CH 25 Powerpoint/Study Guide Flashcards
What is meant by eukaryotes being “combination organisms”?
Eukaryotes have traits from both archaeal and bacterial ancestors due to the engulfment of bacteria by archaea, leading to organelles like mitochondria.
What is the significance of the cytoskeleton in early eukaryotes?
The cytoskeleton allowed early eukaryotes to change shape and move, enabling them to engulf other cells.
What key event led to the origin of mitochondria in eukaryotes?
The engulfment of an aerobic bacterium by an ancestral Archaeal cell.
What are the key similarities between the membranes of mitochondria/plastids and prokaryotic cells?
The inner membranes of mitochondria and plastids resemble prokaryotic plasma membranes in both structure and function, supporting the idea that mitochondria and plastids originated from ancestral prokaryotes through endosymbiosis.
How do mitochondria and plastids divide, and how does this support the endosymbiotic theory?
They divide similarly to prokaryotes by binary fission, supporting their bacterial origin.
What type of DNA do mitochondria and plastids contain, and why is this important?
They contain circular DNA, similar to prokaryotes, reinforcing the idea that they originated from bacteria.
What is the similarity between ribosomes in mitochondria/plastids and prokaryotic ribosomes, why is it important?
Ribosomes in Mitochondria, Plastids, and Prokaryotes are all size 70S, It shows that these organelles share a common evolutionary origin with bacteria.
What is serial endosymbiosis?
The theory that mitochondria evolved first, followed by plastids, in a sequence of endosymbiotic events.
What type of organism gave rise to plastids in red and green algae?
Cyanobacteria, through primary endosymbiosis.
Which two algal lineages arose from primary endosymbiosis?
Red algae and green algae.
What is the difference between primary and secondary endosymbiosis?
Primary endosymbiosis involves a prokaryote being engulfed by a eukaryote, while secondary endosymbiosis involves a eukaryotic cell that already contains a primary plastid being engulfed by another eukaryote.
What is a nucleomorph, and where is it found?
A nucleomorph is a vestigial nucleus found in some organisms that underwent secondary endosymbiosis, such as chlorarachniophytes
What is the evidence that plastids in red and green algae originated from cyanobacteria?
Plastids have two membranes, similar to cyanobacteria, and homologous transport proteins in their membranes.
Why do we think secondary endosymbiosis played a part in the evolution of certain algae?
The presence of a nucleomorph and multiple membranes around plastids in some protists suggests secondary endosymbiosis.
Which two groups of algae were involved in secondary endosymbiosis?
Red algae and green algae.
Provide an example of an organism that evolved through secondary endosymbiosis.
Euglenids evolved when a green alga was engulfed by a heterotrophic eukaryote.
What is the role of cyanobacteria in the evolution of photosynthetic eukaryotes?
Cyanobacteria were engulfed by early eukaryotes, leading to the formation of plastids in red and green algae through primary endosymbiosis.
How does the structure of ribosomes in mitochondria support the endosymbiotic theory?
The ribosomes are more similar to prokaryotic ribosomes, suggesting a bacterial origin.
What is the function of a nucleomorph, and what does it indicate about a cell’s evolutionary history?
A nucleomorph is a remnant of the engulfed cell’s nucleus in secondary endosymbiosis, indicating a more complex evolutionary history involving multiple engulfment events.
What features of mitochondria and plastids suggest they were once free-living prokaryotes?
Their circular DNA, prokaryotic-like division, and prokaryote-sized ribosomes suggest they were once free-living bacteria.
How did secondary endosymbiosis contribute to the diversity of eukaryotes?
By creating new lineages of protists, such as chlorarachniophytes and euglenids, through the engulfment of photosynthetic eukaryotes.
What evidence suggests that mitochondria evolved before plastids?
Mitochondria are found in nearly all eukaryotes, whereas plastids are only found in specific groups, indicating that mitochondria evolved first.
What are the four supergroups of eukaryotes?
Excavata, SAR, Archaeplastida, Unikonta.
How is the eukaryotic domain currently classified based on molecular and morphological data?
Into four supergroups (Excavata, SAR, Archaeplastida, Unikonta).
Why was the kingdom Protista abandoned in modern classifications?
Protists are polyphyletic, with some groups more closely related to animals, plants, or fungi than to each other.
Why are amitochondriates no longer considered the oldest lineage of eukaryotes?
Amitochondriates were found to have reduced mitochondria, not a complete absence of them.
What is the significance of dotted lines in the eukaryotic tree?
They indicate clades under active debate, showing that the relationships between groups are unresolved.
