Question 1

Embryonic induction, the influence of one group of cells on another group of cells, plays a critical role in embryonic development. In 1924, Hans Spemann and Hilde Mangold transplanted a piece of tissue that influences the formation of the notochord and neural tube, from the dorsal lip of an amphibian embryo to the ventral side of another amphibian embryo. If embryonic induction occurred, which of the following observations justifies the claim of embryonic induction?

Accepted Answer

The induction of the formation of a second notochord and neural tube on the ventral side of the developing embryo would indicate that the transplanted tissue influenced the development of the recipient embryo, thus demonstrating embryonic induction. The other options do not necessarily demonstrate induction.

Question 2

The archenteron develops into

Accepted Answer

The answer of The archenteron develops into
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Question 3

Cells transplanted from the neural tube of a frog embryo to the ventral part of another embryo develop into nervous system tissues. This result indicates that the transplanted cells were

Accepted Answer

The fact that cells transplanted from one embryo developed into particular tissues in another embryo suggests that they were already determined to become those tissues. Totipotent cells have the ability to differentiate into all cell types, whereas mesenchymal cells are multipotent stem cells that give rise to cartilage, bone, and fat cells, but not nervous system tissues. Differentiated cells are fully specialized and cannot give rise to other cell types. Therefore, the best choice is B, determined cells.

Question 4

If an egg cell were treated with EDTA, a chemical that binds calcium and magnesium ions,

Accepted Answer

The fertilization envelope formation depends on the release of calcium ions. EDTA blocks calcium ions and thus, the fertilization envelope would not form.

Question 5

Cells transplanted from the neural tube of a frog embryo to the ventral part of another embryo develop into nervous system tissues. This result indicates that the transplanted cells were ________.

Accepted Answer

The fact that the transplanted cells developed into nervous system tissues suggests that they were already determined to become nervous system tissues. This means that they were already committed to a certain developmental pathway and were not totipotent or able to differentiate into any type of tissue. Mesenchymal cells are a type of stem cell found in connective tissue and are not related to neural tissue development.

Question 6

Just prior to the onset of gastrulation in an embryo, the "organizer" cells are specified. If you were to experimentally block the specification of these cells, what would you expect the result to be in the developing embryo?

Accepted Answer

The organizer cells play a crucial role in initiating gastrulation, during which the germ layers of the embryo are established. Without gastrulation, normal development would not proceed. Therefore, blocking the specification of organizer cells would prevent gastrulation and result in the cessation of normal development.

Question 7

Which of the following is common to the development of both birds and mammals?

Accepted Answer

Both birds and mammals develop through epiblast and hypoblast formation. This process is known as gastrulation and leads to the formation of the three germ layers that give rise to all the different tissues and organs in the body. Holoblastic cleavage is a type of cleavage seen in some animals, such as amphibians, but not in birds or mammals. Trophoblast is a layer of cells that forms the outer layer of the blastocyst in mammals and plays a role in implantation and placenta formation. Gray crescent is a feature seen in amphibians during fertilization and early embryonic development.

Question 8

The cortical reaction of sea urchin eggs functions directly in

Accepted Answer

The cortical reaction of sea urchin eggs results in the formation of a fertilization envelope, which is a protective layer that surrounds the egg after fertilization and prevents multiple sperm from entering the egg. This helps to ensure that only one sperm fertilizes the egg, which is necessary for successful development. The cortical reaction does not directly produce a fast block to polyspermy or generate an electrical impulse by the egg, although it may indirectly contribute to these processes. The fusion of egg and sperm nuclei also occurs after the cortical reaction has taken place.

Question 9

What structural adaptation in chickens allows them to lay their eggs in arid environments rather than in water?

Accepted Answer

Extraembryonic membranes, such as the amnion and chorion, allow eggs to be laid in arid environments by providing a protective environment and maintaining the necessary moisture for development. These membranes also allow efficient exchange of gases between the embryo and the surrounding environment, which is essential for development in an arid environment. Yolk, cleavage, and gastrulation are important for embryonic development, but do not directly contribute to the ability to lay eggs in arid environments.

Question 10

In humans, identical twins are possible because

Accepted Answer

Identical twins occur when a single embryo splits into two during early development. This is possible because early blastomeres, when isolated, can form a complete embryo. Therefore, option C is the correct answer. Option A refers to the process of genomic imprinting, which does not explain identical twins. Option B refers to a process of embryonic development where cells intercalate and elongate to cause the stretching and narrowing of tissue, and option D refers to the formation of the dorsal-ventral axis in frogs, but neither of these options explain identical twinning.

Quiz 47: Animal Development