AP Biology : Understanding Embryogenesis and Development

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1221 : Ap Biology

Which of the following contributes to the formation of the blastocoel during blastula development?

Possible Answers:

Gap junctions between embryoblasts

Cell polarization

All of these

Compaction of trophoblasts

Correct answer:

All of these

Explanation:

The blastocoel is a fluid-fill cavity region of the blastocyst. The blastocoel is formed through cell polarization, when trophoblasts and embryoblasts differentiate. The trophoblasts are the outer layer of cells that compact to become watertight. Embryoblasts polarize to one end of the cell and form gap junctions for cell-cell communication and developmental coordination. The trophoblasts then secrete fluid into the cavity, which forms the blastocoel.

Example Question #1222 : Ap Biology

Which of the following cell types secrete fluid into the cavity during the formation of the blastocoel during blastula development?

Possible Answers:

Epiblast

Trophoblast

Embryoblast

Synctiotrophoblast

Correct answer:

Trophoblast

Explanation:

The blastocoel is a fluid-filled cavity that is a part of the blastocyst. A compacted trophoblast cell layer surrounds the cavity, making it watertight. Trophoblast cells then secret fluid into the cavity.

Example Question #1223 : Ap Biology

Which of the following best describes when the zona pellucida disintegrates?

Possible Answers:

After an increase in blastocyst size and subsequent zona pellucida "hatching"

After implantation into the uterine wall

Before the onset of cleavage to allow for growth

Immediately following fertilization as a result of the cortical reaction

Correct answer:

After an increase in blastocyst size and subsequent zona pellucida "hatching"

Explanation:

The zona pellucida is a glycoprotein layer secreted by follicle cells that surrounds the released oocyte and developing embryo. Once the blastocoel grows in size during blastula development, the blastocyst “hatches” out of the zone pellucida, which then disintegrates.

Example Question #1224 : Ap Biology

Which of the following steps does not precede blastocyst implantation in the uterine wall?

Possible Answers:

Breakdown of the endometrial extracellular matrix

"Hatching" from the zona pellucida

Irreversible connections between the blastocyst and the uterine wall

Initial loose contacts between the blastocyst and the uterine wall

Correct answer:

Irreversible connections between the blastocyst and the uterine wall

Explanation:

Implantation is the process in which a blastocyst adheres to the female uterine wall. This is preceded by the exit of the blastocyst form the zona pellucida as well as the degradation of the endometrial extracellular matrix by proteolytic enzymes secreted by the blastocyst and initial loose connections with the endometrium. The blastocyst then adheres to the uterine wall through ligand-receptor systems and cell invasion.

Example Question #1225 : Ap Biology

Which of the following is the leading cause of implantation failure?

Possible Answers:

Decreased uterine receptivity

Foreign substance interference

Embryo abnormalities

Medication

Correct answer:

Decreased uterine receptivity

Explanation:

The leading cause of implantation failure is decreased uterine receptivity. Other causes include problems with the developing embryo. Certain medications can be administered to increase chances of successful implantation.

Example Question #1226 : Ap Biology

Which of the following cell layers both ingressions and invaginates during gastrulation?

Possible Answers:

Blastocoel

Epiblast

Hypoblast

Trophoblast

Correct answer:

Epiblast

Explanation:

The epiblast is an inner cell layer in the blastocoel that sits above the hypoblast. The epiblast ingresses to form the mesoderm and invaginates to form the endoderm.

Example Question #1227 : Ap Biology

Which of the following is established by the primitive streak during gastrula development?

Possible Answers:

Left/right axes

Cranial/caudal axes

Bilateral symmetry

All of these

Correct answer:

All of these

Explanation:

The primitive streak is an arrangement of cells that forms during gastrula development. The location of the primitive streak establishes the left/right axes, cranial/caudal axes, and bilateral symmetry of the developing embryo.

Example Question #1228 : Ap Biology

The process of ingression forms which of the following germ layers during gastrula development?

Possible Answers:

Endoderm

Mesoderm

Ectoderm

None of these

Correct answer:

Mesoderm

Explanation:

In gastrulation, the process of ingression forms the mesoderm. In this process, the epiblast ingresses at the primary streak into the area between the epiblast and hypoblast cell layers.

Example Question #1229 : Ap Biology

During which of the following stages of embryonic development does the process of invagination occur?

Possible Answers:

Gastrulation

Blastula development

Implantation

Fertilization

Correct answer:

Gastrulation

Explanation:

Invagination is the infolding of the epiblast cell layer to form the endoderm germ layer. This process takes place during gastrulation.

Example Question #31 : Reproductive System

Which of the following structures is referred to as the “blastocoel”?

Possible Answers:

The glycoprotein layer around the blastocyst

The fluid-filled cavity of the blastocyst

The area of cellular invasion during implantation

Outer layers of cells in the blastocyst

Correct answer:

The fluid-filled cavity of the blastocyst

Explanation:

The “blastocoel” is a fluid-filled cavity in the blastocyst. It is enclosed by trophoblast cells.

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