Exploring Animal Diversity

Front 1

Classification of organisms

Back 1

Taxonomy- The study of the theory, procedure, and rules of classification of organisms, based on similarities and differences

Classification- The process of delimitation, ordering, and ranking taxa at all levels by inductive procedures

Taxon- is a group created by taxonomists and organised in a hierarchical classification

Front 2

Why classify organisms?

Back 2

1. To make things easier to find, identity and study

2. To understand the relationships among taxa

Front 3

Naming organisms

Back 3

Common vs Scientific name

• Many organisms have ‘common names’

• But sometimes more than one common name for same organism

• Or sometimes same common name for more than one organism

Front 4

Binomial Nomenclature

Back 4

A two name system for writing scientific names

Genus- Written first and always capitalised

Species- Written second and never capitalised

• Both words are to be italicised if typed, it underlined if hand written

• “Formal” scientific names should have a third part, the authority.

• The authority is not italicised or underlined

Front 5

Trinomial System

Back 5

In certain cases, there is a need to add a third name to the binomial to provide further information of the organism. These are names of subspecies, forms, cultivar groups, etc.

Front 6

Hierarchical classification

Back 6

Linnaeus introduces a system for grouping species in increasingly broad categories

The taxonomic groups from broad to narrow are; domain, phylum, class, order, family, genus and species

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Traditionally, taxonomy used anatomical similarities to group organisms

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Phenotypic similarity may not accurately predict evolutionary relationships

• Darwin envisioned that all species were descended from a single common ancestor

• He depicted this history of like as a branching tree

• “Descent with modification”

• Phylogenetic trees show historical relationships, not similarities

Front 8

Tree-thinking

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Phylogenetic trees are the most direct representation of the principle of common ancestry- the very core of evolutionary theory

An evolutionary tree- also known as a phylogeny- is a diagrammatic depiction of biological entities that are connected through common descent

Front 9

Systematics

Back 9

Field of biology whose goal is the determination of the evolutionary history and relationships among organisms

Phylogenetics uses a combination of different lines of evidence:

• Fossil record

• Morphology

• Embryological patterns of development

• Molecular data

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Fossil record

Back 10

The fossil record refers to the order in which fossils appear within layers of rock that mark the passing of geologic time. It does not provide a complete evolutionary history

Front 11

Morphology

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Organisms with similar morphologies sequences are likely to be more closely related than organisms with different structures or sequences

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Embryology

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The formation and early development of living organisms

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Molecular data

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• DNA and RNA sequences of nucleic acids can be compared to determine phylogeny: these nucleic acids retain a record of an organisms evolutionary history.

• Molecular genetics work with alleles/genes that are under neutral selection

• Mitochondrial DNA is also highly variable in natural populations because of its elevated mutation rate, which can generate signals about population history over short time frames

Front 14

Phylogenetic classification

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Based on known evolutionary history

Advantages:

- Classification reflects pattern of evolution

- Classification not ambiguous

Front 15

Cladistic classification

Back 15

A process of phylogeny reconstruction that relies solely on shared, derived characteristics

Front 16

Cladistic Methodology

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• Determine which characters are primitive and which are derived

Outgroup= taxon that is related to, but not part of the set taxa for which we are constructing the tree

• Construct all possible trees for the taxa in the in group

• Map evolutionary transition in character states onto each tree

• Find the most parsimonious tree- the one with the fewest evolutionary changes

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The principle of parsimony

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• Phylogenies can be extremely complicated

• Out hypothesis should be the simplest explanation that is consistent with facts

• A phylogenetic tree is a hypothesis. There may be many possible trees, but the simplest one is probably the most accurate

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Clade

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An ancestral taxon plus the entire set of species that have descended from it

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Sister taxa

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Groups that share immediate common ancestor

Front 20

Analogous structures

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Same function, but are not from the same descent

Front 21

Homologous Structures

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Different function, but from the same descent