Question

Bacteria were the first anaerobic heterotrophs to have evolved on Earth. Which of the

following best describes this type of bacteria?
A) Bacteria that do not require oxygen for their metabolism and obtain energy by consuming organic compounds produced by other organisms.

B) Bacteria that can survive and grow in the absence of oxygen and obtain their nutrients by consuming organic substances from their environment.

C) Bacteria that can live and reproduce without oxygen and rely on external sources of organic matter for their nutrition.

D) Bacteria that lack the need for oxygen and obtain their energy by consuming organic molecules from their surroundings.

Answer 1

The correct description of the first anaerobic heterotrophs that evolved on Earth is Option A, which details bacteria that do not require oxygen for metabolism and derive energy from organic compounds obtained from other organisms. These are anaerobic heterotrophs and can be obligate or facultative anaerobes depending on their tolerance to oxygen.

Step-by-step explanation:

A) Bacteria that do not require oxygen for their metabolism and obtain energy by consuming organic compounds produced by other organisms. These are known as anaerobic heterotrophs. They thrive in environments devoid of oxygen, where they use heterotrophic metabolism, a process that includes fermentation instead of aerobic respiration. Such bacteria rely on organic carbon as a terminal electron acceptor, rather than oxygen.

Examples of such facultative anaerobic bacteria include Staphylococci, Escherichia coli, Corynebacterium, and Listeria species, which can survive in both oxygen-rich and oxygen-poor environments. However, obligate anaerobes, like the Clostridia bacteria, cannot tolerate oxygen and it is typically lethal for them. This question underscores the diversity of metabolic pathways that bacteria can have and the evolutionary adaptability they possess in varying environmental contexts.