Our Evolving Planet

Our Our Evolving Evolving

PlanetPlanet

Life Evolves – It ChangesLife Evolves – It Changes

Everything on Earth that has ever lived is Everything on Earth that has ever lived is connected through, and is the result of, connected through, and is the result of, evolutionevolution. .

It’s a process that’s been happening since the It’s a process that’s been happening since the first tiny life forms appeared some four billion first tiny life forms appeared some four billion years ago. years ago.

Our story begins with our understanding of Our story begins with our understanding of timetime..

Geologic TimeGeologic TimeThe Earth is around The Earth is around 4.5 billion years old4.5 billion years old. . To help organize and understand this immense To help organize and understand this immense expanse of time, scientists divide Earth’s history into expanse of time, scientists divide Earth’s history into smaller chunks, such as smaller chunks, such as eraseras and and periodsperiods..Together, these make up the Together, these make up the geologic time scalegeologic time scale..– Think of the geologic time scale as the table of Think of the geologic time scale as the table of

contents in the history of Earth. contents in the history of Earth. – The eras and periods are chapters in the story of The eras and periods are chapters in the story of

evolution. evolution. – Each chapter has its own tale to tell—when life Each chapter has its own tale to tell—when life

began, when mammals first appeared, when began, when mammals first appeared, when humans entered the scene, etc.humans entered the scene, etc.

In Earth’s first four billion years—the time known as the Precambrian In Earth’s first four billion years—the time known as the Precambrian — — life first evolvedlife first evolved,, flourished, and changed the planet forever. flourished, and changed the planet forever.

The atmosphere contained mostly The atmosphere contained mostly carbon dioxide, nitrogen, and carbon dioxide, nitrogen, and water vapor.water vapor.– Most oxygen molecules were bound to other Most oxygen molecules were bound to other moleculesmolecules, not free in , not free in

the atmosphere. the atmosphere. – You could not have breathed.You could not have breathed.

High levels of carbon dioxide trapped the sun’s heat, creating surface High levels of carbon dioxide trapped the sun’s heat, creating surface temperatures of up to temperatures of up to 120 degrees Fahrenheit. 120 degrees Fahrenheit.

MeteoritesMeteorites bombarded the planet. bombarded the planet.

Volcanoes poured lava and released gases from deep inside the Earth.Volcanoes poured lava and released gases from deep inside the Earth.– As theAs the lava lava cooled, it hardened to form the cooled, it hardened to form the first continents. first continents. – Volcanic Volcanic steamsteam condensed into heavy rains, which accumulated condensed into heavy rains, which accumulated

into into shallow oceansshallow oceans..

Precambrian Time

- Began 4.5 Billion Years Ago -

•Made up of:

•Hadean Era

•Archaean Era

•Proterozoic Era

Origin of Life TheoriesOrigin of Life TheoriesOrganic compounds Organic compounds may have formed on may have formed on Earth, perhaps in Earth, perhaps in underwater thermal underwater thermal ventsvents..

1. Beneath the ocean floor, chemical-rich water is heated by molten rock. This water spews up through openings in Earth’s crust.

2. When the hot water meets cold seawater, dissolved minerals precipitate (they separate out as solids) and accumulate, forming the vent’s chimney.

3. The hot and cold waters have different chemical make-ups, creating an electric charge inside the chimney’s walls.

4. This charge may have caused chemicals to react and combine inside honeycomb-like chambers in the chimney’s walls, forming organic compounds.

Organic compoundsOrganic compounds may may have been carried to Earth have been carried to Earth aboard aboard meteoritesmeteorites from from outer space. outer space.

Scientists who study Scientists who study ancient meteorites have ancient meteorites have discovered that some discovered that some contain organic contain organic compounds, life’s building compounds, life’s building blocks. blocks.

Such meteorites may well Such meteorites may well have brought the have brought the raw raw material of lifematerial of life to Earth. to Earth.

First LifeFirst Life

By 3.5 billion years ago, tiny single-celled organisms By 3.5 billion years ago, tiny single-celled organisms called called prokaryotesprokaryotes were living in Earth’s oceans. were living in Earth’s oceans.

We find fossil evidence of these organisms in some We find fossil evidence of these organisms in some of the oldest rocks on Earth’s surface. of the oldest rocks on Earth’s surface. – These ancient rocks, found in Australia and Greenland, These ancient rocks, found in Australia and Greenland,

range from 3.8 billion to 3.5 billion years old.range from 3.8 billion to 3.5 billion years old.

PhotosyntheticPhotosynthetic bacteria changed the earth bacteria changed the earth dramatically. dramatically. – Used the sun’s energy to make food and water as well as Used the sun’s energy to make food and water as well as

oxygenoxygen that was released into the atmosphere and the that was released into the atmosphere and the oceans.oceans.

EndosymbiosisEndosymbiosisAround 2.5 billion years ago, some cells began Around 2.5 billion years ago, some cells began engulfing engulfing other cells. other cells. These cells were able to function together, These cells were able to function together, forming a new type of cell: a forming a new type of cell: a eukaryoteeukaryote..– These different parts perform different tasks within These different parts perform different tasks within

the cell. the cell.

ReproductionReproduction– For billions of years by For billions of years by binary fissionbinary fission– Later by Later by sexual reproductionsexual reproduction

exchanging DNAexchanging DNANatural SelectionNatural Selection

Paleozoic EraPaleozoic Era

Cambrian and Ordovician PeriodsCambrian and Ordovician Periods - Began 543 Billion Years Ago - - Began 543 Billion Years Ago -

Immense, shallow oceansImmense, shallow oceans covered much of the planet. covered much of the planet. After three billion years of evolution, Earth witnessed an After three billion years of evolution, Earth witnessed an explosion of lifeexplosion of life. (AKA: . (AKA: Cambrian ExplosionCambrian Explosion))

--Arthropods--Arthropods --Sponges --Sponges --Mollusks--Mollusks

Most animal groups living today evolved in the Cambrian Most animal groups living today evolved in the Cambrian seas.seas.– Among the new animal groups, many had developed Among the new animal groups, many had developed

skeletons (plates, shells, and bones), backbones,skeletons (plates, shells, and bones), backbones, and and other new features that would change the shape of life other new features that would change the shape of life forever.forever.

The The first mass extinctionfirst mass extinction came at the end of the Ordovician Period. came at the end of the Ordovician Period. – Global coolingGlobal cooling was probably the cause. was probably the cause.

A A large landmass moved over thelarge landmass moved over the South PoleSouth Pole, causing glaciers to , causing glaciers to form and global temperatures to cool. form and global temperatures to cool. Many species of trilobites, brachiopods, echinoderms, graptolites, Many species of trilobites, brachiopods, echinoderms, graptolites, and corals and corals became extinctbecame extinct. .

– due to cooler conditions and suffered from due to cooler conditions and suffered from habitat losshabitat loss as water turned as water turned to ice, lowering sea levels worldwide.to ice, lowering sea levels worldwide.

If almost all life became extinct, If almost all life became extinct, then how do we know . . . . then how do we know . . . .

If radiometric dating identifies the rock in layer C as 425 If radiometric dating identifies the rock in layer C as 425 million years old, what can you infer about the age of the million years old, what can you infer about the age of the

fossils in layer C? In layers B and D? Explainfossils in layer C? In layers B and D? Explain ..

Silurian & Devonian PeriodsSilurian & Devonian Periods

- Began 443 - Began 443 Million Years Ago -Million Years Ago -

When the Silurian Period began, continents that once were When the Silurian Period began, continents that once were separate had come together along the separate had come together along the equatorequator..Life landed ashoreLife landed ashore during the Silurian & Devonian periods. during the Silurian & Devonian periods.– PlantsPlants colonized the continents, creating habitats for the colonized the continents, creating habitats for the

ancestors of today’s animals.ancestors of today’s animals.The first land plants evolved from The first land plants evolved from water plantswater plants. .

– green algaegreen algaeEarly plants had to live near Early plants had to live near waterwater. .

– NonvascularNonvascularMovement by Movement by osmosisosmosis

StemsStems let plants move away from the water’s edge. let plants move away from the water’s edge.– Vascular Vascular

Movement through Movement through tissuestissues (xylem & phloem)(xylem & phloem)Pollen and seedsPollen and seeds broke plants’ last ties to wet broke plants’ last ties to wet environmentsenvironments..

•In the seas, In the seas, massive reefsmassive reefs — larger than at any other time in — larger than at any other time in history—covered the ocean floor, and fishes. history—covered the ocean floor, and fishes.

•The development of The development of jawsjaws allowed fishes and other allowed fishes and other emerging vertebrates to catch larger prey.emerging vertebrates to catch larger prey.

•The development of The development of tetrapodstetrapods paved the way for animals paved the way for animals that could walk on land. (limbs and digits)that could walk on land. (limbs and digits)

•Arthropods that evolved to live on land during this time are Arthropods that evolved to live on land during this time are ancestors of today’s ancestors of today’s insects and spidersinsects and spiders..

•Mass extinction #2Mass extinction #2 continents had moved over the South continents had moved over the South Pole.Pole.

•Climate too cold for many species.Climate too cold for many species.•70% of life in ocean died out. of life in ocean died out.

CarboniferousCarboniferous

- Begins 354 billion years ago –- Begins 354 billion years ago –

Divided intoDivided into

Mississippi and Pennsylvanian Mississippi and Pennsylvanian

Landmasses moved towards the equator and continents Landmasses moved towards the equator and continents began shifting from began shifting from east to westeast to west. . – A resulting A resulting milder climatemilder climate helped great forests helped great forests

flourish.flourish.

Swampy tropical forestsSwampy tropical forests covered the continents. covered the continents. – Over time and under pressure, the remains of these Over time and under pressure, the remains of these

forests would become the forests would become the great coal fieldsgreat coal fields mined for mined for fuel we use today.fuel we use today.

Fossils tell us Fossils tell us arthropodsarthropods and and tetrapodstetrapods thrived here thrived here (some were giants).(some were giants).

----insectsinsects --millipedes--millipedes --arachnids --arachnids

PermianPermian

- Began 290 Million - Began 290 Million Years Ago - Years Ago -

Earth’s continents had assembled into one giant landmass called Earth’s continents had assembled into one giant landmass called PangaeaPangaea..

Three basic environments:Three basic environments:----aridarid ----tropicaltropical ----temperatetemperate

Ever-increasing diversityEver-increasing diversity of plant and animal life. of plant and animal life.

Tetrapods that waded ashore in previous periods diversified into to two new Tetrapods that waded ashore in previous periods diversified into to two new groups.groups.– ReptilesReptiles

Amniotic EggAmniotic Egg– SynapsidsSynapsids

Ancestor of MammalsAncestor of Mammals

– Third mass extinctionThird mass extinction at the end. at the end.Global warmingGlobal warming (volcanic activity) (volcanic activity)Nearly wiped out all life on earthNearly wiped out all life on earth

– 90% of Marine90% of Marine Animals died out Animals died out– 80% of Land80% of Land Animals died out Animals died out

MesozoicMesozoic

- Began 248 Billion Years Ago- Began 248 Billion Years Ago

Divided intoDivided into

TriassicTriassicJurassicJurassic

CretaceousCretaceous

This era saw the evolution of the This era saw the evolution of the largest animalslargest animals to to have ever walked the earth. have ever walked the earth. – Called the Called the Age of DinosaursAge of Dinosaurs – They would give rise to They would give rise to birdsbirds..– Crocodiles, snakes, and turtles making their first Crocodiles, snakes, and turtles making their first

appearance. appearance.

The The emergence of mammalsemergence of mammals, from which humans , from which humans eventually evolved.eventually evolved.The The emergence of birdsemergence of birds, which are the living dinosaurs , which are the living dinosaurs of today.of today.The The emergence of flowering plantsemergence of flowering plants,, which created rich which created rich and varied habitats where new forms of life could and varied habitats where new forms of life could evolve and diversify.evolve and diversify.– AngiospermAngiosperm

4th Mass Extinction4th Mass Extinction

– Early MesozoicEarly Mesozoic

Volcanic Activity lead to global warming.Volcanic Activity lead to global warming.

–50% of Marine Life went extinct50% of Marine Life went extinct

55thth Mass Extinction Mass Extinction

– Late MesozoicLate Mesozoic

– Possible MeteoritePossible Meteorite

50% of all Life went extinct50% of all Life went extinct

Cenozoic Era:Cenozoic Era:

TertiaryTertiaryPeriodPeriod

- Began 65 Million Years Ago -- Began 65 Million Years Ago -

Age of MammalsAge of Mammals

– hoofed mammals, rodents, and carnivores evolved hoofed mammals, rodents, and carnivores evolved

– First warm tropical forests, then cooler, drier grasslands provided First warm tropical forests, then cooler, drier grasslands provided rich habitatsrich habitats where mammal species could where mammal species could thrive and diversifythrive and diversify..

– Three types of mammals:Three types of mammals:

MonotremesMonotremes - hatch from eggs. - hatch from eggs.

MarsupialsMarsupials - are born before they are fully developed and - are born before they are fully developed and continue development outside the womb, often in a pouch.continue development outside the womb, often in a pouch.

PlacentalsPlacentals - develop completely in their mother’s wombs - develop completely in their mother’s wombs before they are born. before they are born.

– also grouped by differences in their featuresalso grouped by differences in their features

Claws/HoovesClaws/Hooves

Teeth Differences (eating)Teeth Differences (eating)

Grasping Hands & FeetGrasping Hands & Feet

The Age of Early HumanThe Age of Early Human

PrimatesPrimates– Grasping Hands & FeetGrasping Hands & Feet– Forward Facing Eyes (depth perception)Forward Facing Eyes (depth perception)– Large Brain (in relation to rest of body)Large Brain (in relation to rest of body)

Humans belong to the primate group called Humans belong to the primate group called hominidshominids..– First appeared eight million years ago.First appeared eight million years ago.– Evolved from an Evolved from an ape ancestorape ancestor. .

did not all evolve in a single direct progression from apesdid not all evolve in a single direct progression from apes

– Evolved through the same unpredictable process as Evolved through the same unpredictable process as every other living thing every other living thing

Telling Hominids Telling Hominids & &

Apes ApartApes Apart

1. Skull1. Skull

The opening for an ape’s spinal The opening for an ape’s spinal column is towards the back of the column is towards the back of the skull, so the spine extends skull, so the spine extends backwards and down.backwards and down.

The opening for a hominid’s The opening for a hominid’s spinal column is at the bottom of spinal column is at the bottom of the skull, so the spine extends the skull, so the spine extends directly down underneath the directly down underneath the skull.skull.

2. Teeth2. Teeth

An ape’s canine teeth are An ape’s canine teeth are relatively large.relatively large.

A hominid’s canine teeth are A hominid’s canine teeth are smaller by comparison.smaller by comparison.

3. Pelvis3. Pelvis

An ape’s pelvis is tall and narrow.An ape’s pelvis is tall and narrow.

A human’s shorter and wider A human’s shorter and wider pelvis makes for more stable pelvis makes for more stable walking on two legs.walking on two legs.

4. Femur4. Femur

An ape’s femur (upper leg bone) An ape’s femur (upper leg bone) extends straight down.extends straight down.

A hominid’s femur is angled A hominid’s femur is angled inward, positioning the knees and inward, positioning the knees and feet directly under the body’s feet directly under the body’s center of gravity during walking.center of gravity during walking.

5. Foot arches5. Foot arches

An ape’s foot is flat.An ape’s foot is flat.

A human’s foot is arched, A human’s foot is arched, absorbing shock when the foot absorbing shock when the foot falls.falls.

6. Toes6. Toes

An ape’s big toe is splayed off to An ape’s big toe is splayed off to the side. This thumb-like toe is the side. This thumb-like toe is great for grasping, but not for great for grasping, but not for weight bearing.weight bearing.

A human’s big toe is lined up A human’s big toe is lined up parallel with the other toes, bearing parallel with the other toes, bearing the weight of the body during the the weight of the body during the “push-off” to the next step.“push-off” to the next step.

AustralopithecinesAustralopithecinesOne of the earliest hominidsOne of the earliest hominids– Smaller than the average modern humanSmaller than the average modern human– Smaller brainsSmaller brains– Protruding jawsProtruding jaws– Large molarsLarge molars

grinding down tough plant materialgrinding down tough plant material

– Walked upright Walked upright some probably spent time in treessome probably spent time in trees

The female hominid, a young adult named The female hominid, a young adult named “Lucy”, lived in eastern Africa 3.2 million “Lucy”, lived in eastern Africa 3.2 million years ago. years ago.

Homo ergasterHomo ergaster

Earliest species of the genus Earliest species of the genus HomoHomo First appeared in Africa First appeared in Africa – around 2 million years agoaround 2 million years ago

The first true humansThe first true humans– Characteristics:Characteristics:

Larger brainsLarger brains Flatter faces with projecting, flat, nosesFlatter faces with projecting, flat, nosesSmaller teeth Smaller teeth

– Could now eat meatCould now eat meat Larger with shorter arms and longer legsLarger with shorter arms and longer legsA life spent completely on the ground, not in the treesA life spent completely on the ground, not in the trees

Key Trends in Hominid Evolution Key Trends in Hominid Evolution

Leaving the trees and walking on landLeaving the trees and walking on land

Bigger brains relative to body size Bigger brains relative to body size – more sophisticated thinking processesmore sophisticated thinking processes

Remnants of primate body parts that we Remnants of primate body parts that we no longer useno longer use

RemnantsRemnantsWisdom teethWisdom teeth– Needed for chewing to break down plantsNeeded for chewing to break down plants

Third eyelidThird eyelid– Small pink fold in the inner corner of the eyeSmall pink fold in the inner corner of the eye– Helped keep eyes clean. Helped keep eyes clean.

Reptiles have this membrane too, so we have a common ancestorReptiles have this membrane too, so we have a common ancestor Ear wiggling musclesEar wiggling muscles– Early primates could move their ears independentlyEarly primates could move their ears independently

cats and dogs cats and dogs Palmaris musclePalmaris muscle– long, narrow muscle that runs from wrist to elbowlong, narrow muscle that runs from wrist to elbow

important for climbing and hangingimportant for climbing and hangingabout 11% of us are missing this about 11% of us are missing this

GoosebumpsGoosebumps– Muscle fibers that make your hair stand on end Muscle fibers that make your hair stand on end

When cold or scarredWhen cold or scarredEarly primates used for insulation or to intimateEarly primates used for insulation or to intimate

Fifth toeFifth toe– For grasping or clinging to branches. For grasping or clinging to branches. – Big toe used for balanceBig toe used for balance

Climate Shapes EvolutionClimate Shapes EvolutionHomo sapiens VS NeanderthalsHomo sapiens VS Neanderthals

Homo sapiensHomo sapiens– Originated in Africa 195,000 years agoOriginated in Africa 195,000 years ago– Slender body great for warm environmentSlender body great for warm environment

NeanderthalsNeanderthals– first evolved in Europe, at least 400,000 years ago. first evolved in Europe, at least 400,000 years ago. – Stockier body to help retain heatStockier body to help retain heat

Neanderthals were our neighbors, not our ancestors. Neanderthals were our neighbors, not our ancestors.

QuartenaryQuartenary

- Began 1.8 Million Years Ago -- Began 1.8 Million Years Ago - Commonly known as the Commonly known as the Ice AgeIce Age

Changing climate and the formation of Changing climate and the formation of new land new land bridgesbridges..

– Dramatically affected the Dramatically affected the evolution of evolution of mammalsmammals

Led to diversityLed to diversity

Mammals became massiveMammals became massive

Continents moved to their current locationsContinents moved to their current locations

Glaciers at the polesGlaciers at the poles

66thth Mass Extinction Mass Extinction

For the first time in Earth’s history, a For the first time in Earth’s history, a single species is the primary cause of a single species is the primary cause of a mass extinction.mass extinction.

HUMANS

ARE

THAT

SPECIES!

SourcesSources

http://www.fieldmuseum.org/evolvingplanet/exhibition.asp

http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13