AP Biology : Understanding Embryogenesis and Development

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Reproductive Physiology

During embryonic development, which stage begins after the formation of 128 cells and terminates with germ layer differentiation? 

Possible Answers:

Blastula stage

Zygote stage

Gastrula stage

Somitogenesis stage

Cleavage stage

Correct answer:

Blastula stage

Explanation:

The blastula is defined as beginning following the cleavage stages. Following seven cleavages 128 cells have formed, and will later begin to form the differentiated layers of endoderm, mesoderm and ectoderm before going into the gastrula stage.

Example Question #2 : Reproductive Physiology

From what germ layer does the nervous system develop?

Possible Answers:

Endoderm

Somites

Epiboly

Mesoderm

Ectoderm

Correct answer:

Ectoderm

Explanation:

During gastrulation, the ectoderm begins to fold in on itself following the primitive streak. These neural folds form the basis of the neural tube, later developing into the adult nervous system.

Example Question #3 : Reproductive Physiology

What do somites, formed from mesoderm during somitogenesis, go on to form? 

Possible Answers:

Skeletal muscle

The dermis

All of these structures

Vertebrae

None of these structures

Correct answer:

All of these structures

Explanation:

Somites go on to form skeletal muscle, vertebrae, and the dermis. 

Example Question #1 : Understanding Embryogenesis And Development

In humans, fertilization involves the addition of chromosomes from the sperm and the egg. The resulting cell is called a __________.

Possible Answers:

embryo

zygote

gamete

blastocyst

Correct answer:

zygote

Explanation:

The fusion of haploid gametes (sperm and egg) produces a zygote. The addition of the chromosomes from sperm and egg restores the diploid state of the cell and gives rise to a diploid organism.

An embryo refers to the developing organism after the first cellular division, following formation of the zygote. A blastocyst forms during the first stages of embryogenesis, and is defined by cellular replication without cellular growth.

Example Question #231 : Systems Physiology

What is the product of rapid division, but no overall growth during embryogenesis?

Possible Answers:

Gastrula

Morula

Zygote

Blastula

Correct answer:

Morula

Explanation:

The first stage after fertilization is the single-celled zygote, which quickly begins to divide. These divisions, however, do not increase the overall size of the embryo and are known as cleavage divisions. As the mass of cells divides, it is considered a morula.

Eventually, the morula develops an inner cell mass and associated trophoblast. At this stage, it is considered a blastula or blastocyst. It is during this stage that implantation occurs. After implantation, the cell develops the three germ layers through the process of gastrulation. Once the endoderm, mesoderm, and ectoderm have been established, the embryo is considered a gastrula.

Example Question #11 : Reproductive System

Which body part would you not expect to develop from the ectoderm?

Possible Answers:

The cerebellum

The intestinal lining

The skin

The eyes

The spinal cord

Correct answer:

The intestinal lining

Explanation:

The ectoderm is generally credited with the formation of the skin, teeth, nervous system, and sense organs. The lining of the digestive tract is formed from the endoderm.

Example Question #1 : Reproductive Physiology

Which of the following would not be expected during pregnancy?

Possible Answers:

Maintenance of the corpus luteum

Blastocyst implantation

Formation of the placenta

Secretion of human chorionic gonadotropin (HCG)

Formation of the corpus albicans

Correct answer:

Formation of the corpus albicans

Explanation:

The corpus luteum is a structure in the ovary that secretes progesterone, and is preserved during pregnancy with the help of human chorionic gonadotropin (HCG). If fertilization does not take place, the corpus luteum will degenerate into the corpus albicans. As a result, corpus albicans formation only takes place if the woman is not pregnant.

Blastocyst implantation is considered the first event of pregnancy, and the placenta will later form in order to secrete hormones crucial for embryonic development.

Example Question #1 : Understanding Embryogenesis And Development

Early in development, the zygote divides via __________.

Possible Answers:

mitosis

cloning

meiosis

fertilization

Correct answer:

mitosis

Explanation:

Mitosis is the process by which diploid cells duplicate and divide to ensure all cells have the same number of chromosomes and genetic material. Meiosis is the process by which haploid gametes are produced by the primary sex organs.  

Example Question #1 : Reproductive Physiology

Which of the following type(s) of cell movement are involved in the development of the neural plate into the neural tube?

Possible Answers:

Convergence and invagination

Neither convergence nor invagination

Invagination

Convergence

Correct answer:

Convergence and invagination

Explanation:

During the formation of the neural tube, the neural plate—a thick layer of differentiated columnar cells—change shape and undergo certain cell movements. The formation of the neural tube is called primary neurulation. In a complex process, the cells of the neural plate change shape, invaginating the cell layer to form the neural groove. Convergence moves the cells of the neural folds towards the developing neural groove. Eventually, the two edges of the neural plate touch and join together to form the neural tube. 

Example Question #2 : Reproductive Physiology

Which of the following is not a true characteristic of the neural plate?

Possible Answers:

It develops from ectoderm tissue

It invaginates to form the neural tube

It is within the primitive streak of the embryo

It is composed of columnar cells 

Correct answer:

It is within the primitive streak of the embryo

Explanation:

The neural plate is a cell layer opposite of the primitive streak in the developing embryo. It forms from a thickening and flattening of the ectoderm layer. These cells then take a columnar shape. The neural plate develops into the neural tube during primary neurulation.

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