History of Life on History of Life on EarthEarth

Chapter 12Chapter 12

The Age of the EarthThe Age of the Earth 4.5 billion years old4.5 billion years old

– Radiometric datingRadiometric dating– Radioactive isotopes break Radioactive isotopes break

down over timedown over time– Half-life – time it takes for Half-life – time it takes for

half of amount to decayhalf of amount to decay– Using this can estimate age Using this can estimate age

of earthof earth Non-living chemicals Non-living chemicals

reacted and produced reacted and produced organic moleculesorganic molecules

Combination of chemicals Combination of chemicals and energy from and energy from lightning/heat/Sun’s UV lightning/heat/Sun’s UV created organic created organic moleculesmolecules

2 Theories about how2 Theories about how

Primordial SoupPrimordial Soup Oceans filled with Oceans filled with

organic moleculesorganic molecules Sparks simulate Sparks simulate

lightninglightning Amino acids, fatty Amino acids, fatty

acids. And other acids. And other hydrocarbons hydrocarbons formedformed

1 problem: no 1 problem: no ozone to protect ozone to protect from UV, certain from UV, certain compounds couldn’t compounds couldn’t have existedhave existed

Bubble ModelBubble Model Gases from undersea Gases from undersea

volcanoes trapped in volcanoes trapped in bubbles that protect bubbles that protect them from UV and them from UV and concentrate themconcentrate them

Reactions happen Reactions happen fasterfaster

Bubbles rise, burst, Bubbles rise, burst, release compoundsrelease compounds

Energy from UV and Energy from UV and lightning creates lightning creates more reactionsmore reactions

Complex organic Complex organic molecules fall into molecules fall into ocean and start ocean and start againagain

Precursor of 1Precursor of 1stst Cells Cells

Molecules of life can arise from simple Molecules of life can arise from simple chemistrychemistry

RNA can be made in labRNA can be made in lab RNA believed to be 1RNA believed to be 1stst self-copying self-copying

information storing moleculeinformation storing molecule Makes proteins and changes from Makes proteins and changes from

generation to generation; acts as an generation to generation; acts as an enzymeenzyme

MicrospheresMicrospheres– Amino acid chains Amino acid chains

form droplets in form droplets in waterwater

CoacervateCoacervate– Droplet made of Droplet made of

different kinds of different kinds of molecules like amino molecules like amino acids and sugarsacids and sugars

These are steps These are steps toward cellular toward cellular organizationorganization

Microspheres last Microspheres last longer and longer longer and longer and bring other and bring other molecules inmolecules in

Origin of HeredityOrigin of Heredity

DNA came after RNADNA came after RNA RNA catalyzed early proteinsRNA catalyzed early proteins Many believe RNA was brought into Many believe RNA was brought into

microsphere and could pass traits onmicrosphere and could pass traits on But how DNA, RNA, and hereditary But how DNA, RNA, and hereditary

mechanisms first developed is still mechanisms first developed is still not knownnot known

12.2 The Evolution of Cellular 12.2 The Evolution of Cellular Life:Life:

ProkaryotesProkaryotes Fossil preserved or Fossil preserved or mineralized remains mineralized remains or imprints of an or imprints of an organism that lived organism that lived long agolong ago

Oldest (2.5 billion Oldest (2.5 billion years old) years old) photosynthetic photosynthetic prokaryotes - prokaryotes - cyanobacteriacyanobacteria

Created oxygen but Created oxygen but took millions of years took millions of years to build up to current to build up to current amount amount

Two Groups of Bacteria Split Very Two Groups of Bacteria Split Very Early Early

EubacteriaEubacteria– Peptidoglycan in Peptidoglycan in

cell wallscell walls– Many cause disease Many cause disease

and decayand decay

ArchaebacteriaArchaebacteria– No peptidoglycanNo peptidoglycan– Unique lipids in cell Unique lipids in cell

membranemembrane– Believed to Believed to

resemble ancient resemble ancient archaebacteriaarchaebacteria

Evolution of EukaryotesEvolution of Eukaryotes

1.5 bya first eukaryotes showed up1.5 bya first eukaryotes showed up Larger; internal membranes; DNA in Larger; internal membranes; DNA in

nucleusnucleus– Mitochondria in almost allMitochondria in almost all– Chloroplasts in plants and protistsChloroplasts in plants and protists

EndosymbiosisEndosymbiosis

Theory states bacteria entered large Theory states bacteria entered large cells as parasites or undigested preycells as parasites or undigested prey

Begin to live inside host and Begin to live inside host and performed cellular respiration or performed cellular respiration or photosynthesisphotosynthesis

Mitochondria – descendents of Mitochondria – descendents of symbiotic, aerobic eubacteriasymbiotic, aerobic eubacteria

Chloroplasts – descendents of Chloroplasts – descendents of symbiotic, photosynthetic eubacteriasymbiotic, photosynthetic eubacteria

Support for EndosymbiosisSupport for Endosymbiosis Size and StructureSize and Structure

– Mitochondria like eubacteriaMitochondria like eubacteria– Chloroplasts like cyanobacteriaChloroplasts like cyanobacteria

Genetic MaterialGenetic Material– Circular DNA similar to bacteria is Circular DNA similar to bacteria is

different than hosts DNAdifferent than hosts DNA RibosomesRibosomes

– Similar in size to those of bacteriaSimilar in size to those of bacteria ReproductionReproduction

– Simple fission independent of hostSimple fission independent of host

MulticellularityMulticellularity All living things are broken into 6 kingdomsAll living things are broken into 6 kingdoms

– Eubacteria, Archaebacteria, Protista, Fungi, Plants, AnimalsEubacteria, Archaebacteria, Protista, Fungi, Plants, Animals Eubacteria and Archaebacteria oldest; single celled Eubacteria and Archaebacteria oldest; single celled

prokaryotesprokaryotes Protista – first eukaryotic kingdom, multicellular and Protista – first eukaryotic kingdom, multicellular and

unicellularunicellular All other eukaryotes, fungi, plants, and animals, came later All other eukaryotes, fungi, plants, and animals, came later

and all came from protistsand all came from protists

Unicellular is very successful Unicellular is very successful Almost every cell you can see is Almost every cell you can see is

multicellularmulticellular

Origins of Modern OrganismsOrigins of Modern Organisms Cambrian Explosion Cambrian Explosion

– Most animal phyla originated during late Most animal phyla originated during late Precambrian and early Cambrian periodsPrecambrian and early Cambrian periods

– Great evolutionary expansionGreat evolutionary expansion– Many unusual marine organisms appear that Many unusual marine organisms appear that

have no living relativeshave no living relatives

Burgess ShaleBurgess Shale 1909 geological formation in Canada 1909 geological formation in Canada

foundfound Ordovician Period – 505 mya – 438 myaOrdovician Period – 505 mya – 438 mya

– Trilobites – extinct 250 myaTrilobites – extinct 250 mya

Burgess ShaleBurgess Shale

Mass ExtinctionsMass Extinctions Large number of species become extinctLarge number of species become extinct 5 Major extinctions5 Major extinctions

– 440 mya440 mya– 360 mya360 mya– 245 mya – 96% of all species245 mya – 96% of all species– 210 mya210 mya– 65 mya – 2/3 of all land species65 mya – 2/3 of all land species

Today? Human activity might be causing Today? Human activity might be causing anotheranother– ½ of rainforests destroyed½ of rainforests destroyed– Keep up our current rate Keep up our current rate

22% to 47% of plants gone22% to 47% of plants gone 2,000 of the 9,000 birds 2,000 of the 9,000 birds

12.3 Life Invaded Land12.3 Life Invaded Land Ozone LayerOzone Layer

– Life evolved protected Life evolved protected in oceans from in oceans from dangerous UV rays dangerous UV rays from Sunfrom Sun

– No life on land during No life on land during Cambrian periodCambrian period

– 2.5 bya photosynthesis 2.5 bya photosynthesis puts Oputs O22 into air which into air which reacts and forms reacts and forms Ozone, OOzone, O33

– Blocks UVBlocks UV– Eventually enough to Eventually enough to

make it safe to live on make it safe to live on landland

Plants and Fungi on LandPlants and Fungi on Land 11stst organisms on land organisms on land

were probably a were probably a combination of plants combination of plants and fungi; 430 myaand fungi; 430 mya– Plants can make Plants can make

nutrients by nutrients by photosynthesisphotosynthesis

– Fungi can absorb Fungi can absorb minerals from rockminerals from rock

– Together called Together called mycorrhizae, these mycorrhizae, these exist todayexist today

Mutualism – 2 species Mutualism – 2 species live together and both live together and both benefitbenefit

Theory of EvolutionTheory of Evolution

Chapter 13Chapter 13

13.1 The Theory of Evolution 13.1 The Theory of Evolution by Natural Selectionby Natural Selection

Before Darwin most Before Darwin most people believed people believed each species was a each species was a divine creation divine creation existing as it was existing as it was when it was createdwhen it was created

But why were there But why were there fossils of unknown fossils of unknown organisms?organisms?

Jean Baptiste Jean Baptiste Lamarck 1809Lamarck 1809– Features of Features of

organisms change organisms change during life and are during life and are passed on to passed on to offspringoffspring

– Giraffe stretches Giraffe stretches neck to reach neck to reach leaves, offspring leaves, offspring have longer neckshave longer necks

WRONG!!WRONG!!

And now for DarwinAnd now for Darwin Charles Darwin was Charles Darwin was

from a wealthy familyfrom a wealthy family Studied medicine but Studied medicine but

became a minister became a minister (though he never (though he never became ordained)became ordained)

In 1831 Darwin went In 1831 Darwin went on a voyage on the on a voyage on the HMS HMS BeagleBeagle as a as a naturalistnaturalist

Galapagos Islands – Galapagos Islands – plants and animals plants and animals resembled those of resembled those of the coast of South the coast of South AmericaAmerica

Darwin believed the Darwin believed the organisms arrived organisms arrived from the coast and from the coast and changed once they changed once they were therewere there

Called this “descent Called this “descent with modification” with modification” which would which would become known as become known as evolutionevolution

Most famous were Most famous were the finches and the the finches and the tortoisestortoises

He studied the data He studied the data he collected for he collected for many yearsmany years

Things That Affected DarwinThings That Affected Darwin

Thomas Malthus Thomas Malthus essay 1798essay 1798– Human population Human population

was increasing faster was increasing faster than its food sourcethan its food source

– Unchecked Unchecked populations will grow populations will grow geometricallygeometrically

– Humans are checked Humans are checked by disease, war, & by disease, war, & faminefamine

Charles Lyell book Charles Lyell book – Principles of Principles of

GeologyGeology– Surface of Earth Surface of Earth

changed over timechanged over time

Populations are all of the individuals Populations are all of the individuals of a species that live in a specific of a species that live in a specific geographical area and can interbreedgeographical area and can interbreed

Darwin believed Malthus’s idea of Darwin believed Malthus’s idea of unchecked population growth applied unchecked population growth applied to all speciesto all species

““Individuals that have physical or Individuals that have physical or behavioral traits that better suit their behavioral traits that better suit their environment are more likely to environment are more likely to survive and will reproduce more survive and will reproduce more successfully than those that do not successfully than those that do not have such traits”have such traits”

Evolution By Natural SelectionEvolution By Natural Selection Natural Selection – Natural Selection –

Number of individuals Number of individuals with favorable with favorable characteristics that are characteristics that are inherited will increaseinherited will increase

Adaptations are Adaptations are inherited traits that inherited traits that become common become common because it produces a because it produces a selective advantageselective advantage

Publication of Darwin’s WorkPublication of Darwin’s Work 1831 – 1831 – BeagleBeagle voyage voyage 1844 – very low public 1844 – very low public

opinion of evolutionopinion of evolution 1859 – Another scientist, 1859 – Another scientist,

Alfred Russel Wallace, Alfred Russel Wallace, writes Darwin asking for writes Darwin asking for help to publish his work help to publish his work that describes natural that describes natural selection!!selection!!

Darwin publishes his Darwin publishes his work and people aren’t work and people aren’t happy to hear they are happy to hear they are “related to apes”“related to apes”

Major Points of TheoryMajor Points of Theory

Inherited variation exists within the Inherited variation exists within the genes of every population or speciesgenes of every population or species

In environments, some individuals In environments, some individuals are better suited and have more are better suited and have more offspringoffspring

Beneficial traits spreadBeneficial traits spread Evidence that living species evolved Evidence that living species evolved

from extinct organismsfrom extinct organisms

UPDATEUPDATE

Now know genes are responsible for Now know genes are responsible for inherited traitsinherited traits

Natural selection causes the Natural selection causes the frequency of certain alleles in a frequency of certain alleles in a population to increase or decrease population to increase or decrease over timeover time

Species FormationSpecies Formation Reproductive Reproductive

IsolationIsolation– 2 populations of the 2 populations of the

same species do not same species do not breed with each other breed with each other due to geographic due to geographic separation, difference separation, difference in mating periods, or in mating periods, or other barriersother barriers

– Eventually they may Eventually they may not be able to breed not be able to breed with each otherwith each other

– Kaibab squirrel and Kaibab squirrel and Abert squirrelAbert squirrel

Tempo of Tempo of EvolutionEvolution

GradualismGradualism– Slow/gradual Slow/gradual

process of changing process of changing that occurs that occurs continuouslycontinuously

Punctuated Punctuated EquilibriumEquilibrium– Large changes that Large changes that

occur quicklyoccur quickly

13.2 Evidence of Evolution13.2 Evidence of Evolution FossilsFossils

– Many intermediate Many intermediate life forms have been life forms have been found in fossilsfound in fossils

– Not completeNot complete– Certain Certain

environments are environments are better for forming better for forming fossilsfossils

– Animals that live in Animals that live in areas that are not areas that are not good for fossils are good for fossils are missingmissing

– Studied by Studied by paleontologistspaleontologists

Anatomy and developmentAnatomy and development– Comparisons can show similaritiesComparisons can show similarities– Vestigial structuresVestigial structures

Structures that have no use or have a less important Structures that have no use or have a less important function than they do in other related organismsfunction than they do in other related organisms

Whale’s hind limbsWhale’s hind limbs Humans appendixHumans appendix

Vestigial StructuresVestigial Structures

Homologous Homologous StructuresStructures– Share a common Share a common

ancestryancestry– Similar structure in Similar structure in

different organismsdifferent organisms Development of Development of

EmbryosEmbryos– Believe you can see Believe you can see

evolutionary historyevolutionary history– At some point all At some point all

vertebrates have a vertebrates have a tail, buds that tail, buds that become limbs, and become limbs, and pharyngeal pharyngeal pouchespouches

EmbryologyEmbryology

Biological MoleculesBiological Molecules– ProteinsProteins

Smaller differences between closely related Smaller differences between closely related and larger between more distantly relatedand larger between more distantly related

– DNA sequencesDNA sequences Similar to relationships predicted by Similar to relationships predicted by

biologistsbiologists

13.3 Examples of Evolution13.3 Examples of Evolution

Factors in Natural SelectionFactors in Natural Selection– All populations have genetic variationAll populations have genetic variation– The environment presents challenges to The environment presents challenges to

successful reproductionsuccessful reproduction– Individuals tend to produce more Individuals tend to produce more

offspring than the environment can offspring than the environment can supportsupport

– Better suited individuals leave more Better suited individuals leave more offspringoffspring

Example of Natural Example of Natural SelectionSelection

Tuberculosis (TB) kills more adults Tuberculosis (TB) kills more adults than any other infectious diseasethan any other infectious disease

Antibiotics introduced in 50s now Antibiotics introduced in 50s now don’t work because bacteria are don’t work because bacteria are resistantresistant

Mutation in some bacteria made it Mutation in some bacteria made it resistant so it survived and passed on resistant so it survived and passed on genes and becomes more common in genes and becomes more common in populationpopulation

Evolution in Evolution in Darwin’s Darwin’s FinchesFinches– Darwin Darwin

collected 31 collected 31 specimens from specimens from 3 islands3 islands

– 9 distinct 9 distinct species all species all similar except similar except for billsfor bills Large bills fed Large bills fed

on seedson seeds Small bills ate Small bills ate

insectsinsects

Formation of New SpeciesFormation of New Species

Divergence – accumulation of Divergence – accumulation of differences between groupsdifferences between groups

Speciation – process by which a new Speciation – process by which a new species formsspecies forms

Subspecies – populations of the same Subspecies – populations of the same species that differ genetically because species that differ genetically because of adaptations to different living of adaptations to different living conditionsconditions– First step of speciationFirst step of speciation

SubspeciesSubspecies

Maintaining New SpeciesMaintaining New Species– When subspecies become different When subspecies become different

enough a reproductive barrier may formenough a reproductive barrier may form– Geographic isolationGeographic isolation– Different reproduction timesDifferent reproduction times– Physical differencesPhysical differences– Offspring not fertileOffspring not fertile