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 LifeProkaryotes originated ~ 3.8 bya in Archean &
proliferated through ProterozoicChemoautotrophs 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 – prokarys. only
Proterozoic
Paleozoic
Mesozoic
Cenozoic
oldest
youngest
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
MesozoicAdaptive 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 groupGymnosperms 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 namegenus 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
DomainEukarya
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