Euglena (an excavate) and Gymnodinium (an alveolate) are...

Name: Problem 13, Chapter 16: Campbell Biology : Concepts and Connections
Uploaded: 2021-08-26T01:06:31-08:00
Duration: 49 s
Channel: Abigail Schammel
Description: Euglena (an excavate) and Gymnodinium (an alveolate) are both capable of photosynthesis. However, researchers have identified differences in their chloroplasts. Use the theory of endosymbiosis to explain the reason for these differences. (Hint: Review Figure 16.13.)

Euglena (an excavate) and Gymnodinium (an alveolate) are both capable of photosynthesis. However, researchers have identified differences in their chloroplasts. Use the theory of endosymbiosis to explain the reason for these differences. (Hint: Review Figure 16.13.)

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Key Concepts

Secondary Endosymbiosis

Secondary endosymbiosis occurs when a eukaryotic cell that already contains a chloroplast is engulfed by another eukaryotic cell. This event results in chloroplasts that are surrounded by additional membranes compared to those from primary endosymbiosis. The theory helps explain why organisms like Gymnodinium, which underwent secondary endosymbiosis, have chloroplasts that differ in structure and number of membranes compared to those in Euglena.

Endosymbiotic Theory

This theory posits that certain organelles, notably chloroplasts and mitochondria, originated from free-living bacteria that were engulfed by ancestral eukaryotic cells. Over evolutionary time, these internalized bacteria evolved into organelles, leading to the complex eukaryotic cells we see today. This is crucial to understanding why different eukaryotic lineages can have variations in their photosynthetic machinery.

Primary Endosymbiosis

Primary endosymbiosis refers to the initial engulfment of a photosynthetic prokaryote, such as a cyanobacterium, by a eukaryotic host cell. This event led to the formation of the first chloroplasts. The process explains the basic similarities in chloroplast structure among many photosynthetic organisms, while also providing a basis to understand subsequent modifications or variations.

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