1. TEKS 7G: Analyze and evaluate scientific explanations concerning the complexity of the cell. Endosymbiotic Theory Notes

2. TEKS 7G: Analyze and evaluate scientific explanations concerning the complexity of the cell. Is the living cell simple or complex? Cells vary in complexity. Most eukaryotic cells are highly specialized and contain an intricate array of organelles and internal compartments. Many prokaryotic cells lack internal membranes and organelles except for ribosomes. However, even prokaryotic cells are complex in their own way.

3. TEKS 7G: Analyze and evaluate scientific explanations concerning the complexity of the cell. plant and animal cells contain a variety of organelles. Some structures are specific to either plant cells or animal cells only.

4. TEKS 7G: Analyze and evaluate scientific explanations concerning the complexity of the cell. How did cellular complexity come about? The fossil record provides few clues about the history of life at the cellular level. Microscopic fossils generally lack internal detail of cellular structure. However, careful studies of living cells have helped to answer questions about the origins of cellular complexity.

5. TEKS 7G: Analyze and evaluate scientific explanations concerning the complexity of the cell. What is the endosymbiotic theory? The endosymbiotic theory proposes that eukaryotic cells formed from symbiotic relationships among prokaryotes. The theory proposes that mitochondria evolved from free-living aerobic bacteria that began to live inside anaerobic prokaryotes. Chloroplasts evolved from free-living photosynthetic bacteria paired with the earliest eukaryotes. (contd.)

6. TEKS 7G: Analyze and evaluate scientific explanations concerning the complexity of the cell. The endosymbiotic theory is diagramed below.

7. TEKS 7G: Analyze and evaluate scientific explanations concerning the complexity of the cell. What evidence supports the endosymbiotic theory? Mitochondria and chloroplasts are similar in size to bacteria, have their own genomes, contain ribosomes similar to those of prokaryotes, and are formed by division of preexisting mitochondria and chloroplasts. The membrane systems of chloroplasts resemble those of photosynthetic prokaryotes. Some cells today contain endosymbiotic bacteria and algae.

8. TEKS 7G: Analyze and evaluate scientific explanations concerning the complexity of the cell. Do we fully understand the cell? No, but evidence suggests that complex cellular structures and pathways were produced by the process of evolution. However, there are many uncertainties in our current understanding of cellular complexity.