What occurs during gastrulation?
A) A solid embryo is changed into a hollow morula.
B) A solid blastula is changed into a hollow embryo that has four tissue layers.
C) A hollow blastula is changed into a hollow embryo that has three tissue layers.
D) A neural tube is created by invagination of the ectoderm.
Answer: C
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The correct order of the basic steps of virus multiplication is ________
a. attachment, penetration, replication and then synthesis, assembly, and release b. attachment, penetration, replication and then synthesis, release, and assembly c. penetration, attachment, replication and then synthesis, assembly, and release d. attachment, penetration, assembly, replication and then synthesis, and release
DDT was used in the U.S. in the ____ industry
a. plastics b. agricultural c. paint d. manufacturing e. weapons.
Changes in proteins of the lens cause
a. astigmatism. b. retinoblastoma. c. myopia. d. glaucoma. e. cataracts.
The first organisms on Earth were very small, but now when you look around you see many large organisms. Which is the best explanation for this observation?
A) Evolution tends toward larger and larger organisms. B) There were many steps necessary to go from small cells to large organisms. C) Organisms got larger because they needed to use resources more efficiently. D) The goal of evolution is to produce the largest organisms possible.