Atmospheric chemists think that Earth's first atmosphere
a. contained large amounts of molecular oxygen.
b. consisted of carbon in the form of carbon monoxide.
c. contained nitrogen in the form of ammonia and nitrogen gas.
d. contained no oxygen atoms.
e. was very similar to today's atmosphere.
C
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Which of the following amino acids has an aromatic R group?
A. aspartate B. proline C. threonine D. tyrosine E. arginine
In freshwater sponges and other simple freshwater animals, water flows into the body by __________. Fill in the blank(s) with the appropriate word(s)
Each tier of the biomass pyramid depicts the
____ of all the organisms in an ecosystem. a. size b. number of species c. dry weight d. total weight e. total utilization of materials
The nucleus of a differentiated cell contains all of the genetic information necessary to direct the development of an entire organism. This nucleus is therefore said to be ________
Fill in the blank with correct word.