20. Development

Animal Development

Stages of Animal Development: Cleavage, Gastrulation, Organogenesis

Gastrulation

Sexual and Asexual Reproduction Explained

In an experiment, a researcher colored a bit of tissue on the ­outside of a frog gastrula with an orange fluorescent dye. The embryo developed normally. When the tadpole was placed under an ultraviolet light, which of the following glowed bright orange? (Explain your answer.) 
a. the heart 
b. the pancreas 
c. the brain 
d. the stomach

Cleavage and Blastulation

SEA URCHIN DEVELOPMENT

 a defect in immotile cilia that causes them to be motile 

 No. The reverse is true&#8212;a defect in motile cilia that renders them immotile causes this condition. 

 mutations that disrupt monocilia function 

No. Monocilia are stationary primary cilia; situs inversus results from a defect in motile cilia. Malformed monocilia may form kidney disease, however.

 No. Sonic hedgehog is responsible for anterior/posterior positional information, not left-right positional information. 

 No. One of the listed responses is correct. 

 a defect in motile cilia that renders them immotile 

What results in normal asymmetry during embryonic development?

People with Kartagener's syndrome suffer from a variety of ailments, including the intriguing condition known as situs inversus, a reversal of the abdominal and thoracic organs. This condition occurs because of __________.

Which of the following is common to the development of both birds and mammals?
a. holoblastic cleavage
b. epiblast and hypoblast
c. trophoblast
d. gray crescent

 No. The blastocyst is what the embryo is called following cleavage. 

 No. The hypoblast is part of the blastocyst formed around the time of implantation. 

 No. The amnion is an extraembryonic membrane. It develops from the inner cell mass of the blastocyst and cradles the developing child in a cushion of amniotic fluid. 

 No. The epiblast is the part of the blastocyst that develops into an embryo following implantation. 

It is the outer epithelium of the blastocyst.

In mammals, the __________ facilitates implantation in the uterine wall.

Should parents undergoing in vitro fertilization have the right to choose which embryos to implant based on genetic criteria, such as the presence or absence of disease-causing genes? Should they be able to choose based on the sex of the embryo? How could you distinguish acceptable from unacceptable criteria? Do you think such options should be legislated?

Short Video: Sea Urchin Gastrulation

 differentiation does not depend on cytoplasmic determinants 

 No. All embryos depend on cytoplasmic determinants to some degree, but you are on the right track. These cells have not yet differentiated. 

 No. "Polarization" refers to the establishment of an axis, with the position along the axis influencing the developmental fate of the cell. 

 cytoplasmic determinants are unevenly distributed during the early cleavage divisions 

 No. The uneven distribution of determinants influences the developmental fate of each cell in different directions. 

 mammalian embryos do not experience the progressive restriction of potency characteristic of other embryos 

 No. The progressive restriction of potency is a general feature seen in all animals. What varies is the stage in embryonic development when potency is lost or restricted. 

 cells of mammalian embryos remain totipotent until at least the eight-cell stage 

Consider how cell fate is determined.

Up to the eight-cell stage, the blastomeres of a mouse embryo can each form a complete embryo if isolated. This indicates that __________.

Animal Development: We're Just Tubes - Crash Course Biology #16

Embryology Animated - the First Three Weeks

 No. The cortical reaction is a step that occurs soon after fertilization. 

 No. Cleavage partitions the cytoplasm of the zygote into many smaller cells called blastomeres. 

 No. Although this is part of the process, the answer to this question is more specific. 

 No. Gastrulation is a dramatic rearrangement of the cells of the blastula, forming a three-layered embryo with a primitive gut. This is required for morphogenesis, but it is not the complete process. 

This process involves both the formation of specialized cells and their organization into organs and tissues.

As an animal develops, organs form and the body transforms into a shape typical of the species in a process called __________.

three-layered embryo called a gastrula

 No. Eventually the zygote becomes a gastrula, but an important step occurs before gastrulation. 

 multicellular embryo with a blastopore and an archenteron 

 No. The blastopore and archenteron are features of a gastrula. A developmental stage occurs prior to gastrulation. 

 multicellular embryo consisting of a zona pellucida and a zygote 

 No. The zona pellucida is a layer of follicle cells that accompany the ovum after ovulation. 

No. The term fetus indicates a well-developed embryo. In humans, the term fetus is used after the eighth week of development.

multicellular embryo consisting of smaller cells called blastomeres

Consider the name given to the ball of cells produced as a result of cleavage.

During cleavage the single large zygote is converted into a __________.

STAGES IN ANIMAL DEVELOPMENT |CSIR NET| DEVELOPMENTAL BIOLOGY

 All cell divisions are perpendicular to the animal-vegetal pole. 

 No. In most embryos the first two cleavage divisions are polar, or vertical to the axis. In any case, "meroblastic" does not refer to the cleavage orientation. 

 The mesoderm and endoderm differentiate via cell division from mesenchyme. 

 No. The differentiation of embryonic tissues occurs during gastrulation, an event that follows cleavage. 

 Newly formed cells migrate toward the interior of the embryo. 

 No. The migration of cells to the interior of the embryo occurs during gastrulation. 

 The zygote and later blastomeres completely divide with each round of cell division. 

 No. This type of cleavage is called holoblastic cleavage. 

 Cell division is restricted to a small disk of yolk-free cytoplasm at the animal pole of the zygote. 

Contrast meroblastic cleavage with holoblastic cleavage.

Which of the following is true of meroblastic cleavage?

 No. The endoderm does not give rise to the brain. 

 No. The mesoderm does not give rise to the brain. 

 No. However, the brain is derived from one of these germ layers. 

From which primary germ layer does the nervous system develop?

The human brain develops from __________.

 No. The ectoderm does not give rise to this structure. 

 No. The mesoderm does not give rise to this structure. 

 No. The endoderm is the embryonic source of the lining of the digestive tube. 

Which word root means "inner"?

What is the embryonic origin of the lining of the digestive tube?

2-Minute Neuroscience: Early Neural development

Short Video: Sea Urchin Fertilization and Cleavage

 No. The amnion encloses the embryo in a fluid-filled sac. 

 No. The chorion is the outermost of the extraembryonic membranes, and it routinely participates in gas exchange. It is not involved in the storage of nitrogenous waste. 

 No. The fertilization envelope prevents the entry of additional sperm into a fertilized egg. 

 No. The yolk sac stores yolk and thus provides nutritional support to the embryo. 

Another membrane functions only in gas exchange.

Which of the following extraembryonic membranes functions in gas exchange and encloses a chamber for the deposition of wastes of a bird embryo?

General Embryology - Detailed Animation On Neurulation

Early embryogenesis - Cleavage, blastulation, gastrulation, and neurulation | MCAT | Khan Academy

General Embryology - Detailed Animation On Gastrulation

Basic pattern of early embryonic development in animals

Embryology - Neurulation

Organogenesis

 No. Cell migration is an important part of gastrulation. 

 No. The blastocoel, formed earlier by the cleavage of the zygote, is obliterated as the archenteron expands during gastrulation. 

 No. The archenteron is formed and grows larger throughout gastrulation. 

 No. The formation of the multiple germ layers is a main feature of gastrulation. 

Tissues are the building blocks of organs.

Which of the following events occurs only during organogenesis?

 blastula cells are more differentiated than gastrula cells 

 No. The gastrula is a later developmental stage than the blastula; therefore, its cells are more specialized. 

 there are many more cells in a blastula 

 No. The blastula is an earlier embryonic stage with fewer cells. 

 the blastula consists of more cell layers 

 No. The blastula is a hollow sphere of cells without distinct cell layers. 

 the blastula is a solid ball of cells, but the gastrula is hollow 

 No. The blastula and gastrula are both hollow spheres of cells. 

 there is an opening from the cavity inside the gastrula to the outside 

A gastrula develops from a blastula.

One difference between the blastula and gastrula stages of development is that __________.

 The cells of the vegetal hemisphere do not participate in gastrulation. 

 No. All of the cells in both hemispheres participate in gastrulation. 

 The vegetal hemisphere is where the blastocoel is located. 

 No. The blastocoel is located in the animal hemisphere. 

 The cells of the vegetal hemisphere are pigmented more darkly than the cells of the animal hemisphere. 

 No. The cells of the animal hemisphere are pigmented more darkly than the cells of the vegetal hemisphere. 

 The blastomeres in the animal hemisphere are larger than the cells in the vegetal hemisphere. 

 No. The blastomeres in the vegetal hemisphere are larger than the cells in the animal hemisphere. 

 The cells of the vegetal hemisphere have more yolk than the cells of the animal hemisphere. 

Remember that frog embryos show polarity, in which one end of the embryo is distinctly different from the other end.

How is the animal hemisphere of a frog blastula different from the vegetal hemisphere?

In humans, identical twins are possible because
a. extraembryonic cells interact with the zygote nucleus.
b. convergent extension occurs.
c. early blastomeres can form a complete embryo if isolated.
d. the gray crescent divides the dorsal-ventral axis into new cells.

 No. The formation of the blastula precedes gastrulation. 

 No. Formation of the blastula precedes gastrulation. 

 No. Cleavage of the zygote results in formation of the blastula. 

The blastula stage occurs after cleavage.

Which of the following describes the correct sequence of stages during embryogenesis?

 No. Both the ovum and zygote are single cells. Fertilization adds the sperm nucleus to the zygote but produces no appreciable change in size. 

 A zygote consists of more than one cell. 

 No. Both the ovum and zygote are single cells. 

 No. Meiosis results in a reduction of chromosome number. The zygote divides by mitosis. 

Consider how a zygote is formed.

How does a zygote differ from an ovum?

 No. The archenteron is a space that will become the future lumen of the digestive tract. 

 No. The yolk plug consists of the outer food-laden cells protruding through the blastopore. 

 No. The blastocoel is a fluid-filled cavity that forms during cleavage. 

 No. The zona pellucida is an extracellular matrix of a mammalian egg. 

Where does involution occur in a frog?

The primitive streak of a bird embryo is the functional equivalent of the __________ in a frog.

As a frog embryo develops, the neural tube forms from ectoderm along what will be the frog’s back, directly above the notochord. To study this process, a researcher extracted a bit of notochord tissue and inserted it under the ectoderm where the frog’s belly would normally develop. What can the researcher hope to learn from this experiment? Predict the possible outcomes. What experimental control would you suggest?

 No. Fertilization is the formation of the zygote through the fusion of the sperm and egg. 

 No. Gastrulation is a dramatic rearrangement of the cells of the blastula, forming a multi-layered embryo with a primitive gut. 

 No. Implantation is the process by which a developing embryo begins to grow within the uterus. 

 No. Organogenesis occurs much later in embryonic development. 

Review the stages of embryonic development.

The development of a zygote into a blastula is called __________.

What structural adaptation in chickens allows them to lay their eggs in arid environments rather than in water?
a. extraembryonic membranes
b. yolk
c. cleavage
d. gastrulation

Chapter 36   Animal Development

a specialized cluster of cells called Sonic hedgehog

No. Sonic hedgehog is a term given to a protein growth factor. It is one of the molecules that establish a developmental axis.

 No. The AER establishes the proximal-distal axis for the growing limb. 

 No. The dorsal lip of the blastopore (Spemann's organizer) is a specific structure in some amphibian embryos. It is related to development of the notochord. 

 No. The gray crescent is a distinguishable band of cytoplasm seen in a zygote opposite the point of sperm entry. 

This region has a posterior location.

The digits of a developing vertebrate limb respond to molecules that establish an anterior-posterior axis. These molecules originate in __________.

Neurulation

 No. The membrane has no known hormonal function. 

 No. The discharge of contents from cortical granules results in formation of the fertilization envelope. 

 No. In fact, the fertilization envelope prevents additional sperm from contacting receptors on the plasma membrane of the egg. 

 is responsible for the "fast block to polyspermy" 

 No. Depolarization of the egg cell's plasma membrane is the fast block to polyspermy; the envelope is a long-term, slow block to polyspermy. 

 prevents more than one sperm from entering the egg 

How many sperm typically fertilize an egg?

After a sperm penetrates an egg, a fertilization envelope forms. This envelope __________.

Fertilization

Gastrulation | Formation of Germ Layers | Ectoderm, Mesoderm and Endoderm

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
a. totipotent.
b. determined.
c. differentiated.
d. mesenchymal.

If an egg cell were treated with EDTA, a chemical that binds calcium and magnesium ions,
a. the acrosomal reaction would be blocked.
b. the fusion of sperm and egg nuclei would be blocked.
c. the fast block to polyspermy would not occur.
d. the fertilization envelope would not form.

 No. The developing embryo consists of diploid cells. 

 No. Bacterial cells, not animal cells, divide by binary fission. 

 No. Fragmentation is an asexual mode of reproduction that involves breaking the body into several pieces. 

 None of the listed responses is correct. 

This process results in the formation of the blastula.

The period of repeated cell divisions without significant cell growth results in formation of the blastula and is called __________.

 No. Gastrulation is a dramatic rearrangement of the cells of the blastula, forming a three-layered embryo with a primitive gut. 

 No. The cortical reaction is part of the slow block to polyspermy. 

 No. Depolarization is a change in the egg's membrane that is part of the fast block to polyspermy. 

This is a result of a change in the sperm.

A sea urchin sperm penetrates the jelly coat of an egg and adheres to receptor proteins on the egg's surface as a result of __________.

 No. Although gravity can influence development, gravity is not known to influence eye development to this extent. In addition, it is unclear how much effect foil would have on the immediate gravity in this region. 

 rearranged the cytoplasmic determinants in the adjacent cells 

 No. It is unclear whether the foil would have any impact on the arrangement of the cytoplasmic determinants in the adjacent cells. There is a better explanation. 

 No. The cortical reaction occurs in an egg in response to sperm contact. 

 No. The acrosomal reaction occurs in a sperm as part of the process of fertilization, much earlier than when eyes form. 

 prevented the inductive contact that normally stimulates the lens to form 

Think about the two general principles that underlie differentiation during embryonic development.

In an experiment on eye development, a thin piece of aluminum foil was placed between the bulging wall of the brain and the overlying ectoderm where the eye normally forms. Wherever the foil was placed, the lens failed to develop because the foil __________.

 No. The yolk sac is not the outermost membrane. 

 No. The amnion is not the outermost membrane. 

 No. The endoderm is not an extraembryonic membrane. 

 No. The allantois is not the outermost membrane. 

This layer only participates in gas exchange.

If you wanted to examine the extraembryonic membranes surrounding a lizard or mouse embryo, you would first have to cut through which of the following to see all the others?

neural tube formation | Embryology - Neurulation

3840_Chapter 8: Animal Development

 No. The eye does not form during gastrulation. 

 No. However, the germ layer that will give rise to the nervous system forms during gastrulation. 

 No. However, the germ layer that will give rise to the heart forms during gastrulation. 

The archenteron forms during gastrulation.

What primitive feature forms during gastrulation?

Implantion and Gastrulation

 No. The zygote occurs before the blastula. 

 No. The blastula stage occurs before the gastrula stage, which leads to the larval stage. 

 No. The blastula occurs before the gastrula. 