Question

1. how do mitochondria and chloroplasts show evidence for endosymbiosis?

Explanation:

To determine how mitochondria and chloroplasts show evidence for endosymbiosis, we analyze key features:

1. Double Membranes: Both have outer and inner membranes. The outer membrane resembles eukaryotic cell membranes, while the inner membrane is similar to prokaryotic membranes, suggesting engulfment of prokaryotes.
2. Own DNA: They possess circular DNA, like prokaryotes (e.g., bacteria), unlike linear eukaryotic nuclear DNA.
3. Ribosomes: Their ribosomes are similar to prokaryotic (70S) rather than eukaryotic (80S) ribosomes, supporting a prokaryotic origin.
4. Reproduction: They reproduce independently via binary fission, like prokaryotes, not through eukaryotic cell division mechanisms.
5. Size and Structure: Their size and structural features align with prokaryotic cells, further supporting the endosymbiotic theory (e.g., chloroplasts resemble cyanobacteria, mitochondria resemble proteobacteria).

Answer:

Mitochondria and chloroplasts show evidence for endosymbiosis through:

• Double membranes: Outer membrane (eukaryotic - like) and inner membrane (prokaryotic - like, e.g., mitochondrial inner membrane has respiratory enzymes similar to prokaryotes).
• Circular DNA: They have their own circular DNA (like prokaryotes, unlike linear eukaryotic nuclear DNA).
• 70S ribosomes: Their ribosomes match prokaryotic (70S) ribosomes (eukaryotic cells have 80S ribosomes).
• Independent reproduction: They reproduce via binary fission (like prokaryotes), not eukaryotic cell division.
• Prokaryote - like size/structure: Their size and structure (e.g., chloroplasts ≈ cyanobacteria, mitochondria ≈ proteobacteria) align with prokaryotic cells.

These features suggest they were once free - living prokaryotes engulfed by ancestral eukaryotes, evolving into organelles.