Section 5, Part A Flashcards
Important idea section 5, 1
Increased cellular activity evolved in the lineage leading to eukaryotic organisms
Important idea section 5, 2
Eukaryotic organisms diversified and evolved novel strategies for survival and reproduction
Review the differences between prokaryotic and eukaryotic organisms
How old are the oldest known eukaryotic fossils?
The oldest known possible multicellular eukaryote is Grypania spiralis, a coiled, ribbon-like fossil two millimeters wide and over ten centimeters long. It looks very much like a coiled multicellular alga and has been described from banded iron formations in Michigan 2.1 billion years old.
Others report the oldest eukaryotes to be 1.8 billion years old
Do the oldest known eukaryotic fossils date to before or after the rise of atmospheric oxygen?
After.
The great oxygenation event that led to the rise of atmospheric oxygen occurred roughly 2.5 billion years ago.
Explain how cytoskeleton complexity was significant in the evolution of larger, more complex (e.g. eukaryotic cells)?
Some prokaryotes possess a simple cytoskeleton that functions in cell movemen, but the development of a more complex cytoskeleton provided a structural frawework fro the cell and allowed for the movement of materials inside and on the surface of the cell.
The cytoskeleton is composed of microtubules, microfilaments, and intermediate filaments.
Explain how genetic complexity was significant in the evolution of larger, more complex (e.g. eukaryotic cells)?
Greater genetic complexity in eukaryotes has enabled more complex behavior of genes than in prokaryotes. This then resulted in greater genetic diversity allowing for evolution and natural selection to occur.
How was the development of an endomembrane system significant in the development of larger more complex (e.g. eukaryotic) cells?
The development of an endomembrane system resulted in a system of interconnected organelles and infolding of the plasma membrane (forming a nuclear envelope and ER).
A nuclear envelope is a distinct adaptive advantage because limits access to the nucleus and it allows for the selective intake and release of materials. In addition, it separates transcription and translation, allowing better processing of mRNA.
Explain how the development of a mitochondria led to larger more complex (e.g. eukaryotic) cells?
Development of a mitochondria allowed a for a great source of energy within eukaryotes, serving as a power house for the cell. Mitochondria play a critical role in energy metabolism. They are the sites of oxidative metabolism and are thus responsible for generating most of the ATP derived from the breakdown of organic molecules.
What is the endosymbiosis theory and what does it explain about the evolution of eukaryotic cells?
The endosymbiosis theory explains how the mitochondria (a prokaryotic-like organelle) came to be one of the critical organelles within eukaryotic cells.
The theory is that an ancestral eukaryote ingested a prokaryote and the bacteria began living within the eukaryotic cell. They developed a mutualistic relationship (same occurred for chloroplasts in plant cells). The bacteria eventually developed into what we today know as the mitochondria.
The engulfed prokaryote/mitochondria performs anaerobic respiration
The chloroplast/photosynthetic engulfed prokaryote performs photosynthesis.
The eukaryote supplices the bacterium with protection and carbon compounds and in exchange the bacterium supplies the eukaryote with ATP (32 ATP compared to the 2 ATP it could get on its own by fermentation). Thus this is a very favorable relationship for both, but is critical to the development of complexity and size within eukaryotes from prokaryotes.
What evidence supports the endosymbiosis theory? What organisms are thought to have evolved.
Organisms thought to have evolved:
- mitochondria from an engulfed prokaryote
- chloroplasts from an engulfed photosynthetic prokaryote
Evidence in support of the theory:
striking similarities between prokaryotes (like bacteria) and mitochondria:
Membranes — Mitochondria have their own cell membranes, just like a prokaryotic cell does. And mitochondria have 2 membranes.
DNA — Each mitochondrion has its own circular DNA genome, like a bacteria’s genome, but much smaller. This DNA is passed from a mitochondrion to its offspring and is separate from the “host” cell’s genome in the nucleus. Mitochondria ribosome is quite like a bacterial ribosome.
Reproduction — Mitochondria multiply by pinching in half — the same process used by bacteria, which is called binary fission.
DNA homology
