Full 7th chapter paper B miller and harley

 The study of kinds and diversity of organisms
and the evolutionary relationships among them is
called systematics or taxonomy.
 The study of systematics gives the order and
relationship among the organisms. This
relationship arises from evolutionary processes.
 The organisms are organizes into groups (taxa).
This grouping grouping is based on degree of
evolutionary relatedness.
 KHAWAJA TAIMOR SHAHID

Taxonomy
 The original description of
species is called taxonomy.
Systematics
 The arrangement of species
into evolutionary groups is
called systematics.

Taxonomic hierarchy based on
morphology Taxonomic hierarchy based on
evolution Karl von Linne gave the
modern classification
system.
 He believed that different
species could be grouped
into same categories.
 This grouping is based on
the similarities b/w them.
 The group of animal with
similar characteristics forms
a e.g., house fly
similar with other flies.
 Von Linne did not accept
evolution. But his many
grouping show evolutionary
relationship.
 Morphological similarities
b/w two animals have a
genetic basis – it give rise to
common evolutionary
history.
The members of same taxonomic group are more closely related
to each other than to members of different taxa.  KHAWAJA TAIMOR SHAHID

Domain ? Eukarya
Animalia
Chordata
Mammalia
Carnivora
Canidae
Canis
Familaris

 The assignment of a distinct name to each species is called
nomenclature.
 There are two problems with common names.
 First, common names vary
from country to country
even region to region.
 So the there must be a
system of naming
organisms. So biologists
may communicate easily
with each other.
 Second, a common name
often does not specify a
particular species.
 E.g., different kinds of
pillbugs & crayfish cannot
be differentiated easily,
same class (Crustacea) but
diff. orders (Isopoda &
Decapoda, repectively).

There are followings rules:
Genus of
an animal
begins with
a capital
letter.
The species
name
begins with
a small
letter.
These names
are derived
from Latin –
so italicized
or underlined,
human-
Homo
sapiens.
The
binomial
name can
be
abbreviated
i.e., H.
sapiens.

 Molecular approaches includes study of molecules
like proteins, DNA, RNA of different species.
 These approaches provide information which is used
for taxonomic studies.
 For example, gene products (proteins) are same in
certain animals i.e., show the closeness b/w animals.
 So we easily compare the sequence of amino acids
and nucleotides of various organisms through this
techniques.
 In this way the constant mutation rate is seen. The
constant mutation of organism is called molecular
clock.

 Sequencing nuclear DNA and mitochondrial
DNA (mDNA) helps taxonomists to study the
taxonomic relationships.
 mDNA is useful in taxonomic studies because:
◦ Mitochondria have their own genetic system.
◦ They are inherited through cytoplasm, which means
it comes from mother. So we can check the
maternal lineages.
◦ mDNA is in small quantity so it changes at a
relatively constant rate.

 No doubt that molecular techniques are helps
taxonomists but traditional techniques have its own
importance. So they run complement to each other.
 The molecular clocks used to determine rates of
evolutionary changes. This information helps us to
fill the time gaps in the fossil record.
 Molecular clocks run at different rate and depends
on:
◦ Sequence if amino acids in proteins.
◦ Sequence of bases in mDNA.
◦ Sequence of bases in nuclear DNA.
◦ Data from different evolutionary lineages.

System of
classification
Kingdom
classification
system
Domain
classification
system

 In 1969, Robert H. Whittaker describes a system of
classification. The basis of classification of Whittaker
is:
◦ Cellular organization
◦ Mode of nutrition
 There are following five kingdoms:
◦ Monera – prokaryotes (bacteria and cyano bacteria)
◦ Protista – eukaryotes (amoeba, paramecium etc.)
◦ Plantae – eukaryotic, multicellular & photosynthetic. Non-
motile. ( plants)
◦ Fungi – eukaryotic, multicellular & decomposers. Non-
motile. (absorb organic matter)
◦ Animalia – eukaryotic, multicellular & feed by ingestion .
Motile.

 The early five kingdom do not follow
the evolutionary lineages.
 Importance of ribosomal RNA in
domain classification system.?
◦Problems of study of fossils
◦Ribosomal RNA & evolutionary
conservation
◦Basis of domain classification system

 There were very little fossil evidence
is present of 2 billion years ago.
Therefore, ribosomal RNA studies
were used.
 It provides evidence about the
relationships among the organism of
this 2 billion year period.

 Ribosomal RNA is excellent for studying the
evolution of early life on earth. The following
properties makes it excellent:
◦ It is an ancient molecule.
◦ It is present in all organisms.
◦ It changes very slowly. This slowness of change is
called evolutionary conservation.
 We can easily compare & study the link b/w
closely related organisms. There must be a
little difference but the relationship to some
ancestral molecule are still present.

 Molecular systematists compare the base
sequences of ribosomal RNA of different
organisms.
 They enter these data into computer programs
and examine all possible relationship among
different organisms.
 On the basis of studies of ribosomal, the
systematists concluded that all life shares a
common ancestor.
 They find three major evolutionary lineages –
called the domain.

Archaea
• These are prokaryotic
microbes. They live in
extreme environment i.e.,
high temperature, anaerobic
environment.
• The archaea are the most
primitive life form.
Eubacteria
• They include true bacteria.
• These are prokaryotic
microorganisms.
Eukarya
• The Eukarya include all
eukaryotic organisms.
The Eukarya arose about
1.5 billion years ago.
• The Eukarya diverged
more recently than the
Eubacteria from the
Archaea.

 There are certain classification
groups are made to classify them. As
follows:
◦Monophyletic groups
◦Polyphyletic groups
◦Paraphyletic groups

 The groups showing similarities due to single
ancestors are called monophyletic groups. & the
classification is monophyletic classification.
 The species should have single ancestral species. All
the descendants should arise from this single
ancestral species.
 The taxonomists look for characters, (indicate
relatedness), for searching out monophyletic groups.
 A character is anything that has a genetic basis and
can be measured from an anatomical feature to a
sequence of nitrogenous bases in DNA or RNA.

 The group showing similarities but
have separate ancestors are called
polyphyletic groups.
 Each group has a single ancestor.
 Polyphyletic group indicate
insufficient knowledge of the group.

 A group formed temporarily for some
lineage is called Paraphyletic groups.
 Paraphyletic groups are formed due to
insufficient knowledge of the group.
 Simply, taxonomic grouping that is derived
from a single ancestor but does not include all
members of the family group is called a
Paraphyletic group.

 There are certain disagreements are present in
animal systematics & these are:
◦ In the methods of investigation.
◦ In the use of data in describing distant evolutionary
relationship.
 So, on the basis of these differences three
contemporary schools of systematics exist:
◦ Evolutionary systematics (traditional approach)
◦ Numerical taxonomy
◦ Phylogenetic systematics (cladistics)

 The systematics in which evolutionary relationship are developed by study
of fossils of ancestors of closely related animals is called evolutionary
systematics.
 Its basic assumption is that organisms closely are related to an
ancestor.
 According to this there are two similarities b/w organism:
◦ Homologies: The resemblances that result from common ancestry are called
homology. It is called divergent evolution. E.g., wing of bird and arm of
human.
◦ Analogies: The resemblances that result from organisms adapting under
similar evolutionary pressures are called analogy. It is called convergent
evolution. E.g., wings of birds and insects.
 Evolutionary systematics can be shown on phylogenetic trees. The
organisms are grouped according to their evolutionary
relationships in phylogenetic tree.

 The founder of numerical taxonomy believed that there
are no criteria for grouping taxa.
 It is opposite to the evolutionary systematics.
 Numerical taxonomists use mathematical models and computer-aided
techniques to group samples of organisms according to overall similarity.
 There are two differences b/w evolutionary and numerical taxonomy:
1. Numerical taxonomists do not distinguish b/w homologies
and analogies. Numerical taxonomists admit that analogies
exist.
2. Numerical taxonomists limit discussion of evolutionary
relationships to closely related taxa.
 Numerical taxonomy is the least popular of the three taxonomic schools.
However, all taxonomists use the computer programs that numerical
taxonomists developed.

 The development of evolutionary relationship among the
organism on the basis of study of fossil, analysis and tests
is called phylogenetic systematics.
 The cladists are mainly check/study the genealogical
relationship among monophylretic groups of organisms and
use more testing and analysis. Therefore it is more scientific
than evolutionary systematics.
 The cladists differentiate b/w homologies & analogies.
However, they believe that homologies of recent origin are
most useful in phylogenetic studies.
 The cladists study two types of characters:
◦ Symplesiomorphies
◦ Synapomorphies

Symplesiomorphies Synapomorphies
 (Gr. sym, together plesio, near
morphe, form).
 The characters that all
members of a group share are
called basic characters or
Symplesiomorphies.
 These characters are homologies
that may indicate a shared
ancestry.
 But they are useless in describing
relationships within the group.
 To decide what character is
ancestral for a group of
organisms, cladists look for a
related group of organisms, called
an out-group.
 (Gr. syn, together apo, away
morphe, form).
 Characters that have arisen
since common ancestry with the
out-group are called derived
characters or synapomorphies.
 Simply, A character that can be
used to distinguish an animal
from other animals within the
group is called a
Synapomorphies.

Interpreting Cladograms. This hypothetical cladogram shows five
taxa (1–5) and the characters (A–H) used in deriving the taxonomic
relationships. Character A is symplesiomorphic for the entire group.
Taxon 5 is the outgroup because it shares only that ancestral character
with taxa 1–4. All other characters are more recently derived. What
single character is a synapomorphy for taxa 1 and 2, separating them
from all other taxa?
KHAWAJA TAIMOR SHAHID

 The hypothetical lineage shown in diagram is called a
cladogram.
 Cladograms give sequence in the origin of derived characters.
A cladogram is a family tree.
 It follows a hypothesis of monophyletic lineages. New data is
formed in the form of newly investigated character. (or it gives
reinterpretation of old data.
 This new data is used to test the hypothesis the cladogram.

Cladogram of vertebrate phylogeny
 This cladogram shows the evolutionary relationship among the vertebrates. KHAWAJA TAIMOR SHAHID

 The character of extraembryonic membranes is a synapomorphy and it
is used to define the clade containing the reptiles, birds, and mammals.
 But these characters are not present in any of the fish taxa or the
cladogram.
 The

 Showing relationship above the species
 Evolution at specie level
 Showing modern representatives
 Showing modern representatives at tip of branches
 Ladder like progression
 Problem of extinction
 Representation as inverted cone

 The evolutionary-tree diagrams can help to clarify
evolutionary relationships and timescales. But these show
relationships among levels of classification above the species.
So they are often a source of misunderstanding.
2. Evolution at specie level
• Evolution occurs in species groups (populations), not at higher
taxonomic levels. Therefore, showing phyla or classes as
ancestral is misleading.
3. Showing modern representatives
• Some phyla or classes are shown as ancestral, modern
representatives of these “ancestral phyla” . These have just as
long an evolutionary history as animals in other taxonomic
groups. These groups may have descended from the common
ancestor.

 All the modern representatives are shown at tips of a
tree branch. They may be very different from
ancestral species. Zoologists use modern
representatives to help visualize general
characteristics of an ancestral species. But they never
specify details of the ancestor’s structure, function, or
ecology.
5. Ladder like progression
• The evolutionary trees often show a ladder like
progression of increasing complexity. But evolution is
resulted in reduced complexity. So this is misleading.

 In many cases, evolution does not lead to phenotypes that
permit survival under changing conditions. Therefore
extinction occurs. These are not shown in tree diagram.
7. Representation as inverted cone
• The common phylogeny as an inverted cone or a tree but with
a narrow trunk and many higher branches. It is also
misleading. It shows that evolution is a continuous process of
increasing diversification. The fossil records show that this is
often wrong.
• For example, 20 to 30 groups of echinoderms are in the fossil
record, but there are only five modern groups. This
evolutionary lineage underwent rapid initial evolutionary
diversification. After the initial diversification, extinction -not
further diversification- was the rule. Paleontologist Stephen J.
Gould uses the term contingency to refer to rapid evolutionary
explosion followed by a high likelihood of extinction.

 The common phylogeny as an inverted cone or a tree
but with a narrow trunk and many higher branches. It
is also misleading. It shows that evolution is a
continuous process of increasing diversification. The
fossil records show that this is often wrong.
 For example, 20 to 30 groups of echinoderms are in
the fossil record, but there are only five modern
groups. This evolutionary lineage underwent rapid
initial evolutionary diversification. After the initial
diversification, extinction -not further diversification-
was the rule. Paleontologist Stephen J. Gould uses
the term contingency to refer to rapid evolutionary
explosion followed by a high likelihood of extinction.

Full 7th chapter paper B miller and harley

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