Chapter 17 The History of Life

Chapter 17 The History of Life

Fossil imprint

The Fossil Record • Provides evidence about the history of life on Earth. • It also shows how different groups of organisms, including species, have changed over time.

Relative vs. Absolute Dating Comparing Relative and Absolute Dating of Fossils

Can determine

Is performed by

Drawbacks

Relative Dating

Absolute Dating

Age of fossil with respect to another rock or fossil (that is, older or younger)

Age of a fossil in years

Comparing depth of a fossil’s source stratum to the position of a reference fossil or rock

Determining the relative amounts of a radioactive isotope and nonradioactive isotope in a specimen

Imprecision and limitations of age data

Difficulty of radioassay laboratory methods

Principle of Superposition • In an undisturbed sequence of sedimentary rocks, the oldest rocks are on the bottom with the most recent on top.

How fossils are formed Water carries small rock particles to lakes and seas.

Dead organisms are buried by layers of sediment, which forms new rock.

The preserved remains may later be discovered and studied.

Geological Time Scale • After the Precambrian Time, the time scale is divided into eras, which are subdivided into periods. Era

Period

(millions of

Time years ago)

Quaternary

1.8–present

Tertiary

65–1.8

Cretaceous

145–65

Jurassic

208–145

Triassic

245–208

Era

(millions of

Period

Time years ago)

Permian

290 – 245

Carboniferous

360–290

Devonian

410–360

Silurian

440–410

Ordovician

505–440

Cambrian

544–505

Era

(millions of

Period

Time years ago)

Vendian

650–544

Geological Time Scale • The major eras are Paleozoic, Mesozoic, and Cenozoic. Era

Period

(millions of

Time years ago)

Quaternary

1.8–present

Tertiary

65–1.8

Cretaceous

145–65

Jurassic

208–145

Triassic

245–208

Era

(millions of

Period

Time years ago)

Permian

290 – 245

Carboniferous

360–290

Devonian

410–360

Silurian

440–410

Ordovician

505–440

Cambrian

544–505

Era

(millions of

Period

Time years ago)

Vendian

650–544

Geologic Time Scale • Each period hosts significant evolutionary changes to species diversity and extinction. Era

Period

(millions of

Time years ago)

Quaternary

1.8–present

Tertiary

65–1.8

Cretaceous

145–65

Jurassic

208–145

Triassic

245–208

Era

(millions of

Period

Time years ago)

Permian

290 – 245

Carboniferous

360–290

Devonian

410–360

Silurian

440–410

Ordovician

505–440

Cambrian

544–505

Era

(millions of

Period

Time years ago)

Vendian

650–544

Summary of major events (pg. 429-34) Era Cenozoic Mesozoic

Paleozoic

Precambrian Time

Period Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian

Time

(millions of years ago)

1.8–present 65–1.8 145–65 208–145 245–208 290–245 363–290 410–363 440–410 505–440 544–505 650–544

Key Events Glaciations; mammals increased; humans Mammals diversified; grasses Aquatic reptiles diversified; flowering plants; mass extinction Dinosaurs diversified; birds Dinosaurs; small mammals; cone-bearing plants Reptiles diversified; seed plants; mass extinction Reptiles; winged insects diversified; coal swamps Fishes diversified; land vertebrates (primitive amphibians) Land plants; land animals (arthropods) Aquatic arthropods; mollusks; vertebrates (jawless fishes) Marine invertebrates diversified; most animal phyla evolved Anaerobic, then photosynthetic prokaryotes; eukaryotes, then multicellular life

Hypothesis of early Earth • Very hot surface from colliding meteorites • Very hot planet core from radioactive materials • Volcanoes spewing lava and gases that helped to form the early atmosphere

Hypothesis of early Earth • About 4.4 billion years ago, Earth might have cooled enough for the water in its atmosphere to condense. • This might have led to millions of years of rainstorms with lightning, enough rain to fill depressions that became Earth’s oceans. • The oldest rocks dated are 3.9 million years old.

Fossils: evidence of an organism that lived long ago that is preserved in Earth’s rocks

• Paleontologists estimate that about 95% species are extinct from life’s origins. • Climate and ancient geography can be determined from fossils.

Types of Fossils Formation

Fossils Types

A trace fossil is any indirect A trace fossil is anyevidence indirect evidence Trace fossils left by an animal and may include a footprint, a trail, or a burrow. When minerals in rocks fill a space left by a decayed organism, they make a replica, or cast, of the organism.

Casts

Molds

A mold forms when an organism is A mold forms when an organism is

Petrified/ Permineralized fossils AmberPreserved or frozen fossils

buried in sediment and then decays, leaving an empty space. Petrified-minerals sometimes penetrate and replace the hard parts of an organism. Permineralized-void spaces in original organism infilled by minerals. At times, an entire organism was quickly trapped in ice or tree sap that hardened into amber.

What has been learned from fossils • several episodes of mass extinction that fall between time divisions – mass extinction: an event that occurs when many organisms disappear from the fossil record almost at once

• The geologic time scale begins with the formation of Earth about 4.6 billion years ago.

Precambrian – 87% of history • Oldest fossils about 3.4 billion years old resembling cyanobacteria stromatolites. • Stromatolites still form today in Australia from mats of cyanobacteria. • The stromatolites are evidence of the existence of photosynthetic organisms on Earth during the Precambrian. • Only prokaryotic life found in fossil record

End of Precambrian – 543 MYA • multicellular eukaryotes, such as sponges and jelly-fishes, diversified and filled the oceans

Paleozoic and Cambrian Period • Paleozoic Era: more animals and plants – Early: fishes, aquatic vertebrates, ferns – Middle: amphibians – Late: reptiles and mass extinction – Cambrian Period: oceans teemed with many types of animals, including worms, sea stars, and unusual arthropods

Mesozoic - 248 MYA • Triassic Period: mammals and dinosaurs • Jurassic Period: dinosaurs and birds • Cretaceous Period: more mammals, flowering plants, but mass extinction of dinosaurs 65 MYA

Continental drift • Earth’s continents have moved during Earth’s history and are still moving today at a rate of about six centimeters per year.

• The theory for how the continents move is called plate tectonics.

Geologic Time Scale video

Click on image to play video.

Miller-Urey experiment showed one possible way for inorganic molecules to form organic molecules. Mixture of gases simulating atmospheres of early Earth

Spark simulating lightning storms

Condensation chamber Water vapor

Cold water cools chamber, causing droplets to form

Liquid containing amino acids and other organic compounds

How eukaryotic cells evolved • Lynn Margulis proposed the endosymbiotic theory. Chloroplast

Aerobic bacteria

Ancient Prokaryotes Nuclear envelope evolving

Plants and plantlike protists

Photosynthetic bacteria Mitochondrion

Primitive Photosynthetic Eukaryote

Ancient Anaerobic Prokaryote

Primitive Aerobic Eukaryote

Animals, fungi, and non-plantlike protists

Endosymbiotic theory • Heterotrophic bacteria have plasmids (DNA loop) & simple ribosomes in their cytoplasm • Mitochondria have circular DNA & bacteria-like ribosomes • So…Eukaryotic cells may have engulfed prokaryotic cells & by mutualism created the “first mitochondria.”

• Autotrophic bacteria are Cyanobacteria with chlorophyll • So, Eukaryotic cells may have engulfed prokaryotic cyanobacteria & by mutualism created the “first chloroplast.”

• Heterotrophic symbiosis = symbiont produces ATP, host uses ATP, host protects symbiont • Autotrophic symbiosis = symbiont produces sugar, host uses sugar, host protects symbiont • Relationships may allow host to live longer & reproduce more, thus over time creating more complex eukaryotic cells

Evolution of life video

Click on image to play video.

Macroevolution  Large-scale evolutionary patterns and processes that occur over long periods of time.  Includes 6 topics: Extinction Adaptive radiation Convergent evolution Divergent evolution Punctuated equilibrium Changes in developmental genes

Patterns of evolution • Darwin believed that organisms evolved gradually. • Niles Eldredge and Stephen Jay Gould believed punctuated equilibrium is how organisms evolved, periods of rapid evolution followed by periods of stasis.

Adaptive Radiation • Single species or small groups of species evolved into diverse forms living in different ways.

Convergent Evolution • Adaptive radiation can produce unrelated organisms that look similar due to similar environments.

Coevolution The process by which two species evolve in response to changes in each, other over time.

http://ecology.botany.ufl.edu/ ecologyf02

• Example: “This butterfly acquires a cardiac glycoside from members of the genus Asclepias. Because of their milky sap, these are commonly referred to as milkweed plants. The plants produce this toxin as a defense against herbivory, but the Monarch has the ability to sequester the toxin in fatty tissues so that it makes the butterfly unpalatable while not poisoning the butterfly.”