Ch. 47 HW

As cleavage continues, a zygote forms into a solid multicellular ball called a(n) _____. - endometrium - morula - trophoblast - gastrula - blastula

morula The morula is a solid ball of cells produced when the zygote undergoes cleavage.

In vertebrates, the ectoderm gives rise to the _____. - skeleton - circulatory system - outer layer of skin - lining of the digestive tract - pancreas

outer layer of skin The ectoderm gives rise to the outer layer of skin and the nervous system Return to Assignment

Differentiating between cleavage, gastrulation, and organogenesis Determine which terms, phrases, and images describe each phase of development.

https://cdn.discordapp.com/attachments/658536375863214080/968398311587459102/unknown.png Embryonic development proceeds through three stages. - During cleavage, the cytoplasm of the zygote is divided into many different cells called blastomeres. By the end of cleavage, the embryo is called a blastula, which is a ball of cells surrounding a fluid-filled cavity called a blastocoel. - During gastrulation, the embryo is called a gastrula. In this stage, cells undergo dramatic rearrangement, forming the embryonic germ layers and other structures, such as the blastopore. Once gastrulation is complete, the major body axes of the embryo (anterior-posterior and dorsal-ventral) are visible. - During organogenesis, the three embryonic germ layers develop into the rudiments of organs. Structures such as the notochord, the neural tube, and somites form. Somite cells undergo differentiation, giving rise to different body tissues and organs, including the skeleton, muscles, and skin.

Choose the correct developmental sequence of animal development. See Concept 47.1 (Page 1042) - gastrulation → cleavage → fertilization → organogenesis - fertilization → cleavage → gastrulation → organogenesis - organogenesis → cleavage → fertilization → gastrulation - cleavage → gastrulation → organogenesis → fertilization - cleavage → fertilization → gastrulation → organogenesis

fertilization → cleavage → gastrulation → organogenesis

What happens to cells that fold inside the blastula during gastrulation in a triploblast? - They form the lining of the gut cavity. - They are in contact with the mesoderm. - They become mesoderm. - They become endoderm. - They become ectoderm. - They are continuous with the mesoderm. - They are not necessary to the animal after gastrulation.

- They form the lining of the gut cavity. - They are in contact with the mesoderm. - They become endoderm. The cells that fold into the blastocoel and form the archenteron become the endoderm germ cell layer. (The prefix endo- means "inside.") The endoderm forms the lining of the primitive gut cavity, and it is in contact with the mesoderm.

The three-layered embryo is the _____. - archenteron - morula - trophoblast - gastrula - blastula

gastrula The gastrula, formed when the blastula undergoes gastrulation, is a ball of cells that consists of the three primary germ layers.

True or false? Early animal development progresses through distinct stages: first the production of the zygote through fertilization, then cleavage, then the formation of the gastrula, and then the formation of the blastula. - True - False

False The formation of a gastrula is the last stage in early animal development; the zygote undergoes cleavage to form a blastula, which eventually forms a gastrula.

Which of the following stages of development is defined by the three embryonic tissue layers (ectoderm, mesoderm, and endoderm)? - Gastrula - Zygote - Blastula - Yolk

Gastrula Gastrulation is the process that leads to the formation of the gastrula, which contains the three embryonic tissue layers.

In animal development, which of the following best describes the process of cleavage? - Fertilization - Differentiation - Mitosis - Meiosis

Mitosis Cleavage refers to the rapid cell division that takes place in animals after fertilization. Cleavage partitions the egg cytoplasm without additional cell growth taking place.

What are the cells created by cleavage called? - Blastulas - Blastomeres - Blastopores - Blastocoels

Blastomeres A blastomere is a cell created by cleavage division.

Which of the following are the three germ layers contained in the gastrula? - Ectotherm, mesoderm, endoderm - Ectoderm, mesoderm, endoderm - Ectoderm, mesoderm, epidermis - Ectoderm, mesoderm, echinoderm

Ectoderm, mesoderm, endoderm These are the three basic embryonic cell layers of all vertebrate embryos.

A child is born without a fully developed pancreas. He is normal in all other respects, and thus doctors believe that the problem most likely began early in development. During which of the following processes did the original error most likely occur? - Cleavage - Endoderm formation - Ectoderm formation - Mesoderm formation

Endoderm formation The endoderm provides the cells that develop into the lining of the digestive and respiratory tracts, as well as the liver and pancreas. Problems with its formation could result in an unformed pancreas.

What happens to a cell during the process of differentiation? - Material moves across the cell membrane from a region of higher concentration to a region of lower concentration. - It undergoes a change toward a more specialized form or function. - It divides to produce a cell with the same number of chromosomes. - It divides to produce a cell with one-half the number of original chromosomes.

It undergoes a change toward a more specialized form or function. During organogenesis, embryonic cells become progressively more specialized as they develop into their specific cell type (brain, muscle, etc.).

The _____ eventually develops into the sea urchin's digestive tract. - blastocoel - archenteron - blastomere - ectoderm - blastopore

archenteron The archenteron, formed as a result of gastrulation, develops into the sea urchin's digestive tract.

blastopore becomes anus - archenteron - blastocoel - endometrium - blastopore - trophoblast

blastopore During gastrulation, invagination occurs at the blastopore, which develops into the sea urchin's anus.

Several hours after fertilization, cleavage results in the formation of a hollow ball of cells called a _____. - blastomere - morula - trophoblast - gastrula - blastula

blastula The blastula is a hollow ball of cells formed as the result of cleavage.

Part B - Gastrulation in a frog embryo Gastrulation is the stage of embryonic development following cleavage. During gastrulation, cell division slows dramatically, and cells are rearranged in a precise way, forming three germ layers. The diagram below illustrates gastrulation in a frog embryo, represented in cross section.

https://cdn.discordapp.com/attachments/658536375863214080/968398866825224242/unknown.png Gastrulation is the process by which cells formed during cleavage are dramatically rearranged. By the end of gastrulation in a frog embryo, the gastrula has three embryonic germ layers, a primitive gut (archenteron), and a blastopore with a yolk plug. At this point, the major body axes are visible. For example, the blastopore will develop into the frog's anus, indicating the posterior end of the embryo. The events of gastrulation are largely affected by molecules called cytoplasmic determinants. Cytoplasmic determinants originate in the egg and are distributed in embryonic cells during cleavage. These molecules, which may be proteins or nucleic acids, help direct early development, including cell movements during gastrulation. Gastrulation begins with the appearance of the blastopore, which forms from an invagination of cells on the surface of the embryo. Cells roll inward through the blastopore and move to the interior of the embryo in a process called involution. Involution enables the formation of the endoderm and mesoderm. The primitive gut (archenteron) forms from endoderm. The blastocoel becomes smaller as the primitive gut expands. Once the three germ layers are established in the late gastrula, the next stage of embryonic development, organogenesis, can proceed.

Part C - Organogenesis in a frog embryo Tissue and organ formation begins during the process of organogenesis. Which five of the following statements are true about organogenesis in a frog embryo? - Some somite cells migrate to other locations in the developing embryo. - The endoderm gives rise to the lining of the frog's digestive tract. - Somites form along the length of the notochord and neural tube. - The notochord forms from mesoderm and develops into the central nervous system. - The notochord does not persist in adult frogs. - The mesoderm gives rise to the epidermis of the frog's skin. - The neural tube forms from ectoderm and develops into the central nervous system.

https://cdn.discordapp.com/attachments/658536375863214080/968399725701251123/unknown.png - Some somite cells migrate to other locations in the developing embryo. - The endoderm gives rise to the lining of the frog's digestive tract. - Somites form along the length of the notochord and neural tube. - The notochord does not persist in adult frogs. - The neural tube forms from ectoderm and develops into the central nervous system. During organogenesis, the three germ layers develop into rudimentary tissues and organs. The mesoderm gives rise to the notochord, which serves as a transient, organizing element for the developing embryo. Signaling molecules from the notochord help prompt development of the neural tube from foldings of the ectoderm. The neural tube eventually develops into the frog's central nervous system. Somites, which develop from the mesoderm, are blocks of tissue that form along both sides of the neural tube. Somite cells migrate to other locations in the embryo, where they give rise to a variety of tissues. The specific cell type that a somite cell develops into is partly determined by where in the somite the cell is located. The diagram below shows a close-up of one somite next to the neural tube. As you can see, cells located on the dorsal side of the somite are destined to become connective tissue in the skin, whereas cells located on the ventral side of the somite are destined to become bone.

The embryos of all animals undergo gastrulation, a dramatic reorganization of cells critical to formation of the animal body. Do you understand all the terms associated with gastrulation? - blastula - blastophore - gastrula - archenteron

https://cdn.discordapp.com/attachments/658536375863214080/968401796332675132/unknown.png Gastrulation is a dramatic reorganization of the hollow blastula into a two-layered or three-layered embryo called a gastrula. Invagination of cells into the blastocoel forms a tube called the archenteron. The open end of the archenteron is called the blastopore.

What is the cortical reaction? - the formation of a fertilization envelope that bars additional sperm from entry into the egg - the release of hydrolytic enzymes from the sperm cell - a depolarization of the eggs' plasma membrane so that only one sperm cell can fuse with it - a series of rapid mitotic divisions that follow fertilization - the process that forms a three-layered embryo

the formation of a fertilization envelope that bars additional sperm from entry into the egg This is the cortical reaction.

In sea urchins, the process of fertilization produces a(n) _____. - archenteron - morula - gastrula - gamete - zygote

zygote Fertilization, the combination of haploid sets of chromosomes, results in the formation of a diploid zygote.