During implantation, the inner cell mass develops into two flattened layers of cells called the ____
a. blastocyst
b. amnion
c. embryonic disk
d. chorion
e. placenta
ANSWER: c
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Ecology
A. requires the study of plants. B. is the study of the environment. C. primarily studies animals. D. works for the good of the environment. E. includes the study of interactions between organisms and their environment.
Why are the leading causes of death in high-income countries heart disease, stroke, and cancer, while in low-income countries infectious diseases are the leading causes of death?
A. There are genetic differences between populations. B. The population density in high-income countries is clustered. C. Access to sanitation, vaccines, and antibiotics is greater in high-income countries. D. The population density in high-income countries is larger. E. The ecological footprint in high-income countries is larger.
Which of the following does an insect use to excrete
metabolic wastes from the body? a. nephridium b. flame cell c. trachea d. Malpighian tubule e. siphon
Small DNA tumor viruses such as SV40 and HPV have viral oncogenes that are not homologs of host cell genes. Some of these novel viral oncogenes make proteins that exert their tumorigenic effect by
A) binding to and inactivating pRB. B) making Gag, Pol and Env proteins more active. C) causing cellular proto-oncogenes to mutate into oncogenes. D) causing apoptosis in target tissues. E) inactivating the immune system.