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CLASSIFICATION

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Claire Teves

on 29 September 2014

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Transcript of CLASSIFICATION

CLASSIFICATION
THEORIES OF
SPECIES
TAXONOMY
is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups
Organisms are grouped together into taxa (singular: taxon) and given a taxonomic rank; groups of a given rank can be aggregated to form a super group of higher rank and thus create a taxonomic hierarchy
The goal of Taxonomy is to produce a formal system for naming and classifying species
to illustrate their evolutionary relationships
Traditional Evolutionary Taxonomy

Phylogenetic Systematics
Species assumed to have the same species are placed in one genus, based on resemblance
The similarity of species is judged based on comparison of physical attributes, and where available, their DNA sequences
They are ranked to be the highest in the
biological classifications
HISTORY
AND
PHYLOGENY
What is Phylogeny?
TAXONOMY
CONCEPTS
SPECIES
MAJOR SUBDIVISIONS
OF THE
ANIMAL KINGDOM
There are 3 Traditional groupings based on embryological and anatomical characters

Branch A
Branch B
Branch C
MESOZOA
PARAZOA
EUMETAZOA
phylum Mesozoa,
the mesozoa

phylum Porifera, the sponges and phylum Placozoa


all other phyla



The 
Mesozoa
 are enigmatic, minuscule,
worm
-like 
parasites
 of marine invertebrates.
Generally, these tiny, elusive creatures consist of a 
somatoderm
 (outer layer) of 
ciliated
 cells surrounding one or more reproductive cells.
The two main mesozoan groups are the 
Rhombozoa
 and the 
Orthonectida
. Other groups sometimes included in the Mesozoa are the Placozoa and the 
Monoblastozoa
.

Dicyemida
, or 
Rhombozoa
, is a phylum of tiny parasites that live in the renal (kidney) appendages of 
cephalopods

Orthonectida
are found in the body spaces of various marine invertebrates including tissue spaces, gonads,
genitorespiratory
bursae.
The 
Placozoa
 are a basal form of invertebrate. They are the simplest in structure of all non-parasitic
multicellular
animals

Monoblastozoa
are characterised by their distinct anterior/posterior parts and being densely ciliated, especially around "mouth" and "anus". They only have one layer of cells. They reproduce asexually by transverse fission of body.

Rhombozoa
Orthonectida
Placozoa
Monoblastozoa
The 
Parazoa
 are an ancestral subkingdom of animals, literally translated as "beside the animals".
Parazoans
differ from their
choanoflagellate
ancestors in that they are not microscopic and have differentiated cells. 
 
they do not have tissues or organs
.
The only surviving
parazoans
are the sponges, which belong to the phylum Porifera, and the Trichoplax in the phylum 
Placozoa
.

Sponge
 is a clade comprising all major animal groups except sponges, placozoa, and several other obscure or extinct life forms,
 Characteristics of eumetazoans include true tissues organized into germ layers, the presence ofneurons, and an embryo that goes through a gastrula stage.
 The clade is usually held to contain at least Ctenophora, Cnidaria, and Bilateria.

EUMATOZOA
Grade I (
Radiata
): phyla Cnidaria, Ctenophora
Grade II (
Bilateria
): all other phyla

RADIATA
Radiata is a taxonomic rank that has been used to classify radially symmetric animals

are the animals with bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside.
bilateral embryos are triploblastic having three germ layers endoderm, mesoderm, and ectoderm.

BILATERIA
There are two main superphyla (main lineages) of Bilateria.
DEUTEROSTOMES
 a superphylum of animals. They are a subtaxon of the Bilateria in
deuterostomes
,
the first opening (the blastopore) becomes the 
anus
, while in
protostomes
it becomes the 
mouth
.
Deuterostomes are also known as
enterocoelomates
 because their coelom develops through enterocoely.

There are four extant phyla of deuterostomes:

Phylum Chordata
 (vertebrates and their kin)
Phylum Echinodermata
 (sea stars, sea urchins, sea cucumbers, etc.)
Phylum Hemichordata
 (acorn worms and possibly graptolites)
Phylum Xenoturbellida
 (2 species of worm-like animals)

PROTOSTOMIA
Protostomia
 (from Greek meaning "
mouth first
") are a 
clade of animals
. Together with the deuterostomes and a few larger phyla, they make up the Bilateria.
The major distinctions between deuterostomes and protostomes are found in 
embryonic development.

Protostome animals can be divided into three major groups:

Ecdysozoa
, e.g. arthropods, nematodes
Platyzoa
, e.g. platyhelminths, rotifers
Lophotrochozoa
, e.g. molluscs, annelids as well as a number of minor taxa of basal or ambiguous affinity, namely the Chaetognatha.


the history of the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of organisms.

UNDERSTANDING PHYLOGENIES
The root of the tree represents the ancestral lineage, and the tips of the branches represent the descendents of that ancestor. As you move from the root to the tips, you are moving forward in time.

When a lineage splits (speciation), it is represented as branching on a phylogeny. When a speciation event occurs, a single ancestral lineage gives rise to two or more daughter lineages.

Phylogenies trace patterns of shared ancestry between lineages. Each lineage has a part of its history that is unique to it alone and parts that are shared with other lineages.


Basic Tree of Life:

Bacteria (eubacteria)

- “true bacteria”
- prokaryotic cells
- Like the Eukaryotes, they have membranes composed of unbranched fatty acid chains attached to glycerol by ester linkages
-
Ex: methanogens,  halophiles,  thermoacidophiles
Eukarya (eukaryotes)
eukaryotic cells
Ex: plants, fungi
Archaea (archaebacteria)
- prokaryotic cells
- unlike the Eubacteria and the Eukarya, the Archaea have membranes composed of branched hydrocarbon chains attached to glycerol by ether linkages
- Ex: mitochondria, chloroplasts


In the 18th century,
Carolus Linnaeus
designed the hierarchical classification system still in use today.

The Swedish botanist 
Carolus Linnaeus
 is
regarded as the father
of taxonomy, as he
developed a system
known as Linnaean classification for categorization of organisms and binomial nomenclature 
for naming organisms.

Carolus Linnaeus
BINOMIAL NOMENCLATURE
Binomial nomenclature is the system Linnaeus developed for naming species.
The two-part scientific name includes the genus and species
Names are latinized and italicized, only the genus is capatilized.

Sitta carolinensis


PHYLETIC RELATIONSHIPS
A relationship between a taxonomic group and a phylogenetic tree or cladogram can be one of three forms:
MONOPHYLETIC
PARAPHYLETIC
POLYPHYLETIC
includes the most recent common ancestor and all descendants of that ancestor

includes the most recent common ancestor of all members of a group but not all descendants of that ancestor

it does not include the most recent common ancestor of members of that group; the group has at least two separate evolutionary origins

A valid clade is
monophyletic
, it consists of the ancestor species and
all
its descendants.

A
paraphyletic clade
consists of an ancestral species and some,
but not all
, of the descendants.

Polyphyletic clade
includes many species that
lack a common ancestor
.
Traditional Evolutionary taxonomy is based on common descent and the amount of evolutionary change to rank higher taxa.

TRADITIONAL EVOLUTIONARY TAXONOMY
Sometimes this type of classification includes paraphyletic groupings.
PHYLOGENETIC SYSTEMATICS
a.k.a
CLADISTICS
Viewed evolution as the indespensible organising principle of biology and the basis for a taxonomic system

Introduced by
Will Hennig
in 1950.
German Biologist
April 20, 1913 - November 5, 1976
Founder of Phylogenetic Systematics (Cladistics)
With his works on evolution and systematics he revolutionized the view of the natural order of beings
As a taxonomist, he specialized in dipterans

CLADISTICS
Cladists tend to use characters with discrete states and parsimony based analyses to reconstruct the Tree
From this, they take their taxonomic system

SHORT
HISTORY
Mid 1970s
 cladistics had eclipsed phenetics
90s
it was the dominant school of taxonomic thought
North America
the 1980s were the heady era of taxonomic revolution in which cladistic revolutionaries in institutions shaped the future of systematics




PHYLOGENETIC
the study of evolutionary relationships among groups of organisms, which are discovered through molecular sequencing data and morphological data matrices
The result of phylogenetic studies is a hypothesis about the evolutionary history of taxonomic groups: their phylogeny
The term "phylogeny“ is derived from the German Phylogenie, introduced by Haeckel in 1866

PHYLOGENETIC
TREE OF LIFE
is a branching diagram or "tree" showing the inferred evolutionary relationships among various biological species or other entities—their phylogeny—based upon similarities and differences in their physical or genetic characteristics


The taxa joined together
in the tree are implied to
have descended from a common ancestor.
one of the basic units of biological classification and a taxonomic rank
defined as the largest group of organisms capable of interbreeding and producing fertile offspring



NAMING OF SPECIES
All species are given a two-part name
-Binomial name; and
-Just “binomial”

2 parts of “binomial name”:
1st part
-Generic name
-The genus to which the species belong to
2nd part
-Specific name(zoology) or specific epithet(botany)

Example:
Example: Birds
NUMBER OF SPECIES
The total number of eukaryotic species is likely to be 5 ± 3 million of which about 1.5 million have been already named

DID YOU KNOW?
Aristotle(384 BC- 322 BC)
-Used the words genus and species to
mean generic and specific categories
John Ray(1627- 1705)
-English naturalist
-The first to give a biological definition of
the term “species”
Carolus Linnaeus(1707- 1778)
 -classified organisms according to
easily observed differences


TYPOLOGICAL SPECIES CONCEPT
BIOLOGICAL SPECIES CONCEPT
SPECIES IN SPACE AND TIME
EVOLUTIONARY SPECIES CONCEPT
PHYLOGENETIC SPECIES CONCEPT
DYNAMISM SPECIES CONCEPT

According to this concept
the observed diversity of the universe reflects the existence of a limited number of underlying "universals" or types.
Individuals do not stand in any special relation to each other, being merely expressions of the same type.
Variation
is the result of imperfect manifestations of the idea implicit in each species.
Species are groups of actually or potentially interbreeding natural populations, which are
reproductively isolated
from other such groups.
A species is a reproductive community of populations
(reproductively isolated from others)
that occupies a specific niche in nature
.
A
species is a lineage
(an ancestral-descendant sequence of populations)
evolving separately from others and with its own unitary evolutionary roles and tendencies.
A species is a population or group of populations that
shares a common evolutionary fate through time.

A species is the
smallest diagnosable cluster of individual organisms
within which there is a parental pattern of ancestry and descent.
A species is an irreducible (basal) cluster of organisms,
diagnosably distinct from other such clusters, and within which there is a parental pattern of ancestry and descent.
Theodosius Dobzhansky
Ernst Mayr
Geographic Range
-
Species has a distribution through

space
.

Evolutionary Duration -
Species has a distribution through

time.

- Whenever there are new concepts, old ones are refined or replaced.

-Past and present concepts are both beneficial to the meaning of species.
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