AP Biology : Understanding Embryogenesis and Development

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #32 : Reproductive System

During what stage of embryonic development do cells differentiate into primary germ layers?

Possible Answers:

Implantation

Gastrulation

Blastula development

Fertilization

Correct answer:

Gastrulation

Explanation:

Germ layers are primary layers of cells that form during embryogenesis. In mammals, they are the endoderm, ectoderm, and mesoderm. In embryo development, the germ layers differentiate during gastrulation.

Example Question #33 : Reproductive System

Which of the following does not develop from the mesoderm?

Possible Answers:

Red blood cells

Pigment cells

Kidney cells

Muscle cells

Correct answer:

Pigment cells

Explanation:

The mesoderm is a primary germ layer that forms during gastrulation. The mesoderm develops into most of the organ systems of the human body, including the muscular system, circulatory system, and excretory system.

Example Question #1231 : Ap Biology

During which of the following stages of embryogenesis is the developing embryo called a “zygote”?

Possible Answers:

During the entirety of cleavage

Only after implantation

After fertilization

During gastrulation

Correct answer:

After fertilization

Explanation:

The term “zygote” is sued to describe a fertilized egg. The zygote is diploid and formed by the fusion of the sperm and egg gametes. The developing organism is called the zygote until it is composed of 16 cells during cleavage, when it is called the “morula.”

Example Question #1232 : Ap Biology

Which of the following sets of terms best describes the names of the two poles present in developing embryos?

Possible Answers:

Chorionic and vegetal poles

Animal and vegetal poles

Animal and chorionic poles

Animal and blastomeric poles

Correct answer:

Animal and vegetal poles

Explanation:

Developing embryos exhibit an asymmetry; the zygote can be described as having two hemispheres. These two poles are called the animal and vegetal poles. The vegetal pole contains more yolk and will become the endoderm. The animal pole contains less yolk and will become the ectoderm and mesoderm.

Example Question #1233 : Ap Biology

Which of the following is true about holoblastic cleavage?

Possible Answers:

It takes place when the developing embryo has little yolk

It is partial cleavage

One patterning example of holoblastic cleavage is superficial cleavage

It takes place when the developing embryo has a high concentration of yolk

Correct answer:

It takes place when the developing embryo has little yolk

Explanation:

Holoblastic cleavage is the type of cleavage found in developing embryos with a low yolk concentration. This allows for the complete cleavage that forms planes that extend through the entirety of the zygote. Different cleavage patterns in holoblastic cleavage include bilateral, radial, rotational, and spiral. Animals whose zygotes undergo holoblastic cleavage include placental mammals, amphibians, and annelids.

Example Question #1234 : Ap Biology

Which of the following is not a true characteristic about meroblastic cleavage?

Possible Answers:

It is found in developing embryos with a high concentration of yolk

Cleavage planes extend all the way across the zygote

It is partial cleavage

It is found in insects

Correct answer:

Cleavage planes extend all the way across the zygote

Explanation:

Meroblastic cleavage is partial cleavage in zygotes with a high concentration of yolk. In developing embryos that undergo this process, cell divisions do not penetrate the yolk. Two types of meroblastic cleavage are discoidal and superficial cleavage. This process occurs in insects, some fish, and some types of birds.

Example Question #1235 : Ap Biology

In which of the following groups of organisms does indeterminate cleavage take place?

Possible Answers:

Chordates

Protostomes

Deuterostomes

Placental mammals 

Correct answer:

Deuterostomes

Explanation:

Indeterminate cleavage takes place in most deuterostomes. It is a type of cleavage in which embryonic cells can be separated and successfully develop into different organisms.

Example Question #1236 : Ap Biology

Which of the following terms best describes the type of cleavage that occurs in developing mammalian embryos?

Possible Answers:

Radial

Spiral

Bilateral

Rotational

Correct answer:

Rotational

Explanation:

Developing mammalian embryos exhibit rotational cleavage. In this type of cleavage, the first cell division occurs on meridionally. The next cell division in the two resulting daughter cells occurs meridionally in one and equatorially in the other.

Example Question #1237 : Ap Biology

Which of the following best describes when transcription initiates in developing embryos?

Possible Answers:

At the time of implantation

During gastrulation

At the time of fertilization

At the end of cleavage

Correct answer:

At the end of cleavage

Explanation:

In the developing embryo, transcription initiates at the end of cleavage, during a stage called the midblastula transition. 

Example Question #31 : Understanding Embryogenesis And Development

Which of the following best describes what the trophoblast develops into?

Possible Answers:

The spinal cord

The skin

The muscle

The placenta

Correct answer:

The placenta

Explanation:

The trophoblast is the outer layer of cells that make up the blastocyst. These cells provide nutrients to the developing embryo, and eventually develop into the placenta. During the later stages of cleavage, the trophoblast becomes distinguished from the inner layer of cells, which will develop into the embryo. There is a layer of fluid between the trophoblast and inner cell mass.

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