Biology 106

Lecture Topic # 14: Evolutionary History of Earth

I. Concept of Era's

A. pre Darwinian concept- credited to Greeks & Egyptians

B. defn = a period of time marked by distinctive character; Earth's agea ~ 4.5 bybp

II. Archean Era

A. Life appears

B. formation of large cratons (= continental land masses)

ex., U.S.A. on N. Am. craton

C. first fossils - small cells, bacteria like organisms in shallow marine habitats

III. Proterozoic Era

A. Photosynthetic bacteria Stromatolites cyanobacteria) produce O2

B. O2 ppt out in ocean via iron ore.

C. 1st Eukaryotes (acritarchs) -lger size, complex cell wall- free O2 available,

no longer iron ore formation

D. Early multicellular organisms, ex. algae

E. All fossils present are marine

IV. Paleozoic Era

A. Early Paleozoic (Cambrian-Ordovocian)

1. Cambrian Revolution

a. soft body---> skeletonized dispose excess CA w/PO4

b. increase in O2, threshold for functioning mito.(10%)

c. 1st predators (bite marks)

d. crawling and swimming invert's

2. Mass Extinction

a. end of Cambrian

b. radiation of many new animals

c. 1st vertebrates

d. plants invade land

e. Even LARGER MASS EXTINCTION at end of Ordovocian

B. Middle Paleozoic

1. Radiation of fishes

2. 1st flightless insects

3. 1st seed plants & trees

4. Devonian Extinction (before end of Devonian)

a. immediately after extinction, the 1st amphibians (vertebrates) invade land.

C. Late Paleozoic

1. Coal swamps - formed earth's great coal beds

a. seed ferns, horsetails,club mosses

2. Rise of gymnosperms & reptiles

3. 1st flying insects - radiation

4. Permian Extinction

a. climate cooling, drier, alot of mountain formation

b. LARGEST MASS EXTINCTION in earth's history over about 1 myrs

V. Mesozoic Era

A. Radiation of dominant land animals- dinosaurs, birds, flying reptiles,crocodilians

B. Mammals appear (earlyTriassic) - small & nocturnal

C. Angiosperm & Insect 1. flowering plants, 2. 2nd great radiation of insects

D. Cretaceous Extinction- lost dinosaurs,- correlated with major cooling of earth, reason? 5 mill yr ago - meteor impact - nuclear winter

VI. Cenozoic Era

A. Mammal Radiation - filled niches from dinosaurs

B. Climate changed from a "greenhouse effect" to an "ice house effect"

VII. Summary

A. Long history of unicellular life, B. Multicellular life arose rel.late

C. Modern fauna & flora arose via a number of events spread over millions of years.

D. Mass extinctions are important events and follow similar patterns:

1. Associated with prolonged global cooling; 2. Most dramatic effect on tropical shallow marine organisms; 3. Followed by periods of adaptive radiation based on new adaptive innovations and the presence of unfilled niches