History of Life on Earth

• Formation of Universe - approx 13.7 billion years ago

• “A Geological time scale - Arrangement of entire life span of earth - ~ 4.5 billion years ago
• Divided into intervals - Basis of fossils present in rocks & age determination (carbon
dating) - Giovanni Arduino (1760)
• Origination of life - ~ 3.8 billion years ago
• Major divisions - Eras - Periods - Epochs

• Rocks of earth — 1. Primary (Oldest)

2. Secondary (Intermediate)
3. Tertiary (Youngest)
• Geological time scale gives an idea of sequence of events in history of Earth
• Eons - Largest division - Consisting of two or more eras
• 1. Cryptozoic Eon (Precambrian Eon) - The period of rarity of life and absence of fossils
(not available)
• Characterised by absence of life or presence of simple living forms whose fossils are not
available.
• a. Azoic Era
• b. Archeozoic Era
• c. Proterozoic era
• 2. Phanerozoic Eon (Gk. phanero = visible + zoon = life) - Period of visible forms and
abundance of their fossils.
• a. Palaeozoic era
• b. Mesozoic era
• c. Coenozoic era
• Geological time scale -
• 1. Azoic era - Time of no life - Earliest form of earth
• 2. Archeozoic era - Time of beginning of life - ~ 3,600 million years ago
• 3. Proterozoic era - Time of earliest life - ~ 1,600 million years ago
• 4. Palaeozoic era - Time of ancient life - ~ 600 million years ago
• 5. Mesozoic era - Time of middle life - ~ 230 million years ago
• 6. Coenozoic era - Time of recent life - ~ 63 million years ago
 Periods
• The names of most periods derived from the names of the areas in which the rocks were
first studied and described.

• The geological time scale includes 12 periods as follows:

Periods of Palaeozoic Era
1. Cambrian - L. Cambria = Wales (country) - 600 million years ago (m.y.a.)
2. Ordovician - Ancient tribe (Ordovices) lived near the ancient Wales - 500 m.y.a.
3. Silurian - From the Silures, an ancient tribe of Wales - 425 m.y.a.
4. Devonian - From Devonshire, County in England - 405 m.y.a.
5. Mississippian - From the upper Mississippi valley (U.S.A.) - 345 m.y.a.
6. Pennsylvanian - From the state of Pennsylvania (U.S.A.) - 320 m.y.a.
7. Permian - From the province of Perm in Ural Mountains of Russia - 280 m.y.a.
 Periods of Mesozoic Era
8. Triassic - L. trias, meaning three, refers to the natural three fold division of these rocks
in Germany - 230 m.y.a.
9. Jurassic - From the mountains between France and Switzerland - 180 m.y.a.
10. Cretaceous - L. Creta, meaning chalk, refers to chalky limestone - 135 m.y.a.

Periods of Coenozoic Era

• 11. Tertiary - 63 m.y.a.
• 12. Quaternary - 1 m.y.a.

Three fold rock

 The Epochs
• The subdivisions of the periods — Epochs
• Epochs usually represent the upper, middle and lower parts of a period.
• Coenozoic era -
• (a) Tertiary period -
• (i) Paleocene epoch - ~63 million years ago - Duration 5 million years
• (ii) Eocene epoch - ~58-60 million years ago - Duration 22 million years
• (iii) Oligocene epoch - ~36 million years ago - Duration 11 million years
• (iv) Miocene epoch - ~25 million years ago - Duration 12-13 million years
• (v) Pliocene epoch - ~13 million years ago - Duration 12 million years (Man is originated)

• (b) Quaternary period -

• (i) Pleistocene epoch - ~1 million years ago - Ended during 8,000 to 10,000 BC
• (ii) Recent epoch - ~10,000 BC ago - Recent period
 1. Azoic Era (Time of no life)
• Earliest time in the history of Earth

• Complete absence of living organisms

• During this period — Earth was formed, cooled many changes created conditions favourable
for appearance of living organisms

• Rocks - Only Igneous type & devoid of fossils

 2. Archeozoic Era (Time of beginning of life)
• Beginning — About 3,600 million years ago
• Duration — About 2,000 million years
• Geological Conditions — Great volcanic activities & a time of storms and extensive
erosion.
• The rocks of this era are very deeply buried
• On account of excessive heat and pressure along with the catastrophic activity — most of
the fossils were destroyed
• Life: The early organisms in these rocks - Simple, unicellular organisms having soft body.
• No recognisable fossils
• Indirect evidence of living things - From some sedimentary deposits of organic material
in rocks
 3. Proterozoic Era (Era of former life)
• Beginning — About 1,600 million years ago
• Duration — About 500 million years
• Geological Conditions — Deposition of large amount of sediment Sedimentary rocks
• Lava flowed — Due to numerous volcanic eruptions
• There was at least one period of glaciation
• Life — The fossils found from the rocks of Proterozoic Era indicate that not only the
life was present but had reached great complexity
• Algal filaments, fungi, sponge spicules, jellyfishes and worms are represented by fossils
(Marine invertebrates)
• The first organisms were soft-bodied with few or no hard parts that could be converted into
fossils — Hence, fossils are poorly represented
• The Proterozoic Era ended by the Killarney Revolution which resulted in the worldwide
continental uplift, mountain building activity and erosion

• Revolution - Large scale widespread geological disturbances

- Each era was ended by revolutions
- Disturbance of earth surfaces in certain regions — to form mountains
- Lowering of land in other regions - Resulted in formation of inland seas
- Changed the distribution of sea, land and organisms living there
- Wiped many of previous forms — Causing Major extinction
• Disturbances - During each era - Lesser widespread geological disturbances
- Divided an era Periods & Epochs
 4. Palaeozoic Era (Time of ancient life)
(Gk - Palaios = ancient; zoe = life)
• Also called 'the cradle of ancient life’
• Beginning — About 600 million years ago
• Duration - About 370 million years
• Ended by about 230 million years ago

• Very extensive fossil records

• Reflect the prevalence of different plants and animals both in sea and on land
• Almost all major invertebrate phyla are represented even in the early Palaeozoic Era
• Fossils of first vertebrates appeared late in the era (Armoured jawless fishes)
• Reason - Early chordates were soft bodied and were not preserved in the form of
fossils
• The Palaeozoic era has been divided into seven periods

1. Cambrian - L. Cambria = Wales (country) - 600 million years ago (m.y.a.)

2. Ordovician - Ancient tribe (Ordovices) lived near the ancient Wales - 500 m.y.a.
3. Silurian - From the Silures, an ancient tribe of Wales - 425 m.y.a.
4. Devonian -From Devonshire, County in England - 405 m.y.a.
5. Mississippian - From the upper Mississippi valley (U.S.A.) - 345 m.y.a.
6. Pennsylvanian - From the state of Pennsylvania (U.S.A.) - 320 m.y.a.
7. Permian - From the province of Perm in Ural Mountains of Russia - 280 m.y.a.

•
 4.1 Cambrian Period
(Named after Cambria, the Latin name for Wales)
• The earliest subdivision of Palaeozoic Era
• Named as 'Cambrian' by Adam Sedgwick - 1835
• Because the rocks of this period were first discovered in the City of Wales
• Beginning - About 600 million years ago
• Duration - About 100 million years.
• Climate: The Cambrian Period started with the melting of glaciers, slow rise of sea level
and warm climate.
• The oceans flooded inland and as a result North America was under sea in Cambrian
Period.
• In other continents also the major land areas were under sea water
• Flora and Fauna - Fossils are in abundance but are represented only by marine plants
and animals.

• There is no direct evidence of existence of land plants and vertebrates

• Fossils of marine algae are widely distributed.

• Period ended by Green Mountain Disturbances and mountain formation in European

continent
 4.2 Ordovician Period
(Named after Ordovices, a tribe natives of ancient Wales)

• The name was proposed by Charles Lapworth in 1876 to commemorate the Ordovices
• Beginning - About 500 million years ago
• Duration - About 75 million years
• Climate: Warm with glacial activities in certain regions
• Continents were flooded with shallow sea
• Volcanic activities were abundant in eastern North America
• The period ended by Tectonic disturbances in eastern North America leading to the
formation of Tectonic Mountains
• Flora and Fauna - First vertebrates in the form of armoured jawless fishes, called
Ostracoderms, which were dwelling in the freshwater rivers
• The first corals appeared in Ordovician Period and started their reef building activities
• Life flourished in ocean
• Fossils of land animals - not recorded
 4.3 Silurian Period

(Named after Silures, a tribe natives of ancient Wales)

• Proposed by Murchison in 1835

• Beginning — ~ 425 million years ago
• Duration — ~ 20 million years
• Climate — Mild and some areas were arid
• The sea alternately advanced and retarded during this period and volcanic activities took
place
• The period ended by Caledonian disturbance in Europe and resulted in the rise of
Caledonian Mountains in British Isles, Scandinavia, North Africa and East Central Asia
• Flora and Fauna — Appearance of first land plants (Ferns - Don’t have flowers) and air
breathing animals (scorpion like arthropods - Eurypterids)
 4.4 Devonian Period

(Named after Devonshire, County in England)

• The name Devonian' was proposed by Sedgwick and Murchiso in 1839
• ‘Age of Fishes’
• Beginning — About 405 million years ago
• Duration — About 60 million years
• Climate — Mild with local dryness
• Great volcanic activities, formation of coal, oil and gas
• Ended by a localised Acadian Disturbance (USA)
 Flora and Fauna
• The land plants became abundant
• The trees in late Devonian were very tall measuring 30 to 40 feet in height
• The animal life still thrived abundantly in the sea only
• The corals continued their reef-building activities
• Crinoids (sea lilies) and starfish occurred in abundance
• The ammonites, a special group of cephalopods, first appeared in this period
• The Devonian Period is known as the Age of Fishes - Fossil records revealed the existence
of numerous and varied fish indicating their abundance and diversification in this period.
• True sharks (Chondrichthyes) appeared in freshwater during Devonian Period but
migrated to the ocean.
• Ancestors of bony fishes - also appeared in freshwater streams

• By the middle of Devonian Period they diverged into three main forms:
• Lungfish, Lobe-finned fish and the Ray-finned fish

• The Devonian ancestors of modern lung-fish - Able to survive dry periods by burrowing in
the moist beds of streams or lakes because they could take air through their nostrils (Air
breathing) and their air bladder was modified into lung. E.g., Lepidosiren (Extant)
• The lobe-finned fish (Crossopterygians), are characterised by the possession of lobed or
fleshy rounded bases of the paired fins.
[Ray-finned fishes - Fins supported by thin spines or rays.
Lobe-finned fishes - Muscular, bone-filled fins (and early tetrapods)], resemble stump-like
appendages
• E.g., Latimeria (Extant)
• They were on the direct line of evolution from fishes to land vertebrates.

Latimeria
• The ray-finned fish ramified in Mesozoic Era and gave rise to modern living genera of
bony fishes.
• The late Devonian period - appeared first land vertebrates
• They are amphibians - Stegocephalia (4 legged creatures with roof - head) (Skull covered
by bony armour)
• Eg : Ichthyostega

Eusthenopteron

Ichthyostega
 4.5 Mississipian Period or Lower Carboniferous Period

(Named after Mississippi valley (U.S.A.))

• The name Mississipian was proposed by Alexander Winchell in 1869
• Excellent rock formations - Found in Eastern Mississipi basin
• Lower Carboniferous because - Characterised with major coal deposits of the world
• Beginning: About 345 million years ago
• Duration: About 25 million years
• Climate: The climate was warm & dry with dessert conditions.
• Excellent rock formations - found in Eastern Mississipi basin
• The Earth was thickly covered with plants (Ferns, spore-bearing trees, primitive seed
plants)
• In the dense forests the animal life - abundant
• Fossils of salamander - like amphibians have been uncovered from swamps.
• The sharks were most abundant and a particular group of 'Shell-crushing sharks' reached
the highest stage of development.
• Their teeth were adapted for crushing the shells of molluscs and arthropods.
 4.6 Pennsylvanian Period or Upper Carboniferous
• Beginning - about 320 million years ago
• Duration - about 40 million years
• Term "Pennsylvanian" - used by H.S Williams in 1819
• Pennsylvania - State of USA
• Climate - Mild and Wet - became cold with local glaciation
• Numerous mountain disturbances occurred all over the word which were suggestive of
Appalachian Revolution.
• Climate was most suitable for the spread of swamp vegetation which resulted in
the formation of extensive coal beds
• Mississipian and Pennsylvanian Periods are often combined together
and are collectively designated as Carboniferons Period (coal forming)
 Flora and Fauna
• Land flourished with luxuriant plant growth
• Trees attained height over 100ft
• Insect - Abundant (Dragon flies, Cockroaches etc attained maximum size)
• Amphibians - abundant
• First reptile - Stem reptile appeared
• Seymouria from Texas - Amphibian ancestor of reptiles
(Seymouria - Lizard like but exhibit similarities with salamander (Amphibian))

Seymouria
 4.7. Permian Period
• Period of Perm - a Russian Province
• Fossil rocks in this period found in Russian province of Perm
• "Permian" - Introduced by Murchison in 1841
• Beginning - about 280 million years ago
• Duration - about 50 million years
• Climate: End of Palaeozoic Era. It was characterised by great changes in the climate
(Colder and drier) as well as the topography
• Widespread glaciation occurred in Southern Hemisphere that extended from Antarctic to
the Equator in Brazil and Africa
• The sea retreated and continents uplifted all over the world.
• At the end of Permian Period general uplifting of the great mountain chain from Nova
Scotia to Alabama took place which marked the Appalachian Revolution.
• Flora and Fauna: The swamp dwelling plants were replaced by more hard and woody
plants.
• The true Conifers and Cycads - Most abundant and trees
• Marine animals - Similar to those of the two preceding periods
• Trilobites (Invertebrates) - Disappeared completely
• Crinoids (Feather star) - Became rare Conifers
• Spiny-shelled brachiopods declined by the end of Permian Period.
• Ammonites became still more numerous and diversified into several new forms.

Trilobites
Brachiopods Cycads
Crinoids
• Permian insects were similar in size
• New genera of Mayflies, beetles, dragon flies were added.
• Fishes were still abundant in sea - Freshwater fishes more prominent
• Labyrinthodont amphibians still thrived in swamps.
• The reptiles - Progressive development Fossils of Mayflies - Brazil

• A group of mammal-like reptiles, the Therapsids also arose in Permian Period

• Many of the Palaeozoic forms - Perished and became extinct, because they could not adapt
themselves to such drastic changes in the climate.
• Even many of the marine forms also disappeared owing to the cooling of the water and
decrease in sea area

Therapsids
Labyrinthodont amphibians
 5. Mesozoic Era (Era of Intermediate Life)
(Time of middle life)
(Gk - Meso = middle; zoe = life)
• Beginning - 230 million years ago
• Duration - 167 million years

Features
• Disappearance of ancient amphibians and their replacement by reptiles
• Final extinction of numerous variety of reptiles - Dinosaurs (thrived in sea, on air and on
land)
• Mesozoic era - Age of Reptiles
 Flora
• Time of transition from aquatic to terrestrial life
• Diversification in both plants and animals
• Plants such as seed ferns, Lycopods and horsetail which were common in Permian periods
Mass extinction Became insignificant in Mesozoic Era
• Medium-sized ferns, cycad-like plants and coniferous plants Replaced

• Gymnosperms and Angiosperms Appeared in the late Mesozoic

Seed ferns - Extinct Lycopods Horsetail

 Fauna
The Mesozoic animal life can be discussed under followings heads:
• 1. Culmination of cephalopods
• 2. Evolution of reptiles
• 3. Origin of birds
• 4. Origin of mammals

1. Culmination of Cephalopods:
• Ammonites — Dominant invertebrate fauna of Mesozoic oceans
• > 6,000 species of ammonites have been described
• Ammonites saw the culmination in Jurassic Period, but diminished in number
during Cretaceous Period - and completely destroyed by the end of Mesozoic Era
• Other Invertebrates
• Modern squids and Octopus - Abundant
• Gastropods, Pelecypods and Cephalopods - More diversified
• Even freshwater clams and gastropods were plentiful
• Air breathing snails became equally numerous.
• Arthropods attained much diversity
 2. Evolution of Reptiles
• Culmination of Reptiles Attained supremacy Rulers of Earth — Hence
this time period “Age of Reptiles”
• About a dozen different orders of reptiles evolved Dominant position on Earth, in
air and sea.
• Some walked on 4 legs/ 2 legs with the body balanced with a long tail
• Some were herbivorous, other were carnivorous
• Size — Ranged from small size to over 100 feet in length
• Arboreal reptiles, Aerial reptiles, Amphibious reptiles, Aquatic reptiles etc
 Dinosaurs
• Terrible lizards
• Lived on Earth - 200 million years ago (long before the first man appeared on this Earth)
• Ruled the Earth - for more than 100 million years
• Lived on all continents - Max. number dinosaur fossils - Argentina, China, Canada and
USA
• First dinosaur fossils recored from Antarctica - 1990-91
• Cryolophosaurus ellioti — Theropod dinosaur (Bipedal) that lived in Antarctica during the
Early Jurassic period, 199.3–182.7 million years ago.

•
 5.1. Triassic Period (Period of three fold division)
• Beginning - About 230 million years ago
• Duration - About 50 million years
• 'Triassic' was coined by Von Alberti (German geologist) for the striking three fold division
of contrasting rocks of Germany
• Climate: Harsh and dry
Flora:
• Forests — Highly developed Gymnosperms (Non-flowering) — Conifers and cycads
• Seed ferns became extinct
Fauna:
• The primitive amphibians (Stegocephalians) became extinct
• The dinosaurs appeared as very small lizard-like forms Grow enormously Size and
number Lived ~150 million years The rulers of Earth
 5.2 Jurassic Period (Period of Jura Mountains in France)
• Beginning: About 180 million years ago
• Duration: About 45 million years
• Jurassic Period gets its name from mountains which lie between France and Switzerland
• Name first used Von Humboldt (1799)

• Climate:
• Comparatively mild than found in Triassic Period
• Warm & humid and with plenty of rainfall

• Flora and Fauna:

• Conifers, cycads and ferns — Widespread
• Angiosperms (flowering plants) — appeared for the first time.
• Other animals — Lizards and crocodiles
 5.3 Cretaceous Period (Period of Chalk)
• Beginning: About 135 million years ago
• Duration: About 72 million years
• Latin word creta, meaning chalk
• Coined by J. J. d' Omalus d' Halloy (1882)
• Climate:
• Warm & uniform over most of the Earth surface — But became cooler later
• The period ended by Laramide Revolution
 Flora
• The flowering plants spread all over the world
• Deciduous trees — Abundant and dominant
Fauna
• In the sea — Modern forms of Sharks and bony fishes
• Abundant dinosaurs — Majority — Vegetarians
T. rex
— Few — Giant carnivores
• The largest flesh-eater of the period — Tyrannosaurus rex 'Tyrant Lizard King’.
• Pterodactyls (Flying reptile) and Plesiosaurs (Marine reptile) — Attained largest size
• Mesosaurus (Sea lizard) — Most abundant

Pterodactyls Mesosaurus Plesiosaurs

• Snakes — First appeared
• New varieties of birds appeared
• Fossils of Hesperornis and Ichthyornis are found from Cretaceous rocks.
• Mammals were still small and less numerous
• Prototherians - Having long heavy tail, short pentadactyl limbs - Egg laying mammals
• Prototherians Marsupials (Pouched mammals) & Eutherians (Placental mammals)
• The first placental mammals (Juramaia sinensis) were small and subsisted on insects and
worms.

Ichthyornis

Platypus
Kangaroo Hesperornis
• The Laramide Revolution brought the end of Cretaceous Period and the Mesozoic Era.
• It is accompanied by world wide mountain-building activities —
• Dropping temperatures Colder & drier A number of plants
disappeared (which served as food for the herbivorous reptiles)
• Disappearance of herbivorous reptiles (Due to absence of food) Extinction of large-
sized carnivorous reptiles
6. Coenozoic Era (Era of Recent Life)
• “Age of Mammals” - Diversification of different mammalian group
• In addition - Diversification in birds, insects and the culmination of angiosperms
• This era divided into 2 periods
• Tertiary
• Quaternary
6.1. Tertiary period
• Beginning - 63 million years ago
• Duration - 51 million years
• Name coined - Giovanni Arduino (1760)
• Contained fossils resembling those animals which are still in existence or else are
represented by forms closely allied to them
 Climate
• Fairly warm Gradually Colder
• Period ended by Cascadian Revolution (Tectonic plate movement — Volcanic activity, Igneous intrusion) -
Widespread mountain building activities Mountains attained present extent and shape
Flora
• Hardwood trees and conifers of today - Were present in the beginning of this period
• Grassland appeared
Fauna
• Rise in mammalian population
• Mammals (early tertiary period) - Small, short legged and flat footed, jaws relatively longer, limited brain
capacity
• During span of tertiary period ——— Increase in size in various groups, Teeth — More specialised for varied
feeding habits, Brain capacity increased
• Mammals — More and more specialised
• Advanced modern placental mammals - Man like forms (First Ape Man - Australopithecus) appeared - Africa
 Tertiary period —— 5 Epochs
1. Paleocene
2. Eocene
3. Oligocene
4. Miocene
5. Pliocene
Brachiopods Creodonts
6.1.1. Paleocene Epoch
• Beginning - 63 million years ago
• Duration - 5 million years
• Climate - Ideal for mammals, mild climate
• Life - Brachiopods (similar to bivalve) had undergone their peak development
• Primitive mammals
• Creodonts - Carnivores were first represented by an ancient group — Ranged from small Large bear.
Claws - Sharp and well developed. Teeth - Not specialised like modern carnivores
• They extinct by the end of Eocene
 6.1.2. Eocene Epoch
Beginning - 58 million yers ago
Duration - 22 million years
Climate - Slightly cooler, mountains eroded
Flora - Flowering plants (angiosperms) - Abundant and successful
• Fossil indicated - Many of modern genera of plants like maples, dogwoods, walnuts etc were in existence
Fauna
• Archaic mammals/ Prototherians (Monotremes - Highly specialised egg laying mammals - Platypus &
Echidnas) were existing
• Diversification of placental mammals
• By the end of Eocene - Modern mammals came into existence
• Ancestors of camel, pig, horse, rat and monkey were present
• Mammals - Whales and sea cows returned to sea
 6.1.3. Oligocene Epoch (a little modern)
Beginning - 36 million yers ago
Duration - 11 million years
• Geological conditions and Climate - Erosion of land continued and climate slightly cooler

Flora
• Monocots (Grass like plants) increased and flowering plants flourished
Fauna
• Archaic mammals - Mostly extinct
• Eutherian mammals (placental) became still more numerous
• Horse (this epoch) - 3 toes (Currently single toes)
• Rhinoceros - Attained larger size
• Archaic carnivores like creodonts - continued to exist
• Anthropoid apes (like Gorilla, Chimpanzee) - Appeared (No tail, elongated arms and highly
developed brain)
• Turtles, crocodiles and alligators - attain their greatest development

6.1.4. Miocene Epoch

• Beginning - 25 million years ago
• Duration - 12 to 13 million years
• Geological conditions and climate - Alps mountain ranges reached their height and
Himalayas were pushed up
• Some regions became dry and arid while others cooler and wetter.
• Also general lowering of temperature
 Flora
• As climate became cooler - Deciduous tree - More abundant
Fauna
• Carnivores, rodents, elephants, bats, whales and dolphins were well abundant
• Appeared Proconsul (Extinct - Fossils in Eastern Africa (Kenya, Uganda)) - Presumed to be the
ancestor of man and apes.
6.1.5. Pliocene Epoch
• Beginning - 13 million years ago
• Duration - 12 million years
• Geological conditions and climate - Cool and temperate climate away from equator
• Continuous rise of mountains of western north America
Flora
• Tulips and magnolia trees - Extinct from Europe
• Grassland - more widespread
 Fauna
• Placental mammal - Closely approximated modern species
• Elephants were most numerous
• Wild horses - Abundant
• Horses - Evolved into one toed form
• Deers and antelopes - Abundant
• Man like forms appeared in pliocene
• Australopithecus - First ape man discovered from rocks of pliocene
 6.2. Quaternary period
• Duration - 1 million year
• Climate - Characterised by 4 periods of glaciation between which sets of ice retreated
(interglaciation - Interglacial period marked by warm climate) - These described as 4 epochs
of ‘Ice Age’ - Last ‘Ice Age’ ended by about 10,000 years ago
• Buffalos became abundant — Bison latifrons became giant (Later extinct)
• Most important event - Rise of man who became master of earth
• His success - Due to erect posture which freed his arms and hands and a large brain
• This period is Age of Man

Quaternary period - 2 epochs (Pleistocene and Recent)

 6.2.1. Pleistocene Epoch
• Beginning - 1 million years ago
• Ended - 8 to 10 thousand years B.C
• Unusual solar activity and repeated glaciation - Ice formed in the polar regions and the mountains in the
temperate parts and high altitude
• Ice retreated during interglacial period - It left lakes like Swiss Lake, English Lake and Great Lakes
between Eastern Canada and US
Flora
• Herbaceous plants continued to evolve
Fauna
• Pleistocene mammals - Saber toothed tigers, mammoths, wolves, true horses attained very large size
• Saber toothed tiger, ground sloth - Could not withstand cold - Became adapted to cold climate by
developing hair or woollen fur.
• Fossils of ancestral forms of men and apes - found in Pleistocene rocks
 6.2.2. Recent Epoch
• The period of last 10,000 years of Earth’s history
• Time after last glaciation
• Ice retreat - Forest spread over in Europe and North Africa
• Desert grew up
• New vegetation of herbaceous plants become dominant
• The modern species of man, Homo sapiens evolved