20. Development

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

Which stage of development is common in amphibians but not seen in mammals?

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

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 __________.

How does a zygote differ from an ovum?

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

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

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

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

What is the most likely trigger of egg activation?

Which of the following is true of meroblastic cleavage?

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

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 __________.

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

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 __________.

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

What primitive feature forms during gastrulation?

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

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

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

Which of the following events occurs only during organogenesis?

In humans, the skeleton and muscles develop from the embryonic __________.

The human brain develops from __________.

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

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

Evidence suggests that folic acid may help prevent the development of spina bifida, a common disabling birth defect. It is recommended that women increase their folic acid intake during pregnancy, especially in the first three months. Why is the timing of the folic acid intake relevant?

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?

During the development of most animals, cleavage leads to __________.

Which of the following correctly lists the embryonic stages in the order that they develop?

The cortical reaction of sea urchin eggs functions directly in a. the formation of a fertilization envelope. b. the production of a fast block to polyspermy. c. the generation of an electrical impulse by the egg. d. the fusion of egg and sperm nuclei.

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

The archenteron develops into a. the mesoderm. b. the endoderm. c. the placenta. d. the lumen of the digestive tract.

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

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.

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.

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.

You obtain an egg cell from the ovary of a white mouse and remove the nucleus from it. You then obtain a nucleus from a liver cell from an adult black mouse. You use the methods of nuclear transplantation to insert the nucleus into the empty egg. After some prompting, the new zygote divides into an early embryo, which you then implant into the uterus of a brown mouse. A few weeks later, a baby mouse is born. What color will it be? Why?

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

In an embryo, nerve cells grow out from the spinal cord and form connections with the muscles they will eventually control. What mechanisms described in this chapter might explain how these cells 'know' where to go and which cells to connect with?

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?

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?