Describe the endosymbiotic theory with a diagram.

The endosymbiotic theory proposes that eukaryotic cells evolved from a symbiotic relationship between different types of prokaryotic cells. Specifically, it suggests that mitochondria and chloroplasts, which are organelles found in eukaryotic cells, were once free-living prokaryotic cells that were engulfed by a larger host cell.

Here is a diagram illustrating the endosymbiotic theory:

1. Prokaryotic cell A: This cell represents a free-living prokaryotic cell, such as a bacterium. It contains its own DNA, ribosomes, and other cellular structures.

2. Prokaryotic cell B: This cell also represents a free-living prokaryotic cell, such as a cyanobacterium. Like cell A, it contains its own DNA, ribosomes, and other cellular structures.

3. Engulfment: The larger host cell engulfs prokaryotic cell A and prokaryotic cell B, forming a symbiotic relationship.

4. Endosymbiosis: Over time, prokaryotic cell A evolves into a mitochondrion, while prokaryotic cell B evolves into a chloroplast. These organelles retain their own DNA and ribosomes, similar to free-living prokaryotic cells.

5. Eukaryotic cell: The host cell, now containing mitochondria and chloroplasts, evolves into a eukaryotic cell. This cell has a nucleus, membrane-bound organelles, and other features characteristic of eukaryotic cells.

This diagram illustrates how the endosymbiotic theory suggests that mitochondria and chloroplasts were once independent prokaryotic cells that were engulfed by a larger host cell, leading to the evolution of eukaryotic cells.

Endosymbiotic Theory

The endosymbiotic theory proposes that eukaryotic cells (containing a nucleus) evolved through the incorporation of prokaryotic cells (lacking a nucleus) into ancestral eukaryotic cells.

Diagram:

[Image of eukaryotic cell with mitochondria and chloroplasts]

Mitochondria and Chloroplasts:

- Mitochondria are believed to have evolved from aerobic bacteria that were engulfed by an ancestral eukaryotic cell.
- Chloroplasts are believed to have evolved from photosynthetic bacteria that were engulfed by an ancestral photosynthetic eukaryotic cell (plant or alga).

Evidence for the Theory:

- Mitochondria and chloroplasts have their own DNA, similar to prokaryotic DNA.
- They have their own ribosomes, which are smaller than eukaryotic ribosomes.
- They can undergo binary fission, like prokaryotes.

Process of Endosymbiosis:

1. Engulfment: A prokaryotic cell is engulfed by an ancestral eukaryotic cell.
2. Endosymbiosis: The prokaryotic cell forms a symbiotic relationship with the eukaryotic cell, providing specific functions.
3. Host-Symbiont Integration: Over time, the prokaryotic cell becomes integrated into the eukaryotic cell, losing its independence.
4. Acquisition of Organelles: The eukaryotic cell gains mitochondria (from aerobic bacteria) or chloroplasts (from photosynthetic bacteria) as fully functional organelles.

Benefits to the Host:

- Mitochondria: Provide energy through cellular respiration.
- Chloroplasts: Provide food through photosynthesis (in plants and algae).

Benefits to the Symbionts:

- Protection from environmental stresses.
- Access to nutrients and resources within the eukaryotic cell.

Illustrate the circular flow model of an open mixed economy. How does it differ from a two sector economy?