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