Transcript Biology_1_&_2_files/10 Taxonomy ACADEMIC

Taxonomy
Biology 2
Mr. Greene
Unit 10
Bellringer
Look through this chapter and list the name of each type of organism
illustrated, such as cactuses, bees, humans, oaks, etc. Suggest reasons why a
scientific method of clasification is useful to study these organisms.
Key Ideas
 Why do biologists have taxonomic systems?
 What makes up the scientific name of a species?
 What is the structure of the modern Linnaean system of classification?
Taxonomy
 the classification of
organisms
The Need for Systems
 About 1.7 million species have been named and described by scientists.
 Scientists think that millions more are undiscovered.
 Biologists use taxonomic systems to organize their knowledge of
organisms.
 These systems attempt to provide consistent ways to name and
categorize organisms.
 Taxonomic systems do not use common names, which may be confusing
because they are different in different places.
What's in a Scientific Name?
 scientific name - the two-word name each organism on Earth is
assigned
 all biologists over the world use these names
 binomial nomenclature – the system of assigning names
 genus = 1st word = describes organism in a general way
 group of organisms that share major characteristics
 First letter is ALWAYS CAPITALIZED
 species = 2nd word = identifies the exact kind of living thing
 each different kind of organism
 ALWAYS LOWER CASE
 The correct name MUST include both parts of its scientific name
SCIENTIFIC NAMING RULES
 1. Must be Latin or constructed using Latin rules
 2. Two different organisms cannot be assigned the same name
 3. Organisms of the same genus must have different species names
 4. Organisms of different genera CAN have the same species name
 e.g. green anole lizard
= Anolis carolinensis
 chickadee
= Parus carolinensis
 5. Pick name that relates to organisms location, trait, etc.
 e.g. Tyrannosaurus rex = tyrant-lizard king
Why are names in Latin?
 Latin was used in academic
circles in the Middle Ages when
scientists began naming
organisms.
 Hence, it was easier to
communicate regardless of
language barrier.
 Easier to keep names for all 1.7
million organisms in Latin then
renaming them
Who Created the System?
 Carl Linnaeus - Swedish botanist
 long names were used before he
came along
 (some up to 15 words long)
 When reading or writing scientific
names, remember the following:
 if the genus/species is already given
you can abbreviate the genus
 e.g. Homo sapiens = H. sapiens
 based on physical, genetic,
biochemical and behavioral
similarities
 taxon – each level of the naming
system
Biological Hierarchy of
Classification
Taxanomic Hierarchy
Kingdom
Phylum
Class
Order
Family
Genus
Species
North America
United States
Ohio
Lake
Mentor
Center Street
6477
Animalia
Chordata
Mammalia
Primates
Hominidae
Homo
Homo sapiens
Sam gave Fred one copper padlock key.
King Philip came over from Geneva, Switzerland.
Classification of Ursus arctos
Grizzly bear
Black bear
Giant
panda
Red fox
KINGDOM Animalia
PHYLUM Chordata
CLASS Mammalia
ORDER Carnivora
FAMILY Ursidae
GENUS Ursus
SPECIES Ursus arctos
Abert
squirrel
Coral
snake
Sea star
Classification of a Bee
Panthera leo? Part One
Panthera leo? Part Two
The Linnaean System
 The category domain has been invented since Linnaeus’ time.
 This category recognizes the most basic differences among cell types.
 All living things are now grouped into one of three domains.
The Linnaean System, continued
 A species is usually defined as a
unique group of organisms united by
heredity or interbreeding.
 In practice, scientists tend to define
species based on unique features.
 For example, Homo sapiens is
recognized as the only living
primate species that walks upright
and uses spoken language.
Summary
 Biologists use taxonomic systems to organize their knowledge of
organisms. They attempt to provide consistent ways to name and
categorize organisms.
 All scientific names for species are made up of two Latin or Latin-like
terms.
 In the Linnaean system of classification, organisms are grouped at
successive levels of a hierarchy based on similarities in their form and
structure. The eight levels of modern classification are domain,
kingdom, phylum, class, order, family, genus, and species.
Bellringer
Write the names of as many different kinds of cats as you can think of.
Most cats belong to the same genus, Felis. Identify which cats you think
belong to the same species.
Key Ideas
 What problems arise when scientists try to group organisms by apparent
similarities?
 Is the evolutionary past reflected in modern systematics?
 How is cladistics used to construct evolutionary relationships?
 What evidence do scientists use to analyze these relationships?
Traditional Systematics
 Scientists have traditionally used similarities in appearance and structure to group
organisms. However, this approach has been problematic.
 Some groups look similar but turn out to be distantly related.
 Other groups look different but turn out to be closely related.
 For example, dinosaurs were once seen as a group of reptiles that became extinct
millions of years ago.
 Birds were seen as a separate, modern group that was not related to any reptile group.
 Fossil evidence has convinced scientists that birds evolved from one of the many lineages
of dinosaurs.
 Some scientists classify birds as a subgroup of dinosaurs.
Problems with Traditional Classification
 based on structure
 how would you classify dolphins?
 with fish because of aquatic life
and limbs that look like fins
 with mammals because warm
blooded and breathe air
Phylogenetics
 Scientists who study systematics are interested in phylogeny, or the
ancestral relationships between species.
 Grouping organisms by similarity is often assumed to reflect phylogeny, but
inferring phylogeny is complex in practice.
 Reconstructing a species’ phylogeny is like trying to draw a huge family tree
over millions of generations.
 Not all similar characteristics are inherited from a common ancestor.
 Consider the wings of an insect and the wings of a bird.
 Both enable flight, but the structures of the two wings differ.
 Fossil evidence also shows that insects with wings existed long before birds appeared.
Phylogenetics, continued
 Through the process of convergent evolution, similarities may evolve in groups
that are not closely related.
 Similar features may evolve because the groups have adopted similar habitats
or lifestyles.
 Similarities that arise through convergent evolution are called analogous
characters.
Phylogenetics, continued
 Grouping organisms by similarities is




subjective.
Some scientists may think one
character is important, while another
scientist does not.
For example, systematists historically
placed birds in a separate class from
reptiles, giving importance to
characters like feathers.
Fossil evidence now shows that birds are considered part of the “family tree” of
dinosaurs.
This family tree, or phylogenetic tree, represents a hypothesis of the relationships
between several groups.
Cladistics
 Cladistics is a method of
analysis that infers phylogenies
by careful comparisons of shared
characteristics.
 Cladistics is an objective method
that unites systematics with
phylogenetics.
 Cladistic analysis is used to select
the most likely phylogeny among
a given set of organisms.
Cladistics, continued
 Cladistics focuses on finding
characters that are shared between
different groups because of shared
ancestry.
1 Tetrapoda clade
2 Amniota clade
3 Reptilia clade
4 Diapsida clade
5 Archosauria clade
 A shared character is defined as
FEATHERS &
TOOTHLESS
BEAKS.
ancestral if it is thought to have
evolved in a common ancestor of
both groups.
SKULL OPENINGS IN
FRONT OF THE EYE &
IN THE JAW
OPENING IN THE SIDE OF
THE SKULL
SKULL OPENINGS BEHIND THE EYE
EMBRYO PROTECTED BY AMNIOTIC FLUID
 A derived character is one that
evolved in one group but not the
other.
FOUR LIMBS WITH DIGITS
DERIVED CHARACTER
Cladistics, continued
 For example, the production of seeds is a character that is present in all living
conifers and flowering plants, and some prehistoric plants.
 Seed production is a shared ancestral character among those groups.
 The production of flowers is a derived character that is only shared by
flowering plants.
Cladistics, continued
 Cladistics infers relatedness by identifying shared derived and ancestral
characters among groups, while avoiding analogous characters.
 Scientists construct a cladogram to show relationships between groups.
 A cladogram is a phylogenetic tree that is drawn in a specific way.
Cladistics, continued
 Organisms are grouped together through identification of their shared
derived characters.
 All groups that arise from one point on a cladogram belong to a clade.
 A clade is a set of groups that are related by descent from a single ancestral
lineage.
Cladistics, continued
 Each clade is usually compared with an outgroup, or group that lacks some of
the shared characteristics.
 The next slide shows a cladogram of different types of plants.
 Conifers and flowering plants form a clade.
 Ferns form the outgroup.
Cladogram: Major Groups of Plants
Traditional Classification
Versus Cladogram
Appendages
Crab
Conical Shells
Barnacle
Limpet
Crustaceans
Crab
Gastropod
Barnacle
Limpet
Molted exoskeleton
Segmentation
Tiny free-swimming larva
CLASSIFICATION BASED ON
VISIBLE SIMILARITIES
CLADOGRAM
Traditional Classification
Versus Cladogram
Appendages
Crab
Conical Shells
Barnacle
Limpet
Crustaceans
Crab
Gastropod
Barnacle
Limpet
Molted exoskeleton
Segmentation
Tiny free-swimming larva
CLASSIFICATION BASED ON
VISIBLE SIMILARITIES
CLADOGRAM
Cladogram: Major Groups of Plants
Inferring Evolutionary Relatedness,
continued
Morphological Evidence
 Morphology refers to the physical structure or anatomy of organisms.
 Large-scale morphological evidence, like seeds and flowers, have been
well studied.
 Scientists must look carefully at similar traits, to avoid using analogous
characters for classification.
Inferring Evolutionary Relatedness,
continued
 An important part of morphology in multicellular species is the pattern
of development from embryo to adult.
 Organisms that share ancestral genes often show similarities during the
process of development.
 For example, the jaw of an adult develops from the same part of an
embryo in every vertebrate species.
Inferring Evolutionary Relatedness,
continued
Molecular Evidence
 Scientists can now use genetic information to infer phylogenies.
 Recall that as genes are passed on from generation to generation,
mutations occur.
 Some mutations may be passed on to all species that have a common
ancestor.
Similarities in DNA and RNA
 often you cannot compare
organisms that are diverse
 (i.e. elephants and an amoeba)
 all organisms use DNA and RNA to
pass on info and to control growth
and development
 DNA and RNA are a good way of
comparing organisms
 humans – a gene that codes for
myosin (protein in muscles)
 yeast – has same gene that codes for
myosin that enables internal cell
parts to move
Molecular Clocks
 models that use DNA
comparisons to estimate then
length of time that two species
have been evolving
independently
 i.e. pendulum clock
 it marks time with a swinging
pendulum
 molecular clock
 marks time by mutations
Inferring Evolutionary Relatedness,
continued
 Genetic sequence data are now used widely for cladistic analysis.
 First, the sequence of DNA bases in a gene (or of amino acids in a
protein) is determined for several species.
 Then, each letter (or amino acid) at each position is compared.
Similarities in Amino Acid
Sequences
Inferring Evolutionary Relatedness,
continued
 At the level of genomes, alleles may be lost or added over time.
 Another form of molecular evidence is the presence or absence of
specific alleles—or the proteins that result from them.
 From this evidence, the relative timing between genetic changes can be
inferred.
Inferring Evolutionary Relatedness,
continued
Evidence of Order and Time
 Cladistics can determine only the relative order of divergence, or
branching, in a phylogenetic tree.
 The fossil record can often be used to infer the actual time when a group
may have begun to “branch off.”
 For example, using cladistics, scientists have identified lancelets as the
closest relative of vertebrates.
Inferring Evolutionary Relatedness,
continued
 The oldest known fossils of vertebrates are about 450 million years old.
 But the oldest lancelet fossils are 535 million years old.
 So, these two lineages must have diverged more than 535 million years
ago.
Inferring Evolutionary Relatedness,
continued
 DNA mutations occur at
relatively constant rates, so they
can be used as an approximate
“genetic clock.”
 Scientists can measure the
genetic differences between taxa
and estimate time of divergence.
Inferring Evolutionary Relatedness,
continued
Inference Using Parsimony
 Modern systematists use the principle of parsimony to construct
phylogenetic trees.
 This principle holds that the simplest explanation for something is the
most reasonable, unless strong evidence exists against that explanation.
 Given two possible cladograms, the one that implies the fewest character
changes between points is preferred.
Summary
 Scientists traditionally have used similarities in appearance and structure
to group organisms. However, this approach has been problematic.
 Grouping organisms by similarity is often assumed to reflect phylogeny,
but inferring phylogeny is complex in practice.
 Cladistic analysis is used to select the most likely phylogeny
among a given set of organisms.
 Biologists compare many kinds of evidence and apply logic
carefully in order to infer phylogenies.
Bellringer
What are the six kingdoms representing life on Earth?
Key Ideas
 Have biologists always recognized the same kingdoms?
 What are the domains and kingdoms of the three-domain system of
classification?
Updating Classification Systems
 For many years after Linnaeus created his system, scientists only recognized two
kingdoms: Plantae and Animalia.
 Biologists have added complexity and detail to classification systems as they
have learned more.
 Many new taxa have been proposed, and some have been reclassified
 Sponges, for example, used to be classified as plants.
 Microscopes allowed scientists to study sponge cells.
Plantae
 Scientists learned that sponge cells are much more like animal cells, so today
sponges are classified as animals.
Animalia
Updating Classification Systems,
continued
 In the 1800s, scientists added Kingdom Protista as a taxon for
unicellular organisms.
 Soon, they noticed differences between prokaryotic and eukaryotic cells.
 Scientists created Kingdom Monera for prokaryotes.
Plantae
Animalia
Protista
Updating Classification Systems,
continued
 By the 1950s, Kingdoms Monera, Protista, Fungi, Plantae, and Animalia
were used.
 In the 1990s, genetic data suggested two major groups of prokaryotes.
 Kingdom Monera was split into Kingdoms Eubacteria and
Archaebacteria.
Plantae
Animalia
Protista
Monera
Fungi
What Is a Species?
 basic unit of evolution
 gives rise to new genera, families, etc.
 new hierarchy results when enough changes have been made to species
 organisms that are able to interbreed to produce fertile offspring
 works for most animals
 horse and zebra have offspring that are sterile
 dogs, coyotes, wolves can interbreed and make a hybrid
 dogs – different breeds is not the same thing as different species
Concept Map
Living Things
are characterized by
Eukaryotic cells
and differing
Important
characteristics
which place them in
Cell wall
structures
such as
Domain
Eukarya
Prokaryotic cells
which is subdivided into
which place them in
Domain
Bacteria
Domain
Archaea
which coincides with
which coincides with
Kingdom
Eubacteria
Kingdom
Archaebacteria
Kingdom
Plantae
Kingdom
Fungi
Kingdom
Protista
Kingdom
Animalia
The Three-Domain System
 As biologists saw differences between two kinds of prokaryotes, they
saw similarities among eukaryotes.
 A new system divided all organisms into three domains: Bacteria,
Archaea, and Eukarya.
 Today, most biologists tentatively recognize three domains and six
kingdoms.
Phylogenetic Diagram of Major
Groups of Organisms
The Three-Domain System,
continued
 Major taxa are defined by major characteristics, including:
 Cell Type: prokaryotic or eukaryotic
 Cell Walls: absent or present
 Body Type: unicellular or multicellular
 Nutrition: autotroph (makes own food) or heterotroph (gets nutrients
from other organisms)
The Three-Domain System,
continued
 Related groups of organisms will also have similar genetic material and
systems of genetic expression.
 Organisms may have a unique system of DNA, RNA, and proteins.
 The following slide shows major characteristics for organisms in each
domain and kingdom.
Kingdom and Domain
Characteristics
1/2) Monera
 evolved from a common
 unicellular
 ancestor 4 million years ago
 lack nuclei
 lack organelles
 oldest forms of life
ARCHAE
 A) Archaebacteria
 unicellular and prokaryotes and
found in extreme environments
 gave rise to eukaryotes and
evolved before oxygen filled
atmosphere
 cell walls lack peptidoglycan
 extremophiles
BACTERIA
 B) Eubacteria
 unicellular and prokaryotes with





5,000 species
thick, rigid cell walls with
peptidoglycan
common environments
gave rise to eukaryotic cell
organelles
both autotrophic and
heterotrophic forms
some require oxygen and some
do not
The Three-Domain System
 Domain Eukarya is made up of Kingdoms Protista, Fungi, Plantae, and Animalia.
 Members of the domain are eukaryotes, which are organisms composed of
eukaryotic cells.
 These cells have a complex inner structure that enabled cells to become larger
than the earliest cells.
 This complex inner structure also enabled the evolution of multicellular organisms.
 All eukaryotes have cells with a nucleus and other internal compartments.
 Also, true multicellularity and sexual reproduction only occur in eukaryotes.
EUKARYA
 3) Protist
 greatest variety
 some unicellular; some are not
 some autotrophic; some
heterotrophic
 ancestors of plants, fungi, and
animals
 includes protozoa (amoeba and
paramecium); algae (kelp
and seaweed)
EUKARYA
 4) Fungi
 heterotrophic
 most are multicellular and feed





on dead/decaying organic matter
secrete digestive enzymes into
food source
they then absorb smaller food
molecules into their bodies
mushrooms, yeast (unicellular),
molds
thin filaments that penetrate the
soil or decaying organisms
70,000 species
EUKARYA
 5) Plant
 multicellular, photosynthetic






autotrophs
nonmotile (unable to move place
to place)
mosses, ferns, flowers, trees
most grow on dry land, some
grow in water
have cell walls which contain
cellulose
green algae are their ancestors
350,000 species
EUKARYA
 6) Animal
 multicellular and heterotrophic
 1 million known species
 evolved in the ocean
 no cell walls
 nearly all have a nervous system
of some sort
 1 million species
Cladogram of Six Kingdoms
and Three Domains
DOMAIN
ARCHAEA
DOMAIN
EUKARYA
Kingdoms
DOMAIN
BACTERIA
Eubacteria
Archaebacteria
Protista
Plantae
Fungi
Animalia
Summary
 Biologists have added complexity and detail to classification systems as
they have learned more.
 Today, most biologists tentatively recognize three domains and six
kingdoms.
 Domain Bacteria is equivalent to Kingdom Eubacteria.
 Domain Archaea is equivalent to Kingdom Archaebacteria.
 Domain Eukarya is made up of Kingdoms Protista, Fungi,
Plantae, and Animalia.