EvolutionChanges in types of

organisms over a period of time

FossilsFossils• A fossil is some remnant of an A fossil is some remnant of an

organism that proves its existenceorganism that proves its existenceImprints of bacteria, leaves or

footprintsInsects, pollen, or flower parts in

amberTools or pottery shardsBones of organisms in sedimentary

rockCave drawings

Amber, sap fromancient trees, hardens and encases soft-bodies

Cave drawings

Determining fossil ageDetermining fossil age•Relative dating•Oldest fossils are

in the deepest sedimentary rock layers

•Younger layers hold newer, more complex fossils

•Absolute datingAbsolute dating•Can be used to determine a precise age in years

•Use the decay rate of radio-isotopes like carbon 14

•The oldest known fossils are approximately 3 billion years old

• Half Life Half Life = time it takes for half of a radioactive element to decay.

• Radioactive Decay Radioactive Decay = isotope breaking down into another substance.

Radioisotope Half-life

Polonium-215 0.0018 seconds

Bismuth-212 60.5 seconds

Sodium-24 15 hours

Iodine-131 8.07 days

Cobalt-60 5.26 years

Radium-226 1600 years

Uranium-238 4.5 billion years

Comparative Comparative studiesstudies•Researchers use

comparative studies to establish evolutionary relationships between organisms

ComparativeComparative anatomyanatomy•Comparing specific

body structures• Analogous Analogous

structuresstructures have a similar function but the structure is different– Ex the wing of an

insect and the wing of a bird

• HomologousHomologous structuresstructures are similar in structure but may have different functions– Ex) human hand, cat

paw, whale flipper,

bat wing

• VestigialVestigial structuresstructures are reduced in size and have no known function

• They resemble structures in other organisms– Ex) the human

appendix or the pelvis bone in a whale

ComparativeComparative embryologyembryology•The comparison of

embryonic development•Early development is similar in many species

•The closer the relationship between species the more similar is development

ComparativeComparative cytologycytology

• Observing Observing similarities in cell similarities in cell structuresstructures

• All cells have some All cells have some common organelles common organelles that perform that perform identical functionsidentical functions

ComparativeComparative BiochemistryBiochemistry

•Similarities involving proteins, Similarities involving proteins, enzymes and nucleic acidsenzymes and nucleic acids–All organisms share genetic codes

•Transcription and translation

–All organisms carry on cell respiration in the same way

–All autotrophs carry on photosynthesis in the same way

TheoriesTheories ofof EvolutionEvolution

J.B. LamarckJ.B. LamarckUseUse andand disusedisuse

Organisms can change Organisms can change their body structure their body structure over the course of a over the course of a lifetime lifetime ATROPHYATROPHY – structure – structure decreases in mass with decreases in mass with disusedisuseHYPERTROPHYHYPERTROPHY – – structure increases in structure increases in mass with usemass with use

• Lamarck Lamarck believed that believed that ACQUIRED ACQUIRED TRAITSTRAITS could could then be passed then be passed to the offspringto the offspring– Example) the neck Example) the neck

of the giraffeof the giraffe

AugustAugust WeissmanWeissman• Disproved Lamarck’s Disproved Lamarck’s

theory of use and theory of use and disusedisuse– He cut off the tails of He cut off the tails of

mice then mated themmice then mated them– All of the offspring had All of the offspring had

long tailslong tails– This experiment was This experiment was

repeated for 22 repeated for 22 generationsgenerations

– All of the mice were born All of the mice were born with long tails!with long tails!

CharlesCharles DarwinDarwin• Theory of Natural Theory of Natural

SelectionSelection• Darwin served as a Darwin served as a

geologist, botanist, geologist, botanist, zoologist, and zoologist, and general man of general man of science aboard the science aboard the H.M.S. Beagle from H.M.S. Beagle from 1831-1836 1831-1836

DarwinDarwin

• OverproductionOverproduction – organisms – organisms produce more offspring than can produce more offspring than can possibly survivepossibly survive

• StruggleStruggle forfor existenceexistence – there are – there are only limited resources availableonly limited resources available– Not all offspring will surviveNot all offspring will survive

• NaturalNatural selectionselection – those organisms – those organisms with advantages in a given with advantages in a given environment are most likely to environment are most likely to survive and reproducesurvive and reproduce– Those who survive and reproduce Those who survive and reproduce are the are the FITTESTFITTEST

• VariationVariation – offspring tend to be different from their parents and each other

• SpeciationSpeciation – after many generations are involved in natural selection– A population may be so different from

the original population that it can be classified as a different species

–SPECIES = organisms who can mate and produce fertile offspring

DNA analysis has confirmed that a bear shot in the Canadian Arctic last month is a half-polar bear, half-grizzly hybrid. While the two bear species have interbred in zoos, this is the first evidence of a wild polar bear-grizzly offspring.

Wildlife officials seized the bear after noticing its white fur was interspersed with brown patches. It also had long claws, a concave facial profile, and a humped back, which are characteristic of a grizzly. Now the genetic tests have confirmed that the hybrid's father was a grizzly and its mother was a polar bear.

SpeciationSpeciation•InvolvesInvolves isolationisolation

–Anything which prevents two groups within a species from interbreeding

GeographicGeographic isolationisolation•A population is divided by a A population is divided by a

natural barriernatural barrier– Mountains– Deserts– Body of water– Landslide cause by an earthquake– But genetic changes are necessary

to complete the process

Reproductive Reproductive isolationisolation•Differing selection pressures Differing selection pressures

on the new environments can on the new environments can complete the differentiation of complete the differentiation of the new species. the new species.

MicroevolutionMicroevolution•Small, gradual Small, gradual changes which are changes which are detectable within a detectable within a few generationsfew generations

• IndustrialIndustrial MelanismMelanism – changes in – changes in the colors of a population as a the colors of a population as a result of human industrial activityresult of human industrial activity

MacroevolutionMacroevolution•Long term changes that Long term changes that

make a new speciesmake a new species

General patterns for General patterns for evolutionevolution

•Divergent evolution – Divergent evolution – different groups evolve different groups evolve from one ancestorfrom one ancestor

• ConvergentConvergent evolutionevolution – two or more – two or more different groups evolve so that they different groups evolve so that they resemble one another stronglyresemble one another strongly

• AdaptiveAdaptive radiationradiation – organisms – organisms spread into new environments and spread into new environments and become adapted through natural become adapted through natural selectionselection

AdaptationsAdaptations• an anatomical structure, an anatomical structure,

physiological process or physiological process or behavioral trait of an organism behavioral trait of an organism that has evolved over a period that has evolved over a period of time by the process of of time by the process of natural selectionnatural selection – it increases the expected long-

term reproductive success of the organism

•Organisms that are adapted Organisms that are adapted to their environment are able to their environment are able to:to:– obtain air, water, food and nutrients – cope with physical conditions such as

temperature, light and heat – defend themselves from their natural

enemies– reproduce – respond to changes around them

• Camouflage and mimicry are Camouflage and mimicry are adaptations some animals use as adaptations some animals use as protection from predators. protection from predators.

• An animal that uses camouflage An animal that uses camouflage looks like things in its looks like things in its environment. It might look like a environment. It might look like a leaf, a twig, or a rock. leaf, a twig, or a rock.

• Animals that use mimicry use Animals that use mimicry use colors and markings to look colors and markings to look like another animal. like another animal. – Example) the Monarch Example) the Monarch Butterfly and the ViceroyButterfly and the Viceroy

HeterotrophHeterotroph HypothesisHypothesis

•1920-30s•Formulated by a small group

of scientists•Suggests a probable

sequence in which organisms appeared

• Life on Earth began about 3.5 Life on Earth began about 3.5 billion years ago. billion years ago.

• The atmosphere was very The atmosphere was very different from what it is today. different from what it is today.

• The early Earth atmosphere The early Earth atmosphere contained mostly hydrogen, contained mostly hydrogen, water, ammonia, and water, ammonia, and methane.methane.

• There was very little oxygenThere was very little oxygen

• There were abundant energy There were abundant energy sources for chemical sources for chemical reactions to occurreactions to occur– HeatHeat– UV radiationUV radiation– Electrical activity Electrical activity

Primordial soupPrimordial soup

•Gases in the atmosphere Gases in the atmosphere reacted with each other to reacted with each other to form simple organic form simple organic moleculesmolecules–Example ) Amino acids, nucleotides

Atoms combined to form Atoms combined to form molecules molecules

Amino acids were formedAmino acids were formed

Stanley MillerStanley Miller•Miller built an

apparatus to test these ideas in 1953– A mixture of gases

thought to resemble the Earth’s primitive atmosphere was passed through an electric spark

• After one week the contents were After one week the contents were analyzedanalyzed

• Miller found that it contained Miller found that it contained organic moleculesorganic molecules– UreaUrea– Amino acidsAmino acids– Lactic acidLactic acid– Acetic acidAcetic acid

• The The HeterotrophHeterotroph HypothesisHypothesis SUGGESTSSUGGESTS– The first organisms were anaerobic

•No O2 was available in Earth’s primitive atmosphere

• The first organisms used the organic molecules in the water for food

• They released CO2 as a waste product

• These organisms were ANAEROBIC HETEROTROPHS

• Organisms that were able to use Organisms that were able to use the COthe CO22 evolved next evolved next

• These organisms wereThese organisms were ANAEROBICANAEROBIC AUTOTROPHSAUTOTROPHS (have chloroplast) (have chloroplast) – They used the COThey used the CO22 for photosynthesis for photosynthesis

– OO22 was released as a waste product was released as a waste product• Organisms that were able to use OOrganisms that were able to use O22

evolved nextevolved next• These wereThese were AEROBIC AUTOTROPHSAEROBIC AUTOTROPHS

andand AEROBIC HETEROTROPHSAEROBIC HETEROTROPHS

RateRate ofof EvolutionEvolution•GradualismGradualism = occurs slowly and continuously over time

•PunctuatedPunctuated equilibriumequilibrium = = evolution can occur evolution can occur quicklyquickly