Download Early Earth

Learning Objectives
To understand:
I. the history of our planet
– Non-living periods
– Periods with life
II. that the Earth and the diversity of life has
changed over time
III. trends in diversity over time
Early Earth
• Earth began forming ~ 4.5 bya
– Evidence:
• 1st atmosphere = N2, H2, CO and CO2
– no O2 or ozone, high UV & winds
• H2O was present
• Experiments mimicking conditions on early earth
demonstrate that organic compounds can form
from inorganic compounds
– Amino acids, nucleotides, carbs, ATP, NAD(P)
– Phospholipid ‘bubbles’ provide structure for a cell
First Life
Prokaryotes originated ~ 3.8 bya in Archean &
proliferated through Proterozoic
Chemoautotrophs made carbohydrates using chemicals in
environment - non-oxygen releasing; released sulfur
Oxygen releasing photosyn. arose later (=photoautotrophs)
Breakdown of carbohydrates to ATP did not req’ oxygen at
first (=fermentation), but later organisms use O2
• Photosynthesis ~ 3.2 bya
• Effects of oxygen:
– Mass extinction of many organisms
• Prokaryotic diversity of a different kind starts to diversify
– ozone layer develops ~2 bya
Origin of eukaryotic cells
• ~ 1 bya
• Endosymbiosis
– partnerships between prokaryotic ancestors
– chloroplasts and mitochondria
– Evidence?
Archean
oldest youngest
– prokarys. only
Proterozoic
Paleozoic
Mesozoic
Cenozoic
youngest
oldest
Paleozoic
• Started with mass extinction,
then adaptive radiation of
multicellular organisms
• Life proliferated in seas
– Cambrian explosion of inverts
– Armored fish follow
– Then land invasion: plants,
insects, amphibians
Mesozoic
Adaptive radiation of seed
bearing plants and reptiles
followed by mass extinction
Cenozoic
• Adaptive radiation of mammals
– H. sapiens evolved in last 40,000 yrs. Agriculture arose 10,000 yrs.
• Average extinction rates
– 1 spp./1 million spp./year
• 20th century extinction rates
– 1,000 -10,000 spp. / 1 million spp. / year
Biodiversity
• Millions of species now on earth (~2 million)
– Diversity has changed radically over time
• Observations - Many species look like other species
– Broad similarities = lineages with similar phenotypes &
life histories
• Reptiles = snakes, lizards, crocs
• Gymnosperms = pines, spruce, fir, larch
• Primates = great apes, chimps, humans
– Within a very closely related group, the different species
of the group tend to live in different habitats
• White Pine and Jack Pine and tamarack live in different habitats
• Great apes (baboons, gorillas, orangutans) live in different
habitats
Conclusions
• Broad similarities in life histories are
present because lineages are related
– Supported by initially by studies of anatomy,
development, and now by molecular data
• Similar species in different habitats exist b/c
each habitat ‘selects’ for traits in slightly
different ways
Taxonomy classifies organisms to reflect relatedness.
Taxon - a group of organisms with similar form(s) that
are related.
Reptiles are a taxonomic group
Gymnosperms are a taxonomic group
Then, all of the pines (white, red, limber, lodgepole, etc) are
another more specific taxonomic group. All pines are closely
related.
Classification system
• developed by Linnaeus (~1758)
• hierarchial organization
• binomial species name
genus and epithet = species
• Used to identify organisms
•Species belong to a genus
(1st part of name)
•Genera grouped into families
•Families grouped into orders
•Orders --> classes
•Classes --> Phyla
•Phyla
•Kingdoms – 6 kingdoms
•Domains are the largest unit
•Eukarya, Bacteria, Archaea
Eukarya
Domain