TOPIC 5.3 - CLASSIFICATION

5.3 – A – Taxonomy & Naming

Understandings

U3: Taxonomists classify species using a hierarchy of taxa.

Key Terms

Taxonomy

Taxa

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Taxonomy is the branch of Biology concerned with classifying

organsims. Taxonomists do this using a hierarchy of taxa (groups).

From broadest to most specifc, the taxa used are:

• Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

Understandings

U3: Taxonomists classify species using a hierarchy of taxa.

Key Terms

Taxonomy

Taxa

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Moving upwards, each level of hiearchy includes all of the taxa below

it. So, domains are the most general and have the highest

population while species are the most specific (population of 1).

Understandings

U4: All organisms are classified into three domains.

Key Terms

Bacteria

Archaea

Eukarya

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All organisms can be classified into three domains of life. Organisms

in each domain have common characteristics. The three are:

Bacteria Archaea Eukarya

Understandings

U4: All organisms are classified into three domains.

Key Terms

Bacteria

Archaea

Eukarya

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Domain Characteristics

BACTERIA EUKARYOTA ARCHAEA

Histones Absent PresentProteins similar to

histones

Introns Rare ManyPresent in some

genes

Cell Wall Structure

Made of peptidoglycan

Not present in all

Not made of peptidoglycan

Not made of peptidoglycan

Size / Organization

Small / Unicellular

Large / Uni- or Multicellular

Small / Unicellular

Reproduction Asexual Sexual / Asexual Asexual

The following chart shows similarities and differences between the

three domains:

Understandings

U4: All organisms are classified into three domains.

Key Terms

Bacteria

Archaea

Eukarya

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Compared to bacteria & eukarya, archaeans are found in a broad

range of habitats. This includes extreme habitats with high salt

concentrations and temperatures close to boiling.

Understandings

U4: All organisms are classified into three domains.

G5: Viruses are not classified as living organisms.

Key Terms

Viruses

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Viruses cannot perform all the

functions of life on their own.

Instead, they depend on the

metabolic processes of host

cells to reproduce.

So, they are not classified as

living organisms and do not fall

into any domain.

Understandings

U5: The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family, genus and species.

Applications

A1: Classification of one plant and one animal species from domain to species level.

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Most eukaryotes can be split into: animals, plants, protists or fungi.

Below are classification examples of two types of Eukarya.

Eukarya Domain

Examples

Understandings

U1: The binomial system of names for species is universal among biologists and has been agreed and developed at a series of congresses.

Key Terms

Binomial Nomenclature

IB BIO – 5.3 10Binomial nomenclature is the

naming system used by scientists

to identify species.

It names them by combining their

genus and species classifications.

The binomial naming rules are:

• The full name is italicized

• Genus is capitalized

• Species is lower-case

• After the first use, the genus

can be shortened to the first

letter.

Domain Eukarya

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Carnivora

Family Canidae

Genus Canis

Species Lupus

Dog Classification

Species Name

Genus + Species

Canis lupus → C. lupus

Understandings

U1: The binomial system of names for species is universal among biologists and has been agreed and developed at a series of congresses.

Key Terms

Binomial Nomenclature

IB BIO – 5.3 11Binomial Nomenclature Practice

http://study.com/cimages/multimages/16/Human_vs_Ostrich_Taxonomy.png

What would the binomial name be for the organisms below?

Understandings

U2: When species are discovered they are given scientific names using the binomial system.

Key Terms

Binomial Nomenclature

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When scientists discover new species,

they assign them a scientific name

using the binomial system.

This allows them to communicate

efficiently to deduce potential

relationships with known species.

VID

EO

SIB BIO – 5.3 13• Mahalo: Taxonomic Hierarchy

https://www.youtube.com/watch?v=kKwOlAqQoLk

• Eco Sapien: An Introduction to Taxonomy

https://www.youtube.com/watch?v=NRVJyUZoQow

• Educational Tree of Life: The Three Domains

https://www.youtube.com/watch?v=s9Yf_G7LU3c

5.3 – B – Natural Classification

Understandings

U6: In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species.

Key Terms

Natural Classification

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In natural classification, scientists

aim to classify species in a way that

reflects evolutionary paths.

So, all members of a

genus or higher should

have a common ancestor.

Understandings

U6: In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species.

Key Terms

Natural Classification

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Because of common ancestry, we

can expect species that fall in the

same higher taxa to share

characteristics.

Moving from broader to more

specific taxa, members will share

more and more traits.

Understandings

U7: Taxonomists sometimes reclassify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species.

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Natural classification can sometimes be difficult as some species

appear to have similar traits, but are not actually related. For

example, many unrelated species have evolved wings for flying.

Improvements in molecular technology have been used to address

this. New evidence can be used to reclassify species more

appropriately.

Understandings

U8: Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group.

Key Terms

Natural Classification

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Natural classification is helpful

in the research of biodiversity,

particularly when new species

are discovered.

• Identification of species

When unknown species are

encountered, their traits can

be compared to those of

known species.

This allows scientists to

predict its classification in

many taxa.

Understandings

U8: Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group.

Key Terms

Natural Classification

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• Prediction of characteristics

Because members of a group

have common ancestry, they

inherit similar traits.

So, chemicals or processes in

an organism are likely to be

found in organisms of the

same taxa.

The internal structures of

organisms can also be

predicted without direcly

oberving them.

REVIE

WIB BIO – 5.3 201. Define taxonomy.

2. List the levels of hierarchy of taxa from broadest to

most specific.

3. Outline the application of binomial nomenclature in

constructing a species’ scientific name.

4. Define natural classification.

5. Outline two benefits of natural classification when

encountering unknown species.

5.3 – C – Recognition Features

Applications

A2: External recognition features of bryophyta, filicinophyta, coniferophyta and angiospermophyta.

Key Terms

Recognition Features

IB BIO – 5.3 22Plants Recognition

Plants are classified together in a single kingdom, but can be divided

into four different phyla. Recognition features that can be used to

differentiate between them are shown here:

Applications

A2: External recognition features of bryophyta, filicinophyta, coniferophyta and angiospermophyta.

Key Terms

Recognition Features

IB BIO – 5.3 23Plants Recognition

Applications

A3: Recognition features of porifera, cnidaria, platylhelmintha, annelida, mollusca, arthropoda and chordata.

Key Terms

Recognition Features

IB BIO – 5.3 24Animal Recognition

Animals are divided into over 30 phyla, based on their

characteristics. Recognition features for 6 phyla are shown here:

Applications

A3: Recognition features of porifera, cnidaria, platylhelmintha, annelida, mollusca, arthropoda and chordata.

Key Terms

Recognition Features

IB BIO – 5.3 25Animal Recognition

Applications

A4: Recognition of features of birds, mammals, amphibians, reptiles and fish.

Key Terms

Recognition Features

IB BIO – 5.3 26Vertebrate Recognition

Most species of chordate belong to one of five major classes, each of

which contains more than a thousand species.

Skills

S1: Construction of dichotomous keys for use in identifying specimens.

Key Terms

Dichotomous Keys

IB BIO – 5.3 27Dichotomous keys are tools that can be used to determine the

identity of an unknown species sample. Each key is made up of

dichotomous (yes/no) questions.

For example, for a given set of organisms:

1. Does it have feathers? Yes go to Q2No go to Q3

2. Does it swim? Yes DuckNo Hen

3. Does it have legs? Yes LizardNo Snake

Skills

S1: Construction of dichotomous keys for use in identifying specimens.

Key Terms

Dichotomous Keys

IB BIO – 5.3 28Dichtomous Key Practice

1. Is it symmetrical? Yes go to Q2No Phylum Porifera

2. Symmetry is… Radial Phylum CnidariaBilateral go to Q3

3. Gastric tube… Mouth & Anus go to Q4Mouth, no anus Phylum Platyhelminthes

4. Segmentation… Yes go to Q5No, or not visible Phylum Mollusca

5. Exoskeleton? Yes Phylum ArthropodaNo Phylum Annelida

Skills

S1: Construction of dichotomous keys for use in identifying specimens.

Key Terms

Dichotomous Keys

IB BIO – 5.3 29Dichotomous keys can also be represented in tree form. Answering

the questions down the treel reveals a specimen’s identity.

http://ib.bioninja.com.au/_Media/dichotomous3_med.jpeg

REVIE

WIB BIO – 5.3 301. Outline the external recognition features of:

- Bryophyta - Filicinophyta

- Coniferophyta - Angiospermophyta

2. Compare the following pairs:

- Porifera & Chordata - Cnidaria & Mollusca

- Annelida & Arthropoda

3. Outline the characteristics of the five major classes

of chordates.

REVIE

WIB BIO – 5.3 314. Construct a dichotomous key that would identify

the following organisms: