Explain why the presence of free oxygen in our atmosphere marks an important step in the evolution of life on Earth

What will be an ideal response?


Earth's atmosphere became oxygen rich about 2.5 billion years ago and fundamentally changed Earth's ability to support life. Increased atmospheric oxygen caused the ozone concentration in the upper atmosphere to build up, thereby shielding Earth's surface from ultraviolet radiation. This effectively eliminated the food supply for anaerobic bacteria. Oxygen is also highly reactive with organic matter. When anaerobic bacteria are exposed to oxygen and light, they are killed instantaneously. By 1.8 billion years ago, the atmosphere's oxygen content had increased to such a high level that it began causing the extinction of many anaerobic organisms. Because aerobic respiration releases nearly 20 times more energy than anaerobic respiration aerobic respiring organisms were able to thrive.

Environmental & Atmospheric Sciences

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Mutations can occur in any cell type, however only those that occur in ____________________ are passed on to offspring, thus allowing for evolution

Fill in the blanks with correct word

Environmental & Atmospheric Sciences

Soil is a complex medium containing ________ principle components

A) three B) four C) five D) six

Environmental & Atmospheric Sciences

As opposed to cyclones, ________ are often associated with good weather

Fill in the blank(s) with the appropriate word(s).

Environmental & Atmospheric Sciences

Explain and give an example of biomagnification

What will be an ideal response?

Environmental & Atmospheric Sciences