Problem 17 - Campbell Biology Concepts & Connections

Question

This chapter explains how the emergent properties of water contribute to the suitability of the environment for life. Until fairly recently, scientists assumed that other physical requirements for life included a moderate range of temperature, \(\mathrm{pH}\), and atmospheric pressure. That view has changed with the discovery of organisms known as extremophiles, which have been found flourishing in hot, acidic sulfur springs and around hydrothermal vents deep in the ocean. What does the existence of life in such environments say about the possibility of life on other planets?

Step-by-Step Solution

Answer

The existence of extremophiles suggests that life could exist in extreme conditions on other planets.

Step 1: Understanding Extremophiles

Extremophiles are organisms that can survive in extreme environmental conditions such as very high temperatures, high acidity, or high pressure. These conditions were previously thought to be inhospitable for life.

Step 2: Reassessing Physical Requirements for Life

The discovery of extremophiles has led scientists to reconsider the physical requirements for life. It shows that life can exist outside the previously assumed 'moderate' range of temperature, \(\text{pH}\), and atmospheric pressure.

Step 3: Implications for Extraterrestrial Life

If life can thrive in the extreme environments found on Earth, it raises the possibility that life could also exist in similar extreme conditions on other planets. This broadens the scope of the search for extraterrestrial life to include planets and moons with extreme environments.

Key Concepts

Emergent Properties of Water

Water is essential for life as we know it, thanks to its unique properties. These 'emergent properties' make water indispensable for biological systems.
One of these properties is its ability to act as a solvent. Water can dissolve many substances, making it crucial for transporting nutrients and waste products in living organisms.
Another important property is water's high specific heat capacity. This means it can absorb a lot of heat without changing temperature much.
This stabilizes environments, making them more suitable for life. Water also has cohesion and adhesion properties. It sticks to itself and other surfaces, aiding in processes like water transport in plants through capillary action.
Lastly, water's ability to expand upon freezing ensures that ice floats. This phenomenon creates an insulating layer on bodies of water, protecting aquatic life during cold periods.

Physical Requirements for Life

Traditionally, scientists believed life could only exist within specific physical limits. These included moderate temperature ranges, a stable pH, and certain levels of atmospheric pressure.
However, the discovery of extremophiles has changed this perspective. Extremophiles are organisms able to thrive in extreme environments such as boiling hot springs, highly acidic lakes, and deep ocean hydrothermal vents.
These organisms have specialized adaptations that allow them to survive and even flourish under conditions that would be lethal to most other life forms.
The existence of extremophiles demonstrates that the physical requirements for life are much broader than previously thought. It opens up new possibilities for where life could exist.

Extraterrestrial Life

The discovery of extremophiles on Earth has significant implications for the search for extraterrestrial life.
If life can thrive in Earth's extreme environments, it might also be possible on other planets and moons with similar conditions. For instance, Europa, one of Jupiter's moons, has an icy surface but may harbor liquid water beneath, potentially heated by hydrothermal vents.
Scientists are now more open to the idea that life could exist in a variety of extreme environments beyond Earth, such as the acidic clouds of Venus or the sub-surface ocean of Enceladus, a moon of Saturn.
This broadens the scope of the search for life in the universe, encouraging the exploration of a wider range of celestial bodies.