Problem 4 - Biology Today and Tomorrow Without Physiology

Question

Mitochondria are most likely descendants of __________. a. archaeans b. aerobic bacteria c. cyanobacteria d. anaerobic bacteria

Step-by-Step Solution

Answer

b. aerobic bacteria

Step 1: Understand the Question

The question is asking about the evolutionary origins of mitochondria and which type of organism they are most closely related to.

Step 2: Recall the Endosymbiotic Theory

Remember that according to the endosymbiotic theory, mitochondria originated from free-living organisms that entered into a symbiotic relationship with a host cell. This theory suggests that these organisms were once independent.

Step 3: Identify Traits of Mitochondria

Mitochondria have their own DNA and ribosomes and are involved in aerobic respiration, suggesting they share traits with aerobic bacteria.

Step 4: Analyze Answer Choices

Evaluate the given options: - Archaeans are a separate domain of life distinct from bacteria. - Aerobic bacteria are known for performing processes like aerobic respiration, similar to mitochondria. - Cyanobacteria are known for photosynthesis, not respiration. - Anaerobic bacteria do not use oxygen, unlike mitochondria.

Step 5: Select the Correct Choice

Based on the endosymbiotic theory and the traits of mitochondria, the descendants of mitochondria are most closely related to aerobic bacteria.

Key Concepts

Mitochondria Evolution

Mitochondria are known as the powerhouses of the cell because they play a crucial role in energy production. They are involved in cellular respiration, a process that converts biochemical energy from nutrients into adenosine triphosphate (ATP), which is used by cells for energy. According to the endosymbiotic theory, mitochondria evolved from free-living organisms that were engulfed by another cell around 1.5 billion years ago.

This theory was proposed by Lynn Margulis in the 1960s and has since gained wide acceptance. It suggests that the engulfed organism formed a symbiotic relationship with its host, leading to a mutual benefit for both entities. Over time, these once-independent organisms evolved to become the organelles known as mitochondria. Today, mitochondria retain some features of their ancestral existence, such as their own circular DNA, similar to bacteria, and their own ribosomes for protein synthesis. This evolutionary link highlights the fact that mitochondria share essential characteristics with aerobic bacteria, such as the ability to conduct aerobic respiration.

Aerobic Bacteria

Aerobic bacteria are microorganisms that need oxygen to survive and grow as they utilize it in their energy-making process, known as aerobic respiration. This is similar to how mitochondria operate within eukaryotic cells. The process of aerobic respiration in these bacteria involves breaking down glucose in the presence of oxygen to produce energy in the form of ATP.

The link between mitochondria and aerobic bacteria is significant. Both conduct aerobic respiration and have similar cellular machinery and biochemistry. Mitochondria, like aerobic bacteria, have inner membranes rich in proteins that are crucial for respiration. These similarities support the endosymbiotic theory, suggesting that mitochondria descended from ancient aerobic bacteria that entered into a symbiotic relationship with early eukaryotic cells.

• They perform cellular respiration using oxygen.
• They produce ATP, the energy currency of cells.
• They are structurally similar to mitochondria.

Organelle Origins

The origin of organelles such as mitochondria and chloroplasts is a fascinating area of study within cell biology and evolutionary biology. The endosymbiotic theory provides a compelling explanation for how eukaryotic cells, which possess these organelles, came to be. According to this theory, primitive eukaryotic cells engulfed different types of bacteria - aerobic bacteria, in the case of mitochondria, and photosynthetic bacteria, in the case of chloroplasts.

Over time, these engulfed bacteria became permanent residents within the host cell, evolving into organelles. This symbiotic partnership was beneficial: the host cell gained new capabilities, such as increased bioenergetic efficiency from mitochondria, while the engulfed bacteria received protection and nutrients from the host. This win-win scenario allowed these ancestral eukaryotic cells to thrive and diversify, resulting in the vast array of eukaryotic life we see today.

• Eukaryotic organelles have bacterial ancestry.
• Endosymbiosis was the driving force behind eukaryotic evolution.
• Organelles retain features of their free-living ancestors.