Which structure is responsible for keeping the fetus from slipping out of the uterus prematurely?
a. cervix
b. vagina
c. endometrium
d. placenta
e. umbilical cord
ANSWER: a
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The accompanying figure shows the history of large meteorite impacts on both the earth and the moon. What is the graph's major implication for the origin of life on Earth?
A) Huge impacts make it unlikely that life arose and survived on Earth before about 3.8 billion years ago. B) Meteorites could not have brought the organic molecules that were necessary for life appear. C) The moon is considerably older than the Earth. D) Life must have originated on a different body in the solar system and been brought to Earth. E) The Oparin-Haldane model of life's origins applies to the moon as well as to the Earth.
Which of the following was NOT part of the Earth’s primitive atmosphere?
a. oxygen b. nitrogen c. hydrogen d. water vapor e. inert gases
The Panamanian golden frog is in decline because of ________, which are being driven by ________.
A. introduced species; increased global trade B. outbreaks of a fungus; deforestation C. outbreaks of a fungus; global climate change D. outbreaks of a virus; global climate change E. outbreaks of a virus; deforestation
Of the four chambers of the human heart, which has the thickest walls, and why?
What will be an ideal response?