1. The Geological Time Scale

2. Events in Your Life ___When you started second grade
Construct a timeline of the important events in your life. Be sure to include all of the events listed below and any other events you feel are important. Your timeline should be constructed TWO ways:
Numerical Order (use actual dates)
Sequential Order (most recent at top)
___When you started second grade
___When you were born
___ When you started kindergarten
___When you learned to ride a bike.
___ When you learned to walk.
___ When you learned to read.
___ When you lost your first tooth.
___ Today’s date.

4. Diversity (1): Simple organisms
Bacteria
Presenter notes: The richness of life on Earth is simply incredible. Around 1.8 million species have been discovered and named so far. However, conservative estimates suggest that an additional 8 million are left to describe - so less than a quarter of all living species are known to Science! Despite all this diversity, all organisms fall into just one of two categories. One group of organisms has simple cells with DNA strands floating within a capsule. These prokaryotes, as they are called, are all single celled bacteria. We still know very little about the diversity of bacteria.
en.wikipedia.org/wiki/Image:Halobacteria.jpg
Two types of organism exist on our planet. One group has simple cells with DNA strands floating in a capsule. These prokaryotes, as they are called, include various types of bacteria

5. Diversity (2): Complex organisms
en.wikipedia.org/wiki/Image:Chlamydomonas_(10000x).jpg
en.wikipedia.org/wiki/Image:Laurencia.jpg
Golden algae
Fungi
Protozoa
Presenter notes: The second group of organisms, which we call eukaryotes, have complex cells that have compartments with special jobs and DNA located in a nucleus. This group includes the familiar kingdoms of organisms like animals, plants and fungi. Most of the organisms in these kingdoms are multicellular, made up of many cells working together. However, other eukaryotes include the single-celled kingdoms of the protozoa and the ‘golden brown algae’ or chromists.
A second group, eukaryotes,
have complex cells that have
compartments with special jobs
and DNA in a nucleus
Plants
Animals
en.wikipedia.org/wiki/Image:Elephant_near_ndutu.jpg
en.wikipedia.org/wiki/Image:Amanita_muscaria_(fly_agaric).JPG

6. Geological Time The whole geological timescale
The Phanerozoic in detail
Presenter notes: The history of the Earth stretches back over 4550 million years (or 4.55 billion years). Geologists have divided up this vast abyss of geological time into an orderly series of eons, eras, and periods. By determining the age of the strata in which the fossils are found, their order of occurrence can be worked out, and the History of Life established. At the bottom of every slide in this talk, you will see a geological time scale like the ones shown here. This will pictorially show the age of the fossils discussed in that slide. Also note that a common abbreviation used throughout this talk is mya, which stands for ‘million years ago’ (e.g. 500 mya is shorthand for 500 million years ago)
Note: There is another Your Planet Earth talk that specifically deals with Geological Time. You can download it here:
The study of fossils in the context of the 4500 million years of
geological time allows us to piece together the History of Life

7. What is the Earth’s time scale?
The Geological time scale is a record of the life forms and geological events in Earth’s history.
Scientists developed the time scale by studying rock layers and fossils world wide.
Radioactive dating helped determine the absolute divisions in the time scale.

10. Divisions of Geologic Time
Eras are subdivided into periods...periods are subdivided into epochs.
Era
Period
Epoch
E + P = EP

11. Divisions of Geologic Time
Geological time begins with Precambrian Time. Precambrian time covers approximately 88% of Earth’s history.

12. FOUR Eras… PRE-CAMBRIAN – 88% of earth’s history
Paleozoic (ancient life)
544 million years ago…lasted 300 million yrs
Mesozoic (middle life)
245 million years ago…lasted 180 million yrs
Cenozoic (recent life)
65 million years ago…continues through present day

13. In the Sea (1): Bombardment
Early Earth
Cratered moon
Mars ?
© Julian Baum with permission
NASA
NASA
During its early history, the Earth was bombarded by meteorites.
Such inhospitable conditions probably prevented life from evolving.
Presenter notes: So let’s begin our story of the History of Life and travel back in time to the origin of the Earth. For much of its earliest history, the Earth was probably not a very hospitable place for life to evolve. For 700 million years after its origin, the Earth was bombarded by massive meteorites, chunks of rock left over from the formation of the Solar System. Plate tectonics, together with weathering, has all but erased the numerous impact craters that must have been formed on Earth at this time. However, on the moon, where weathering and plate tectonics do not occur, the heavily cratered surface has survived. Life probably began sometime after the phase of heavy bombardment ended about 3800 million years ago. No one has yet figured out how life began, and there are even question marks over whether life started on Earth. Some scientists hypothesize that life could have begun on Mars, or somewhere else in Space, only later ‘seeding’ the Earth. In support of this idea is the fact that certain meteorites contain the basic building blocks of life, and the fact that some dormant bacteria can potentially survive in the vacuum of space for millions of years. Nevertheless most scientists think that life began on Earth.
million years ago

14. In the Sea (2): First living things
Life evolved
shortly after the
bombardment
ended, early in
Earth History.
The first living
things were
simple bacteria
Modern bacterial mounds
Fossil bacteria?
Presenter notes: Whatever the origin of life, there is fossil evidence of the simplest prokaryotic life-forms that had evolved by million years ago. Structures found in rocks of this age include small layered domes called stromatolites. Similar structures are found today in places like Shark Bay on the western coast of Australia and form by the growth of sticky bacterial films. The sticky bacteria trap mud, which results in the build up of the small layered domes. The existence of stromatolite domes in the fossil record therefore implies that bacteria had evolved in the sea by this time. One fossil site in Australia called the Apex Chert contains organic filaments that may represent actual bacteria. However some scientists dispute whether these features are really fossil bacteria and say that they could have a non-biological origin.
en.wikipedia.org/wiki/Image:Stromatolites_in_Sharkbay.jpg
million years ago

15. In the Sea (3): Oxygen Early photosynthetic bacteria produced
oxygen and released
it as a waste product.
This added oxygen
to the atmosphere
for the first time.
Iron oxide rocks
Photosynthetic
bacteria
Presenter notes: Although the fossil record of the early Earth is difficult to interpret, other evidence supports the idea that simple bacteria evolved in the sea very early the planet’s history. One important bit of evidence is the thick deposits of iron oxide that occur in rocks of this age. Geologists believe that the early Earth lacked oxygen. If that was the case then where did all the oxygen come from which combined with the iron to form the iron oxide deposits? One idea is that the first bacteria grew by capturing energy from the sun by photosynthesis like do plants today. Oxygen is the waste product of photosynthesis, so as the bacteria grew they would have released oxygen into the seas. This would have reacted with any iron in the seawater causing it to ‘rust’ and form a layer of iron oxide on the seabed. The iron oxide deposits are therefore indirect evidence for the existence of bacteria at that time.
en.wikipedia.org/wiki/Image:Anabaena_sperica.jpg
million years ago

16. In the Sea (4): Complex cells
Acritarch
Two billion years later complex
eukaryote cells appeared.
These had compartments with
special functions such as energy
factories called mitochondria.
Eukaryote cells need oxygen -
this explains their late evolution
Presenter notes: Simple prokaryotic bacteria were the only life forms on our planet for the first half of its history! However, nearly two billion years after the evolution of the first bacteria cells, there was amazing leap forward in the way that living things were constructed. About 1900 million years ago, fossils called acritarchs appear in the fossil record. These comprise a single eukaryotic cell with compartments with special jobs like mitochondria to make energy and a nucleus to store the DNA. No one knows exactly how eukaryotic cells evolved. One idea is that a prokaryotic bacterium enveloped another prokaryotic cell, but rather than digesting it as might normally happen, it incorporated as a special compartment in the cell. What is known is that eukaryotes are oxygen-hungry cells so their evolution was probably delayed until enough oxygen had built up in the seas. The evolution of the eukaryote cell paved the way for the diversity of complex life forms seen today.
1900 million years ago

17. In the Sea (5): Multicellular life
Grypania
After another half billion years
many-celled life appeared
Grypania was a coiled
tube, 2 mm wide and up to
5 cm long
Presenter notes: It’s amazing to reflect on the fact that for the first two-thirds of our planet’s history, the only life-forms were single-celled. However, all that changed around 1400 million years ago, when the fossil record shows that many-celled organisms evolved. One fossil from this time period is called Grypania. This is a coiled tube about 2 mm wide and up to 5 cm long that is found in rocks from North America, China and India. No one knows what kind of organism Grypania was, but its large size strongly suggests that it must have been made up of many cells working together.
© Bruce Runnegar with permission
1400 million years ago

18. In the Sea (6): Biology’s Big Bang!
evolution.berkeley.edu/evolibrary/images/bangiomorpha1.jpg
Red algae
Presenter notes: Another major event in the History of Life that happened about this time was the origin of sex! In Canadian rocks more than 1200 million years old, a fossil called Bangiomorpha has been found. This is a kind of red algae, the group that includes most seaweeds today. Not only was Bangiomorpha another early example of a many-celled organism, it also occurs in two forms, male and female, that demonstrate that sexual reproduction had evolved. Sex allowed life-forms to juggle their genes and increase the speed at which evolution could take place. This important event has been called ‘Biology’s Big Bang’ by some smutty palaeontologists!
en.wikipedia.org/wiki/Image:Sexual_cycle.svg
A short time later, 1200 mya, algae evolved sexual reproduction
1200 million years ago

19. In the Sea (7): Ediacara Evidence
By 630 mya, the familiar kingdoms of animals, plant and fungi
had evolved. The Ediacara fauna of this time interval were strange
bizarre organisms from the dawn of animal life
Presenter notes: By about 630 million years ago, and probably earlier, fossils show that the three familiar kingdoms of animals, plants, and fungi had probably evolved. However, not all fossils from this time interval are easy to interpret. In rocks aged million years old, strange fossils are present known as the Ediacara Fauna. No one is quite sure what these fossils represent, but it is likely that some are early marine animals - though quite different from any animals today. These weird but important fossils were first brought to the world’s attention by a English schoolboy in the 1950s who found specimens at Charnwood Forest in Leicestershire. This just goes to show that sharp-eyed amateurs can make fossil discoveries of huge importance.
million years ago

20. Beginnings (8): Diversity explodes
palaeo.gly.bris.ac.uk/palaeofiles/lagerstatten/Burgess/Anomalocarishunts.jpg
Fossils/Anomalocaris-canadensis.jpg
Burgess Shale fossils
Claw of Anomalocaris
Around 542 mya, several fossil sites show that the diversity of
animal life on Earth dramatically exploded over a short time.
Presenter notes: Once the animal kingdom had evolved, it quickly exploded into a wide diversity of different species. This explosion happened so quickly that it is difficult to explain in term of normal evolutionary processes. Evolution usually happens slowly but between 542 and 515 million years ago, animal life took an incredible leap forward. In less than 30 million years, almost every major group of animals evolved from jellyfish to snails to vertebrates. In addition, some weird animals also appeared that subsequently went extinct. These evolutionary experiments included a 2 metre long sea monster called Anomalocaris (see slide). One of the best places in the world to study marine life just after this explosion in animal life is the 515 million year ago Burgess Shale of British Columbia, Canada. This fossil site preserves the remains of animals in beautiful detail and even the soft tissue has survived.
million years ago

21. Paleozoic Era (Ancient Life)
The Cambrian period is the 1st period of the Paleozoic Era. “Age of the Trilobites”
Explosion of life in the oceans began during this era.
Most of the continents were covered in warm, shallow seas.
Invertebrates were dominate - Trilobites
Fish emerged during this time
Fish led to the arrival of amphibians
The end of the Paleozoic era is called the “Age of Amphibians”
Early land plants including mosses, ferns and cone-bearing plants.
The early coal forming forests were also formed during this time.

22. Paleozoic Era
Much of the limestone quarried for building and industrial purposes, as well as the coal deposits of western Europe and the eastern United States, were formed during the Paleozoic.
The Cambrian (beginning) opened with the breakup of the world-continent Rodinia and closed with the formation of Pangaea, as the Earth's continents came together once again.
This event is thought to have caused the climate changes that led to mass extinction event.
The Appalachian mountains were formed during this time.

23. Paleozoic Era
At the end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species and 70% of land animals.
Possible causes of this Mass Extinction Event
Lowering of sea levels when the continents were rejoined as Pangaea (convergent boundary)
Increased volcanic activity (ash and dust)
Climate changes – cooler climate

24. Onto Land (1): Making tracks
Around 500 mya, tracks in
ancient coastal dunes
show that some marine
animals started to make
temporary visits to the
sea shore to feed or mate
Eurypterid
Presenter notes: About the time that the Burgess Shale animals were alive, the History of Life was experiencing another major development. Up to this point in time, life had been largely restricted to the sea, but 500 million years ago, the invasion the land commenced. The earliest evidence we have for the invasion of land comes from tracks left in coastal dune sands in North America. The tracks were probably made by giant lobster-like creatures called eurypterids, or their relatives. Eurypterids mostly lived in the sea but made temporary excursions onto land to feed and mate in much the same way that horseshoe crabs do today.
© Simon Braddy
500 million years ago

25. Trilobites Lived in Earth’s ancient seas
Extinct before the dinosaurs came into existence
Cambrian Period is know as the “Age of the Trilobites” (put in on table)

26. Brachiopods
Marine animals that resemble clams.

27. Early Fish Early fish did not have jaws.
Some species of sharks were in existence at this time.

28. Frilled Shark that was found in Japan in January 2007
Frilled Shark that was found in Japan in January This shark was considered a “living fossil”

29. Onto Land (2): Permanent residents
upload.wikimedia.org/wikipedia/commons/4/41/Liverwort.jpg
Liverworts similar to the first plants
Ancient worm burrows
Presenter notes: Eurypterids were only temporary visitors to land and permanent residents did not establish themselves for quite some time later. However, about 460 million years ago, fossil soils in the USA contain complex burrow systems. The diagram on the left reconstructs what these burrows looked like in three dimensions. They were probably made by worms mining through the soil and show that land animals had arrived. At exactly the same time, remains of primitive plants start to appear in the fossil record. These include fragment of liverworts, the most primitive of the living plants today. Liverworts probably formed a spreading mat over the surfaces of wet soils and created a habitat which other animals could begin to colonize.
Worms and primitive plants started to colonize the land, 460 mya
460 million years ago

30. Early Land Plants
Mosses
Cone bearing plants
Ferns

31. Onto Land (3): A taste for Plants
Analysis of fossil
poo shows that
animals started
to eat plants,
420 mya
Fossil millipedes
Fossil poo contains plants
Presenter notes: The first animals to come onto land were either carnivores, eating other animals, or detritivores, living off dead and decaying organic matter in the soils. However, about 420 million years old, the fossil record tells us that animals started to get a taste for plants. The evidence is in the form of fossilized faecal pellets, or poo (!), excreted by millipedes and related animals and found in the famous Ludlow Bone Bed of Shropshire. The poo contains the remains of plants, showing that the first herbivores, or plant-eating animals, had evolved.
Millipedes and their poo in the Ludlow Bone Bed of Shropshire
420 million years ago

32. Onto Land (4): Time Capsule
© Jason Dunlop
Around 400 mya, a whole land ecosystem became a time capsule
at Rhynie in Scotland when a volcanic hot spring erupted.
Presenter notes: We have already stressed the fact that only a tiny proportion of living organisms are ever preserved in the fossil record and as result it is often incomplete. However, this is not always the case, as illustrated by an amazing 400 million year old fossil site at Rhynie in Aberdeenshire, Scotland. The Rhynie Chert preserves an entire land-based ecosystem in amazing detail. This unique ‘time capsule’ was formed when a nearby volcanic geyser, or hot spring, erupted and overwhelmed the adjacent ecosystem in boiling water. The boiling water carried lots of silica in solution that mineralized every cell of every organism, preserving them in extraordinary detail. The Rhynie Chert is a rare ‘snap shot’ of what life was like on land 400 million years ago. It demonstrates that the tallest plants were no more than 10 cm high and scurrying through this vegetation was a diverse group of invertebrates including mites, springtails, and spiders.
400 million years ago

33. Onto Land (5): First Forests
Tree trunks
Large leaves
Seeds
Forests were born 380 mya as plants grew trunks, leaves and
seeds for the first time
Presenter notes: This world of ankle-high plants didn’t stay like that for long because huge evolutionary change was transforming the plant kingdom. Fossils show that by 380 million years ago, some plants had acquired huge tree trunks that formed leafy forest canopies more than 30 metres high. At the same time plants were changing the way they reproduced. The earliest plants had reproduced using spores, as ferns do today, but now they developed seeds. Seeds help germinating plants to better survive drought. Once the seed had evolved, plants had the capacity to colonize dry land away from the coastal wetlands.
million years ago

34. Onto Land (6): Amphibians
en.wikipedia.org/wiki/Image:Panderichthys_BW.jpg
Also around 380 mya
certain fish evolved limbs
and lungs for life on land
The first land-dwelling
amphibians retained
many fishy characteristics
Panderichthys
Presenter notes: At the same that plants were undergoing this radical transformation, similarly dramatic changes were occurring amongst back-boned animals, or vertebrates. Fossil skeletons show that the first amphibians, the ancestors of frogs, evolved about 380 million years ago. Several early amphibian fossils have been found but one of the most famous is Ichthyostega from Greenland. Amphibians like Ichthyostega may have evolved from lungfish, or similar fish. Lungfish are freshwater fish that have the ability to breathe air for limited periods. As they live in ponds that occasionally dry up, the fish will burrow into the mud, slow down their heart beat and breathe air until the next rains fill the pond again. Whatever were the ancestors of amphibians, they had to undergo many evolutionary adaptations to life on land. Changes included the development of limbs instead of fins, the acquisition of lungs instead of gills, and changes to sensory organs like eyes and ears.
Ichthyostega
en.wikipedia.org/wiki/Image:Ichthyostega_BW.jpg
million years ago

35. Onto Land (7): Reptiles Hylonomus lyelli Lay eggs on land
Hylonomus lyelli
Lay eggs on land
Presenter notes: As anyone who’s ever seen frog spawn in ponds knows, one of the characteristics of amphibians is that they need to return to water to breed and reproduce. About 315 million years ago, fossil skeletons found in Nova Scotia, Canada show that the first reptiles had evolved from amphibian ancestors. The fossil were found by a famous North American geologist called William Dawson at a place known as the South Joggins. In a slightly unorthodox approach to fossil collecting, Dawson used dynamite to blast fossils out of the cliff. Fortunately some of the fragile reptile fossils survived this ordeal! One of the features that makes reptiles distinct from amphibians is that they lays eggs on land. Somewhat similar to the evolution of the seed in the plant kingdom, the reptile egg allowed these animals to colonize drier areas away from rivers and ponds
Bones found in Canada show that reptile evolved, 315 mya
315 million years ago

36. Onto Land (8): First Rainforests
Around 300 mya,
coal seams in North
America and Europe
show that the first
tropical rainforests
had evolved.
© Howard Falcon-Lang
Fossil plant
Presenter notes: By 300 million years ago life on land was really thriving. Across Europe and North America at this time, thick layers of coal were formed. These coal layers are the remains of the first tropical rainforests to develop on our planet. Next time you have a coal fire, see if you can find any fossil leaves compacted in the coal. Fossils show that these rainforests were inhabited by a rich diversity of animals including giant-sized dragonflies and millipedes!
Coal Forests
million years ago

37. Boom & Bust? (1): The Great Dying
Extinction
intensity
upload.wikimedia.org/wikipedia/commons/0/01/Pahoeoe_fountain_original.jpg
Life nearly died in a massive wave of extinction around 251 mya in
the largest of the so-called “Big Five” mass extinctions
Presenter notes: Around 251 million years a devastating event threatened to wipe out life on Earth entirely. No one knows what happened exactly but more than 95% of all species in the sea disappeared and life on land was also brought to brink of collapse. Such events are known as mass extinctions. There have been five “big” mass extinctions since the invasion of land, 500 million years ago, but this extinction was by far the biggest of all time. The perplexing thing is that no one really knows what caused it. Some scientists argue that there was a massive volcanic eruption at that time that went on for thousands of years but others disagree that this was the cause.
251.4 million years ago

38. Mesozoic Era – Middle Life
At the beginning of this era the continents were joined as Pangaea.
Pangaea broke up around the middle of this era.
Reptiles became the most abundant animals because of their ability to adapt to the drier climate of the Mesozoic Era.
Skin maintains body fluids
Embryos live in shells

39. Mesozoic Era Dinosaurs were also very active in this era.
First small dinosaurs appeared in the Triassic Period.
Larger and more abundant dinosaurs appeared in the Jurassic Period.
Small mammals and birds also appeared during this era.
The mammals were small, warm-blooded animals. Hair covering their bodies.
These characteristics help them survive in changing environments.

40. Mesozoic Era
The main plant life of this time were Gymnosperms or plants that produce seeds, but no flowers.
Pine Trees
Flowering plants appeared during the END of this era.

41. Boom & Bust? (2): Dinosaurs
About 220 mya, shortly after the extinction, dinosaurs appeared.
These reptiles dominated the land for the next 150 myrs!
Presenter notes: Following this “mother of all extinctions”, 251 million years ago, life slowly recovered. Subsequently, it went from strength to strength, getting ever more diverse over time. One of the great success stories of this boom time in the History of Life were the dinosaurs. They evolved 220 million years ago and dominated the land for the next 150 million years. As everyone knows “dinosaur” means “terrible lizard” but these giant reptiles included both plant-eating giants such as Diplodocus as well as ferocious meat-eating dinosaurs like T. rex. Scientists used to think that dinosaurs were sluggish cold-blooded animals like modern reptiles, but now evidence has emerged to show that at least some dinosaurs were warm-blooded. One piece of evidence comes from dinosaur footprints that show that some could run as fast as Olympic sprinters (up to 27 miles per hour). Cold-blood animals could not achieve such speeds.
Note: You can learn much more about dinosaurs in another Your Earth talk that can be downloaded here:
million years ago

42. Boom & Bust? (3): Birds Microraptor Archaeopteryx is a small
upload.wikimedia.org/wikipedia/commons/d/d6/SArchaeopteryxBerlin2.jpg
Microraptor
is a small
feathered
dinosaur
Archaeopteryx
is one of the
earliest known
birds
About 155 mya, birds evolved from dinosaurs. The similarity
between birds and dinosaurs has been recognized for 160 years.
Presenter notes: One of the most exciting recent revelations in the History of Life is that birds evolved directly from two-legged dinosaurs like T. rex about 155 million years ago. In fact some palaeontologists now refer to birds as ‘avian dinosaurs’. The similarity between birds and dinosaurs has been recognized since the 1840s but only recently has fossil evidence proved this relationship beyond reasonable doubt. Some dinosaurs have even been found with feathers!
Much controversy remains as to how birds evolved the ability to fly. Some scientists think the first birds hunted from the tree tops and developed wings to control descent when pouncing on prey from above. Others think they developed wings to help them run along the ground.
155 million years ago

43. Boom & Bust? (4): Mammals Mammals evolved about the Yanoconodon
same time as the dinosaurs,
220 mya, but lived in their
shadow for a 150 million years
Many were small, nocturnal
insect-eating animals. The need
to be active at night may be why
mammals are warm-blooded
Yanoconodon
Presenter notes: About the time that dinosaurs were starting out, another important group was also evolving: the mammals. The mammals lived in the shadows of the dinosaurs for 150 million years. Based on their skeletons, scientists think that many early mammals were small insectivores. They were also probably nocturnal, being active in the night to avoid being eaten by dinosaurs. This may explain why mammals independently evolved as warm-blooded animals. Not all mammals lived in this way, however. Some fossils from China show that certain dog-sized mammals actually preyed on and ate baby dinosaurs!
© Nicolle Rager Fuller, National Science Foundation
220 million years ago

44. Mesozoic Era
This era ended with a mass extinction event about 65 million years ago.
Many groups of animals, including the dinosaurs disappeared suddenly at this time.
Many scientists believe that this event was caused by a comet or asteroid colliding with the Earth.

45. Mesozoic Era – Mass Extinction Event
Asteroid or Comet collides with Earth.
Huge cloud of smoke and dust fills the air
Blocks out sunlight
Plants die
Animals that eat plants die
Animals that eat plant-eaters die.
However, not all forms of life died during this event. Many animals that you see today are descendants from the survivors of this extinction event.

46. Boom & Bust? (5): Deep Impact
NASA
NASA
Shocked quartz
The Crater of Doom
miac.uqac.ca/MIAC/qtz-chic.jpg
Around 65 mya, various lines of geological evidence suggest that
the Earth was hit by a 10 km meteorite, wiping out the dinosaurs
Presenter notes: We have already noted that there have been five mass extinction events on our planet since the invasion of land, 500 million years ago. Earlier we discussed the greatest of all extinctions that happened 251 million years ago. However, arguably a much more famous mass extinction occurred 65 only million years – the extinction that wiped out the dinosaurs and many other organisms. For years, there was great controversy as to what killed the dinosaurs but now scientists mostly agree that the likely cause was the impact of a 10 km diameter meteorite with the Earth. The evidence for a meteorite impact is compelling. One piece of evidence is the occurrence of quartz grains in rocks that date from the extinction of the dinosaurs that show fracture patterns characteristic of a massive explosion. More recently a 200 km diameter impact crater has been found in the Gulf of Mexico which shows exactly where the meteorite struck! This Crater of Doom is a lasting reminder of how vulnerable life is to extraterrestrial impacts. The meteorite would have caused global tsunamis and wildfires in the first few hours after impact but over the longer term the planet would have been plunged into a nuclear winter-like scenario with dust blocking out the light of the sun.
65 million years ago

51. Dinosaurs

52. Mesozoic Reptiles

53. Mesozoic Mammals

55. Mesozoic Plants
Flowering plants evolved towards the end of the Mesozoic Era.

56. Boom & Bust? (5): Deep Impact
NASA
NASA
Shocked quartz
The Crater of Doom
miac.uqac.ca/MIAC/qtz-chic.jpg
Around 65 mya, various lines of geological evidence suggest that
the Earth was hit by a 10 km meteorite, wiping out the dinosaurs
Presenter notes: We have already noted that there have been five mass extinction events on our planet since the invasion of land, 500 million years ago. Earlier we discussed the greatest of all extinctions that happened 251 million years ago. However, arguably a much more famous mass extinction occurred 65 only million years – the extinction that wiped out the dinosaurs and many other organisms. For years, there was great controversy as to what killed the dinosaurs but now scientists mostly agree that the likely cause was the impact of a 10 km diameter meteorite with the Earth. The evidence for a meteorite impact is compelling. One piece of evidence is the occurrence of quartz grains in rocks that date from the extinction of the dinosaurs that show fracture patterns characteristic of a massive explosion. More recently a 200 km diameter impact crater has been found in the Gulf of Mexico which shows exactly where the meteorite struck! This Crater of Doom is a lasting reminder of how vulnerable life is to extraterrestrial impacts. The meteorite would have caused global tsunamis and wildfires in the first few hours after impact but over the longer term the planet would have been plunged into a nuclear winter-like scenario with dust blocking out the light of the sun.
65 million years ago

57. Cenozoic Era – Recent Life
Began about 65 million years ago and continues today!!!!!
Climate was warm and mild.
Marine animals such as whales and dolphins evolved.
Mammals began to increase and evolve adaptations that allowed them to live in many different environments – land, air and the sea.
Grasses increased and provided a food source for grazing animals
Many mountain ranges formed during the Cenozoic Era
Alps in Europe and Himalayas in India; Rocky Mountains in the USA

58. Cenozoic Era
Growth of these mountains may have helped to cool down the climate
Ice Ages occurred late in the Cenozoic Era (Quaternary Period).
As the climate changed, the animals had to adapt to the rise and fall of the oceans caused by melting glaciers.
This era is sometimes called the “Age of Mammals”

59. Boom Bust? (6): Grass and Grazers
i.pbase.com/o4/15/700115/1/ sOPB0thD.serengeti2.jpg
Around 35 mya, climate became cooler and drier and grasslands
and grazing mammals became widespread
Presenter notes: Long after the extinction of the dinosaurs, climate became cooler and drier. Grasses that had evolved right at the end of the age of the dinosaurs spread over much of the world. The mammals that for so long had lived in the shadow of the dinosaurs became the dominant large animals on land. In particular, a variety of grazing mammals evolved, feeding off the grasslands of this increasingly modern-looking world. Grass contains a hard compound, silica and as mammals started to eat grass they had to evolve a battery of teeth that continued to grow throughout their lives. This was because the silica in the grass constantly ground down their teeth as they grazed.
35 million years ago

60. Cenozoic Era Marine animal examples: Land animal examples:
Algae, Mollusks, Fish and Mammals
Land animal examples:
Bats, Cats, Dogs, Cattle and Humans
Humans are thought to have appeared around 3.5 million years ago (during the most recent period – Quaternary).
Flowering plants were now the most common plant life.

61. Cenozoic Mammals

62. Boom & Bust? (7): Humans Cave art Neanderthal
en.wikipedia.org/wiki/Image:Neanderthal_2D.jpg
en.wikipedia.org/wiki/Image:Lascaux2.jpg
Cave art
Neanderthal
© Chris Stringer
Around 2 mya, humans evolved. They pioneered the use of fire
and tools to control their world, and developed society and culture
Presenter notes: As recently as 2 million years ago, our human ancestors evolved from primates, the group of mammals that include the apes. We belong to the genus, Homo. Today there is only one human species, Homo sapiens, which means “wise human”. However, earlier in our evolutionary history several human species lived side by side including Homo erectus (Upright Man) and Homo neanderthalensis (The so-called Neanderthal Man). Some major milestones in the evolution of humans included the ability to walk upright, the ability to use fire and tools to control the world around them, and perhaps most importantly of all, the development of society and culture. The walls of the famous Lascaux Cave in France are covered by paintings of animals and human hunters dating back more than 10,000 years and show that art had been born by this time.
2 million years ago

63. Flowering Plants were common during the Cenozoic Era

64. Today…
Today we are in the Holocene Epoch of the Quaternary Period of the Cenozoic Era.
Which unit is the largest?
Which unit is the smallest?

65. Boom &Bust? (8): Sixth Extinction
Following their evolution
humans have caused
huge species loss, and
this has accelerated in
since the 19th century
Are we now in the midst
of a sixth mass extinction?
NASA
Presenter notes: Shortly after the evolution of Homo sapiens in Africa, about 130,000 years ago, modern humans spread worldwide. Around 15,000 years ago many large mammals like the woolly mammoth started to go extinct and it is possible (though difficult to prove) that human hunting was responsible. As human society continued to develop, forests were cleared for agriculture, and the industrial revolution began, so the rate of extinction related to human activity increased. It is difficult to estimate the rate at which species are going extinct today but famous ecologist E.O. Wilson believes that half of all species will go extinct before We have already noted that there have been five mass extinction events over the past 500 million years. Given the facts, it seems unavoidable to believe that we are now in the midst of a sixth mass extinction.
Today