Chapter 49

The main function of the acrosome reaction is to (a) activate the cgg (b) improve sperm motility (c) prevent interspecific fertilization \((\mathrm{d})\) facilitate penetration of the egg coverings by the sperm (c) cause fusion of the sperm and egg pronuclei.

The fast block to polyspermy in sea urchins (a) is a depolarization of the egg plasma membrane (b) requires exocytosis of the cortical granules (c) includes the elevation of the fertilization envelope (d) involves the hardening of the jelly coat (e) is a complete block.

Place the following events of sea urchin fertilization in the proper sequence. (1) fusion of egg and sperm pronuclei ( 2 ) DNA synthesis 3 increased protein synthesis (4) release of calcium (a) 4,3,1,2 (b) 3,2,4,1 (c) 2,3,1,4 ions into the egg cytoplasm (d) 1,2,3,4 (c) 4,1,2,3.

Meroblastic cleavage is typical of embryos formed from ______ eggs. (a) moderately telolecithal (b) highly telolecithal (c) isolecithal (d) b and c (e) a, b, and c.

The primitive groove of the bird embryo is the functional equivalent of the ______ in the amphibian embryo. (a) yolk plug (b) archenteron (c) blastocoel (d) gray crescent (e) blastopore.

Which of the following are mismatched? (a) endoderm; lining of the digestive tube (b) ectoderm; circulatory system (c) mesoderm; notochord (d) mesoderm; reproductive system (e) ectoderm; sense organs.

Which of the following has three germ layers? (a) morula (b) gastrula (c) blastula (d) blastocyst (e) trophoblast.

An unidentified substance (or substances) released from the developing notochord causes the overlying ectoderm to form the neural plate. This phenomenon is known as (a) activation (b) determination (c) induction (d) implantation (e) mosaic development.

Which of the following consists of both fetal and maternal tissues? (a) umbilical cord (b) placenta (c) amnion (d) allantois (e) yolk sac.

The embryo proper of a mammal develops from the (a) trophoblast (b) umbilical cord (c) inner cell mass (d) entire blastocyst (e) yolk sac.

Which of the following statements about vertebrate organogenesis is not true? (a) The notochord, brain, and spinal cord are among the first organs to develop in the early embryo. (b) The developing notochord causes the overlying ectoderm to differentiate into the neural plate. (c) The neural folds meet and fuse, forming the four-chambered heart. (d) Some neural crest cells differentiate into neurons. (e) Blocks of mesoderm known as somites form on either side of the neural. tube

On about the seventh day of development, the human embryo (a) implants in the wall of the uterus (b) has a fully developed placenta for obtaining nutrients and oxygen (c) releases human chorionic gonadotropin (d) both a and c (e) a, b, and c.