Chapter 19Chapter 19

The History of LifeThe History of Life

The Fossil recordThe Fossil record

Palentologists study fossilsPalentologists study fossils These records provided evidence These records provided evidence

about the history of life on earthabout the history of life on earth It shows that different organisms It shows that different organisms

have changed over timehave changed over time Some even became extinctSome even became extinct

Interpreting Fossil EvidenceInterpreting Fossil Evidence

Relative dating- used to determine Relative dating- used to determine the age of a fossilthe age of a fossil

You compare the fossil’s placement You compare the fossil’s placement in the rock layer with other fossils in in the rock layer with other fossils in the rockthe rock

The rock layers are formed by age The rock layers are formed by age with the oldest on the bottomwith the oldest on the bottom

Index fossilIndex fossil

Can be used if the species is easily Can be used if the species is easily recognized and existed for a short recognized and existed for a short period but have a wide geographic period but have a wide geographic rangerange

Radioactive datingRadioactive dating

Scientists calculate the age of a Scientists calculate the age of a sample based ion the amount of sample based ion the amount of remaining radioactive isotopes it remaining radioactive isotopes it containscontains

The half life is the minimum amount The half life is the minimum amount of time it takes for half of a of time it takes for half of a radioactive element to decayradioactive element to decay

Geological time scaleGeological time scale

Used to divide timeUsed to divide time After precambrian time, the basic After precambrian time, the basic

divisions of the geological time scale divisions of the geological time scale are eras, periods, and epochsare eras, periods, and epochs

eraseras

Paleozoic era- 544 million years ago, Paleozoic era- 544 million years ago, vert and invertvert and invert

Mesozoic- 251 million yrs ago, dino Mesozoic- 251 million yrs ago, dino and mammalsand mammals

Cenozoic- 65 million yr ago, mammal Cenozoic- 65 million yr ago, mammal ageage

Periods and epochsPeriods and epochs

Period range in length from 10 Period range in length from 10 million years to less than 2 million million years to less than 2 million yearsyears

Further divide periods into epochsFurther divide periods into epochs

Earths Early HistoryEarths Early History

Formation of the earth occurred 8.2 Formation of the earth occurred 8.2 billion years agobillion years ago

Its early atmosphere contained Its early atmosphere contained hydrogen cyanide, carbon dioxide, hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, carbon monoxide, nitrogen, hydrogen sulfide, and waterhydrogen sulfide, and water

First organic moleculesFirst organic molecules

Miller and Urey did an experiment Miller and Urey did an experiment which suggested how mixture of which suggested how mixture of compounds could have arisen from compounds could have arisen from simplier compounds present on simplier compounds present on primitive earthprimitive earth

How Did Life begin?How Did Life begin?

1. formation of microspheres1. formation of microspheres 2. evolution of RNA and DNA2. evolution of RNA and DNA 3. free oxygen in air drove some life 3. free oxygen in air drove some life

forms to extinction and evolved forms to extinction and evolved othersothers

Origin of Eukaryotic CellsOrigin of Eukaryotic Cells

The endosymbiotic theory proposes The endosymbiotic theory proposes that eukaryotic cells arose from that eukaryotic cells arose from living communities formed by several living communities formed by several organismsorganisms

After eukaryotic cells arose, those After eukaryotic cells arose, those cells began to reproduce sexuallycells began to reproduce sexually

This enabled evolution to take place This enabled evolution to take place at a greater rateat a greater rate

Evolution of multicellualr life formsEvolution of multicellualr life forms

90% of Earth’s history occurred during 90% of Earth’s history occurred during PrecambrianPrecambrian

Simple anaerobic forms appeared and Simple anaerobic forms appeared and were followed by photosyntheitc forms were followed by photosyntheitc forms which added oxygen to the airwhich added oxygen to the air

Aerobic forms evolved and eukaryotes Aerobic forms evolved and eukaryotes appearedappeared

Early in Paleozoic era the fossil record Early in Paleozoic era the fossil record became rich with evidence of many types became rich with evidence of many types of marine lifeof marine life

Life was highly diverse by the first part of Life was highly diverse by the first part of Paleozoic eraPaleozoic era

Cambrian PeriodCambrian Period

This is when diversification of life This is when diversification of life occurredoccurred

Organisms had hard part and first Organisms had hard part and first animilia phyla evolvedanimilia phyla evolved

Trilobites were commonTrilobites were common

Ordovician and silurian periodsOrdovician and silurian periods

Octopus and squid ancestors Octopus and squid ancestors appeared along with aquatic appeared along with aquatic arthropodsarthropods

Devonian periodDevonian period

Animals began to invade the landAnimals began to invade the land Fish developed the ability to crawl on Fish developed the ability to crawl on

leglike finsleglike fins Fish had jaws, bony skeletons, and Fish had jaws, bony skeletons, and

scalesscales

Carboniferous and permian periodCarboniferous and permian period

Life expanded over the earth’s continentsLife expanded over the earth’s continents Other groups of vert evolved from Other groups of vert evolved from

amphibiansamphibians Mass extinction occurred at the end of the Mass extinction occurred at the end of the

Paleozoic eraPaleozoic era It affects both plants and animals on land It affects both plants and animals on land

and on seaand on sea 95% of the complex life in the ocean 95% of the complex life in the ocean

disappeareddisappeared

Mesozoic eraMesozoic era

Increase dominance of the dinosaursIncrease dominance of the dinosaurs 1. triassic period-fish, reptiles insects1. triassic period-fish, reptiles insects 2. jurassic period-dinosaurs dominant2. jurassic period-dinosaurs dominant 3. cretaceous period-reptiles still 3. cretaceous period-reptiles still

dominated, but another mass dominated, but another mass extinction occurredextinction occurred

Cenozoic eraCenozoic era

Mammals evolved adaptations that Mammals evolved adaptations that allowed them to live in various allowed them to live in various environmentsenvironments

Patterns of evolutionPatterns of evolution Macroevolution- large scale change that Macroevolution- large scale change that

take place over a long timetake place over a long time There are 6 important patterns to There are 6 important patterns to

macroevolution:macroevolution: 1. mass extinction1. mass extinction 2. adaptive radiation2. adaptive radiation 3. convergent evolution3. convergent evolution 4. coevolution4. coevolution 5. punctuated equilibrium5. punctuated equilibrium 6. changes in developmental genes6. changes in developmental genes

Mass extinctionMass extinction

Causes food webs to collapseCauses food webs to collapse

Adaptive radiationAdaptive radiation

Unrelated organisms come to Unrelated organisms come to resemble one anotherresemble one another

coevolutioncoevolution

The process by which 2 species The process by which 2 species evolve in response to changes in evolve in response to changes in each other over timeeach other over time

Ex flowering plantsEx flowering plants

Punctuated equilibriumPunctuated equilibrium

Patterns of long stable periods Patterns of long stable periods interrupted by brief periods of more interrupted by brief periods of more rapid changerapid change