Earth’s Historical Highlights•Major stages in the history of Earth •Major Extinctions

The Beginning• Earth is formed

from dust and debris orbiting the sun– A process named

Accretion• Like snowballing

– ~4.6 BYA (billions of years ago)

• Then the crust formed

The Eons of TimeMillions of Years Ago

PhanerozoicEon

Cenozoic era Quaternary, Tertiaray Mammals

200 Mesozoic era Cretaceous, Jurassic, Triassic Reptiles, birds

400 Paleozoic Permian, Carboniferous, Devonian Fish, amphibians

600 Silurian, Ordovician, Cambrian Invertebrates

800

ProterozoicEonSingle Cells & colonial

Neoproterozic Ediacaran, Cryogenian, Tonian

Stenian, Ectasian, Calymmian

1000 MYA (1 BYA) Mesoproterozic

1200 Colonial Organisms?

1400

1600

1800 Paleoproterozoic StatherianOrosirianRhyacianSiderian

2000 MYA (2 BYA)

2200

2400 Eukaryotes?

2600Archean EonBacteria only

Neoarchean (not yet divided into periods)

2800 Meoarchean

3000 MYA (3 BYA) Paleoarchean

3200 Eoarchean Bacteria?

3400

Hadean EonNo Life

Early Imbrian Bombardment ends

3600 Nectarian Era Earth cools, Oceans form

3800 Basin Group Era cometary bombardment!

4000 MYA (4 BYA) Cryptic Era Sun & Planets form

Eons divided into Eras divided into Periods (what was going on)

This scale of years is approximate, and may vary from other sources by a million years or so

NO

LIFEB

AC

TE

RIA

L LIFEC

OM

PLE

XLIFE

In Your TextbookThis whole time is simply called

Precambrian

MIC

RO

SC

OPIC

LIFE

Geological Timetable Era From/to events periods Ends with

Cenozoic“Age of Mammals”

Now Mammalsbirds

Quaternary

65mya Tertiary

Mesozoic(middle animals)“Age of Reptiles”

65 MYA DinosaursEarly mammals Reptiles

Cretaceous

Jurassic

250 MYATriassic

Paleozoic(ancient animals)“Age of Invertebrates”

250 MYA

540 MYA

Early reptilesAmphibiansInsects, molluskstrilobites

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

Earlier Eras“Precambrian”

540 MYA

4 BYA

bacteria, etc First Life,. Earth cools

Pre-cambrianSee previous slide

1

2

3

4

5

ERAS (simplified)• Cenozoic Era: Our era… lots of

mammals, birds, flowering plants• Mesozoic Era: Age of reptiles.

Dinosaurs and other large reptiles, gymnosperm plants

• Paleozoic Era: Age of invertebrates. Molluscs, insects, trilobites, worms etc. Algae and mosses.

• “Precambrian”: Age of microscopic life. Bacteria and some protozoans. Algae and cyanobacteria

The Major Eras• Life begins ~3.8bya• Beginning of

Precambrian Era– Bacteria and prokaryotes

appear

Palaeozoic Era“the age of invertebrates”

• paleo/old + zoic/animals = ancient life

• There was only one continent at the beginning– Rodinia (the mother continent)

• The land started off cold, but the seas warmed up quickly

• Life proliferates– Extensive variety of sea life– The predominant animal forms were

invertebrates (animals without backbones) like trilobites, insects, squids, snails etc.

• Then most life dies at the end of the Palaeozoic

The Paleozoic Era started about 543 million years ago, and lasted nearly 300 million years

(until 245 million years ago)

During the Paleozoic Era life proliferated. Many new and strange creatures populated earth’s oceans– sponges,

molluscs, trilobites, worms etc.

PALEOZOIC ERAThe “age of invertebrates”

Predominant life forms were invertebrates (no backbones)

The Paleozoic era is divided into six periods

PALEOZOIC ERA: Part I

• The Cambrian Period (540 MYA)– There was only one continent at the beginning– Rodinia: the first supercontinent (the mother

continent)

Most life was aquatic (ocean life)Sponges (formless animals)Jellyfish (soft aquatic animalsTiny molluscs (snails, clams)Marine Worms

Tiny mollusc shells from Cambrian Period (early Paleozoic)

PALEOZOIC ERA: Part II

• The Ordovician Period• The supercontinent began to break apart

– Into Gondwana ,Laurentia and Baltica

Africa, South AmericaAntarctica & India

North America Europe

Common life forms included:Trilobites (ancient arthropods)Jawless Fish (eels)Cartilage Fish (ancestors of sharks)

Plants and animals began to colonize the land

• Silurian Period (439-409 MYA): • Plants spread across the land

– Mostly mosses and primitive fern ancestors.– No really big trees yet

PALEOZOIC ERA: Part III

PALEOZOIC ERA: Part IV

• Devonian Period: (409-363 MYA)– First amphibians appeared– First insects appeared– Plants became larger and

more varied

• Underwater, fish were becoming larger and more diverse

PALEOZOIC ERA: Part V• The Carboniferous era (363-290 MYA)• AKA: Mississippian/Pennsylvanian Era

Great forests covered the land.

Much of our fossil fuel (coal and oil) comes from plants that died in the carboniferous period.

PALEOZOIC ERA: Part VI

The Permian period ended with the greatest of all mass extinctions.90% of aquatic life became extinct75% of terrestrial life

This also brought the paleozoic era to an end.

• Permian Period. (290-245 MYA)• By the end of the Paleozoic era, some of the

continents had rejoined, forming a new supercontinent called Pangea.

• More varied reptiles appeared.

Dimetrodon

The Palaeozoic Earth

End of the Palaeozoic

• Although the palaeozoic era is called the “age of invertebrates”, towards the end of the era some primitive fish, amphibians and reptiles had evolved.

• A mass extinction occurred to end the era.• We can identify mass extinctions in the fossil

record by finding a layer with very few fossils just above a layer with lots of fossils.

• This extinction was one of the biggest:– 95% of marine life and 75% of land life disappeared.

The Mesozoic Era: Age of Reptiles

• Meso/middle + zoic/animal = middle animals

• AKA the Dinosaurs’ era

• Albertosaurus

Mesozoic Earth

Periods of the Mesozoic Era

• Triassic Period:– Dinosaurs appeared

• Jurassic Period– Dinosaurs grew larger and more diverse. Small

mammals and primitive birds may have developed

• Cretaceous Period– Pangea broke up into the modern continents– The largest dinosaurs appeared

The End of the Mesozoic Era

• The Mesozoic era ended when a large asteroid smashed into Mexico, about 65 million year ago.

• The dinosaurs and many other life forms became extinct during the climate changes that followed.

• This was the 5th mass extinction

Cenozoic Era: The age of MammalsKnown for the

success and diversification of mammals

Periods of the Cenozoic Era

• Tertiary period: there were many large and unusual mammals

• Quaternary Period: primates and hominids evolved

The Quaternary Period• (Periods are smaller

divisions of Eras)• Known for global

glaciations– Ice ages

• Modern man has been evolving for– Over a million years

(perhaps as much as three million years)

– But has been sedentary for only ~10000 years• civilized

Chapter 17: Human Evolution

Hominid Fossils

• Humans and some of their extinct relatives belong to a family known as hominids.

• Hominids are classed within the order primates, along with apes and monkeys.

• The oldest hominid fossils have been found in Africa.

“Lucy” a hominid fossil from About 3 million years ago

• The complete classification of humans is:– Kingdom Animalia (animal kingdom)

– Phylum Chordata (chordates have a notochord)– Subphylum Vertebrata (with proper backbone)– Superclass Tetrapoda (decendants of four-limbed

vertebrates)

– Class Mammalia (the mammals)– Subclass Theria (live-birth mammals), – infraclass Eutheria (placental mammals)

– Order Primates (the primates: monkeys, apes, hominids)– Superfamily Hominoidae (anthropoids, greater apes)

– Family Hominidae (the hominids: humanlike. All other hominids except humans are now extinct)

– Genus Homo (Humans and early humans)

– Species sapiens (Modern “wise” humans)

This is presented for your information. You don’t need to copy or memorize it

The First Hominid?A newly discovered fossil

• Ardipithicus ramidus (Ardi): a chimpanzee sized hominid found in Africa and dated to about 4.4 million years, making it the oldest nearly intact hominid skeleton ever found.

On October 1, 2009, paleontologists formally announced the discovery of the relatively complete A. ramidus fossil skeleton first unearthed in 1994. The fossil is the remains of a small-brained 50-kilogram (110 lb) female, nicknamed "Ardi", and includes most of the skull and teeth, as well as the pelvis, hands, and feet

Some Other Identified Hominid Species

• Australopithicus afarensis “Lucy” is a species found in the Afar valley of Africa. They lived between 3 million and 4 million years ago

• Australopithicus africanus, Taller and heavier than “Lucy” lived in Africa between 2.3 and 3 million years ago

• Paranthropus* robustus and Paranthropus* boisei “nutcracker man” both lived between 1 and 2 million years ago in Africa* These two were formerly placed in genus Australopithicus

Australopithicus

Paranthropus

More Identified Hominid Species• Homo Habilis “Handy Man” lived in

Africa about 2.5 million years ago. This fossil used tools and may be the earliest representative of the human genus.

• Homo Erectus, “upright human” was first discovered in Java, and since then all over Asia, Africa and Europe. This may well be the ancestor of modern humans. They existed from 1.8 million years ago to as recently as 40,000 years.

Two Modern Human Species• Homo neanderthalensis (or possibly Homo

sapiens- neanderthalensis) lived in Europe from about 1.8 million years ago to as recently as 30,000 years ago. It has not been established if this was a separate species of human, or a “race” that would be capable of breeding with “modern” humans (hence the disputed classification)

The most recent evidence is that these two types of human were different species, so I will use the terms homo sapiens and homo neanderthalensis

• Homo sapiens (or perhaps Homo sapiens sapiens) is the designation of modern humans. The first fossils of modern humans were found in the Cro-magnon caves in southern France.

Because of where they were first found, early homo sapiens are occasionally referred to as “Cro-magnon man”. This is not an official designation, as they were undoubtedly the same species as modern man.

Some lesser-known and disputed hominid fossils

• Homo Floresiensis? “hobbit”: a very small hominid fossil recently found in Malasia dating to about 13000 years ago. Its authenticity is still under dispute. It may be a malformed human.

• Homo Heidelburgensis “Goliath” is a large fossil homind found in Germany. It may be a separate species or a variety of Neanderthal, Homo Erectus or Antecessor

• Homo Antecessor is a fossil found in Spain which may be an ancestor of both Neanderthals and modern humans, or it may simply be a variety of Neanderthal or Homo Erectus

Hominids (Human Ancestors)

Ardipithicus sp.

Australopithicus sp.

Paranthropus sp.

Homo Habilis

Homo Ergaster

Homo Erectus

H. Heidelbergensis

Homo antecessor

Neanderthal

? H. Floresiensis ?

H.sapiens

1 millionYears ago

2 millionYears ago

3 millionYears ago

4 millionYears ago

Now|A

rdi

Lucy

“Nut

crac

ker”

man

Ancestral Tree of Humans

Homo Sapiens Homo Erectus (Homo Heidelbergensis)

Homo Habilis (Homo Floresiensis) Paranthropus Boisei Neanderthal

Probable Brain Sizes 500 cm3 700 cm3 1000 cm3 1450 cm3 1400 cm3

He thinksHe’s so Smart!

Homo neanderthalensis

30000 to 1.8 million years ago

Homo sapiensHomo erectus40000 to 1

millionyears ago.

Homo habilis1-2 million years ago

Paranthropus robustus

1-2 million years ago

Geological Timetable: Extinctions Era From/to events periods Ends with

Cenozoic“Age of Mammals”

Now Mammalsbirds

Quaternary Extinction?

65mya Tertiary

Mesozoic(middle animals)“Age of Reptiles”

65 MYA DinosaursEarly mammals Reptiles

Cretaceous Extinction!

Jurassic

250 MYATriassic Extinction.

Paleozoic(ancient animals)“Age of Invertebrates”

250 MYA

540 MYA

Early reptilesAmphibiansInsects, molluskstrilobites

Permian Extinction!!

Carboniferous

Devonian Extinction.

Silurian

Ordovician Extinction.

Cambrian

Earlier Eras“Precambrian”

540 MYA

4 BYA

bacteria, etc First Life,. Earth cools

Pre-cambrianSee previous slide

1

2

3

4

5

Assignment

• Read through chapter 10 in your text book, and answer the questions on pages 325 to page 329. – There are 20 questions in all .– See blackboard for due date.

Answers to Questions Page 325

• 1. a) The matter that formed our planet came from a great cloud of dust and gas that orbited our sun after it first formed.– B) The earth formed about 4.6 billion years ago (but it

took about a billion years for it to cool off and form oceans).

– C) The moon may have formed when a large celestial body collided with Earth with such force that it broke off a piece of the planet. The debris from the impact condensed, eventually forming the moon

• 2 A) The photo illustrates the presence of liquid water.

– B) The photo illustrates lightning, a source of energy for the formation of life.

– C) Other conditions not illustrated are:• Presence of elements necessary for life.• A long period of time.

• 3. A) The elements most needed for life include carbon, hydrogen, oxygen, nitrogen and sulfur.– B) Scientists believe that these elements

came from the atmosphere of earth.– C) It took a long time to form cells because

the probability of them forming was low– D) Life appeared between 3.5 and 3.8 billion

years ago.– E) The earliest forms of life resembled

bacteria • (your textbook mentions cyanobacteria, but I think

they more closely resembled archaebacteria)

• 4 A) the slow process that brings about modification of living beings is evolution

• B) Natural Selection gradually results in organisms better adapted to their environment.

• 5– A) Cenozoic is the era we live in– B) The Mesozoic era is when the dinosaurs

lived and became extinct– C) The “Precambrian” Era was the longest era– D) The Cenozoic era is when most of the

mammals appeared.– E) The Paleozoic era ended with the largest

mass extintion

• 6.

Event Era Period

Appearance of our species Cenozoic Quaternary

Extinction of dinosaurs Mesozoic Cretaceous

Appearance of dinosaurs Mesozoic Triassic

Extinction of 90% marine life Paleozoic Permian

Appearance of amphibians, insects Paleozoic Devonian

Appearance of fish Paleozoic Ordovician

Appearance of vertebrates Paleozoic Ordovician

Appearance of soft invertebrates Precambrian Precambrian

First evidence of life Precambrian* Precambrian*

• 7. The 380 million year old fish lived in the Paleozoic era and the Devonian period.

• 8. Jurassic Park was an appropriate name for a movie about dinosaurs, because many types of dinosaur existed in the Jurassic period

• I personally think a better name would have been Cretaceous Park, because the two “Star” dinosaurs (T-Rex and velociraptor) were more common in the Cretaceous Period.

• 9. – A) The chimpanzee is our closest “cousin”– B) The main feature used to distinguish between

humans and apes is bipedalism (the ability to walk upright)

• 10.– A) Three human genera are Australopithicus,

Paranthropus, and Homo– B) the scientific name of humans is homo sapiens.a– C) Two other human species were Homo floresiensis,

and Homo neanderthalensis..

• 11. Adaptations include:– A) Bipedalism, allowed us to use our hands to

carry things and use tools– B) Our brain allowed us to reason, become

inventive, develop tools, and communicate using complex languages.

– C) Our fine hair allowed us to keep cool– D) Our sweat glands also allowed us to cool

off during hot African days.

• 12. It is difficult to establish exactly how humans evolved because there is not as much fossil evidence as we would like.

• 13. Fossils are usually found in sedimentary rock.

14.

Fossil Type Formation

Footprints Trace The traces left in soil hardened

Bones Petrified The bones hardened and mineralized

Trilobite Cast Impression of trilobyte filled in with minerals

15. a) a body fossil is not shownb) A mammoth frozen in ice or an insect preserved in amber are examples of body fossils

• 16– A. False a palaeontologist studies fossils

– B. True there are petrified trees

– C. False most fossils come from sedimentary rocks

– D. False most organisms just decay

– E. True some fossils show both bones and impressions

(like archaeopteryx, the first bird, on page 322)

– F. False relative dating is less accurate

– G. True The carbon 14 gradually disappears

17.

• The law of continuity says that all sedimentary rock in a single layer formed at the same time. The law of superposition says that the deeper a layer is, the older it is

• 18 – A) If you think a tree is older because it is

larger, you are using relative dating– B) If you count the tree rings it is absolute

dating

• 19– A. Carbon-14 dating is based on the decay of

radioactive isotopes (radiometric dating)– B. The older the fossil, the less radioactive

carbon-14 it will have in it

• 20.– A. The orange layer is the oldest, since by the law of

superposition the oldest layer is the deepest– B. Species “B” probably appeared first, since its

fossils appear in an older layer– C. Species “B” probably disappeared last, since its

fossils are also found in a higher layer– D. Yes, they both existed during the time the middle

layer was deposited.– E. Relative dating helps us establish the dates of the

stratigraphic layers– F. Elements like uranium would be better than carbon

14 for determining the age of these fossils.