Origin of Life eon era periods explained.pptx

1. Origin of Life
On Earth

2. Geological time scale

3. Geological time scale

4. The Hadean Eon
The Hadean Eon is the earliest and shortest of the three eons of the Precambrian era and covers the time interval
between the formation of the Earth and the start of the Archean Eon, approximately 4 billion years ago.
During the Hadean Eon, the Earth was still in its early stages of formation, and the conditions were extremely harsh. The
Earth’s surface was constantly bombarded by asteroids, comets, and other debris, resulting in frequent impacts and the
formation of large craters. The early atmosphere was also composed of mostly hydrogen and helium, with little to no
oxygen, making it hostile to life as we know it today.
Despite these harsh conditions, the Hadean Eon was a critical time in the history of the Earth, as it set the stage for the
evolution of life. It was during this time that the first oceans formed, and the first minerals and rocks were created,
providing the building blocks for life to eventually emerge.
4.54 billion years ago to 4 billion years ago

5. The Archean Eon was a time of significant change and evolution in the history of the Earth.
During this time, the first single-celled life forms evolved and the first primitive
ecosystems were established. The Archean Eon also saw the formation of the first continents
and the first stable environments suitable for life.
One of the most significant events of the Archean Eon was the emergence of the first living
organisms. The exact origin of life on Earth is still uncertain, but the evidence suggests that life
evolved sometime during the Archean Eon. This was a major milestone in the history of the
Earth and represents a critical step forward in the evolution of life on our planet.
Archean Eon
4 billion years ago to 2.5 billion years ago

6. Proterozoic Eon
2.5 billion years ago to 541 million years ago
The Proterozoic Eon was a time of significant change and evolution in the history of the Earth.
During this time, the first multicellular life forms evolved, and the first primitive ecosystems
were established. The Proterozoic Eon also saw the first signs of plate tectonics and the
development of the first oceanic crust.
One of the most significant events of the Proterozoic Eon was the evolution of oxygen-
producing photosynthetic organisms, which eventually led to the buildup of free oxygen in
the atmosphere. This had a profound effect on the evolution of life on Earth and set the stage for
the evolution of complex life forms.

7. Phanerozoic Eon

8. Paleozoic Era
541 million years ago to 252 million years ago
1. Cambrian Period
2. Ordovician Period
3. Silurian Period
4. Devonian Period
5. Carboniferous Period
6. Permian Period

9. Cambrian Period
The Cambrian Period is particularly significant in the history of the Earth because it marks the
beginning of the “Cambrian Explosion”, a time of rapid diversification in the evolution of life on
Earth. During this time, the first complex life forms (arthropods, mollusks, and chordates), such as
trilobites, brachiopods, and mollusks, evolved. This was a major milestone in the evolution of life on
Earth and represented a significant step forward in the development of complex organisms.
The Cambrian Period was also a time of significant environmental change on Earth. This period saw
the formation of the first shallow seas, which were home to an incredible diversity of life. In
addition, the first continents began to form and the first land masses began to emerge
from the oceans.
541 and 485 million years ago
Age of Explosion

10. Ordovician Period
485 and 443 million years ago
The Ordovician Period was a time of significant change and diversification in the evolution of life
on Earth. During this time, the first jawless fish and primitive jawed fish evolved, which were
important steps in the evolution of vertebrates. This period also saw the evolution of the first
invertebrates with hard shells, such as trilobites, which dominated the oceans.
In addition to the evolution of early fish and invertebrates, the Ordovician Period was marked by
significant changes in the Earth’s environment.
Age of Invertebrates

11. The Silurian Period was a time of significant change and diversification in the evolution of life on
Earth. During this time, the first vascular plants evolved, which allowed for the colonization of
land by plants for the first time. This was a major milestone in the evolution of life on Earth and
paved the way for the evolution of land-dwelling animals in later periods.
The oceans of the Silurian Period were also home to a diverse array of life, (Jawless ostracoderms reach
their peak diversity) including the first armored fish, which were well-adapted to life in the ancient
oceans.
Silurian Period
443 and 419 million years ago
Age of Scorps

12. Devonian Period
419 and 359 million years ago
The Devonian Period is characterized by several
important events in the evolution of life on Earth. It
was during this time that the first jawed fish
evolved, which were a major step in the
evolution of vertebrates. The first tetrapods, or
four-limbed vertebrates, also appeared during the
Devonian Period.
The Devonian Period is also known as the “Age of
Fishes” because of the incredible diversity of fish
that evolved during this time, including the first
sharks, bony fish, and lobe-finned fish. This
diversity of fish helped to establish the oceans
as the dominant habitat for life on Earth.
In addition to the evolution of fish, the Devonian
Period was also marked by significant changes on
land. For the first time, plants evolved that
could survive out of water, including the first
ferns, mosses, and liverworts. This paved the
way for the evolution of the first land-dwelling
animals, including arthropods and the first
tetrapods.
Age of Fishes

13. Carboniferous Period
(359-299 million years ago)
Age of Amphibians as these creatures dominate land-based ecosystems.
•Key characteristics:
Giant Swamps: Warm, humid climates fueled the growth of vast swamp forests dominated by towering ferns, club
mosses, and horsetails. These lush ecosystems eventually formed the coal deposits we mine today.
Dominant Amphibians: Amphibians like the massive Eryops ruled the land, hunting insects and other smaller
creatures. Some even developed sails on their backs, hinting at possible adaptations for water temperature regulation.
Rise of Reptiles: From amphibian ancestors, the first reptiles emerged, paving the way for the age of dinosaurs in the
following Mesozoic Era. Early reptiles like Hylonomus were small and lizard-like, but laid the foundation for future
diversification.
Diverse Insect Life: The oxygen-rich atmosphere of the Carboniferous supported a thriving insect community. Giant
dragonflies with wingspans exceeding 2 feet (Meganeura) were some of the largest flying insects ever to exist.
Evolutionary Innovations: This period saw the development of several crucial evolutionary innovations, including the
amniotic egg (protecting embryos on land) and the ability to regulate body temperature (seen in early reptiles).

14. Mississippian Period
359 and 323 million years ago
The Mississippian Period is characterized by the growth of abundant vegetation on land, including
the first large trees, which changed the Earth’s ecosystems and provided habitats for new groups
of animals. During this time, the Earth’s climate was warm and moist, with high levels of
atmospheric oxygen, and the oceans were home to a diverse array of life.
One of the most notable events of the Mississippian Period was the evolution of the first land-
dwelling vertebrates, such as the tetrapods. Tetrapods, four-limbed first vertebrates were well-
adapted to life on land, where they could breathe air and escape predators.
The Mississippian Period also saw the formation of the first extensive coal-forming swamps,
which produced coal that would become an important energy source for humans in later periods.

15. Pennsylvanian Period
323 and 298 million years ago
One of the most notable events of the Pennsylvanian Period was the evolution of the first
amphibians, which were well-adapted to life on land and in water. Amphibians were highly diverse
and ranged in size from small, agile predators to large, herbivorous animals, such as Eryops.
The Pennsylvanian Period also saw the evolution of the first reptiles, which were small, terrestrial
animals that were well-adapted to life on land. These early reptiles eventually gave rise to the
dinosaurs and other groups of reptiles that dominated the Earth’s ecosystems during the Mesozoic Era.
Pennsylvanian Period is a critical time interval in the history of the Earth, characterized by
significant changes in the Earth’s ecosystems, the growth of vegetation on land, and the evolution of
amphibians and reptiles.

16. Permian Period
298 and 252 million years ago
The Permian Period is known for several defining events, including the formation of the
supercontinent Pangea (comprising all the present continents joined together) and the largest mass
extinction event in Earth’s history, the Permian-Triassic mass extinction event (wiping out nearly
96% of marine and 70% of land species).
During this time, the Earth’s climate was warm and arid, with high levels of atmospheric
carbon dioxide, and the oceans were home to a diverse array of life.
One of the most notable events of the Permian Period was the evolution of the first reptiles, which
became the dominant group of land-dwelling vertebrates..
The Permian Period also saw the decline of the dominant group of marine animals, the trilobites,
which were replaced by new groups of animals, such as ammonites and brachiopods and reef
forming organism.
Age of Reptiles

17. Mesozoic Era
252 million years ago to 66 million years ago
1. Triassic Period
2. Jurassic Period
3. Cretaceous Period

18. Triassic Period
252 and 201 million years ago
One of the most notable events of the Triassic Period was the Rise of early dinosaurs,
which became the dominant group of land-dwelling reptiles. Dinosaurs were highly diverse
and ranged in size from small, agile predators to large herbivores, such as Plateosaurus.
The Triassic Period also saw the evolution of the first mammals, which were small,
nocturnal, and insect-eating. The evolution of these early mammals had a significant impact
on the Earth’s ecosystems and led to the development of new habitats for animals.
Pangaea, the supercontinent, begins to break apart.
Gymnosperms (conifers) dominate land flora.
The recovery of life following the Permian-Triassic mass extinction event
Age of Reptiles

19. Jurassic Period
201 and 145 million years ago
Age of Dinosaurs
The most notable events of the Jurassic Period was the evolution of the dinosaurs, which became
the dominant group of land-dwelling reptiles. Dinosaurs were highly diverse and ranged in size
from small, feathered birds to large herbivores and carnivores, such as Stegosaurus and
Allosaurus.
The Jurassic Period also saw the evolution of the first birds, which were closely related to
dinosaurs and evolved from small, feathered theropod dinosaurs. The evolution of these early
birds had a significant impact on the Earth’s ecosystems and led to the development of new
habitats for animals.

20. The Cretaceous Period also saw the evolution of the first flowering plants, which quickly
diversified and became the dominant form of vegetation on land. The evolution of these plants
had a significant impact on the Earth’s ecosystems and led to the development of new habitats for
animals.
Giant sauropods like Brachiosaurus and Titanosaurus reach immense sizes.
Tyrannosaurs like T. Rex become apex predators.
Mammals evolve and diversify in small niches.
Angiosperms revolutionize ecosystems, providing new food sources for herbivores.
Cretaceous Period
Age of Flowering Plants" as angiosperms (flowering
plants) explode in diversity.
145-66 million years ago

21. Assignments:
1. Write classification of Dinosaurs? Why they
underwent mass extinction?

22. Cenozoic Era
(66 million years ago - present)
1. Paleogene Period
2. Neogene Period
3. Quaternary Period

23. Paleogene Period
66 and 23 million years ago
This period saw the aftermath of the mass extinction that wiped out the dinosaurs at the end of the
Cretaceous, allowing for the evolution and diversification of mammals.
One of the defining events of the Paleogene Period was the evolution of modern mammals,
including primates, rodents, and carnivores. These mammals took advantage of the new opportunities
created by the extinction of the dinosaurs and quickly diversified into a wide range of new species.
Rise of early primates, ancestors of humans and other apes.
Diversification of hoofed mammals (ungulates) and carnivores.
Evolution of whales and dolphins from land-dwelling ancestors.
Angiosperms (flowering plants) dominate land flora, providing diverse food sources.
“Dawn of Modern Life" as recovery from the dinosaur
extinction and radiation of new mammal and bird
lineages occurs

24. Neogene Period
23-2.6 million years ago
"Age of Mammals"
The Neogene Period is characterized by significant
changes in the Earth’s climate, as well as the
evolution and dispersal of many modern plant and
animal species. During this time, the Earth’s
climate became increasingly warmer, and the
continents began to take on their present-day
positions. This led to the development of new
ecosystems and the evolution of many new species
of plants and animals.
One of the most notable events of the Neogene
Period was the evolution of modern mammals,
including primates, whales, and elephants.
The evolution of these mammals was driven by
changes in the Earth’s climate and the formation
of new ecosystems.

25. Assignments:
2. Why few mammals went back to ocean?
(Name mammals of oceans, fossil records of
intermediate species and why they moved
back discuss)

26. Quaternary Period
2.6 million years ago - present
"Ice Age Period" due to recurring glacial cycles
significantly impacting landscapes and life.
The Quaternary Period is characterized by significant changes in the Earth’s climate, as well as
the evolution and dispersal of modern human civilizations.
One of the defining features of the Quaternary Period is the presence of multiple ice ages, during
which large portions of the Earth’s surface were covered in ice. During the ice ages, the Earth’s
climate was much colder than it is today, and sea levels were much lower. These changes had a
significant impact on the distribution of plants and animals, as well as the evolution of human
civilizations.
Another key event of the Quaternary Period was the evolution of modern human species, such as
Homo sapiens, and their dispersal across the Earth. During this time, human populations developed
sophisticated technologies and societies, and they began to have a significant impact on the natural
world.

27. The Quaternary began about 2.6 million years ago and stretches to the present day.
Throughout this period, the Earth has experienced alternating cycles
of glacial and interglacial periods.
 During glacial periods, vast ice sheets cover significant portions of land, particularly in the
Northern Hemisphere. These periods can last for tens of thousands of years.
 In interglacial periods, like the one we're currently in (the Holocene), the ice sheets shrink
significantly, revealing more landmass.
It's these repeated glacial cycles, especially the vast ice sheets characterizing them, that
earned the Quaternary the "Ice Age Period" nickname. However, it's important to understand
that:
We are currently not in a glacial period. We've been in the Holocene interglacial for the past
11,700 years.
Even during glacial periods, not the entire planet is covered in ice. The equator and some other
regions remain ice-free.
•The Quaternary has seen its share of warmer periods between glacials, emphasizing the
cyclical nature of the phenomenon.