Theme 5C Flashcards
What is the hypothesis for the origin of biological molecules
Originated in the ocean
Ocean environment was reducing - sulphur bacteria/thermophiles habitat
Vents provide habitats
What was the Urey Miller experiment
Simulated early Earth conditions and tested chemical origin of life
2% of carbon was amino acids 13/22 used in living cells
How old is the earth and when did life start to evolve
Earth is 4.5 billion years old
Unicellular prokaryotes arrived 3.5 bya
Simple multicellular life 2.1 bya
Complex multicellular life 650 mya
What is the importance of the shift to an oxygen atmosphere
Allowed for higher metabolic rates and a larger body size
Why was the rise of oxygen slow
Long period of anoxygenic photosynthesis
Oxygen was a result of Cyanobacteria
Was an oxidizing agent, so would react with reducing agents before it was able to accumulate at all
Was only when ocean became a CO2 sink did oxygen start to accumulate
What was the great oxygenation event
Free oxygen accumulates about 2.5 bya in atmosphere with huge increase 850 mya
Evidence: banded iron formations abundant 2.5 - 1.8 bya, declined after, major changes in rock types, hydrated and oxidized minerals
What were the first eukaryotes
Evolved from a symbiotic relationship between mitochondria and plastids (chloroplasts)
Larger then prokaryotes, have a nucleus, membrane bound organelles
What was the evidence for the symbiotic relationship between mitochondria and plastids
Organelles bound by membranes
Organelles have own DNA sequence separate from DNA in nucleus
Mitochondrial DNA is similar to bacteria/chloroplast DNA
Mitochondria and bacteria both replicate by pinching
How long ago was the ediacaran fauna
Ended 640 million years ago
All organisms are extinct
How long ago was the palaeozoic era
542-252 million years ago
How long ago was the Mesozoic era
252-65 million years ago
How long ago was the Cenozoic era
65 million years ago to present
What was the Cambrian explosion
Occurred in the palaeozoic era (about 530 mya)
Rapid appearance of many groups of organisms, started with small shell parts
Include evidence of arthropods, echinoderms and features of many modern groups appear (head, mouth, eyes, limbs)
Very high mutation rate, lots of diversity
What is a mass extinction
Rate of extinction great,y exceeds rate of speciation
Has to be more the 75% of all species of extinct
Why is mass extinction important
Niches are cleared and ecological opportunities are made available
Leaves low diversity of once diverse lineages
