The "Telome theory" of Walter Zimmermann (1930, 1952) is the most accepted theory that is based on fossil record and synthesizes the major steps in the evolution of vascular plants.
It describes how the primitive type of vascular plants developed from Rhynia like plants.
Vascular Cambium & Seasonal activity & its Role in Stem & RootFatima Ramay
Vascular Cambium & Seasonal activity & its Role in Stem & Root:
The vascular cambium (pl. cambia or cambiums) is a lateral meristem in the vascular tissue of plants.
The vascular cambium is a cylindrical layer of cambium that runs through the stem of a plant that undergoes secondary growth.
In Dicots:
The vascular cambium is in dicot stems and roots, located between the xylem and the phloem in the stem and root of a vascular plant, and is the source of both the secondary xylem growth (inwards, towards the pith) and the secondary phloem growth (outwards).
In Monocots:
Monocot stems, such as corn, palms and bamboos, do not have a vascular cambium and do not exhibit secondary growth by the production of concentric annual rings. They cannot increase in girth by adding lateral layers of cells as in conifers and woody dicots.
Cambium of some plants remains active for the entire period of their life, i.e., cambial cells divide and resulting cells mature to form xylem and phloem elements.
This type of seasonal activity usually found in the plants present in the tropical regions, and not all plants show cambial activity.
Percentage of ringless trees in the rain forests of;India : 75%Amazon : 43%Malaysia : 15%
In regions with definite seasonal climate; seasonal activity of cambium ceased with onset of unfavorable conditions; In Autumn, it enters the dormant state and lasts for the end of summer; In Spring, cambium again becomes active.
Duration of cambial activity is also affected by day-length, e.g., In Robinia pseudoacacia, cambium is dormant under short-day condition.
The cambium cells formed in circular in cross section from the beginning onwards.
The cambial ring is partially primary (fascicular cambium) and partially secondary (interfascicular cambium).
Periderm originates from the cortical cells (extra stelar in origin).
In Dicot stem, for mechanical support xylem is with comparatively smaller vessels, greater fibers and less parenchyma.
More amount of cork is produces for protection.
Lenticels on periderm are very prominent.
The cambial ring formed is wavy in the beginning and later becomes circular.
The cambium ring is completely secondary in origin.
Periderm originates from the pericycle (intra stelar in origin).
In Dicot root, xylem is with big thin walled vessels with few fibers and more parenchyma.
Less amount of cork is produced as root is underground.
Lenticels on periderm are not very prominent.
The "Telome theory" of Walter Zimmermann (1930, 1952) is the most accepted theory that is based on fossil record and synthesizes the major steps in the evolution of vascular plants.
It describes how the primitive type of vascular plants developed from Rhynia like plants.
Vascular Cambium & Seasonal activity & its Role in Stem & RootFatima Ramay
Vascular Cambium & Seasonal activity & its Role in Stem & Root:
The vascular cambium (pl. cambia or cambiums) is a lateral meristem in the vascular tissue of plants.
The vascular cambium is a cylindrical layer of cambium that runs through the stem of a plant that undergoes secondary growth.
In Dicots:
The vascular cambium is in dicot stems and roots, located between the xylem and the phloem in the stem and root of a vascular plant, and is the source of both the secondary xylem growth (inwards, towards the pith) and the secondary phloem growth (outwards).
In Monocots:
Monocot stems, such as corn, palms and bamboos, do not have a vascular cambium and do not exhibit secondary growth by the production of concentric annual rings. They cannot increase in girth by adding lateral layers of cells as in conifers and woody dicots.
Cambium of some plants remains active for the entire period of their life, i.e., cambial cells divide and resulting cells mature to form xylem and phloem elements.
This type of seasonal activity usually found in the plants present in the tropical regions, and not all plants show cambial activity.
Percentage of ringless trees in the rain forests of;India : 75%Amazon : 43%Malaysia : 15%
In regions with definite seasonal climate; seasonal activity of cambium ceased with onset of unfavorable conditions; In Autumn, it enters the dormant state and lasts for the end of summer; In Spring, cambium again becomes active.
Duration of cambial activity is also affected by day-length, e.g., In Robinia pseudoacacia, cambium is dormant under short-day condition.
The cambium cells formed in circular in cross section from the beginning onwards.
The cambial ring is partially primary (fascicular cambium) and partially secondary (interfascicular cambium).
Periderm originates from the cortical cells (extra stelar in origin).
In Dicot stem, for mechanical support xylem is with comparatively smaller vessels, greater fibers and less parenchyma.
More amount of cork is produces for protection.
Lenticels on periderm are very prominent.
The cambial ring formed is wavy in the beginning and later becomes circular.
The cambium ring is completely secondary in origin.
Periderm originates from the pericycle (intra stelar in origin).
In Dicot root, xylem is with big thin walled vessels with few fibers and more parenchyma.
Less amount of cork is produced as root is underground.
Lenticels on periderm are not very prominent.
• Gymnosperms (Gymnos = naked, Sperma = seed) include the small group of plants with naked seeds.
• The Gymnosperms originated in the Devonian period of the Paleozoic Era and formed the supreme vegetation in the Mesozoic Era.
Wall layers of anther have different functions most importantly they help in providing nutrition to developing pollens and also help in anther dehiscence.
From its initiation in 1998, the Angiosperm Phylogeny Group (APG) has focused on the production of an ever-more stable system of classification of the flowering plants (angiosperms). Based largely on analyses of DNA sequence data, the system is compiled by a larger group of experts than any previous system and has the advantage of being testable, allowing for confidence levels in the system to be estimated for the first time.
Angiosperms are the flowering plants also known as Magnoliophyta. The botanical term "Angiosperm" meaning ‘bottle or vessel’ is derived from the ancient Greek. These are the most diverse group of land plants. Angiosperms are seed-producing plants and the distinguished features of angiosperms over gymnosperms are angiosperms bear flowers, endosperm within the seeds and the production of fruits that contain the seed. According to the botanists the flowering plants diversified and widespread 120 million years ago. The classification of the flowering plants also has a long history.
In the past, classification systems were typically produced by an individual botanist or by a small group resulting large number of systems. Different systems and their updates were generally favored in different countries. Bentham and Hooker’s system was popular in the Britain and the Engler’s system was famous in the Europe etc. These systems were introduced before the availability of genetic evidences and angiosperms were classified using their morphology and biochemistry. After the 1980’s genetic evidences were available and phylogenetic methods came into the classification procedures.
In the late 1990s, an informal group of researchers from major institutions worldwide came together and they established the Angiosperm Phylogeny Group (APG). The objective was to provide a widely accepted and more stable point of reference for angiosperm classification. APG I was published in 1998 as their first attempt in Annals of the Missouri Botanical Garden. The initial 1998 paper by the APG made angiosperms the first large group of organisms to be systematically re-classified primarily on the basis of genetic characteristics. The group emphasized the need for a classification system for angiosperms at the level of families, orders and above. The existed systems are rejected is because they are not phylogenetically classified. The outline of a phylogenetic tree of all flowering plants became established and several well supported major clades involving many families of flowering plants were identified. The new knowledge of phylogeny revealed relationships in conflict with the then widely used modern classifications.
The principles of APG system are retaining the Linnean system of orders and families, Use of monophyletic groups (Consist of all descendants of a common ancestor), taking a broad approach to defining the limits of groups such as orders and families and use of term ‘clades’ above or parallel to the level of orders and families. A major outcome of the classification is the disappearance of the traditional division of the flowering plants into two groups, which are monocots and dicots.
Even though there are several controversies about APG the botanists worldwide are influenced by the concept and are currently practice the system.
It is called as “living fossil”
The whole order is extincted except one species Ginkgo biloba
This order was occurred in Triassic periods of Mesozoic age (200,000,000 years ago)
This order consists of 16 genera and many species (all in fossil forms except one)
Double fertilization is the process found in angiosperms in which out of the two male gametes released inside the embryo sac, one fuses with the egg cell (syngamy) and another fuse with secondary nucleus (triple fusion).
A Powerpoint presentation about a brief introduction to Plant Evolution and Evolution as a whole. It's definition and how it came to be.
Includes basic apomorphies from the ViridiPlantae up to the Angiosperms...
• Gymnosperms (Gymnos = naked, Sperma = seed) include the small group of plants with naked seeds.
• The Gymnosperms originated in the Devonian period of the Paleozoic Era and formed the supreme vegetation in the Mesozoic Era.
Wall layers of anther have different functions most importantly they help in providing nutrition to developing pollens and also help in anther dehiscence.
From its initiation in 1998, the Angiosperm Phylogeny Group (APG) has focused on the production of an ever-more stable system of classification of the flowering plants (angiosperms). Based largely on analyses of DNA sequence data, the system is compiled by a larger group of experts than any previous system and has the advantage of being testable, allowing for confidence levels in the system to be estimated for the first time.
Angiosperms are the flowering plants also known as Magnoliophyta. The botanical term "Angiosperm" meaning ‘bottle or vessel’ is derived from the ancient Greek. These are the most diverse group of land plants. Angiosperms are seed-producing plants and the distinguished features of angiosperms over gymnosperms are angiosperms bear flowers, endosperm within the seeds and the production of fruits that contain the seed. According to the botanists the flowering plants diversified and widespread 120 million years ago. The classification of the flowering plants also has a long history.
In the past, classification systems were typically produced by an individual botanist or by a small group resulting large number of systems. Different systems and their updates were generally favored in different countries. Bentham and Hooker’s system was popular in the Britain and the Engler’s system was famous in the Europe etc. These systems were introduced before the availability of genetic evidences and angiosperms were classified using their morphology and biochemistry. After the 1980’s genetic evidences were available and phylogenetic methods came into the classification procedures.
In the late 1990s, an informal group of researchers from major institutions worldwide came together and they established the Angiosperm Phylogeny Group (APG). The objective was to provide a widely accepted and more stable point of reference for angiosperm classification. APG I was published in 1998 as their first attempt in Annals of the Missouri Botanical Garden. The initial 1998 paper by the APG made angiosperms the first large group of organisms to be systematically re-classified primarily on the basis of genetic characteristics. The group emphasized the need for a classification system for angiosperms at the level of families, orders and above. The existed systems are rejected is because they are not phylogenetically classified. The outline of a phylogenetic tree of all flowering plants became established and several well supported major clades involving many families of flowering plants were identified. The new knowledge of phylogeny revealed relationships in conflict with the then widely used modern classifications.
The principles of APG system are retaining the Linnean system of orders and families, Use of monophyletic groups (Consist of all descendants of a common ancestor), taking a broad approach to defining the limits of groups such as orders and families and use of term ‘clades’ above or parallel to the level of orders and families. A major outcome of the classification is the disappearance of the traditional division of the flowering plants into two groups, which are monocots and dicots.
Even though there are several controversies about APG the botanists worldwide are influenced by the concept and are currently practice the system.
It is called as “living fossil”
The whole order is extincted except one species Ginkgo biloba
This order was occurred in Triassic periods of Mesozoic age (200,000,000 years ago)
This order consists of 16 genera and many species (all in fossil forms except one)
Double fertilization is the process found in angiosperms in which out of the two male gametes released inside the embryo sac, one fuses with the egg cell (syngamy) and another fuse with secondary nucleus (triple fusion).
A Powerpoint presentation about a brief introduction to Plant Evolution and Evolution as a whole. It's definition and how it came to be.
Includes basic apomorphies from the ViridiPlantae up to the Angiosperms...
FEATURING THE SUMMARY OF SCIENCE 10 UNIT 3 MODULE 3
GEOLOGIC TIME SCALE
THEORIES OF EVOLUTION
BIODIVERSITY
FOSSILS
RELATIVE DATING METHOD
RADIOMETRIC DATING METHOD
HOMOLOGOUS
ANALOGOUS
THEORY OF NATURAL SELECTION
To determine the variation and the limitation between species, many concepts have been proposed.
When a taxonomist study a particular taxa, he/she must adopted a species concept and provide a species limitation to define this taxa.
Plant kingdom as other living kingdoms has a hierarchy structure ends mostly with species rank.
Species are one of the basic units to compare in almost all fields of biology.
A species is defined as the largest group of organisms in which two individuals are capable of reproducing fertile offspring, typically using sexual reproduction.
Definition of a species as a group of interbreeding individuals cannot be easily applied to organisms that reproduce only or mainly asexually.
If two lineages of oak look quite different, but occasionally form hybrids with each other, should we count them as different species?
Idea of a species is something that we humans invented for our own convenience.
‘‘No matter what variations occur in the individuals or the species, if they spring from the seed of one and the same plant, they are accidental variations and not such as distinguish a species permanently; one species never springs from the seed of another nor vice versa” - JOHN RAY.
Used a sexual system ‘‘natural system” for defining species - LINNAEUS.
‘‘A species is a collection of all the individuals which resemble each other more than they resemble anything else, which can by natural fecundation produce fertile individuals, and which reproduce themselves by generation, in such a manner that we may from analogy suppose them all to have sprung from one single individual” - DE CANDOLLE.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
This presentation intends to explore the communication of the cell within and others for sustainability along the regulation mechanisms by the cellular neural networks and others to sing the song of the life.
Bioenergetics is an important domain in biology. This presentation has explored ATP production and its optimum utilization in biological systems along with certain theories and experiments to give a bird's eye view of this important issue.
This presentation offers the bird's eye view of the cell as the basic structural and functional unit of life. It also addresses the origin of eukaryotic cells from the prokaryotic cell by the endosymbiotic theory.
This presentation has been intended to offer a bird's eye view about the phylogenetic classification of the plant kingdom in general and the Engler and Prantl system in particular with merits and demerits.
This PPT has been made to explore the plant classification in general and the classification as made by Bentham & Hooker for the classification of the flowering plants. It also offers the history of plant classification along with the merits and demerits of this aforesaid classification.
Energy and the biological systems are joined together and no biological world is almost impossible without ATP. This study material intends to explore the beauty of ATP to drive different biological processes.
This PPT offers a bird's eye view of ICBN and its different rules along with regulations for the naming of plants. It also highlights the history of IBC and its contribution to plant taxonomy.
This presentation intends to offer the basic features of plant metabolism along with the different types of mechanisms to regulate and control the metabolic pathways.
This presentation has been designed to give the foundation of taxonomy in general and Plant Taxonomy in particular as a matter of pleasure to explore the diversity of the plant world.
Sex and sexuality are very common words in biology but para-sexuality is a little bit uncommon, several organisms in general and fungi in particular have the pleasure of sexuality to bring variations by beside sex. This PPT explores the beauty of para-sexuality for the academic fraternity.
Sex life in fungi is not less fascinating than in other organisms. Heterosexuality is a matter of pleasure to explore the diversity of sex in fungi along with its cause and consequences. You can find a pleasure to go through the content.
This PowerPoint wants to explore the bird's eye view of the reproduction of bacteria in general and the genetic recombination of bacteria in particular.
This presentation gives the bird's eye view of bacterial nutrition along with some other issues required to understand bacterial diversity as far as nutrition is concerned.
This presentation explores the food value of mushrooms along with the long-term and short-term storage procedures. It also offers a detailed account of the nutrients that remain present in the edible mushrooms.
If you want to explore the role of Cyanobacteria in soil fertility in general & Azolla-Anabena association in particular, you can visit this PowerPoint Presentation.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...
ORIGIN& EVOLUTION OF ANGIOSPERMS.pdf
1. A BIRD’S EYE VIEW
ORIGIN & EVOLUTION OF ANGIOSPERMS
2.
3.
4. Angiosperms or flowering plants form the largest group of plant kingdom,
including about 300 families (411 families, Hutchinson), 8,000 genera and
300,000 species. They are considered to be highest evolved plants on the
surface of the earth. From Cretaceous age, the angiosperms eclipsed all other
vegetation and now they are dominant. They are found almost everywhere in
each possible type of habitat and climate. They occur in deep lakes, deserts, in
beds of seas and even on high peaks of mountains. The species of Opuntia
(Cactaceae) can survive without water in acute desert conditions, whereas on
the other hand the species of Hydrilla (aquatic plant) are extremely sensitive to
drought conditions. Some species are found on rocks, some in waterfalls and
also some are marine. The species of Rhizophora, popularly known as
‘mangrove vegetation’ are found near the water of the sea. The epiphytes,
parasites, saprophytes, symbionts and even insectivorous plants are also not
uncommon. They may be annual, biennial or perennial herbs, shrubs, trees,
climbers, twiners and lianas. On one hand the angiosperms may be as minute
in size as a pin head, e.g., Wolffia microscopica, on the other extremity like
Eucleptiles of Australia may reach up to 300 feet in height.
5. i. The sporophyte which is the dominant plant in the life-cycle is
differentiated into roots, stem and leaves.
ii. The highest degree of perfection of the vascular system with true vessels
in the xylem and companion cells in the phloem.
iii. The organization of the microsporophyll’s (stamens) and
megasporophylls (carpel) into a structure called the flower, which is
typical only of the angiosperms.
iv. The presence of four microsporangia (pollen sacs) per microsporophyll
The ovules are always enclosed in an ovary which is the basal region of
the megasporophyll.
v. Production of two kinds of spores, microspores (pollen grains) and
megaspores. Angiosperms thus are heterosporous.
vi. Presence of single functional megaspore which is permanently retained
within the nucellus or mega-sporangium.
vii. Adaptation of flower to insect pollination.
viii. Pollination consists in the transference of pollen grains from anther to
stigma.
6. X. Extreme reduction in size, duration of existence and complexity of the
structure of the gametophytes which are entirely parasitic.
XI. The male gametophyte has reached the limits of reduction. It consists only
of the pollen grain and the pollen tube contains the tube nucleus and two
male gametes or nuclei. The male cells (gametes) are non-ciliated.
XII. The female gametophyte lacks any extensive development of vegetative
tissue. It consists of three egg apparatus cells, three antipodal cells and
two polar nuclei in the centre of the embryo sac.
XII. The non-motile male cells or nuclei are carried bodily to the neighborhood
of egg apparatus by the pollen tube.
XIV. The seed or seeds remain enclosed in the ripened ovary called the fruit.
XV. The phenomenon of double fertilization or triple fusion is the
characteristic of the angiosperms.
XVI. The endosperm develops after fertilization. It is triploid.
XVII. The angiosperms are completely adapted to life on land.
XVIII. Spore dimorphisim having resulted in the production of gametophytes,
male and female
7. The angiosperms appeared suddenly in Cretaceous age about 65 million
years back. Charles Darwin described this sudden appearance of
angiosperms in lower or upper Cretaceous as an ‘abominable mystery.
When angiosperms appeared for the first time in lower or upper
Cretaceous, they were full fledged like the trees and the herbs of today. In
support of this view Prof. Knowlton advocates in his ‘Plant of the past’,
“from the time of their appearance they did not progress at all due to
their full-fledged appearance in the Cretaceous”.
The fossil records of the angiosperms also support their appearance full-
fledged in lower or upper Cretaceous. The fossils of that age are so
characteristic and modem in appearance that most of them can be referred
unmistakably to living families, general and even to some species.
The forms of cycads and conifers, which long dominated the universe were
already pushed background and the earth had become infact the earth of
flowering plants. Charles Darwin has called this sudden appearance of
angiosperms as an “abominable mystery”.
8. However, some workers do not agree with the doctrine of ‘abominable
mystery’. According to H.H. Thomas (1936), the angiosperms of the past
replaced many of older gymnosperms in estuarine and marshy waters.
Graud Eury (1906) believes that the angiosperms came into existence
through mutation. Guppy (1919) however, supported the view of mutation.
Prof. Bertrand is of opinion that all the great groups of vascular plants
(Pteridophyta, Gymnosperm and Angiosperms) not only arose quite
independently of each other but also they originated simultaneously as far
back in the Archian period (2000 million years old-oldest)
These possibilities are:
1. That the angiosperms are monophyletic in their origin but have had a
very much longer history than at present known, perhaps stretching back
into Paleozoic times and with a whole series of missing links;
2. That the angiosperms are monophyletic but that the first and at present
unknown group diverged quickly in terms of geological time, into a
considerable number of different groups;
3. That the angiosperms are polyphyletic.
9. HOMOLOGY is the resemblance between two organisms due to
inheritance from a common ancestry. • Characters with same origin, but,
different in appearance or function • The resemblances due to homology are
real. • Homology between two organisms can result only from their having
evolved from a common ancestor, and the ancestor must also contain the
same feature or features for which the two organisms are homologous.
Through divergent evolution, organisms may develop homologous
structures.
ANALOGY • Analogy is the resemblance between two organisms due to
functional similarity and not due to inheritance from a common ancestry. •
Characters with different origin, but, similar in appearance. • The
resemblances due to analogy are generally superficial. • Analogy between
two organisms can be due to superficial resemblance, i.e., occurrence of a
part or an organ in one organism which has the same function as another
part or organ in a different organisms.
10. Darwin(1959) defined homology as that relationship between
which results from their development from the corresponding
embryonic parts but Simpson (1961) stated that the homology
is the resemblance due to inheritance from a common
ancestry and analogy is the resemblance from functional
aspect but not due to inheritance from a common ancestry.
Wilen (1981) stated that the homology may arise between
two characters, two characters states or between two
organisms for a particular character state. Two characters are
homologous if one is directly derived from the other. These
series of characters in question are called morphoclines or
phenoclines. The original pre-existing character is called as
plesiomorphic and the derived one as apomorphic . The two
terms apomorphic and plesiomorphic may be relative.
11. In ‘Parallelism’, the organisms have a common ancestor but the
character-state was not present in their common ancestor while in
convergence, two different characters in different ancestors evolving
identical character –states. According to Simpson (1961) parallelism is
defined as the independent occurrence of similar changes in groups with
a common ancestry. In Rananculus two species R. tripartius and R.
hedevacea have similar characters of aquatic habit and dissect leaves
which happen due to parallel evolution. In case of Gentum and
Dicotyledons with related vessels, there is parallelism.
While convergence , similarity is observed between the two distinct
phyletic lines with regard to individual organ or to the whole individual.
Similar features arise separately in two or more genetically diverse and
not related taxa or lineages , In case of Ochidaceae & Asclepiadaceae,
pollinia is found and it shows divergence.
12. In general, monophyly refers to derivation from a single ancestor
whereas polyphyly refers to derivation from more than one ancestor. In
paraphyly, all descendents of the most recent common ancestors are
kept in the group.
Simpson(1961) defined monophyly as the deviation of a taxon through
one or more lineages or descendents from the immediately ancestral
taxon of the same or the lower rank. Let one example-say genus B has
been derived from the genus A through a single species . The genus is
monophyletic at the genus as well as species level. It evolved from the
two species of A it shows monophyletic origin at genus level but
polyphyletic at the lower rank that is at the species level.
There are two different levels of monophyly-a minimum monophyly
and strict monophyly. In case of former one, one supraspecific taxon is
derived from an equal rank but in case of latter, higher taxon is derived
from a single evolutionary species.
13. Henning defined monophyletic group as a group of species descended from
a single species and which included all the descendents from this species.
In a simpler way, all descendents of a species at a time are placed in a
monophyletic group Two type of monophyletic groups has been
demarcated- holophyletic & paraphyletic. In holophyletic, all the
descendents of the most common ancestor remain in the group. In
paraphyletic, all descendents of the most recent common ancestor are not
included in the group. In other words, a paraphyletic taxon is one that
includes the most common ancestor, but not all the descendents. A
paraphyletic is defined as one that does not include the common ancestor
of the members of the taxon. Now, the holophyletic and monophyletic are
synonymous.
14. Within a cladograms, a branch that includes a single common ancestor and
all of its descendants is called a clade. A cladograms is an evolutionary tree
that diagrams the ancestral relationships among organisms. A Group of
individuals producing successively, similar and genetically related
individuals are called Clades. A clade can be represented by the line
diagram is called cladograms which shows woody habit, alternate leaves,
cymose inflorescence, 5 red petals, 5 stamens, 2 free carpels and dry fruit
with many seeds inside it. A phylogenetic tree depicts phylogenetic tree.
The vertical axis shows the geologic period. The branch in the tree
represents the origin of the group and the terminal portion indicates the end
of the group. The branching emerges from the main axis are the fossil
groups which end in the geologic time when the group become extinct.
15. Living groups are marked by their distance from the centre. Primitive
groups are close to the centre and the advanced groups remain towards the
periphery. The branching diagrams are called dendrograms.
Wiley (1981) defines phylogenetic tree as a branching diagram portraying
hypothesized events linking individual organisms , population or
taxa.Accoding to him, it is branching diagram of entities where the
branching is based on inferred historical connections between the entities
as evidenced by the synapmorphies. It is thus, a phylogenetic or historical
dendrogram. Recently all the evolutionary diagrams are drawn are known
as evolutionary tree or phyletic tree . These are synonymous with
cladograms.
16.
17. In Biology, evolution is the change in heritable characteristics of biological
populations over successive generations. These characteristics are the
expressions of genes, which are passed on from parent to offspring during
reproduction. Evolution is the most interesting domain of the biology as it
induces to explore the magic of the reality of life since the time immemorial
along with their changes with the passage of time during the geological
period. The most dominant group of the plant kingdom with some unique
features induces a number of questions regarding its origin and evolution as
the scanty fossil records are enough to come any clear cut distinct
conclusion. A form genus, Clavitopollenites reported by Couper (1958) from
Berremian and Aptian strata belonging to the early Cretaceous of England
about 132-112 mY is the most important examples in this regard. Many
fossils show the herbaceous nature of angiosperms similar with
Magnoliidae, Magnoliales, Laurales etc and the late cretaceous era contains
50% fossils being angiosperm in nature. Archaestrobilus cupulanthus , a
form genus has resemblance with Welwitschia, a gymnosperm of late
Triassic of Texas with spirally arranged macro cupules on constructed male
and female spikes.
18. With the help of several findings, it can be concluded that there are
two probable dates regarding the origin of angiosperms.-one in the
Triassic
when stem angiosperms reported by Doyle and Donoghue in 1993
as ‘angiophytes’ and the second one refers to crown group of
angiosperms of late Jurassic period that splits into extant subgroups.
1. Axelrod(1970) proposed the origin of angiosperm in mild uplands
at low latitudes,
2. South east Asia near to Malaysia as the site of the origin by
Smith, 1970,
3.According to Stebbins (1974), it has been evolved under
environmental stress and drought,
4.Bailey & Takhtajan (1969) studies the flora of Southern Pacific
Islands and supplied the missing link as the polyphyletic origin of
angiosperms.
19. Although the origin of angiosperms is an abominable mystery,
there arte two schools of thoughts- Monophyletic & polyphyletic
origin. Hutchinson(1973), Thorne(1983-2007). Takhtajan(1997),
Bremer et al. APGII, 2003 and others in favor of the Monophyletic
origin of angiosperms and they proposed that monocotyledons
have evolved from their primitive dicotyledons and this is based
on sieve tubes, companion cells, closed carpels, 8 nucleate embryo
sac, reduced gametophytes, triploid endosperm. Sporne (1974)
viewed that gymnosperms are the ancestors of angiosperms and
independent development of characters took place in the passage
of evolution. Melville(1983) argues for the polyphyletic origin and
the Glosspteridae is the ancestor of many angiosperms. Campbell
(1930) believed that angiosperm might have been evolved from
pteridophytes due to their similarity with eusporangiate ferns and
monocotyledons have been evolved from Isoetes as far as the
position of embryo sac , mode of lateral growth and formation of
stem apex as in Alisma & Isoetes although it was rejected by the
group of phylogenists.
20. 1. Pteridosperm theory: On the basis of histology and stellar
structure (Andrew, 1947; Arnold, 1949; Cronquest, 1968)), seed
ferns are thought to be ancestor of angiosperms. In both the cases,
eusporangiate type development, two traces to one gap and
amphiphloic stele, they share some common characters and the
laminar type of placentation is somehow related to the soral
distribution of the ferns. But the simple structure of angiosperm
ovule and complex seed of pteridophytes are points of
disagreement.
2.Anthrostrobilus theory: Angiosperm flower evolved from an
unbranched bisexual strobilus bearing spirally arranged pollen
and ovulate organs. It got similarity with the reproductive
structure of ancient Bennettitalean gymnosperms. Bisexual;
flowers of Magnoliales seems to have evolved from such stock.
Bennettialean origin along with seed bearing organs, Caytonia
and leaf structure of cycas show a degree of similarity in this
regard.
21. 3. Pseudanthial Theory: Angiosperms took origin from Gnetopsida as
proposed by Wettstein (1907) from the stocks like Ephedra, Gnetum and
Welwitschia due to the following resemblances-
Reticulate dicot -like leaves in Gnetum,
Presence of vessels,
Male flower with perianth and bract,
Reduction in male gametophyte with ventral canal nucleus,
Ephedra shows Casuarinas like habit
Homology between compound strobilus of Gentales with the inflorescence
of wind pollinated Amentiferae along with insect pollinated bisexual flowers
of Magnolia . This theory was not supported by Carlquist (1996), Young
(1981) and others. But Cornet (1996) discovered Welwitschia like fossils
Archaestrobilus cupularanthus and this strengthen the Gnetopsida origin of
angiosperms. The male and female spikes of fossil plant possess many
spirally arranged microcupules. Each macrocupule carried an ovule
surrounded by sterile scales. With these features, Gentospda considered to be
close member of angiosperms.
22. 4. Anthocorm Theory: It is based on polyphyletic origin of angiosperms
proposed by Niemeyer (1924). As far as this theory, the angiosperm flower has
several separate origin. In Magnoliidae and their derivatives, they are modified
pluriaxial system i.e. holoanthocorms which are thought to be derived from
gnetopsida via the piperales. But the original modified uniaxial system i.e.
gonoclads or anthroid gave rise to the flower of Chloranthaceae. Meeuse
(1963) advocated for the origin of monocotyledons from the fossil order
Pentoxyales through monocot order of Pandanales.The Pentoxylales were
woody plants and their stem had many conducting strands each with its
cambium. The feature gives a clue for the link with the many monocotyledons
due to their many vascular bundles in the stem. The leaf genus Of Pentoxylon
known as Pentophyllum that are star shaped and had a dominant midrib with
parallel venation. The pollen bearing organs. Sahania were similar to the
Bennettiales . The seed bearing structure was similar to Mulberry and the outer
fleshy sarcasta was considered homologous to the cupule of the seed ferns.
Taylor and Hickey (1996) excluded Pentoxylon from Anthophytes through the
latter contains angiosperm lineage and its sister groups Benenettiales and
Genetopsida.
23. 5. Gonophyll Theory: this theory was put forwarded by Melville (1962,
63, 83) on the basis of the angiosperm was a leaf with an epiphyllous
fertile branch known as gonophyll. According to him, angiosperm arose
240mya in the Permian and took around 140mya before they widely
spread in the cretaceous. In simple glossopteris scutum and Ottokoria,
the fertile branch contained a bivalve scale having two wings called
scutella.The latter carried terminal ovules on dichotomous groups of
branches. Folding of the scutella along the cluster of ovules forms the
angiosperm condition. The closure condition was found in the Permian
fossil Breytenia. The3 fertile branch of Lidgettonia carries 4-8 disc-like
bearing several seeds. A genus Denkania discovered from Raniganj,
W.B. India bears 6 seed bearing cupules that are attached to the long
stalks borne from the midrib of the fertile scale. The leaves of
glossopteris are lanceolate with reticulate venation . The cone structure
has spirally arranged fertile leaves and forms the anthostrobilus. The
anthofasciculiu i.e. leaves structure with two fertile branches , one
unable and other is reported in Mudgea.It is comparable with the
angiosperm flowers like Ranunculus and Acacia.
24. 7.Herbaceous origin Hypothesis: The ancestral plants are thought to be
considered as rhizomatous herbs not the trees. Donoghue and Doyle
(1989) coined the term paleoherbs for a group of plant of Magnoliidae.
They found to occur the features like anomocytic stomata, two whorls of
perianth and trimerous flowers in the plants and it includes the families
like Lactoridaceae, Aristolochiaceae, cobombaceae, Piperales,
Nymphaceae & monocots. According to this hypothesis, the ancestral
plants possess the following features-
Ancient angiosperm plants were perennial with rhizomatous to
scrambling habit,
Leaves were simple, reticulate veined and dichotomous branching of
secondary veins,
Sieve elements with treachery elements with both circular bordered and
scalriform pitting with oblique end walls,
Flowers with racemose or cymose inflorescence,
Small monosulacate had perforate to reticulate sculpturing,
25. Carpels free, ovules attached proximally to the closure. There are one to
two orthotropus, bitegtmic, crassinucleate ovule and the dicotyledonous
embryo.
The recent findings suggest that Gneopsids are the closest to the living
relatives of the angiosperms and the closest fossil group of the
Bennettiales. Anthophytes during the Late Jurassic divided into stem
Angiophytes , the early angiosperms and crown Angiophytes
constituting the extent group of angiosperms.
A group of Proangiosperms Caytoniales, Zcekanowskiales and
Dirhopalostachyceae was identifies by Krassilor in the Jurassic. He
argued to consider these plants as angiosperm instead of researching
their ancestors. He further traced Laurales -Rosales series from
Caytoniales. Zcekanowskiales possessed bivalve capsules having
stigmatic bands that showed links with monocots.
Dirhopalostachyaceae probably evolved in Hamamelidales due to
paired ovules exposed on shield-like lateral appendages.
26. 6. Transitional-Combinational Theory: J. Stuessay (2004) put forth this
theory as far as the origin of angiosperm is concerned. The angiosperms
evolved gradually and slowly from seed ferns in the Jurassic. He considers
that Carpels, double fertilization and the flowers to evolve one after
another. These three fundamental transitions might have taken more than
100 mya to complete the process. The fossil record confirmed that the
living angiosperm did not come up until Early cretaceous when the final
combination of these three important angiosperm features took place . The
theory attempts to remove discrepancy between fossil and molecular
phylogenetic data. The latter gives indication o0f Pre-cretaceous origin of
angiosperm. But DNA sequences showed first change was in carpel
evolution. The event is much earlier than the final combination of all the
three angiosperm features. This theory give emphasis on the origin of
angiosperm from seed ferns and no other gymnosperms had direct
phylogenetic link to modern angiosperm.
It is accepted that the early angiosperms were small trees or woody
shrubs with simple evergreen entire and pinnately veined leaves having
stipule. Further it is believed that primitive angiosperms evolved in very
late Jurassic period. There are
27. Two schools of thought regarding the origin of angiosperms.
The Englerian school considers Casurinaceae as the most primitive among
dicots whereas Bessey school thinks bisexual flowers of Magnoiliales to be
the most primitive. During the last few years, paleoherbs provide the
essential clue on primitive angiosperm.
The primary basal groups were chosen as primitive include Casuarinaceae,
Magnoliaceae, Winteraceae, Degeneriaceae and Calcanthaceae. APG II
considered Magnoliidae and Nympheidae as the true basal group instead of
Degeneriaceae and Placed Amborellaceae at the beginning.
At the end of the 20th century, the herbaceous origin of angiosperms has
been gaining much more emphasis in this regard.
As far as the origin of monocots, different theories have been put forward
by the number of scientists as stated below:
Bailey (1944) & Cheadle (1953) gave emphasis on origin of vessels and
they concluded vessels had independent origin and special in monocots and
dicots.
Cronquist ( 1968) did not agree with the independent origin of vessel in
two groups.
28. He believed in aquatic origin of monocots that resemble with
Nympheales.
Kjosakai , Mosely and Cheadle (1970) did not accept the view of
Cronquist. Advance vessels are observed in Alismatiaceae in an aquatic
environment and the terrestrial monocots evolved with ancient vessels
elements in the metaxylem of roots.
Monocotyledons evolved in two lines- One from Ranunculoideae giving
rise to Alismatiales and another from heleboroideae giving rise to
Butamales as per Hutchinson (1973).
Takhtajan (1980, 1987) believed in a common origin of Nympheales and
Alismatiales from hypothetical terrestrial herbaceous group of
Magnoiliidae.
Dahlgren et al. (1985) described that monocots evolved 110 mya ago
during Early cretaceous.
Chase et al. (1993) observed the monophyletic origin of and from within
monosulcate pollen of Magonliidae.
29. References:
1. Google for images
Different websites for content,
Plant taxonomy- O.P.Sharma
Text Book of Plant Systematics- Chittaranjan Mohanty,
A Textbook of botany- Hait, Bhattacharyya & Ghosh
Advanced Plant taxonomy- A.K. Mondal
Disclaimer: This PPT has been prepared to enrich open source of
knowledge for the academic fraternity without any financial interest.