Lesson 6: Levels of Organization / Prokaryote vs Eukaryotes

5. What effect does hypoxia caused by algae blooms have on aquatic organisms, and what is its relationship to cellular respiration?
   (1) Hypoxia increases respiration in aquatic organisms, improving their survival.
   (2) Hypoxia limits oxygen availability, reducing energy production in cells.
   (3) Hypoxia decreases the need for respiration in decomposers, stabilizing the ecosystem.
   (4) Hypoxia enhances the photosynthetic activity of algae.

6. Explain one strategy humans can implement that could prevent algae blooms (Short Response)

Prokaryotes and Eukaryotes: Cell Types and the History of Life on Earth

All living things are made of cells, but not all cells are the same. Scientists classify cells into two main types based on their structure and complexity: prokaryotic cells and eukaryotic cells. Understanding these two cell types helps explain both how living organisms function today and how life on Earth began billions of years ago.

Prokaryotic cells are the simplest and oldest type of cells. They do not have a nucleus, so their genetic material (DNA) is found floating freely in the cytoplasm. Prokaryotes also lack membrane-bound organelles such as mitochondria and chloroplasts. These cells are usually very small and are almost always unicellular. Bacteria are the most common examples of prokaryotic organisms. Because of their simple structure, prokaryotes can survive in extreme environments, including very hot, salty, or acidic conditions.

Prokaryotes were the first life forms on Earth. Scientists estimate that they appeared around 3.5 to 4 billion years ago, shortly after Earth formed. For billions of years, prokaryotes were the only organisms on the planet. Some early prokaryotes were able to perform photosynthesis, releasing oxygen as a waste product. Over time, this oxygen accumulated in the atmosphere during an event called the Great Oxygenation Event, which dramatically changed Earth’s environment and made it possible for more complex life to evolve.

Eukaryotic cells are larger and more complex than prokaryotic cells. They contain a nucleus that stores DNA and membrane-bound organelles that perform specific functions. For example, mitochondria release energy from food, and chloroplasts carry out photosynthesis in plant cells. Eukaryotic organisms can be unicellular or multicellular and include animals, plants, fungi, and protists.

Eukaryotic cells evolved much later than prokaryotes, around 1.5 to 2 billion years ago. Scientists believe eukaryotes formed when one prokaryotic cell began living inside another in a mutually beneficial relationship. This idea, known as the endosymbiotic theory, explains how mitochondria and chloroplasts became permanent parts of eukaryotic cells. Having these energy-producing organelles allowed eukaryotic cells to become larger and more complex.

The evolution of eukaryotic cells led to multicellular organisms with specialized cells, tissues, and organs. This increased complexity resulted in the wide variety of life forms that exist on Earth today. Although prokaryotes remain simple in structure, they are still incredibly important and are found in nearly every environment on the planet.

In summary, prokaryotic cells are simple, nucleus-free cells that were the first life forms on Earth, while eukaryotic cells are more complex and evolved later. Together, these two cell types help scientists understand both the structure of modern organisms and the long history of life on Earth.