The evolution of organisms that use oxygen in their respiration was possible only because of the action of a group of bacteria that produced oxygen and changed the Earth's atmosphere from an anoxic one to one rich in oxygen. That group of bacteria was:

A. Cyanobacteria
B. spirochaetes
C. Proteobacteria
D. Staphylococcus
E. Actinobacteria


A. Cyanobacteria

Biology & Microbiology

You might also like to view...

Specialized outgrowths of the plant epidermis called ____ are hairlike projections, such as root hairs

a. cuticles b. protoplasts c. stomata d. trichomes e. bark

Biology & Microbiology

Which characteristic is typical of a cancer cell but not of a normal cell?

A) Cell division is inhibited when the cell contacts neighboring cells. B) The cell cycle lacks S phase. C) The cell has the ability to invade surrounding tissue. D) Cell death occurs after a limited number of divisions.

Biology & Microbiology

Greenhouse gasses act to

a. warm the Earth's surface to support life. b. cool the atmosphere. c. block out ultraviolet radiation. d. contribute to acid rain. e. increase carbon monoxide concentrations.

Biology & Microbiology

Scientists have identified approximately ________ million species of organisms, but millions more are thought to exist

Fill in the blank(s) with correct word

Biology & Microbiology