Bio II Ch 25: The History of Life on Earth

Macroevolution

Broad pattern of evolution above the species level. The fossil record shows this over large time scales such as

1. the emergence of terrestrial vertebrates

2. the impact of mass extinctions

3. the origin of key adaptations, such as flight

A.I Oparin and J.B.S. Haldane (1920s)

Independently hypothesized that the early atmosphere was a reducing environment

Stanley Miller and Harold Urey (1953)

-Conducted lab experiments demonstrating that the abiotic synthesis of organic molecules in a reducing atmosphere was possible

-Reanalysis of molecules formed in one of these scientists’ experiments found that numerous amino acids formed under conditions simulating volcanic eruption

Abiotic Synthesis of Macromolecules

RNA monomers have been produced spontaneously from simple molecules

Small organic molecules polymerize when they are concentrated on hot sand, clay, or rock

Protocells

May have formed from fluid-filled vesicles with a membrane-like structure.

Contain properties such as replication and metabolism

Ribozymes

RNA molecules that have been found to catalyze many different reactions

EX: Can make complementary copies of short stretches of RNA

Radiometric dating

Used to determine the age of a fossil (Up to 75,000 yrs old)

A radioactive “parent” isotope decays to a “daughter” isotope at a characteristic rate

-each isotope has a known half-life (time required for half the parent isotope to decay)

Stromatolites

Rocks formed by the accumulation of sedimentary layers on bacterial mats

Date back 3.5 billion years ago

Endodymbiosis

Eukaryotes originated via this process when a prokaryotic cell engulfed a small cell that would evovled into a mitochondrion.

-An endosymbiont is a cell that lives within a host cell

-Oldest fossils of eukaryotic cells date back 1.8 billion years

The Cambrian Explosion

-Refers to the sudden appearance of fossils resembling modern animal phyla in the Cambrian period (535 to 525 million years ago)

-Provides the first evidence of predator-prey interactions

-Had a “long fuse”

Quaternary Period (0.01-2.6 mil yrs ago)

-Historical Time

-Ice ages

-Origin of genus Homo

Neogene Period (5.3-23 mil yrs ago)

-Appearance of bipedal human ancestors

-Continued radiation of mammals and angiosperms; earliest direct human ancestors

Stromatolites

-Rocks formed by the accumulation of sedimentary layers on bacterial mats

-Date back 3.5 billion years ago

Endosymbiosis

-Process in which eukaryotes originated

-Prokaryotic cell engulfed a small cell that would evolve into a mitochondrion

Theory of Plate Tectonics

Theory that Earth’s crust is composed of plates floating on Earth’s mantle

Pangaea

Formation of the supercontinent Pangaea about 250 million years ago and had many effects

Effects of Pangaea

• Deepening of the ocean basins

• Reduction in shallow-water habitat

• Colder and drier climate inland

• Organisms must adapt, move or risk extinction as the climate changes in response to continents moving toward or away from the equator

• Separation of landmasses can lead to allopatric speciation

Mass Extinctions

-Can be caused by changes to a species’ biotic or abiotic environment

-Occurs when the rate of extinction has increased dramatically

The Permian Extinction

-Defines the boundary between the Paleozoic and Mesozoic eras 252 million years ago

-Occurred in less than 500,000 yrs and caused the extinction of about 96% of marine animal species

Factors contributing to The Permian Extinction

-Extreme volcanism in Siberia

-Global warming and ocean acidification resulting from the emission of large amounts of CO2 from volcanoes

-Anoxic (O2 deficient) conditions resulting from nutrient enrichment of ecosystems

Cretaceous Mass Extinction

-Occurred 66 million years ago

-Dinosaur/birds; jurassic park

-MOST RECENT

-Iridium presence in sedimentary rocks suggest METEORITE IMPACT off the coast of Yucatan Peninsula

Adaptive radiation

The rapid evolution of diversely adapted species from a common ancestor

Adaptive radiations may follow:

-Mass extinctions

-Evolution of novel characteristics

-Colonization of new regions

Reasons a Sixth Mass Extinction is Under Way:

-Many species are declining rapidly due to habitat loss, introduced species, over-harvesting, and other factors

-Climate change (higher temperatures can increase extinction rates)

Paleogene Period (66-23 mil years ago)

-Origins of many primate groups

-Angiosperm dominance increases; continued radiation of most-present day mammalian orders

-Major radiation of mammals, birds, and pollinating insects

Cretaceous Period (66-145 mil yrs ago)

-Flowering plants (angiosperms) appear and diversify;

many groups of organisms, including most dinosaurs; become extinct at end of period.

Jurassic Period (145-201 mil yrs ago)

-Gymnosperms continue as dominant plants; dinosaurs abundant and diverse

Triassic (252-201 mil yrs ago)

-Cone-bearing plants (gymnosperms) dominate landscape; dinosaurs evolve and radiate; origin of mammals

Permian (252-299 mil yrs ago)

-Radiation of reptiles; origin of most present-day groups of insects; extinction of many marine and terrestrial organisms at end of period

Carboniferous (299-359 mil yrs ago)

-Extensive forests of vascular plants form; first seed plants appear; origin of reptiles; amphibians dominant

Devonian (359-419 mil yrs ago)

-Diversification of bony fishes; first tetrapods and insects appear 

Silurian (419-443 mil yrs ago)

-Diversification of early vascular plants

Ordovician (443-485 mil yrs ago)

Marine algae abundant; colonization of land by diverse fungi, plants, and animals

Cambrian (485-541 mil yrs ago)

-Sudden increase in diversity of many animal phyla (explosion)

Ediacaran (541-4600 mil yrs ago)

-Diverse algae and soft-bodied invertebrate animals appear 

-Oldest fossils of eukaryotic cells appear

-Concentration of atmospheric oxygen begins to increase 

-Oldest fossils of cells (prokaryotes) appear

-Oldest rocks on Earth’s surface

-Orgin of Earth