The document summarizes the recent APG system of plant classification based on phylogenetic analysis. It describes the following key points:
1. The APG system adopted in 1998 uses DNA sequences and morphology to arrange angiosperms into monophyletic groups or clades at different hierarchical levels, from informal groups to orders and families.
2. Major clades include basal angiosperms, magnoliids, eudicots, rosids, and asterids. Monocots are placed within basal angiosperms.
3. The classification recognizes relationships between groups more accurately than previous systems, adopting the phylogenetic principle of monophyly for formal taxonomic ranks. It is based on evidence from multiple sources
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.
Angiosperm Phylogeny Group classification
APG I
APG II
APG III
APG IV
Molecular Based system
features and organization
Merits and demerits
Difference in APG system.
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.
Angiosperm Phylogeny Group classification
APG I
APG II
APG III
APG IV
Molecular Based system
features and organization
Merits and demerits
Difference in APG system.
This presentation was given by Dr. Avishek Bhattacharjee in Botanical Nomenclature Course held in Botanical Survey of India, Eastern Regional Centre, Shillong in November 2016. This may be helpful to the undergraduate and post graduate Botany students to understand different types of taxonomic literature, especially Flora, Revision and Monograph.
Plant Taxonomy with the passage of time deserves holistic approach in the domain of biology.Now, it becomes a synthetic science due to application of other branches of knowledge like Chemistry, Molecular biology etc.This slide is intended to UG & PG students of Botany.
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 presentation was given by Dr. Avishek Bhattacharjee in Botanical Nomenclature Course held in Botanical Survey of India, Eastern Regional Centre, Shillong in November 2016. This may be helpful to the undergraduate and post graduate Botany students to understand different types of taxonomic literature, especially Flora, Revision and Monograph.
Plant Taxonomy with the passage of time deserves holistic approach in the domain of biology.Now, it becomes a synthetic science due to application of other branches of knowledge like Chemistry, Molecular biology etc.This slide is intended to UG & PG students of Botany.
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.
The APG system (Angiosperm Phylogeny Group system) is the first version of a modern, mostly molecular-based system of plant taxonomy.
Published in 1998 by the Angiosperm Phylogeny Group, it was replaced by the improved APG II in 2003, APG III system in 2009 and APG IV system in 2016.
It describes the basics of Plant classification, morphological, anatomical, palynological, embryological, chemical and cytological evidences of classification
Plant taxonomic keys are important for plant identification for students and budding taxonomists. The PPT gives a brief insight into few basic identification plant characters
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
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.
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.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
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.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
3. A BRIEF INTRODUCTION
Earlier plant classification ----- Artificial system.
From 1990’s started using --- Phylogentic analysis to classify the
plants.
Phylogenetic character used for Classification are:
Rapidly accumulating DNA sequences from the plastid gene rbc L
(this gene codes for large subunit of RUBISCO ENZYME).
cp DNA mat K gene ( maturase enzyme encoding gene located with
in the intron of chloroplast trn K gene).
Mitochondrial gene atp A (atp genes providing information for
making transporter proteins called ATPases) and 18 Sr DNA (satellite
related DNA) gave informative data useful in plant classification
Further development of polymerase chain reaction techniques
which help in bio-chemical as well as anatomical analysis has paved a
way for a new system of plant classification.
5. Preface of the APG System of classification
According to traditional system of classification Angiosperms are divided
into Monocots and Dicots based on presence of one or two cotyledons.
But recent study based on Phylogentic analysis ie., nuclear, plastid and
mitrochondrial DNA sequences and morphology do not support this
dicotomy.
Dicots earlier were considered Monophyletic in origin but present study
indicates in the Polyphyletic origin.
Monocots are considered as a Holophyletic group.
A majority of dicots showing similar characters are grouped in to one
branch called the Eudicots or Tricolpates (flowers with 4 or 5 sepals/
petals, tricolpate pollen etc).
The remaining dicots are grouped informally into Paleodicots
6. The APG system of classification proposed in 1998(APG 1,1998)by
The systematists
B. Bremer,
] K. Bremer,
M.W. Chase
J.L. Reveal
D.E. Soltis,
P.S. Soltis and P.F. Stevens
.
It compromised 462 Families arranged in to 40 Monophyletic orders
under a small number of informal higher groups:
Monocots,
Commelinoids
Eudicots,
Core eudicots,
Rosids,
Eurosids I
Eurosids II,
Asterids,
Euasterids I and Euasterids II.
Austrobaileyales order which is unassigned in kept at the beginning.
7. 11 unclassified families and four orders with no supra ordinal
groups were kept at the beginning of the classification.
25 families of uncertain position were kept at the end of the
classification.
Judd et al. (1999) made few modifications in APG-1 classification
by recognising a total of 51 orders by shifting a few families from
informal groups.
This classification includes only major families hence nearly 200
families were left out.
APG II (2003), a recent revision includes 470 families under 45
orders of which 44 are monophyletic and Austrobaileyales order
which is unassigend in kept at the beginning
8. HEIRARCHY OF APG CLASSIFICATION
Recognition of plants based Monophyletic groups called CLADES at all
levels.
The hierarchy of the classification is as follows-
Informal groups
Orders
Families
The informal groups include-
Basal Angiosperms,
Magnolids,
Eudicots,
Rosids
Asterids.
According to APG II ‘Monocots’ is considered Monophyletic group
placed under Basal Angiosperms.
9.
10. CLADE 1: BASAL ANGIOSPERMS
They represent a clade that includes following groups-
Amborellaceae,
Nymphaceae,
Austrobaileyales,
Ceratophyllales,
Monocots.
Amborellaceae: the monotypic Amborella trichopoda --the most basal
linkage to all basal angiosperms with spirally arranged floral organs, ethereal
oil cells.
Nympheaceae: 8 Genera, cosmopoliton in distribution and is consistent with
the fossil records.generally aquatic in habitat, also found in tropical and
temperate regions.
The floral diversity ranges from small, simple, trimerous
flowers(Cabomba) to large, showy, elaborate flowers(Nympheae, Victoria).
Austrobaileyales : represented by Austrobaileyaceae and Trimeniaceae
from Australia and recently added Schizandraceae and Illicaceae.
Ceratophyllales: based on phytogentic analysis based on rbcL.
Ceratophyllum is considered as ‘sister’ of all other Dicots.
11. MONOCOTS---considered as the major clade among extant
angiosperms and also the oldest among the angiosperm fossils
comprises of 52,000 species (22% of the total angiosperms.)
Orchidaceae and Poaceae are the largest families accounting to 34% and
17%.
Ray identified Monocots based on single character ie,. Presence of single
cotyledon but phylogenetic studies of non molecular data include 13 similar
identifying characters
----single cotyledon, parallel veined leaves, sieve cell
plastid with several cuneate protein crystals, secondary vascular bundles in
the stem, adventitious root system and sympodial growth.
Earlier trimerous condition was considered as unique feature in Monocots,
but it is also observed in Nympheaceae and magnolids.
APG II considers Monocots as a monophyletic group with 10 orders and 2
unassigned families(Petrosaviaceae and Dasypogonaceae).
The orders include – Acorales, Alismatales, Asparagales, Dioscorales,
Liliales, Pandanales, Arecales, Poales, Commelianales, and
Zingeberales.
Molecular analysis shows that Acorus as sister to all other Monocots
12. CLADE 2:-MAGNOLIDS
‘Primitive Angiosperms’ with 4 orders according to APG II viz. Piperales,
Canellales, Magnoliales and Laurales.
characterized by the presence of primitive characters like long, broad, net-
veined leaves, large flowers, numerous petals , sepals, stamens and carpels,
Magnoliales: based on molecular analysis includes 6 families such as
Magnoliaceae, Annonaceae, Myristicaceae etc.
----common character i.e. deletion of Apetela 3 gene.&
characterized by presence of reduced fibre pits, palisade parenchyma, continuous
tectum in the pollen etc.
Laurales: includes 7 families characterized by the presence of perigynous
flowers, gynoecium embedded in fleshy receptacle, inner staminodes, ascendant
ovules etc.
Piperales: includes 4 families with characters such as distichous leaves,single
prophyll & oil cells.
Canellales: includes 2 families viz. Canellaceae and Winteraceae. The family
Winteraceae is considered as most primitive extant Angiosperm.
13. CLADE 3: -EUDICOTS
Eudicotyledons (Doyle and Hotton) also termed as Tricolpates or Non-
magnolids (represent 75% of the total Angiosperm population)
Includes 2 groups‘Basal Eudicots’ and ‘Core Eudicots’.
Basal Eudicots: includes five lineages viz
Ranunculales,
Proteales,
Sabiaceae,
Trochodendraceae
Buxaceae.
Core Eudicots: includes seven major clades viz.
Gunnerales,
Berberidopsidales,
Saxifragales,
Santanales,
Caryophyllales,
Rosids
Asterids.
The molecular data supports the fact that Gunnerales is the sister to the
other core eudicots.
14. CLADE 4: -ROSIDS
This clade includes 140 families having common characters like
nucellar endosperm , reticulate exine, tricolpate pollen, simple
perforations of vessel end walls, mucilaginous leaf epidermis, two or
more whorls of stamens, ellagic acid.
Molecular analysis reveals two large sub clades i.e. Eurosids
I(fabids) and Eurosids II(malvids).
A few orders that do not fit into both the
sub clades include : Crossosomatales, Geraniales and Myrtales.
The Eurosids I include Celestrales, Zygophyllales, Malpighiales,
Oxalidales.
Other orders like Fabales, Cucurbitales, Rosales, Fagales form the
‘nitrogen fixing clade’.
The Eurosid II compromises of Brassicales ,Malvales, Sapindales
and Tapiasciaceae.
15. CLADE 5: - ASTERIDS
This is also a large clade with 114 families, 10 orders and 80,000
species.
This group is recongnized based on morphological as well as chemical
data which include iridoid chemical compounds, sympetalous corolla,
unitegmic and tenuinucellate ovules and cellular endosperm.
Previously considered as a polyphyletic group, Asterids are now
considered as monophyletic group based on analysis of three genes rbc
L, atp B and mat K.
Asterids now include four major groups viz. Cornales, Ericales,
Euasterids I(lamids) and Euasterids II(campanulids).
16. Merits of the APG classification
The APG classification system strictly adopts the phylogenetic
principle of monophyly
The APG classification system strictly adopts the phylogenetic
principle of monophyly
The APG classification system strictly adopts the phylogenetic
principle of monophyly
The APG classification system strictly adopts the phylogenetic
principle of monophylyThe APG classification system strictly adopts the phylogenetic
principle of monophyly – reconstructing the phylogeny on the
basis of established monophyletic
The APG classification system strictly adopts the phylogenetic principle ofThe APG classification system strictly adopts the phylogenetic principle of
monophyly .monophyly .
It is based on the synthesis of information derived from multiple sources –It is based on the synthesis of information derived from multiple sources –
morphology, anatomy, embryology, palynology, phytochemistry, molecular biology,morphology, anatomy, embryology, palynology, phytochemistry, molecular biology,
etc.etc.
Formal names have been given only to those groups (i. e. orders) where monophylyFormal names have been given only to those groups (i. e. orders) where monophyly
has been firmly established.has been firmly established.
In order to overcome the problem of paraphyly,In order to overcome the problem of paraphyly, the traditional separation ofthe traditional separation of
angiosperms into monocots and dicots has been discarded. Various monocotangiosperms into monocots and dicots has been discarded. Various monocot
groups have been placed in between primitive dicots and advanced dicots, e. g.groups have been placed in between primitive dicots and advanced dicots, e. g.
Poales are placed in between Magnoliales and Ranunculales.Poales are placed in between Magnoliales and Ranunculales.
17. Cladograms – evolutionary diagrams - based on morphological and molecularCladograms – evolutionary diagrams - based on morphological and molecular
data are presented for showing the phylogenetic relationships, both within anddata are presented for showing the phylogenetic relationships, both within and
among the monophyletic groups.among the monophyletic groups.
The orders, such as Amborellales, Nymphaeales, Austrobaileyales,The orders, such as Amborellales, Nymphaeales, Austrobaileyales,
Chloranthales, which show several primitive features, are placed at the start of theChloranthales, which show several primitive features, are placed at the start of the
APG classification.APG classification.
The number of unplaced and uncertain families has been gradually reduced fromThe number of unplaced and uncertain families has been gradually reduced from
APG-I (40) to APG-III (10).APG-I (40) to APG-III (10).
Based on the recent advances in research. The APG classification is increasinglyBased on the recent advances in research. The APG classification is increasingly
becoming an authoritative point of reference and a significantbecoming an authoritative point of reference and a significant
number of major herbaria, including Kew, Harvard, etc. are arranging their plantnumber of major herbaria, including Kew, Harvard, etc. are arranging their plant
specimen collections in accordance withspecimen collections in accordance with APG.
18. Demerits of APG Classification
APG classification is restricted at the taxonomic levels of only
order and family.
The classification may seem to be sound in theory, but it has
still found few followers in practice.
Although majority of families or genera have been recognised
as monophyletic orders, yet there are several unplaced
families or genera in APG – III.
The orders have been recognised under informal groups
(e.g. Magnoliids, Eudicots, etc), the names of which do not
conform to the ICBN.
Angiosperms have been given the rank of a division, followed
by the rank of order. In contrast to the previous classification
systems, there are no formal taxa between the rank of
division and order.