Ch. 6 Flashcards
3 lines of evidence to consider for evolution
Stromatolites, microfossils, isotopic evidence
Stromatolites are?
Distinctively layered rocks with living microbes interweaved with sediments
Stromatolites date life to how many years ago
3.5 billion
What suggests that a form of life must predate stromatolites
Photosynthesis
Microfossils are?
Very tiny fossils
Microfossils give evidence dating back to how many years ago?
3.0 billion
Isotopic evidence is?
Life tends to assimilate carbon-12 atoms more easily than carbon-13
Isotopic evidence gives evidence dating back how many years ago?
3.85 billion
Why is it likely that life originated in water?
No oxygen in the early atmosphere allowed for harsh ultraviolet radiation
What are the three possible ways simple organic chemicals manifested?
From space, near the surface of the earth, deep in the ocean
The Miller-Urey experiment?
Mimicking the water cycle with lightening. Created amino acids and other organic compounds were found to exist.
How did life come from outer space?
Asteroids and comets contained amino acids and chemicals that can survive to the surface
What is Panspermia
The relocation of life from elsewhere in the universe to Earth
What must life survive to meet the criteria for Panspermia
Initial impact on other planet, harsh space, impact on earth
Abiogenesis
How life starts from the basic organic chemicals
RNA World hypothesis
RNA came before DNA
Organic molecules formed from
RNA forming on clays, RNA replicates in pre-cells, complexity increases to form life, DNA evolves
Anaerobic
Organisms that don’t need oxygen
The history of evolution starting on earth
Simple anaerobic organisms that developed rapidly in complexity shorty after the earth formed, diversification lead to RNA. Photosynthesis generated oxygen in the atmosphere. Oxygen based life forms dominated
Bacteria
single cell organisms that have no cell nucleus
Early life was in the form of?
Single cell organisms that reproduced only by cell division
Two superkingdoms began before one
Archea and Bacteria came before Eukarya
Eukarya are different from bacteria and archea
Only cells with a nucleus and are capable of more complex reproductive strategies
Sexual reproduction led to
A huge increase in the diversity of life and the rate of evolution due to genetic mixing
Animal life began prolific when
1.2 billion years ago
Reasons for explosion in Cambrian era?
oxygen level reached current levels, climate change, genetic diversification, predator efficiency was lacking
Plants appear in fossils how many years ago
475 million
What is essential for the development of atmospheric ozone
O3
When did the “Great Oxidation Event” occur
2.35 billion years ago
What is the evidence for the asteroidal extinction of dinosaurs
Large 10km diameter wide asteroid hitting the earth depositing iridium
Where did the asteroid hit?
Yacatan Peninsula
What were the ramifications of the impact of the asteroid that killed the dinosaur
Pushed material into the atmosphere causing global winter, tsunami, global fires, intense heat, reduced sunlight, mammals rose to dominance
Causes for extinction
Volcanic eruption, climate change, mutation, magnetic pole reversal, proximity to a supernova explosion, impact of gamma ray bursts
