Origin of Life in the Oceans

What Is Life?

How do scientists know what is living and what is not living? For some organisms, it may be an obvious decision, but for others it can be more difficult. In this interactivity, you will learn about how scientists classify life. Click the player button to get started.

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The Origin of Life

Scientists theorize that the Earth was formed from the Big Bang. Once the Earth was formed, basins on the Earth’s surface were filled with water and these water-filled basins became the oceans. The early oceans were composed of a lot of organic molecules which resulted from the formation of the Earth; therefore, they have been referred to as a "prebiotic soup". That, together with all of the energy present from lightning, cosmic rays, and the internal heat of the Earth, may have created the precursors to living organisms. These precursors were complex molecules such as proteins and DNA. Scientists theorize that these molecules came together to form more complex molecules. These complex molecules were the building blocks for future generations of molecules that eventually began to take on the qualities of life.

In 1952, a scientist named Stanley Miller conducted an experiment whereby he showed that a mixture of carbon dioxide, methane, ammonia, hydrogen and water (similar to early Earth’s atmosphere and oceans makeup) when exposed to UV light (Sun) and a spark (lightning) formed organic molecules. Some of these molecules that formed were amino acids.  Amino acids are the basic components of life.

There are approximately 250,000 known marine species in existence and this number makes up about 14% of the total known species on Earth. Why are there fewer marine species than those found on land? Species diversity is created and supported by environmental variability. The higher environmental variability found on land is not found in the more stable ocean environment; therefore, species in the ocean are not as diverse in function and appearance as their land-dwelling relatives. The known oceanic species range from as tiny as microscopic bacteria and algae, to the largest marine mammal, the blue whale.

 

Origin of Life in the Oceans Review

Now that you have learned about the seven characteristics of life and how marine life originated, review your knowledge. In this non-graded interactivity, determine if the item listed is living or nonliving. Click SUBMIT to check your responses. Click the player button to begin.