Chapter 47 Homework

cleavage ... a cluster of cells Gastrulation and organogenesis are developmental stages that follow cleavage.

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.

Blastomeres A blastomere is a cell created by cleavage division.

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

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

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.).

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.

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.

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

the formation of a fertilization envelope that bars additional sperm from entry into the egg

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

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

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

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

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

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

notochord This rod of mesoderm forms the notochord, a physically supportive structure.

ectoderm Cells from the animal pole form the ectoderm.

backbone In vertebrates, the notochord functions as a core around which mesodermal cells form the frog's backbone.

neural plate The ectodermal thickening above the frog's notochord forms the neural plate.

neural tube The question describes the formation of the neural tube.

brain The anterior end of the neural tube develops into the brain.

spinal cord The posterior portion of the neural tube develops into the spinal cord.

skeletal and muscular systems The muscles and skeleton are of mesodermal origin.

they have extra-embryonic membranes that develop an aqueous environment in which development occurs These three groups of vertebrates form the amniotes. Fish and amphibians lay their eggs in water and do not require a special water-filled enclosure.

trophoblast The trophoblast is the outer epithelium of the blastocyst.

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.

The neural tube forms from ectoderm and develops into the central nervous system. The notochord does not persist in adult frogs. The endoderm gives rise to the lining of the frog's digestive tract. Some somite cells migrate to other locations in the developing embryo. Somites form along the length of the notochord and neural tube.

by itself, give rise to the entire embryo, as cleavage proceeds In Sperman's work on frog embryos, he showed that the first two blastomeres can develop into all of the cells of the frog embryo.