Fossils provide important information about past plant and animal life on Earth. They form through a process called fossilization when remains become buried in sediment and over time the sediment hardens into rock, preserving the remains. There are many types of fossils including body fossils, trace fossils, molds/casts, and carbonized or permineralized fossils. The geological time scale maps Earth's history in distinct periods based on fossils and rock layers. Key periods include the Paleozoic, Mesozoic, and Cenozoic eras. Fossils are important for understanding evolution and how life has changed over geological time.

1. Palaeobotany: Plant life through ages, Geological time table, Fossils -
definition, types, process of fossilization, factors for fossilization,
Importance.

3.  The word, ‘Fossil’ derived from the Latin word, ‘fodere ’ means ‘to dig’. Due
to sudden changes on the earth by means of the different geological process s
with the passage of evolution parallel to the earth’s flora & fauna, plants and
animals lie on the rocks millions years back and the remnant of the plants and
animals are excavated treated as fossil. Thus, it indicates about the climate and
environment of the geologic age experienced by the earth.
 The scientific study of the fossils of the plants preserved in the rock are
generally termed as Paleobotany and it also addresses the preserved vestiges of
plant life in the geological past. Therefore, paleobotanical studies rely on those
naturally preserved materials, the fossils which are usually available in the
different rock strata, especially on the sedimentary rocks as the relics of the
ancient past vegetation.
 Paleontology is a branch of biology that studies fossils of all organisms such as
plants, animals and microbes , which existed on the earth’s surface , millions
and millions years ago.
 The study of how the organisms or their parts became fossils are called
Taphonomy and the Taphonomic pathways can establish how the plants and
animals undergo fossil.

5.  Geologic time scale (GTS) is a means of mapping history of earth since its
inception and it is an essential tool for the understanding the geological
history of the earth experienced with the passage of time.
 Soon after the discovery of radioactivity, GTS was first proposed by Arthur
Holmes ( 1890-1965) and it was calculated the 400 million years of old
earth existence.
 Stratigraphy of the earth on the basis of the sedimentary rocks deposited
layer after layer is treated as the framework for the construction of the GTS
Generally deeper the rocks, older the layer with old fossils along with the
observations of the earth’s magnetic field show different magnetic fields in
rocks from the different geologic age.
 Radioactive dating technique provides the direct evidence of the sequence
of events on the rock.
 The construction of geological time table indicates the successive layer
formation.

6.  Radioactive dating is a method of dating rocks and minerals using
radioactive isotopes. This method is useful for igneous and metamorphic
rocks, which cannot be dated by the stratigraphic correlation method used
for sedimentary rocks. Over 300 naturally-occurring isotopes are known.
Among the best-known techniques are radiocarbon dating, potassium–
argon dating and uranium–lead dating. Potassium-Argon (K-Ar) dating is
the most widely applied technique of radiometric dating. Potassium is a
component in many common minerals and can be used to determine the
ages of igneous and metamorphic rocks. The Potassium-Argon dating
method is the measurement of the accumulation of Argon in a mineral. As
its name implies, radioactivity is the act of emitting radiation
spontaneously. This is done by an atomic nucleus that, for some reason, is
unstable; it "wants" to give up some energy in order to shift to a more
stable configuration. A material's radioactivity is measured in Becquerel
(Bq, international unit) and curies (Ci, U.S. unit). This is very convenient
on the basic law of radioactivity that measures the ratio of proton: neutron
> 1.5.

7.  The GTS is comprising of the following units:
 Eon- Two or more geological eras formed Eon,
 Era- comprising of two or more periods,
 Periods-Basic part of geological time in which single type of rock system is
formed,
 Epoch- division of geologic period , expands million years,
 Age- Unit of geological time distinguished by some features like ‘Ice age’.
 Eon → Era → Periods → Epoch → Era (descending order)
 The modern GTS comprising of four “Eons”- Hadean ( 4.6-3.9 Bya),
Archeozoin (3.9-2.5 BYA), Proterozoic eon ( 2.5 BYA-540 Million Years
age , MYA), Phanerozoic eon (540 Myra to till date).
 Hadean Eon is symbol of volcanism & explosions,
 Archeozoic Eon- Reducing free oxygen first time,
 Proterozoic Eon comprises Colonial algae, soft bodies Invertebrates called
age of hidden life,
 Phanerozoic Eon- Paleozoic, Mesozoic & Cenozoic , eon of advanced life.

8.  1. The Paleozoic Era ( 540-248 Mya)- Ancient age of Earth's life lasted up
to 292 Mya , divided into seven periods-
 The Cambrian ( 540-500 Mya)- the age of Trilobites
 The Ordovician (540-438 Mya)-Primitive plants like Bryophytes appeared
 The Silurian ( 438-408 Mya)-First vascular plants & Arthropods
 The Devonian ( 408-360 Mya)-Land plants, Fishes, Shark, Mollusks age
 The Mississippian (360-325 Mya)-
 The Pennsylvanian (325-280 Mya)
 The Permian ( 280-248 Mya)
 According to recent modification, the Mississippian and Pennsylvanian
have been to Carboniferous period- coal age
 The Permian is the age of Gymnosperms , amphibians, massive spread of
conifers; ended with the mass extinction largest moss, Trilobites went into
extinction, Seed ferns became extinct.

9.  Mesozoic (252-66 million years ago) means 'middle life' and this is the
time of the dinosaurs. This era includes the Triassic, Jurassic, and
Cretaceous Periods, names that may be familiar . It is the middle age of life
, often termed as age of reptiles, lasted for approximately 183 Mya, divided
into three periods-
 Triassic- ( 248-208 Mya), appearance of first Dinosaurs and mammals,
abundance of turtles, appearance of Cycads.
 Jurassic (208-146 Mya)-significant for reptiles, appearance of first bird,
Arceopteris; many ferns, ginkgo, conifers & cycads.
 Cretaceous ( 146-65 Mya)- first placental animals with the primitive
flowering plants like Magnolia, Ficus along with the development of other
groups like Ferns, horsetails , Cycads & ginkgo etc, ager of reptiles came
to an end and the age of mammals begin due to the climate change.

10.  Ceno’ means ‘recent’ and ‘zoic’ means ‘life’; the recent age from 65 Mya
to today.
 Two periods- Tertiary & Quaternary
 TERTIARY (65-1.8 Mya) divided into two-Paleogene & Neogene
 Paleogene divided into three epochs comprising-
 A. Paleocene epoch (65-54 Mya) –evolved first large mammals and
primitive primates,
 B. Eocene ( 54-38 Mya)- Appeared first rodents and whales with abundant
mammals,
 C. Oligocene (38-24 Mya)- Grasses common with the appearance of cats,
Deer, Rhinos
 NEOGENE (24-1.8 Mya) consists two epochs-
 Miocene (24-5 Mya)- appearance of Horses, dogs, Bears, Modern birds,
Monkeys, apes,
 Pliocene (5-1.8 Mya)- Modern whales and first Hominids appeared

11.  Ii. Quaternary Period (1.8-today) called the age of man comprising of two
epochs- Pleistocene Epoch (1.8 Mya- .011 Mya) & Holocene Epoch
(11000 Yrs ago).
 A. Pleistocene Epoch ( 1.8-.011 Mya) called Great Ice age, sudden fall of
temperature, thick mantle of snow appeared in America and polar regions,
large number of mammals, many birds and plants undergo mass extinction,
First human, homo sapiens evolved and the land surface was dominated
with angiosperm.
 B. Holocene Epoch (11000 yrs ago) – This is the epoch of the human
evolution, the land masses formed by the retreat of snow cover, subjected
to erosion, fertile land turned into barren lands, man developed intellectual
establishment with the control over the animal and plant kingdom by
means of domestication; human civilization established, flourished and
continued since today; random development of concrete technology with
the spred of the human pleasure of happiness by the innovation and
technological pleasure.

12.  In paleontology, a fossil is the remains or traces of a plant or animal that
lived in the past. Fossils can take many different forms, including bones,
teeth, shells, and even impressions of plants or animals that have been
preserved in rock or sediment. They are usually formed when the remains
of an organism are buried in sediment, and over time the sediment turns to
rock, preserving the remains in the rock. Fossils are an important source of
information about the history of life on Earth and can help scientists
understand how different species evolved over time.
 There are many different types of fossils, depending on the type of
organism that was preserved and the way in which it was preserved. Some
common types of fossils include:
 Body fossils: These are the actual remains of an organism, such as bones,
teeth, shells, and other hard parts.
 Trace fossils: These are the marks or impressions left by an organism, such
as footprints, burrows, and other traces of its activity.

13.  Mold and cast fossils: These are formed when an organism is buried in
sediment and the sediment hardens into rock, leaving an impression or
“mold” of the organism. A cast is formed when the mold is later filled in
with sediment, creating a three-dimensional replica of the original
organism.
 Permineralized fossils: These are formed when the pores or other openings
in an organism’s hard parts are filled in with minerals, preserving the
structure of the original tissue.
 Carbonized fossils: These are formed when the organic matter in an
organism is preserved by being converted into a carbon film.
 Amber fossils: These are formed when an organism is preserved in amber,
a type of tree resin that hardens over time.
 The available Plant Fossils are of the following types-
 Compressions- 2 dimensional with organic content,
 Impressions- 2 dimensional, imprints, devoid of organic content,
 Cast or Mold- 3 dimensional, may have surface of organic material

15.  Per mineralization- 3 dimensional, tissue in filtered by minerals showing
internal preservation,
 Compaction- 3 dimensional, reduced volume, flattened, wholly organic,
 Molecular fossils- Non-structural, preserves organic compounds like
nucleic acids and proteins,
 Others- dead of preserved fossils like index fossil
 An index fossil is a fossil of a species that was present for a relatively short
period of time and had a wide geographic distribution, making it useful for
determining the age of rocks and the relative ages of rocks in different
locations. Index fossils are often used to correlate the ages of rocks in
different areas, as they can help to establish the relative ages of rocks that
are found in different places.
 To be a good index fossil, a species must have lived during a specific time
period, be easily recognizable and abundant, and have a wide geographic
distribution. For example, ammonites, which are extinct marine animals
with a coiled, snail-like shell, are often used as index fossils because they
were present during a specific time period (the Mesozoic Era), are easily
recognizable, and had a wide geographic distribution.

17.  Fossils are formed in numerous ways, and the process is called
fossilization.
 Most of the fossils are formed in seas and oceans. When a living organism
(such as a plant or animal) dies, it is quickly buried by sediment (such as
mud, sand or volcanic ash) carried in by big rivers.
 Decomposers decompose the soft parts of these organisms leaving only the
hard parts like bones, scales and shell etc. in animals and wood or leaf in
plants.
 However, in special circumstances, the soft tissues of organisms can also
be preserved.
 With the addition of more sediments, volcanic ash or lava over the top of
the buried organism, all the layers eventually harden into sedimentary rock
through the process of petrification or lithification.
 The rocks are worn back down and washed away with the continuous
process of erosion which reveal the prehistoric life forms within the rocks
and stones known as fossils.
 5 common ways of formation of fossils are as follows:
 Petrifaction, Impression, Amber, Trace fossil and soft tissues

18.  The complex fossilization process involves the different levels of
organization in this respect as follows:
 1. Cellular levels-Chemical degradation is the first steps but thick cuticle
surrounding the cell wall, lining, waxes, sporopollenin of pollen grains,
spore coats, cysts of some marine algae can escaped from decomposition
due to their stable molecular conformation.
 2. Tissue level-As the decay-resistant materials distributed over the plants
in general and sclerenchyma tissues, collenchymatous tissues are xylem
can escaped from decomposition other than the soft tissues of the plants.
 3. Organ level-During the burial process, the broken plant materials
undergo two process of deposition-
 Autochthrounus where assemblage of plant fossils are preserved close to
the place where the parent plants grow; Allocahthronus where the
assemblage takes place in the distant places. Although the different
hydrodynamic process play a very significant role in this regard and the
organs associated with the preservation are identified by Form genus and
organ genus in this regard.

19.  Organisms Level-In a community, different organisms have different
degree of fossilization large woody plants with resistant tissues are
fossilized better than the herbs and pollen fossils are very common than
animals. Plants adjacent to preservation due to sedimentation than those
grow far away.
 Environment Level- Preservation becomes more easy when it is close
Organic molecules are completely hydrolyzed and molecule to molecule
replacement takes place by mineral molecules available in the surrounding
sediments. After the replacement, it is replaced by the sedimentary rock.
 Infiltration Theory- Here, a to mud in swamps, deltas, lakes, lowland flood
plains and volcanic area.
 THEORIES OF FOSSIALIZATION
 1. Infiltration Theory - Here the body of the organism becomes
disintegrated and releases free carbon into the surrounding water, as a
result, carbonates of Ca, Mg & Fe take place. These molecules along with
silica gradually infiltered into the space and fossil is formed.

20.  Molecule by molecule replacement theory- During the process, original
organic molecules become completely hydrolyzed and the molecules to
molecules replacement of organic molecules take place by the mineral
molecules available in the vicinity in the surrounding mud or sediments.
After the complete replacement, the organism becomes preserved in the
sedimentary rock.
 FACTORS OF FOSSIALIZATION
 Anoxic environment: low oxygen conditions repel scavengers while
slowing the rate of bacterial decay
 No scavengers: scavengers scatter and destroy remains, stopping
fossilization before it starts
 No bacteria: bacteria can completely decompose remains, leaving nothing
behind to fossilize
 High deposition rate: this allows the organism to be buried before
scavengers, bacteria, or the environment can take their toll, allowing the
fossilization process to begin

21.  Simple skeleton: complex, articulated skeletal parts tend to separate,
making reconstruction difficult
 High population numbers: the more organisms of a species that exist, the
greater the chances that one of them will be fossilized
 Benthic in faunal lifestyle: this means the organism lives in the sediment,
so it's already buried.
 The ideal conditions favoring preservations are-
 Presence of more amount of hard tissues,
 Presence of water and more amount of toxic substances,
 Less disturbance by the biotic and abiotic agents,
 More quickly the organism get buried,
 No or less wind,
 Other inheritable factors also expedite the process of preservation and
fossilization.

22.  Fossils give us a useful insight into the history of life on Earth. They can
teach us where life and humans came from, show us how the Earth and our
environment have changed through geological time, and how continents,
now widely separated, were once connected. Paleontological resources, or
fossils, are any evidence of past life preserved in geologic context. They
are a tangible connection to life, landscapes, and climates of the past. They
show us how life, landscapes, and climate have changed over time and how
living things responded to those changes. Those lessons are particularly
important as modern climate continues to change.
 1. Identification and distribution of Fossils in the Geological Past-To
reconstruct the life of plants and animals in the passage of evolution, fossils
play crucial role,
 2.Geologic conditions of the Past-Fossils provide a complete pictiure of
various changes in the geographic structures associated with climatic
conditions of the earth through ages.
 3. Searching fossil fuels as source of energy
 Evolution of plants and animals through ages and the possible changes to
trace the evolution.

25.  1. Google for images,
 2. Different websites to enrich the domain,
 3. Archegoniates - Biman Chandra Acharya,
 4. A text Book of Botany- Bhattacharya, Hait , Ghosh
 An Introduction to Paleobotany- Arnold
 A Text book of Paleobotany – S.R. Mishra
 Paleobotany & Evolution- Stewart
 Disclaimer:
 This PPT has been developed to enrich free online resources for Biology
students without any financial interest.