers. The other options are not relevant to the stage of development described.

Question 20

Which statement about chick development is true?

Accepted Answer

During chick development, cells migrate through the primitive groove into the blastocoel to form the endoderm and mesoderm layers.

Quiz 43: Animal Development