Transcript Advanced Biology Chapter 18 Classification

Zoology
Classification
The branch of biology that names and groups
organisms according to their characteristics
and evolutionary history.
Classify the thousands of new species
discovered each year.
Biologists use the characteristics of newly
discovered to classify it with organisms
having similar characteristics.
The way we group organisms today continues
to change and reflect the evolutionary
history of organisms.
Aristotle
• Greek Philosopher 384-322 BC
• First classified organisms more than
2000yrs ago as either plants or animals.
– Animals: land dwellers, water dwellers, or air
dwellers.
– Plants: three categories based on differences
in their stems.
Aristotle
Carolus Linnaeus
• Swedish naturalist (1707-1778)
• Devised a system of grouping organisms
into hierarchical categories. Nested
hierarchy.
• Used an organism’s morphology (form and
structure)
Levels of Classification
Kingdom
Phylum or Division
Class
Order
Family
Genus
Species
Under the modern Linnaean system, the classification of an organism places the
organism within a nested hierarchy of taxa. The hierarchy ranges from the most general
category (domain) to the most specific (species).
Binomial Nomenclature
• Scientific Name has two parts.
– 1st part is the genus
– 2nd part is the species which is the identifier
or descriptive word.
• Genus name is capitalized and both
names are underlined or written in italics.
• Latin used by all scientists as a standard.
• Linnaeus classified 1000’s of organisms.
Versions of his system are still used today.
Scientific Names
• May describe the organism, suggest
geographic range, or honor a person
• Homo sapiens (sapiens = wise)
• Chaos chaos (amoeba never appear the
same shape)
• Canus familiaris (family dog)
Seven-level System was arbitrary
• There is significant variation in
some species to establish
additional levels.
• Variations of a
species that occur in
different geographical
areas. Example:
Terrapene carolina
triungui is a
subspecies of the
common eastern box
turtle Terrapene
carolina that has 3
rather than 4 toes on
its hind foot.
Subspecies of rat snake
Phylogeny
• Phylogeny is evolutionary history
• Much of Linnaeus’ work in
classification is relevant even in the
context of phylogeny because
morphological features are largely
influenced by genes and are clues of
common ancestry.
18-2 Modern Phylogenetic
Taxonomy
• Systematics
• Cladistics
Systematics
• Molecular biology revealed a wealth of
information on organisms’ molecular
nature (DNA & Amino acid sequence) and
changed the nature of taxonomy.
• Taxonomists organize the tremendous
diversity of living things in the context of
evolution.
Systematic Taxonomy
• Systematic Taxonomists use several lines
of evidence to construct a phylogenetic
tree.
• Modern taxonomic placement involves:
– Morphology
– Chromosomal characteristics
– Nucleotide and amino acid sequences
(chromosomes)
– Embryological development
– Information from the fossil record.
Phylogenetic tree
• Family tree that shows the evolutionary
relationships thought to exist among
groups of organisms.
• Represents a hypothesis and is based on
several lines of evidence.
• Subject to change as new information
arises.
Phylogenetic Tree
Interpreting a Phylogenetic Tree
• Organism at base of tree is common
ancestor to all the others in the tree.
• Branch points indicate the evolution of
some characteristic that splits a group into
two groups.
• Groups shown at tips of branches include
organisms that have evolved most
recently.
The Fossil Record
• Provides clues to evolutionary
relationships
• Some organisms such as some ocean
invertebrates have fairly complete fossil
records. Others are incomplete.
• May provide framework for phylogenetic
tree which can then be confirmed with
other lines of evidence.
Fossil Record
Fossil record (horse, whale)
Morphology
• Homologous features:
– Show descent from a common ancestor.
– Common basic structure. Example bird
wings and bat wings.
– The greater the number of homologous
features two organisms share, the more
closely related they are thought to be.
Homologous Features
Homologous Features
• Analogous features:
–Evolved independently.
–Differ in structure. Example: fly’s
wings and bat’s wings.
Analogous Features
Embryological Patterns of
Development
• Early patterns of embryological
development provide evidence of
phylogenetic relationships.
• Provide means of testing hypothesis about
relationships that have been developed
from other lines of evidence.
• Blastopore formation: In echinoderms and
chordates, indentation forms the posterior
end of the digestive system, in other
animals it forms the anterior end.
Embryonic Development
Chromosomes and Macromolecules
• Taxonomists use comparisons of
macromolecules such as DNA, RNA and
proteins as a kind of “molecular clock”.
• Scientists compare amino acid sequences for
homologous protein molecules of different
species.
– The number of amino acid differences is a clue to
how long ago two species diverged from a shared
evolutionary ancestor.
– Not perfect because it assumes that all changes in
amino acid sequencing are random and not affected
by natural selection. Additionally amino acids can
change at different rates in different organisms.
Chromosomes and Macromolecules
- continued
• Molecular clock model is used together
with other data to estimate degrees of
relatedness.
• Scientists also compare karyotypes or
patterns of chromosomes of two related
species.
– Regions of chromosomes that have the same
pattern of banding are clues to the degree of
relatedness.
DNA comparisons (Artic bluegrass)
DNA banding patterns
This cladogram is based on similar amino acid sequences in a specific protein
produced by these plants. The initials M,G, and so on indicate different amino acids.
The yellow squares indicate differences within the otherwise-identical sequences.
This phylogenetic diagram is based on analyses of the DNA of many kinds of mammals.
These analyses do not support a systematic grouping of pangolins with either African
aardvarks or South American anteaters. Instead, pangolins seem to be most closely
related to carnivores, such as bears and dogs. Biologists sometimes revise their
classifications in light of such new evidence.
Cladistics
• Relatively new system of phylogenetic
classification.
• Uses certain features of organisms called
shared derived characteristics to establish
evolutionary relationships.
• Derived character: feature that apparently
evolved only within the group under
consideration. Example: feathers in birds
are inherited from a common ancestor.
Cladograms
• Ancestral diagrams made by means of
cladistic analysis.
• To interpret a cladogram:
– Begin at the bottom and move up the axis that
shows branch points.
– Groups and derived characteristics appeared
in the order shown.
– Example: all groups branching above “hair”
have hair. Those below do not.
Cladogram
This cladogram groups several major kinds of plants according to their shared, derived
characters. The most common character (vascular tissue) is shared by all groups. The
least common character (flowers) separates flowering plants from all other plants.
Conflict between tradition taxonomy
and newer cladistics
• Traditional: Snakes, lizards,
crocodiles are all reptiles. Birds in
class by themselves.
• Newer: Dinosaurs are more closely
related to birds and crocs than to
snakes and lizards. Reptiles did not
spring from one common ancestor but
are a composite of several branches
that have occurred during evolution of
vertebrates.
Traditional systematists placed crocodiles in the class Reptilia, but placed birds in
the class Aves. In contrast, cladistic taxonomists have grouped crocodiles and birds
together in a clade named Archosauria. Notice that clades do not have category
18-3 Two Modern Systems of
Classification
• Six Kingdom System
• Three Domain System
Six Kingdom System
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Kingdom Archaebacteria
Kingdom Eubacteria
Kingdom Protists
Kingdom Fungi
Kingdom Plantae
Kingdom Animalia
Six Kingdoms
Kingdom Archaebacteria
Kingdom Archaebacteria
• Unicellular
• Prokaryotes with distinctive cell
membranes
• Biochemical and genetic properties
that differ from all other kinds of life.
• Some autotrophic – produce food by
chemosynthesis and methane waste.
• Many live in harsh environments –
sulfurous hot springs, salty lakes,
anaerobic environments, intestines of
animals
• “archae” = ancient
• May be directly descended from and
very similar to first organisms on
Earth
Kingdom Eubacteria
Kingdom Eubacteria
• “eu” = true
• Unicellular, prokaryotes
• Bacteria that affect your life: tooth
decay, turn milk to yogurt, food
poisoning, illness
• Most use oxygen, but a few cannot live
in O2
• Both Eubacteria and archaebacteria
make up the greatest number of living
things on Earth.
• Both Eubacteria and archaebacteria
reproduce by binary fission but do
have methods of genetic
recombination to allow evolution to
occur.
• Short generation times (as little as 30
minutes) allow rapid evolutionary
response to environmental change.
Example: antibiotic resistant bacterial
infection.
Kingdom Protista
Kingdom Protista
• Eukaryotic (membrane-bound true nucleus,
linear chromosomes, membrane bound
organelles)
• Mostly single-celled organisms, but some
multicellular but lack specialized tissues
• Many species distantly related. Broad kingdom
contains all eukaryotes that are not plants,
animals, or fungi. 50,000 species.
• Sexual cycles of many are unknown but thought
to have some process of genetic recombination.
Kingdom Fungi
Kingdom Fungi
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Heterotrophic
Unicellular and multicellular
Eukaryotic
Absorb nutrients rather than ingesting them the
way some protists such as amoebas do.
• Sexual cycles not known for many fungi. It is
likely that all species have some way of
promoting genetic recombination.
• 100,000 species – mushrooms, puffballs, rusts,
smuts, mildews, and molds.
Kingdom Plantae
Kingdom Plantae
• Multicellular plants
• All except for a few parasitic forms are
autotrophic and use photosynthesis as a
source of energy
• Eukaryotic
• Most live on land
• Most have a sexual cycle based on
meiosis
• 350,000 species identified including
mosses, ferns, conifers, flowering plants.
Kingdom Animalia
Kingdom Animalia
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Eukaryotic
Multicellular
Heterotrophs
Most have symmetrical body organization
and move about their environment
• Standard sexual cycle that employs
meiosis for the recombination of genes.
Three Domain System
• The young science of molecular biology has led
to an alternative to the 6 kingdom system
• Carl Woese (1928- ) of University of Illinois.
Comparing sequences of ribosomal RNA in
many organisms. Estimated how long ago pairs
of organisms shared a common ancestor.
• Phylogenetic tree drawn from this data shows
that living things seem to fall naturally into 3
broad groups or domains.
This phylogenetic diagram represents hypotheses of the evolutionary relationships
between the major recognized groups of organisms. Notice the alignment of the three
domain names (Bacteria, Archaea, and Eukarya) with three major “branches” of the “tree”
of life.
The six-kingdom system of classification can be aligned with the newer system of three
domains. However, biologists have proposed adding, subdividing, or replacing some
kingdoms. Biologists have also proposed other levels of taxa.
The Three Domains
• Bacteria (Eubacteria)
• Archaea (Archaebacteria)
• Eukarya (Eukaryotes): includes Protista,
Fungi, Plantae, Animalia
Three Domains
Three Domains
Conclusions from the
Three Domain System
• All eukaryotes have true nuclei with linear
chromosomes and membrane-bound
organelles.
• The most variation in Eukarya is among
protists.
• When considered from the perspective of
the complete diversity of life on Earth, the
fungi, plants, and animals are quite similar
to each other.