Classification Notes

Classification

Lesson Outcomes

• Measures of biodiversity rely on classification and are used to make comparisons across spatial and temporal scales.

• Define classification.

• Outline the binomial system of classification.

• Explain the hierarchy of classification.

• Explain why and how scientists classify organisms

• Biological classification is hierarchical and based on molecular sequences, different levels of similarity of physical features and methods of reproduction.

• Describe the different sources of information we can use to classify species

• Recall the Linnean classification system and describe how species diversity changes down the groups

• Know characteristics of the five main kingdoms.

Classification

• Classification: the process of grouping, naming, and organizing using non-ambiguous criteria.

Classification Systems

• Classification systems are based on international conventions and are subject to change through debate and resolution; changes are based on all currently available evidence

• Classification systems in Biology are standard worldwide.

Reasons for Classification

• It’s a way of organizing information – the diversity of life is vast!

• It helps biologists to observe and analyse patterns, trends and relationships between organisms.

• It allows biologists to communicate with one another.

• Invasive species can be identified more easily and accurately.

Classification of Species

• We can classify species using different sources of information:

  • Molecular sequences

  • Physical features

  • Methods of reproduction

Molecular Sequences

• By comparing DNA and proteins between organisms, we can see how similar or different they are.

• This can also be used to see if two populations are the same or separate species.

• Biologists can analyze the chemical sequences in molecules such as DNA and proteins to classify organisms.

Physical Features

• Also known as Structural / morphological features

• Before genetic technologies, physical comparisons were the main way to classify living creatures

• Issues arose due to convergent evolution.

Methods of Reproduction

• Methods of reproduction refers to whether a species reproduces sexually or asexually.

• Some species may be able to reproduce both ways, depending on environmental conditions.

• Modes of reproduction typically refers to the method of embryonic development;

• For example, do they lay eggs? Is there a placental connection?

Taxonomy

• Taxonomy: The practice of classifying organisms according to their presumed natural relationships.

• A biologist named Carolus Linnaeus started this naming system.

• He also chose to use Latin words.

• Hierarchy:

  • Kingdom

  • Domain

  • Phylum

  • Class

  • Order

  • Family

  • Genus

  • Species

Levels of Classification

• Organisms are classified into a hierarchy of groups called taxa or taxonomic levels.

• At each level of classification below the Domain taxa, the groups contain fewer types of organisms and the organisms become more similar.

Levels of Classification - Example

• The heirarchy listed from Kingdom to Species

  • Kingdom

  • Phylum

  • Class

  • Order

  • Family

  • Genus

  • Species

• An example with the Grizzly bear

  • KINGDOM Animalia

  • PHYLUM Chordata

  • CLASS Mammalia

  • ORDER Carnivora

  • FAMILY Ursidae

  • GENUS Ursus

  • SPECIES Ursus arctos

Taxonomic Levels: Domain

• Domain is the broadest taxonomic level; there are only three.

• The division of life into these domains is based on cellular characteristics:

• Organisms in Domains Archaea and Bacteria have differences in the way DNA is stored and proteins are synthesized which means that they are classified in separate domains.

Taxonomic Levels: Kingdoms

• We can further divide the Domains into five kingdoms: Animalia, Plantae, Fungi, Protista and Monera.

• Classification to the Kingdoms is mostly based on cellular differences.

Kingdom: Animalia

• Animal cells are more classified by what they don’t have.

• Animal cells will never have:

  • Any type of cell wall (not the same as a cell membrane)

  • Chloroplasts

Kingdom: Plantae

• Plants cells often have a rectangular shape and contain:

  • Cell wall made of cellulose (in addition to a cell membrane).

  • Chloroplasts (green)

Kingdom: Fungi

• Fungi grow much like plants but ‘eat’ like animal cells do.

• Specialized cell structures include:

  • Cell wall made of chitin (in addition to a cell membrane).

Kingdom: Protista

• Protists share similarities but do not fit into the Animalia, Plantae or Fungi kingdoms.

• Some cellular features include:

  • No cell wall

  • Chloroplasts (green)

Kingdom: Monera

• Monera have a relatively simple structure. They have:

  • Cell wall and cell membrane

  • No nucleus or mitochondria (prokaryotes)

Summary: Domain & Kingdoms

• Domain

  • Archaea

  • Bacteria

  • Eukarya

• 5 Kingdom System Example

  • Monera

  • Protista

  • Fungi

  • Plantae

  • Animalia

Scientific Naming

• Aka. binomial nomenclature

• Scientific names (binomial names) are given to individual species to reduce confusion between scientists.

• Common names are not prescriptive (have no rules).

• This leads to confusing names and the use of the same name many times.

• Each species only have one name, this aids in communication

Scientific Names

• Scientific names are the latin, genus and species words for an organisms.

• For example, humans are Homo sapiens.

Binomial Nomenclature Rules

• This system for naming organisms is recognized by scientists world-wide and often derived from Latin or Green root words that describe the features of the organism.

• When writing scientific names, it is important to:

  • Write the Genus with a Capital Letter.

  • Write the species in lower case.

  • Write the whole name in italics. (or underline if handwritten)

Abbreviating Scientific Names

• When a scientific name is used the first time both names are written.

• In subsequent uses the genus name is abbreviated to its first capital letter and the whole species name is used.

• EXAMPLE:

  • Tulip: Tulipa gesneriana → T. gesneriana

  • Wolf: Canis lupus → C. lupus

Glossary

• DNA: Deoxyribonucleic acid – a double helix structure composed of adenine, thymine, cytosine and guanine bases which code for the various characteristics of an organism.

• Convergent Evolution: Convergent evolution is when organisms independently find their way to the same evolutionary solution for the same environmental problem – it creates analogous structures.

• Sexual Reproduction: The mixing of gametes (sex cells) from two individuals.

• Asexual Reproduction: Without the formation of gametes (sex cells).

Recommended resources

• Biology WA: CHAPTER 2: Biological Classification (pages 43 - 50)

  • Question set 2.3: Question 1 (page 44)

  • Question set 2.4: Questions 2-5 (page 44)

  • Question set 2.5: Questions 1-2 (page 50)

• Biozone:

  • Act 168 – The New Tree of Life (page 218)

  • Act 170 – Features of the five kingdoms (page 224)

  • Act 171 – Classification System (page 225-6)