What mechanism makes it difficult to classify bacteria into distinct species groups?
A. vertical evolution.
B. horizontal gene transfer.
C. sexual reproduction.
D. asexual reproduction.
E. low mutation rates.
B. horizontal gene transfer.
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Which two organisms should be used for quality control purposes to determine the validity of the indole reagent?
a. E. meningoseptica and Empedobacter brevis b. Chryseobacterium spp. and E. meningo-septica c. E. meningoseptica and Sphingobacterium multivorum d. Agrobacterium group and Sphingobacte-rium spiritivorum
In a human pedigree that traces the inheritance of albinism, a filled square represents a
A) male with albinism. B) female with albinism. C) heterozygous male. D) heterozygous female.
__________ results in an early embryo that has two or three primary tissue layers. Fill in the blank(s) with the appropriate word(s)
Evidence shows that the earliest life may have existed how long ago?
a. 2 billion years ago b. 3.5 billion years ago c. 1.3 billion years ago d. 630 million years ago e. 250 million years ago