The History of Life on Earth Flashcards
Extinction
the end of a species or group of taxa; first established by Georges Cuvier in a 1796 lecture.
The Bone Wars
rivalry between Marsh and Cope, uncovered 142 new species but ruined both men financially and socially.
o Macroevolution
broad pattern of change in living things, above the species level
How old is Earth?
4.6 billion years old
When did living cells appear?
(fossil bacteria 3.6 billion years old) Organic molecules and then protocells evolved on an Earth very different than today. Protocells can have inside different than outside. Self-replication made inheritance possible. RNA was likely the first heritable factor.
Fossil Dating
a. relative age of fossils come from the sequence fossils were laid down
b. absolute dating calculated from Half-life - The time required for 50% of the parent isotope to decay into something else
Stromatolites
ayered rocks formed by prokaryotic cyanobacteria. Oldest is 3.5 billion years old.
Photosynthesis
“Oxygen Revolution” from 2.7 to 2.2 billion years ago.
– Evidence is rust layer in aquatic sedimentary then terrestrial rocks.
– Changes selective pressures for living things. Extinctions and new niches.
4) Eukaryotic cell evolution
allowed greater range of unicellular forms
a. Endosymbiont theory- explains origin of organelles. Evidence for serial endosymbiosis (Lynn Margulis) :
i. Structure and function similarities - organelle inner membrane & prokaryote membrane
ii. Division in organelles similar to some prokaryotes
iii. Organelles transcribe and translate their own DNA
iv. Ribosomes are more similar to prokaryote than eukaryote
Multicellularity evolved
gave rise to algae, plants, fungi, and animals
Ediacaran fauna’
Cambrian explosion
most phyla of animals originate.
i. 535-525 MYA
ii. had a long fuse
iii. 1st predator/prey interactions
Colonization of Land
began 500 mya -
Adaptations:
a. Internal fertilization and shelled eggs for reproduction on dry land
b. Scaly skin, waxy layers, vascular system, for preventing dehydration
Continental drift
continents move over hot liquid mantel. Three times a supercontinent formed
a. e.g. Supercontinent Pangea formed 250 mya – associated with many ecological changes:
b. When faced with such changes in climate, organisms:
1) adapt
2) move to a new location
3) or become extinct
c. Promotes allopatric speciation
d. Explains much about the former and current distribution of organisms
Mass extinction
a sharp decrease in the diversity and abundance of life.
a. 98% of species that ever lived are now extinct
b. 5 mass extinction in Earth’s history
5 mass extinction in Earth’s history
a. The Permian Extinction- the 3rd mass extinction of 5, 251 mya
i) Defines the boundary between the Paleozoic and Mesozoic eras
ii) Occurred in less than 5 million years
iii) 96% of marine animal species extinct
iv) 70% of terrestrial vertebrate species extinct
v) Maybe caused by volcanism, which lead to global warming, and a decrease in oceanic oxygen
vi) Crinoids and Gorgonopsids extinct
b. The Cretaceous mass extinction
i) 65.5 million years ago
ii) Separates the Mesozoic and Cenozoic
iii) Half of all marine species and many terrestrial plants and animals, including most dinosaurs extinct
c. Current mass extinction is the 6th
i) Many species have been pushed to extinction by actions of man: Tasmanian Tiger, Dodo bird, Quagga, Passenger Pigeon, The Caribbean Monk Seal, Pyrenean Ibex.
