II B Sc Video Links Geological Time Scale: ...

II B Sc Video Links

Geological Time Scale: https://youtu.be/wOfNFKFDquo

Geological Age Determination: https://youtu.be/gvxwW5yoOPM

https://youtu.be/wOfNFKFDquo

https://youtu.be/gvxwW5yoOPM

Botany: III-Sem Unit-I Session 2

Digital learning-DCE Bangalore University

MCQs on Stelar evolution in Pteridophytes

1.The vascular tissue is confined to the central region of the stem forming:

a. Bundles b. Stele c. Cortex d. Pericycle

Answer: Stele

2.The protostele in which xylem core is star like is called:

a. Haplostele b. Actinostlele c. Plectostele d. Siphonostele

Answer: Actinostele

3. Stele includes

a. Vascular tissue

b. Vascular tissue and pith

c. Vascular tissue, pith and pericycle

d. Pith

Answer: Vascular tissue, pith and pericycle

4. ------------- Is the primitive type of stele

a. Haplostele b. Actinostele

c. Pletostele

d. Mixed protostele

Answer: Haplostele



5. The stele in which xylem forms several plates is:

a. Haplostele b. Actinostlele c. Plectostele

d. Polycyclic stele

Answer: Plectostele

6. In amphiphloic siphonostele, phloem cylinder is present

a. Inner to the xylem cylinder

b. outer to the xylem cylinder

c. Inner as well as outer to the xylem cylinder

d. None of the above

Answer: Inner as well as outer to the xylem cylinder

7. The siphonostele in which two concentric cylinders of vascular tissue are

present in the stele is:

a. Haplostele b. Actinostlele

c. Plectostele

d. Polycyclic stele

Answer: Polycyclic stele

8.The siphonostele in which two concentric cylinders of vascular tissue are

present in the stele is:

a. Haplostele b. Actinostlele

c. Plectostele

d. Polycyclic stele




9. ----------- is an example of medullated protostele

a. Actinostele

b. Siphonostele

c. Solenostele

d. Dictyostele

Answer: Siphonostele

10.In evolutionary point of view, which of the stele is most highly evolved

a. Protostele

b. Siphonostele

c. Solenostele

d. Polycyclic stele




Stelar Evolution in Pteridophytes

Introduction:

Pteridophytes are first vascular land plants with stelar organization. The name stele is

derived from Greek word, which means pillar or column. The central core of vascular cylinder

with or without the pith, which separates the cortex by the endodermis is known as stele. It

composed of two types of conducting tissues like xylem and phloem. Where xylem conducts

the water and phloem conducts the food material.

Types of steles:

According to Esau and Smith there are two main types of stelar organizations among the

vascular plants, 1) Protostele

2) Siphonostele

1. Protostele:

The stele without the pith or medulla is known as protostele. It is the simplest and most

primitive type of stele found in case of pteridophytes, where the solid xylem core is surrounded

by the phloem mass, pericycle and endodermis. Protostele is regarded as the most primitive

one from which other types of steles have evolved during the course of evolution. Based on

the arrangement of xylem and phloem tissues, the protostele is of four different types.

A) Haplostele:

If the central solid smooth xylem core is surrounded by uniform phloem mass is known

as haplostele. It is more primitive among other types of protostele. It is found in fossil

pteridophyte Rhynia and also in living pteridophyte Lycopodium cernuum. But in Selaginella

several haplosteles are present, this condition is known as polystelic.



B) Actinostele:

In this type the xylem is in star shape hence called actinostele. During elaboration of

stele either smooth surfaced xylem may expand at certain places towards the periphery or

surrounding phloem may slightly invaginates here and there, which results in a star shaped

xylem. Eg. Psilotum nudum and Lycopodium serratum

C) Plectostele:

If the xylem occurs in the form of parallel plates alternating with phloem plates such

type of stele is known as plectostele. This type of stele results either due to the continuous

expansion of the xylem towards the periphery or continuous invagination of phloem only in a

particular directions Eg. Lycopodium clavatum

D) Mixed protostele:

In this type of stele, irregular group of xylem is embedded in phloem mass. This

condition may arise due to the splitting of xylem plates into number of places either by plates

themselves or by phloem during further elaboration. It is the most advanced type of protostele

eg. Lycopodium cernuum



2. Siphonostele:

A protostele with pith or medulla is known as siphonostele. It is evolved from

protostele, where vascular tissues are arranged in the form of a hollow cylinders around the

central pith. On the basis of the position of phloem and xylem the siphonostele is of two types.

1) Ectophloic siphonostele 2) Amphiphloic siphonostele.

A) Ectophloic siphonostele:

In this type of siphonostele pith is surrounded by xylem cylinder, which in turn is surrounded by

phloem cylinder Eg. Equisetum

B) Amphiphloic siphonostele:

If the hollow xylem cylinder is surrounded by external phloem cylinder as well as internal

phloem cylinder is known as amphiphloic siphonostele Eg. Marsilea



Modification of siphonostele:

Appearance of leaf gaps in the siphonostele leads to a number of modifications which are as

follows:

1. Ectophloic or amphiphloic siphonostele with single leaf gap is known as solenostele Eg.

Adiantum.

2. Ectophloic siphonostele with several leaf gaps is called Eustele. In some cases, the

vascular strands are scattered, then such a stele is known as Atactostele.

3. In some ferns, the leaf gaps overlap. Amphiploic siphonostele with several leaf gaps are

called as dictyostele, where each individual strand is called as meristele (which looks like

a haplostele) eg. Pteris



4. In certain pteridophytes complex type of stelar structure is observed, where we come

across 2-4 concentric rings of vascular tissues. Such a stele is called as polycyclic stele.

eg. Pteridium

Stelar evolution:

According to Jeffery the simplest and primitive type of stele is protostele. In the course of

evolution, this simplest vascular system undergoes several progressive changes leading to the

formation of complex steles.



Evolution of the stelar system occurred in the following lines:

1. During elaboration of the haplostele, the central core of xylem becomes irregular and

assumed star shaped structure to form an Actinostele

2. As a result of further elaboration the xylem splits into a number of pareallel plates

alternating with phloem plates to form plectostele

3. Origin of pith in the protostele is a significant evolutionary change, which results in

siphonostele, is further elaborated during course of evolution

4. Ectophloic siphonostele is interrupted by a single leaf gap and results in formation of

solenostele

5. In ectophloic siphonostele, the appearance of several overlapping leaf gaps results in

formation of eustele

6. Amphiphloic siphonostel might have undergone another line of evolution giving rise to

dictyostele formation due to the formation of several overlapping leaf gaps

7. The most comlex and advance type of ploycyclic stele might have originated from

protostele by further elaboration or from siphonostele.



References:

1. Prof. Singh, V., Dr. Pande, P. C. and Dr. Jain, D. K. 2000. A text book of Botany for undergraduate students. Rastogi publications, Meerut.

2. Dr. Pandey, B. P. 2012. College Botany volume II. S. Chand & company Pvt. Ltd., New Delhi

3. docs.google.com

4. https://images.app.goo.gl/4KwSiACpQbrSSjHa8

5. www.plantscience4u.com

https://images.app.goo.gl/4KwSiACpQbrSSjHa8

http://www.plantscience4u.com/

Paper: III - Pteridophytes, Paleobotany, Environmental Biology

and Phytogeography

Programme BSc

Subject Botany

Semester 3rd

University Bengaluru University

Session 02

Unit: 1 - Pteridophytes

Stelar Evolution in Pteridophytes

Recap of previous session

• Vascular cryptogams

• Sporophytic plant body with true root, stem and leaves

• Presence of vasculature – Stele

• Reproduction by spores -homosporous or heterosporous

• Sporangial development - Eusporangiate or Leptosporangiate type

• Strobilus by aggregation of sporophylls

• Alternation of sprorophytic and gametophytic phase

Learning objectives of the session

To impart knowledge on the organization or arrangement of vascular tissues leading to different stelar types

Session outcomes

Students understand the stelar patterns evolved from simple to complex types with suitable examples

Definition and types of stele

• Stele – Pillar or column in Greek

• Definition of Stele: Central cylinder or core of the axis composed of xylem & phloem

or vascular tissues

• Organization of xylem and phloem in stele varies

• Types:

1. Protostele

2. Siphonostele

3. Solenostele

1. Protostele

Types:

1. Haplostele

2. Actinostele

3. Plectostele

4. Mixed protostele

2. Siphonostele

Siphonostele – presence of pith or medulla

Types:

1. Ectophloic siphonostele: Phloem external to xylem Eg. Equisetum

2. Amphiphloic siphonostele: phloem on either sides of xylem Eg. Marsilea

Stelar types

1. Solenostele: Siphonostele with non-overlapping leaf gaps

Eg. Adiantum

2. Dictyostele: Siphonostele with overlapping leaf gaps

Eg. Ophioglossum

3. Polycyclic stele: Possess two or more concentric rings of vascular tissues

Eg. Pteridium aquilium

Evolution of the stelar system

Progressive changes leading to formation of complex steles

Protostele (Haplostele) Actinostele

origin of pith Plectostele

Mixed protostele

Siphonostele

interruption of leaf gap

Solenostele

Overlapping leaf gaps

Eustele Polycyclic stele

Further

elaboration

Elaboration

Session Summary

• Stele is the central vascular cylinder (core of the axis) with or without pith

• Protostele includes: Haplostele, Actinostele, Plectostele & Mixed protostele

• Siphonostele includes: Ectophloic & Amphiphloic siphonostele

• Siphonostele: With single leaf gap – Solenostele;

With multiple leaf gap- Dictyostele

With two or more concentric rings of vasculature - Polycyclic stele

• During evolution the simple vascular system undergoes several progressive

changes leading to formation of complex steles

Multiple Choice Questions

1. The vascular tissue is confined to the central region of the stem forming

a) Bundles

b) Stele

c) Cortex

d) Pericycle

Ans: Stele


2. The protostele in which xylem core is star shaped ------

a) Haplostele

b) Actinostlele

c) Plectostele

d) Siphonostele

Ans: Actinostele


3. The stele with plates of xylem is a-----

a) Haplostele

b) Actinostlele

c) Plectostele

d) Polycyclic stele

Ans: Plectostele


4. An amphiphloic siphonostele has -----

a) Inner phloem

b) Outer phloem

c) Inner and outer phloem

d) None of the above

Ans: Inner and outer phloem


5. Solenostele is provided with

a) Non-overlapping leaf gaps

b) Overlapping leaf gaps

c) Both a and b

d) None of the above

Ans: Non-overlapping leaf gaps


6. The siphonostele with two concentric vascular cylinders is a -----

a) Haplostele

b) Actinostlele

c) Plectostele

d) Polycyclic stele

Ans: Polycyclic stele


7. ------------- is an example of an Actinostele

a. Psilotum

b. Selaginella

c. Marsilea


Ans: Psilotum

References

• Prof. Singh, V., Dr. Pande, P. C. and Dr. Jain, D. K. 2000. A text book of

Botany for undergraduate students. Rastogi publications, Meerut.

• Dr. Pandey, B. P. 2012. College Botany volume II. S. Chand & company Pvt. Ltd., New Delhi.

• Doc: Plant tissue system NEET notes/Edu Rev

• www.easybiologyclass.com

• docs.google.com

Botany- III Sem Unit 2- Session 17

Digital Learning-DCE Bangalore University


1. Dating of fossils refers to

a. study of fossils

b. finding out the age of fossils

c. digging the fossil materials


A: finding out the age of fossils

2. Geochronology is the science of determining the age of

a. Rocks

b. Fossils

c. Sediments

d. All the above

A: All the above

3. The method of fossil age determination by analyzing radioactive elements is called as

a. Stratigraphy

b. Radiometry

c. Biostratigraphy

d. Radiography

A: Radiometry

4. Techniques for fossil study includes

a. Ground thin section

b. Peel technique

c. Maceration technique

d. All the above

A: All the above


Digital Learning-DCE Bangalore University

5. Maceration technique is most suitable to study

a. Compressions

b. Impressions

c. Peat, lignite and coal

d. Petrifactions

A: Peat, lignite and coal

Botany: III semester Unit 2: Session 17

Digital Learning: DCE Bangalore university

Geological age determination and techniques to determine age of fossils

Introduction:

The age of the fossil must be determined, so it can be compared to other fossil species

from the same time period. Understanding the ages of related fossil species helps scientists

piece together the evolutionary history of a group of organisms. Geologists have established a

set of principles that can be applied to sedimentary and volcanic rocks that are exposed at the

Earth's surface to determine the relative ages of geological events preserved in the rock

record. A geologic age is a subdivision of geologic time that divides an epoch into smaller parts.

A succession of rock strata laid down in a single age on the geologic timescale is a stage.

Dating of fossils:

Finding out the age of fossils refers to the dating of fossils. The age of fossils indicates

the age of strata and the rock from which it is collected. Geochronology- is the science of determining the age of rocks, fossils and sediments using the signatures inherent in the rock themselves. Today, scientists use a variety of techniques to date rocks and fossils precisely.

Most often, they measure the amounts of particular radioactive elements—often radiocarbon

or potassium—present to determine when a rock was formed, or when an animal or plant

died. Some techniques work best with materials millions or even billions of years old. Others

only work for much younger materials. And each method only works for certain materials,

ranging from volcanic rock to charcoal to bone.

Techniques to determine the age of fossils:

Scientist use three important methods for dating fossils: 1. Stratigraphy 2.

Biostratigraphy and 3. Radiometry.

1. Stratigraphy:

It is a crude method of dating, which does not give the accurately consists of

analysis of the succession of strata that have been laid down one after the other

in a more or less regular fashion. The basis of this method is that the earth’s

crust is formed of number of strata arranged one above the other, which formed

by the deposition of sediments. So the lowest strata is the oldest and the upper

strata is formed recently. This method is applied in places where the strata have

been tilted so that one can pass over the earth’s surface from older to



progressively younger strata. The principle of stratigraphy help us to understand

the relative age of rock layers.

The layers of sedimentary rock, or strata, can be seen as horizontal bands of differently colored

or differently structured materials exposed in this cliff. The deeper layers are older than the

layers found at the top, which aids in determining the relative age of fossils found within the

strata.

2. Biostratigraphy:

This method consists of recognizing strata having similar fauna and flora in

different parts of the world. Here the different strata of the earth are identified

by comparing the fossils available in the strata of different parts of the earth.



3. Radiometry:

In this method the age of fossil is determined by analyzing the radioactive

elements present in it. The main principle underlying this method is that many

rocks have natural clocks in the form of radioactive isotopes, which change into

stable elements slowly, but at a steady rate. One gram of radioactive element

changes into half a gram in a particular duration of time. This duration is called

half- life of that element. Half-life is defined as the time taken for the activity

of a radioactive element to decay to one half of it original value. The more

common radioactive elements used for dating the fossils are uranium, carbon14

,

potassium and rubidium etc.

Lead method:

Here radioactive element uranium238

is used, which continuously but slowly

disintegrates into lead and helium. One half of the total number of uranium atoms will

breakdown, forming lead & helium in a period of 4.51 billion years (half-life of uranium). The

age of rock or fossil can be calculated by estimating the ratio of uranium & lead present in it.

Some rocks may not contain uranium, in such cases this method cannot be utilized for dating

the fossils. This method can only used for old rocks, which should be of lakhs of years

Carbon method or Radiocarbon Dating:

Living plants and animals absorb carbon from the atmosphere, including carbon14—a

radioactive form of the element produced when cosmic rays from the sun interact with

nitrogen in the upper atmosphere. But when organisms die, they no longer take in any carbon,

and the carbon14

in their bodies begins to decay at a known rate. Scientists use particle



accelerators to measure the amount of carbon14

in biological materials to determine when that

organism died. The half-life of C14

is 5568 years (i.e. 1 gm of C14

disintegrates into half a gram in

5568 years). The age of fossil can be calculated by measuring the amount of C14

present in the

fossil. This method cannot be used for fossils which are more than 70.000 years old and is

applicable only when the fossil contains at least some of the organic materials. Radiometric

dating is a technique used to date materials such as rocks or carbon, usually based on a

comparison between the observed abundance of a naturally occurring radioactive isotope and

its decay products, using known decay rates

Potassium-argon method:

Natural potassium contains a small amount of radioactive isotope K42

(half-life is 1350

years) it decays into 88% calcium & 12% Argon. By calculating the amount of argon emitted in a

particular unit of time it is possible to calculate age of fossil.

Rubidium-Strontium method:

Rubidium87

is another radioactive isotope, which decays into stontium88

. The half-life of

rubidium87

is 6 billion years. By this method age of good old fossils can be calculated.

Fission track method:

This method is used when a rock contains glass or crystal. When uranium238

is present in

rock, it undergoes spontaneous fission. This radiation damage causes the appearance of tracks in

the rock. When such a rock is etched with hydrofluoric acid, the tracks are revealed, which can



be seen through a microscope and counted. From the count the age of the glass or rock can be

computed. May be used for rocks with glass as young as 2000 years

Ash Analysis:

Gray volcanic tuffs—produced when layers of hot ash are laid down after volcanic

eruptions—are dateable and can help date fossils found in adjacent layers. As ash layers cool,

radioactive potassium-40 contained within begins to break down into the rare gas argon at a

known rate. By comparing the amounts of stable potassium and argon, paleontologists can

estimate how much time has passed since the volcanic tuff was formed.

Sometimes index fossils are used to date a rock of unknown origin, which must be

carefully studied with a precise information about its systematics & age. Using such index

fossils, the age of an unknown rock can be determined.

References:

• Bhattacharya, K., Hait, G. and Ghosh, A. K. 2007. A text book of Botany, volume II. New Central Book agency (P) Ltd, London.

• Dr. Arumugam, N., Dr. Ragland, A. and Prof. Kumaresan, V. 2016. College Botany, volume 3. Saras publications, Tamil Nadu.

• Natures.com

Paper: III - Pteridophytes, Paleobotany, Environmental Biology and Phytogeography

Programme UG

Subject Botany

Semester III

University Bangalore University

Session 17

Unit: 2 - Paleobotany

Geological age determination and techniques to determine age of fossils

Recap of previous class

• Fossils are the remnants of previously existing animals and plants preserved in the earth’s crust

• Processes of fossil formation is called as fossilization

• Fossils are of different types: Compressions, Impressions, Pertifactions, Incrustations & Compactions


• To impart knowledge on Geological age determination and also on techniques to determine the fossil age

Session outcomes

• Students understand how one can determine the geological age

• Students become aware of different techniques involved in fossil age determination

Geological age determination

• Finding the age of fossils - refers to Dating of fossils

• Geochronology- is the science of determining the age of rocks, fossils and sediments using the signatures inherent in the rock themselves

• The age of the fossil indicates the age of the strata and the rock from which it is collected

• Three important methods for dating fossils includes

1. Stratigraphy: Analysis of the succession of strata

2. Biostratigraphy: Recognizing strata having similar fauna & flora in different parts of the world

3. Radiometry: By analyzing radioactive elements present in fossils. Which in turn includes Lead method, Carbon method, Potassium-Argon method & Fission track method

Techniques to determine the fossils

1. Ground thin section: suitable to study petrified fossils

specimen cut into convenient size using lapidiary’s saw and is smoothened on one surface with abrasive.

Smooth surface is attached to a glass slide with melted resin

Specimen is cut as close to the glass as possible to obtain thin sections

Fixed to glass slide, further ground on a resolving lap with 100 carborundum till become translucent, so the section can be viewed under microscope

Slice is mounted with a cover glass using suitable mountant

Techniques to determine the fossils cont…

2. Film or Peel technique: suitable to study petrifaction with organic materials

Specimen is ground & smoothened & etched with 5% Hydrochloric acid for 5 m

Surface is washed in running water & air dried

Covered with a solution or a thin film of nitrocellulose

Specimen is air dried for at least 6 hours

Film is carefully peeled & mounted on a slide with a cover glass using a mountant


3. Transfer technique: suitable to study coalified compression

Specimen is cleaned by washing in acid

Prepared surface is coated with nitrocellulose or a film of cellulose acetate

Colified material adhered to the film is treated with strong oxidizing agent

Film is dried & permanently mounted on the slide with a cover glass using a mountant


4. Maceration technique: suitable to study peat, lignite & coal

Sample is cleaned, disaggregation & weighing

2-3gm of coal/lignite pulverized & decalcified

Treat with 10% HCl & oxidation with Schulze’s solution

Treat with 5% HCl/ dilute NH4OH/20%K2CO3/acetone to remove humic acid

Sample containing pollen/spores are stored in 50% glycerine

Stain with safranin

A drop of sample mounted on slide & observe under microscope

Session Summary

• Finding the age of fossils - refers to Dating of fossils

• Three important methods for dating fossils includes, Stratigraphy, Biostratigraphy and Radiometry

• Ground thin section, Film or Peel technique, Transfer technique and Maceration are the 4 important techniques in used to study the fossils


1. Dating of fossils refers to

a. study of fossils

b. finding out the age of fossils

c. digging the fossil materials

d. non of the above

finding out the age of fossils


2. Geochronology is the science of determining the age of

a. Rocks

b. Fossils

c. Sediments

d. All the above

All the above


3. The method of fossil age determination by analyzing radioactive elements is

called as

a. Stratigraphy

b. Radiometry

c. Biostratigraphy

d. Radiography

Radiometry


4. Techniques for fossil study includes

a. Ground thin section

b. Peel technique

c. Maceration technique

d. All the above

All the above


5. Maceration technique is most suitable to study

a. Compressions

b. Impressions

c. Peat, lignite and coal

d. Petrifactions

Peat, lignite and coal

References

• Bhattacharya, K., Hait, G. and Ghosh, A. K. 2007. A text book of Botany, volume

II. New Central Book agency (P) Ltd, London.

• Dr. Arumugam, N., Dr. Ragland, A. and Prof. Kumaresan, V. 2016. College Botany,

volume 3. Saras publications, Tamil Nadu.


Digital Learning- DCE Bangalore University


1. The sequential arrangement of various units of geological time is called

a. Physiological time scale

b. Chemical time scale

c. Geological time scale

d. Biological time scale

A: Geological time scale

2. Geological time scale consists of ----- major eras

a. Four

b. Three

c. Six

d. Eight

A: Six

3. The geological time has been divided into

a. Eras

b. Periods

c. Both a & b

d. Eras, periods & epochs

A: Eras, periods & epochs

4. Palaezoic era has ----- period

a. Cambrian & Devonian period

b. Triassic period

c. Jurrassic period


A: Cambrian & Devonian period


Digital Learning- DCE Bangalore University

5. Mesozoic era is also called as

a. Age of pteridophytes

b. Age of angiosperms

c. Age of gymnosperms

d. Age of bryophytes

A: Age of gymnosperms

Botany: Paper 3 Unit 2: Session 19

Digital Learning: DCE Bangalore University

Geological time scale with emphasis on Paleozoic and Mesozoic era

Introduction: The duration between the time of origin of earth & the present day is called geological

time. It has been divided into eras, periods and epochs for explaining various phenomenon during the earth’s history. The sequential arrangement of various units of geological time is called as Geological time scale. On the basis of time the geological history of earth consists of six eras like Azoic, Archaeozoic, Proterozoic, Palaeozoic, Mesozoic and Coenozoic eras. Each era includes many periods and each period is further divided into Epoch. Similarly, on the basis of strata the geologic history of earth is divided into system, series, stage and zone. Each & every era ended with great changes called revolutions, which brought about death of existing plants and animals, leading to their preservation in rock sediments as fossils.

Geological time-table



Geological time scale with special emphasis on Palaeozoic era:

Paleozoic era is the era of ancient life, started from 600 million years ago & ended by 230 million years back.it is divided into 7 periods like: Cambrian, Ordovician, Silurian, Devonian, Mississipan, Pennsylvanian & Permian period. Vegetation of this period includes both aquatic & land plants. The first fossils of land plants were found in the Silurian and Devonian period of this era.

Cambrian period: this was between 600 million years & 525 years ago. Here, the climate was very cool & it shows the fossils of cryophycean algae.

Ordovician periods: this period lasted for 65 million years, characterized by fossils of chara and red algae.

Silurian period: It last for 35 million years. The fossils of diatoms, brown algae, club mosses and

herbaceous marshes were discovered from rock deposits

Devonian period: this period started from 460 million years ago and ended by 425 million years back. It lasted for 35 million years. The fossils of Psilopsids, Lycopsids, Spenopsids, ferns & liverworts were discovered from sediments of this period.

Mississipian period: lasted for 25 million years. Coal beds were discovered and fossils of tree like Lycopods were discovered from the rock of this period.

Pennsylvanian period: it lasted for 25 million years. The Mississipian & Pennsylvanian period together called Carboniferous period.

Permian period: this period lasted for 30 million years. The fossils of Ginkogoales & primitive coniferales were discovered from this period.

In carboniferous and Permian period most dominant tree sized plants appeared and formed dense forests. Since seed ferns were abundant, this period is also known as age of seed

ferns. During late carboniferous period, there were significant changes in the environment-

resulted in the development of swampy regions. Such habitat was unsuitable for woody

vegetation. In late Devonian period, vegetation converted into coal due to geological events.



Palaeozoic Era

Geological time scale with special emphasis on Mesozoic era:

Mesozoic era is the period of middle life, started 225 million year ’s ego & ended in 75 million years back. Cycads had well flourished- hence called ‘age of cycads’ or ‘age of gymnosperms’. This era is divided into Triassic, Jurassic and cretaceous periods.

Triassic period: this is the first period of Mesozoic era, which lasted for 60 million years. The environment of Triassic period is arid & shows Cycadales, Bennettitales and Taxales in the rock beds.

Jurassic period: this is the second period of Mesozoic era, named after Jura mountains, lasted for 30 million years. The climate was warm & humid. The fossils of Pentoxylales were discovered in the rock deposits.

Cretaceous period: it is the last period of Mesozoic era, lasts for 60 million years ago. The fossils

of Lauraceae, Nymphaeales and Magnoliaceae were discovered. Gymnosperms were pre-dominant in this period and pines started to flourish on the earth.



Mesozoic rea- the age of dinosaurs

References:

• Prof. Singh, V., Dr. Pande, P. C. and Dr. Jain, D. K. 2000. A text book of Botany for undergraduate students. Rastogi publications, Meerut.

• Bhattacharya, K., Hait, G. and Ghosh, A. K. 2007. A text book of Botany, volume II. New Central Book agency (P) Ltd, London.

• Dr. Arumugam, N., Dr. Ragland, A. and Prof. Kumaresan, V. 2016. College Botany, volume 3. Saras publications, Tamil Nadu.

• Google.com

Paper: III - Pteridophytes, Paleobotany, Environmental Biology and Phytogeography

Programme UG

Subject Botany

Semester III

University Bangalore University

Session 19

Unit: 2 - Paleobotany

Geological time scale with emphasis on Palaeozoic and Mesozoic era

Recap of previous class

• Fossils are the remnants of previously existing animals and plants preserved in the earth’s crust

• Processes of fossil formation is called as fossilization

• Fossils are of different types: Compressions, Impressions, Pertifactions, Incrustations & Compactions

• The age of the fossil indicates the age of the strata


• To impart knowledge about the geological history of the earth coupled with

climatic changes, geographical conditions.

Session outcomes

• Students will comprehend the geological time scale and geological history of the earth

• Also learn the changes in the environment and vegetational types in different eras

• Students gain the knowledge of fossil records of different geological strata

Geological time scale

• Geological time: Is the duration b/w the time of origin of earth & the present day. It has been divided into eras, periods and epochs

• Geological time scale: the sequential arrangement of various units of geological time

• It consists of six eras like Azoic, Archaeozoic, Proterozoic, Palaeozoic, Mesozoic

and Coenozoic eras.

• Each & every era ended with great changes called revolutions, which brought about death of existing plants and animals, leading to their preservation in rock sediments as fossils.

Geological time scale with special emphasis on Palaeozoic era

• Paleozoic era started from 600 million years ago & ended by 230 million years back.

• Divided into 7 periods like: Cambrian, Ordovician, Silurian, Devonian, mississipian, Pennsylvanian & Permian period

• Vegetation of the period includes both aquatic & land plants

• Cambrian & Ordovician periods characterized by diverse group of algae & bryophytes

• In Silurian period land plants were evolved

• In Devonian period land plants with vasculature appeared

• In carboniferous and permian period most dominant tree sized plants appeared

• In late Devonian period, vegetation converted into coal due to geological events

Geological time scale with special emphasis on Mesozoic era

• Mesozoic era is the period of middle life, started 225 million years ego & ended in 75 million years back

• Cycads had well flourished- hence called ‘age of cycads’ or ‘age of gymnosperms’ • It divided into Triassic, Jurassic and cretaceous periods

• The environment of Triassic period is arid & shows Cycadales, Bennettitale and Taxales in the rock beds

• In Jurassic period, the climate was warm & humid. The fossils of Pentoxylales were discovered in the rock deposits

• In Cretaceous period gymnosperms were pre-dominant. The fossils of Lauraceae and Magnoliaceae & Salicaceae were discovered

Session Summary

• The sequential arrangement of various units of geological time is called Geological time scale

• It consists of six eras like, Azoic, Archaeozoic, Proterozoic, Palaeozoic, Mesozoic

and Coenozoic eras.

• Vegetation of Paleozoic rea includes both aquatic & land plants, as seed ferns were abundant, is known as ‘ age of seed ferns’

• Fossil records of Mesozoic era indicates cycadophytes & conifers hence known as ‘age of cycads’


1. The sequential arrangement of various units of geological time is called

a. Physiological time scale

b. Chemical time scale

c. Geological time scale

d. Biological time scale



2. Geological time scale consists of ----- major eras

a. Four

b. Three

c. Six

d. Eight

Six


3. The geological time has been divided into

a. Eras

b. Periods

c. Both a & b

d. Eras, periods & epochs

Eras, periods & epochs


4. Palaezoic era has ----- period

a. Cambrian & Devonian period

b. Triassic period

c. Jurrassic period


Cambrian & Devonian period


5. Mesozoic era is also called as

a. Age of pteridophytes

b. Age of angiosperms

c. Age of gymnosperms

d. Age of bryophytes

Age of gymnosperms

References

• Prof. Singh, V., Dr. Pande, P. C. and Dr. Jain, D. K. 2000. A text book of Botany for

undergraduate students. Rastogi publications, Meerut.

• Bhattacharya, K., Hait, G. and Ghosh, A. K. 2007. A text book of Botany, volume

II. New Central Book agency (P) Ltd, London.

• Dr. Arumugam, N., Dr. Ragland, A. and Prof. Kumaresan, V. 2016. College Botany,

volume 3. Saras publications, Tamil Nadu.

• http://www.nps.gov/subjects/geology/time-scale.htm

II B Sc Video Links Geological Time Scale: ...

Documents

Transcript of II B Sc Video Links Geological Time Scale: ...