AP Biology › Understanding Embryogenesis and Development
Which of the following type(s) of cell movement are involved in the development of the neural plate into the neural tube?
Convergence and invagination
Convergence
Invagination
Neither convergence nor invagination
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.
During which of the following stages of embryogenesis is the developing embryo called a “zygote”?
After fertilization
During the entirety of cleavage
During gastrulation
Only after implantation
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.”
Which of the following contributes to the formation of the blastocoel during blastula development?
All of these
Cell polarization
Gap junctions between embryoblasts
Compaction of trophoblasts
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.
Which of the following is not a true characteristic of the neural plate?
It is within the primitive streak of the embryo
It develops from ectoderm tissue
It invaginates to form the neural tube
It is composed of columnar cells
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.
Which of the following sets of terms best describes the names of the two poles present in developing embryos?
Animal and vegetal poles
Chorionic and vegetal poles
Animal and blastomeric poles
Animal and chorionic poles
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.
Which of the following cell types secrete fluid into the cavity during the formation of the blastocoel during blastula development?
Trophoblast
Embryoblast
Epiblast
Synctiotrophoblast
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.
Which of the following best describes the structure that the neural tube develops into?
All of these
Brain
Spinal cord
Central nervous system
The neural tube develops into the central nervous system, which is composed of the brain and spinal cord. The neural tube develops during primary neurulation from the neural plate.
Which of the following is true about holoblastic cleavage?
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
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.
Which of the following best describes when the zona pellucida disintegrates?
After an increase in blastocyst size and subsequent zona pellucida "hatching"
After implantation into the uterine wall
Immediately following fertilization as a result of the cortical reaction
Before the onset of cleavage to allow for growth
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.
Which of the following is not a true characteristic about meroblastic cleavage?
Cleavage planes extend all the way across the zygote
It is partial cleavage
It is found in developing embryos with a high concentration of yolk
It is found in insects
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.