Why are mass extinctions significant?
Mass extinctions clear niches, create ecological opportunities and reduce diversity. They behave as a sort of ecological reset and provide less dominant species the opportunity to expand and diversify.
Mass extinctions are _________ and are typically caused by significant ____________ changes.
Mass extinctions are periodic and are typically caused by significant environmental changes.
Mass extinction occurs when the rate of __________ greatly exceeds the rate of __________.
Mass extinction occurs when the rate of extinction greatly exceeds the rate of speciation.
What first appears in the Cambrian Explosion?
Major animal groups all first appear in the Cambrian Explosion.
The Cambrian Explosion is characterized by the ______ appearance of many groups of organisms such as __________ and __________.
The Cambrian Explosion is characterized by the ______ appearance of many groups of organisms such as arthropods and echinoderms.
What is endosymbiosis? What did it produce?
Endosymbiosis is the result of symbiosis between separate single-celled organisms.
The first eukaryotic cell was formed when a bacteria came to live inside an archaic cell.
What event can be characterized by a significant increase in available atmospheric oxygen? What evidence supports that this event occurred?
The Great Oxidation Event. The presence of Banded Iron Formations demonstrates the way in which the oxygen reacted with iron (and sulphur) to form iron oxides.
How did cyanobacteria produce oxygen and what effect did this have on the composition of life forms on Earth?
Cyanobacteria produced oxygen by way of photosynthesis wherein oxygen is a by-product. This led to:
- the dramatic increase in biodiversity
- extinction of oxygen-intolerant organisms
Stromatolites are layers of ___________ that provide evidence of the first ________ organisms.
Stromatolites are layers of cyanobacteria that provide evidence of the first oxygen-producing organisms.
What was demonstrated/proven through the Urey-Miller experiment?
It was proven that organic molecules such as amino acids (the foundation of proteins and life) could be formed using inorganic molecules and lighting as a source of energy. This provides a theory as to the origin of life.
Oxygen was _______, but oxidation was prevented since the free oxygen was immediately ______ from the atmosphere to form hydrogen sulphide, methane and carbon dioxide.
Oxygen was present, but oxidation was prevented since the oxygen was immediately removed from the atmosphere to form molecules such as hydrogen sulphide, methane and carbon dioxide.
The Earth was originally in a _______ state with ________ atmospheric ________.
The Earth was originally in a reduced state with little to no atmospheric oxygen.
How can the term reducing be defined?
Reducing can be defined as a lack of/deficiency of oxygen.
The first eukaryotes made their appearance during the __________ era.
The first eukaryotes made their appearance during the Proterozoic era.
What is the evidence for Endosymbiotic Theory?
- Mitochondria and chloroplasts evolved from bacteria that came to live inside another cell.
- They have circular DNA - similar to prokaryotic cells
- They have membranes similar to prokaryotes
- Highly conserved mitochondrial and chloroplasts DNA sequences are very similar to those of prokaryotes
Place these events in order of occurrence:
1. First evidence of life
2. First appearance of major animal groups
3. Diversification and development of eukaryotic organisms
4. First evidence of an oxygen rich environment
5. First eukaryotic organisms
1, 4, 5, 3, 2
