Chapter 14, Problem 30A

Summary Introduction

To infer:

The similar conditions in hot springs and early Earth and to explain the kind of organisms could survive in that type of environment.

Introduction:

Scientists did not know what the first cells were like as the first cells left no fossils. The earliest fossils are 3.5 billion years old. Chemical markings in rocks as old as 3.8 billion years suggest that life was present at that time even though no fossils remain.

Answer to Problem 30A

Hot springs have conditions similar to early Earth as it consists of organic and inorganic compounds at very high temperatures. There was no oxygen present in the early atmosphere.

The organisms that can survive in these harsh conditions are autotrophic prokaryotes such as archaebacteria. They extract energy from inorganic compounds such as sulfur.

Explanation of Solution

The hot spring shown in the given photo is of Yellowstone National Park. It has an environment similar to the environment of early Earth. It is believed that early Earth had very high temperatures due to colliding meteorites, compression of minerals and decay of radioactive materials. Volcanoes were frequently releasing gases and lava. The gases formed the early atmosphere although it lacked free oxygen.

Scientists hypothesize that prokaryotes were the first cells to have occurred on Earth. These are smaller than eukaryotes, lack a well-defined nucleus and other organelles. Many scientists think that modern prokaryotes called archaebacteria are the closest relatives of Earth’s first cells. These organisms live in extreme conditions such as the hot springs of Yellowstone National Park.

These organisms are autotrophic but they do not obtain energy from the Sun. They obtain energy from inorganic compounds such as sulfur.