Discuss the events that occurred during the oxygen revolution. What will be an ideal response?
The first primary producers, probably an early form of cyanobacteria, assembled their own
food from inorganic molecules and then broke the food down to release energy. With the
success and proliferation of these simple autotrophs, and with the abundance of oxygen they
eventually provided, the way was clear for the evolution of animals. The first animal-like
creatures were single-celled organisms. They began to prosper in the ocean during the
oxygen revolution, a time of radical change in Earth’s atmosphere. During the oxygen
revolution, between about 2 billion and 400 million years ago, the activity of photosynthetic
autotrophs changed the composition of the atmosphere from less than 1% free oxygen to its
present oxygen-rich mixture of more than 20%. The growing abundance of free oxygen made
aerobic respiration practical, speeding the disassembly of food molecules that early animals
obtained by eating the autotrophs. Ozone derived from this oxygen blocked most of the sun’s
dangerous ultraviolet radiation from reaching Earth’s surface, permitting life to survive at the
surface of the ocean and, later, on land.
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Which of the following best describes a sustainable use of nonrenewable minerals?
a. recycle and reuse 60-80% of mineral resources b. stop focusing on population growth as a factor c. stop all mining of nonrenewable mineral resources d. reduce mining subsidies e. reduce mining subsidies and recycle and reuse 60-80% of mineral resources
Determine the gradients of three segments of the Eds Creek drainage basin: a first-order stream between Points 1 and 2; a second-order stream between Points 2 and 3; and a thirdorder stream (Eds Creek) between Points 3 and 4. Use the ruler function to determine distances (to the nearest 0.01 miles) and the elevation change between points.
To answer the following questions, go to the Hess Physical Geography Laboratory Manual, 12th edition, website at www.MasteringGeography.com, then Exercise 39 and select “Exercise 39 Part IV Google Earth™” to open a KMZ file in Google Earth, or scan the QR (Quick Response) code for this exercise and view “Exercise 39 Part IV Google EarthTM video.” In this exercise you’ll compare the characteristics of streams in the Eds Creek drainage basin in Montana (also shown in Map T-3 and Figure 39-3).
(a) Fly to Point 2, then determine the gradient of the first-order stream (between Point 1 and Point 2).
(b) Fly to Point 3, then determine the gradient of the second-order stream (between Point 2 and Point 3).
(c) Fly to Point 4, then determine the gradient of the third-order stream (between Point 3 and Point 4).
The ocean floor topography is
A) smooth. B) varied. C) flat. D) unknown.
The main difference between hard path and soft path energy policy is
A) the reliance on fossil fuels and centralized power generation B) their contrasting economic viability C) their contrasting reliance on known energy sources D) their contrasting reliance on government subsidies