Question

As we learned in Chapter 27 , some bacteria and archaea are able to use energy from the oxidation of sulphur, iron, or hydrogen. These organisms can be classified as a. heterotrophs. b. autotrophs. c. producers. d. both a and b. e. both b and c.

Short answer

The correct answer is e. both b and c.

Step-by-step solution

Define terms

Heterotrophs are organisms that cannot produce their own food and need to consume other organisms for their energy and nutrients. Autotrophs, on the other hand, are organisms that can produce their own food from inorganic substances, using light or chemical energy. Producers are organisms that make their own food from sunlight and/or chemical energy, which are typically plants and algae but also bacteria that perform photosynthesis or chemosynthesis.

Identify Correct Category

In this case, the bacteria and archaea that use the energy from the oxidation of sulfur, iron, or hydrogen are doing chemosynthesis, which is a type of autotrophic production of food. Therefore, these bacteria and archaea can be considered as autotrophs.

Final Answer

The bacteria are not heterotrophs, as they can produce their own energy through chemical processes. As for producers, this term is used primarily in the context of ecosystems to refer to organisms that create complex organic substances (essentially, food) from simple inorganic substances. Autotrophic bacteria and archaea, by creating energy through chemosynthesis, can be considered producers in this sense. Thus, the most fitting categories for these bacteria and archaea are 'autotrophs' and 'producers'.

Key concepts

Chemosynthesis

Chemosynthesis is a process some organisms use to produce energy and organic compounds from simple inorganic molecules, without any sunlight. It is an alternative to photosynthesis, which is more commonly known.
Unlike photosynthesis, which relies on sunlight, chemosynthesis derives its energy from chemical reactions.
The main elements involved in these reactions are typically those found in harsh environments, such as sulfur, iron, and hydrogen.

• For example, in deep sea vents, bacteria use hydrogen sulfide to fuel their metabolic processes.
• These bacteria oxidize hydrogen sulfide, reacting it with oxygen to obtain energy and produce sulfur or sulfate as by-products.

In environments without sunlight, like the deep ocean or underground, chemosynthesis is crucial for the survival of certain microorganisms, which in turn support entire ecosystems.

Producers

Producers are essential in ecosystems because they create their own food and supply energy to other organisms. They are the very first level in a food chain.
Typically, when we think of producers, plants and algae come to mind. Yet, certain bacteria and archaea, through processes like chemosynthesis, also serve as producers.

• Autotrophic bacteria and archaea can convert inorganic molecules into organic matter.
• This organic matter then forms the base of the ecosystem, supporting more complex life forms.

These organisms do not rely on other organisms for food, making them self-sustainable and fundamental to sustaining various life forms in ecosystems.

Bacteria

Bacteria are single-celled microorganisms that can be found in a wide variety of environments, from soil to human guts to deep sea vents.
They exhibit extreme versatility in the ways they produce energy.
Bacteria involved in chemosynthesis are particularly interesting because they can thrive in environments that are inhospitable to many other life forms.

• They play a significant role in nutrient cycling, breaking down materials in their environment.
• These bacteria are often essential partners in ecosystems, facilitating energy flow.

By converting inorganic compounds into energy through chemosynthesis, they perform a critical function in ecosystems that do not receive sunlight.

Archaea

Archaea are microorganisms similar to bacteria in appearance but genetically distinct. They are part of the group of life forms known as extremophiles because many live in extreme environments – super hot, super cold, or very salty places.
One fascinating aspect is their ability to conduct chemosynthesis.

• Some archaea perform chemosynthesis using hydrogen or other simple compounds to produce energy.
• They are often found in extreme conditions where traditional photosynthesis is not possible.

Archaea's chemosynthetic activity is vital in supporting ecosystems where sunlight never reaches, allowing energy and nutrients to flow from even the most unexpected places.