Question at position 29 What evidence indicates mitochondria evolved before chloroplasts in eukaryotic cells?Chloroplasts can reproduce independently, while mitochondria cannot.Mitochondria are larger and more complex than chloroplasts.All eukaryotes have mitochondria, but only some groups have chloroplasts.Mitochondria contain linear chromosomes, whereas chloroplasts have circular chromosomes.Clear my selection

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When evaluating the evidence about the order of evolution between mitochondria and chloroplasts, we need to test each statement against established cell biology.
Option 1: 'Chloroplasts can reproduce independently, while mitochondria cannot.' In reality, both organelles replicate by fission and contain their own DNA, and neither strictly reproduces independently in the sense of a separate cellular lineage. This claim overstates independence and is not accurate evidence for the evolutionary sequence.
Option 2: 'Mitochondria are larger and more complex than chloroplasts.' Size and complexity can vary among species, and overall, chloroplasts can be quite large and structurally complex in plants and algae. This generalization is not a reliable indicator of the evolutionary order between the two organelles, making the statement misleading as evidence.
Option 3: 'All eukaryotes have mitochondria, but only some groups have chloroplasts.' This pattern matches what we know from phylogeny: mitochondria are present in nearly all eukaryotic cells, whereas chloroplasts are restricted to photosynthetic lineages (such as plants, algae, and some protists). The universal presence of mitochondria across eukaryotes, contrasted with the patchy distribution of chloroplasts, supports the idea that mitochondria originated earlier in eukaryotic evolution, with chloroplasts being acquired later (via primary or secondary endosymbiosis) in certain lineages.
Option 4: 'Mitochondria contain linear chromosomes, whereas chloroplasts have circular chromosomes.' In fact, both organelles typically contain circular genomes, not linear ones. This assertion is factually incorrect and cannot be used as evidence for evolutionary order.
In summary, the reasoning considers accuracy and how each statement aligns with established evolutionary evidence. The third option aligns with the widely accepted view that mitochondria appeared earlier in eukaryotic evolution, while chloroplasts were incorporated later in specific lineages. The other statements contain factual inaccuracies or overgeneralizations that do not reflect how these organelles evolved or function today.

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