History of Life Flashcards
How many years ago was this description accurate?: The prehistoric ocean was teeming with life. Living organisms had not yet ventured out onto land and the skies were absent of any birds, insects, or winged dinosaurs.
550 million years ago.
Which era is referred to as the age of fish?
Paleozoic
Which era is referred to as the age of dinosaurs and reptiles?
Mesozoic
Which era is referred to as the age of mammals?
Cenozoic
How is the geologic record divided?
The Hadean, Archaean, Proterozoic, and Phanerozoic eons (the last half billion years).
How is the Phanerozoic eon divided?
Into three eras: the Paleozoic, Mesozoic, and Cenozoic.
The fossil record is biased in favor of species that:
- Existed for a long time
- Were abundant and widespread
- Had hard parts
What is the first step in the sequence of life’s origination?
Abiotic synthesis of small organic molecules such as amino acids and nucleotides.
What is the second step in the sequence of life’s origination?
The joining of these smaller molecules into macromolecules, such as proteins and nucleic acids.
What is the third step in the sequence of life’s origination?
The packaging of these macromolecules into protocells (droplets with membranes that maintained a different internal chemistry).
What is the fourth step in the sequence of life’s origination?
The origin of self-replicating molecules that eventually made inheritance possible.
What happened about 3.5 bya?
The first single-celled organisms. Prokaryotes were earth’s sole inhabitants for more than 1.5 billion years.
What are the oldest known fossils? How old are they?
The oldest known fossils–dating back some 3.5 billion years–are stromatolites, rocks formed by the accumulation of sedimentary layers on bacterial mats.
What was happening 2.7 bya?
Most atmospheric O2 is of biological origin. By 2.7 bya, it began accumulating in the atmosphere and rusting iron-rich terrestrial rock.
What was the oxygen revolution? When did it occur?
The oxygen revolution (2.7-2.3 bya) caused the extinction of many prokaryotic groups. Some groups survived and adapted using cellular respiration to harvest energy.
How old are the oldest fossils of eukaryotic cells?
1.8 billion years.
What does endosymbiosis attempt to explain?
The origin of eukaryotic cells.
What does endosymbiosis posit?
Mitochondria and plastids were formerly free-living prokaryotes that began living within larger cells, eventually giving rise to eukaryotic cells.
How old are the oldest known fossils of multicellular eukaryotes that can be resolved taxonomically?
They are of small algae that lived about 1.2 bya.
When do larger and more diverse multicellular eukaryotes appear in the fossil record?
About 600 mya–multicellularity in these lineages evolved independently, giving rise to plants, fungi, and animals.
What is the Cambrian explosion?
The Cambrian explosion refers to the sudden appearance of fossils resembling modern animal phyla within a ~10 million year window of the Cambrian period. This is where the first evidence of predator-prey interactions in the fossil record were found.
What is the range of the Precambrian period?
4.5 bya - 543 mya
When did animals with hard outer parts evolve?
During the Cambrian period. As a result, many of these shells became fossilized.
When did the first tectonic plates form?
During the precambrian period.
