Although it contributes no cells to the embryo, this structure guides the formation of the primitive streak:
A) endoderm
B) mesoderm
C) ectoderm
D) neural crest
E) hypoblast
Answer: E) hypoblast
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Based on the tree shown above, a grouping composed of Species A, Species, B and Species D only is considered:
A. paraphyletic. B. polyphyletic. C. monophyletic. D. sister groups. E. None of the of the answer options is correct.
Answer the following statements true (T) or false (F)
1. Soil can contain the spores that cause botulism, gas gangrene, and tetanus. 2. Chlamydial genital infections and gonorrhea are the two most common nationally notifiable infectious diseases in the United States. 3. The levels of chlorine routinely used for water treatment are sufficient to kill Giardia cysts and Cryptosporidium oocysts. 4. Yersinia pestis, the bacterium that causes plague, is one of the pathogens most often discussed as a potential biologic weapon. 5. Gonorrhea is considered to be a communicable disease, but not a contagious disease.
Baleen plates are composed of:
a. calcium carbonate. b. cellulose. c. keratin. d. chitin. e. silica.
The accompanying hypothetical pedigree is for a family where some members have symptoms of Leigh syndrome, which is caused by an mtDNA mutation that reduces ATPase activity
Which of the following in the youngest generation might transmit the condition in the future? A) any of the women B) any of those affected C) any of the members of this generation D) only those with an affected mother E) any of the affected women