Scientists now believe that comets falling to early Earth played a role in the evolution of life. What role did these comets play?
A) They brought CO2 and H2O.
B) They generated a lot of energy when they hit Earth.
C) They brought ammonia ions (NH4).
D) All of the above are true.
Answer: D
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Indicate whether the statement is true or false.
Gymnosperm phyla include
_____ Cycadophyta. _____ Ginkgophyta. _____ Coniferophyta. _____ Lycophyta. _____ Angiospermae.
As part of his or her job, a genetic counselor may do all of the following except
a. analyze family pedigrees. b. advise a couple to have direct testing for altered proteins. c. advise a couple to have DNA testing. d. predict the chances of a couple having a child with a specific trait. e. tell a couple not to have children
Amniocentesis involves sampling ____
a. the embryo at the eight cell stage b. fetal cells in the amniotic fluid c. sperm or egg cells d. fetal skin tissue e. placental cells