The Linnaean System of Classification

Questions and Answers

How can organisms be classified?

On physical similarities.

What is the science of naming and classifying organisms?

Taxonomy.

What is a group of organisms in a classification system called?

Taxon.

What system gives each species a two-part scientific name using Latin words?

Binomial nomenclature. Signup and view all the answers

What includes one or more species that are thought to be closely related?

Genus. Signup and view all the answers

How does the Linnaean taxonomy classify organisms?

It classifies organisms based on traits into groups called taxon, taxa. Signup and view all the answers

How does the Linnaean taxonomy name species?

It names species using a system called binomial nomenclature which gives each species a two-part scientific name. Signup and view all the answers

How are the seven levels of the Linnaean classification system organized?

Kingdom, phylum, class, order, family, genus, and species. Signup and view all the answers

Describe the trend in the levels, or taxa, as you move down from kingdom to species.

The taxa groups get smaller. Signup and view all the answers

List the seven levels of the Linnaean classification system.

Kingdom, phylum, class, order, family, genus, and species. Signup and view all the answers

Why did Linnaeus base his system of classification on physical similarities alone, as opposed to including molecular and genetic similarities?

Linnaeus didn't have the technology to find molecular and genetic similarities. Signup and view all the answers

Why are physical similarities among species not always the result of being closely related?

The species might have evolved similar physical features due to the environment, but can still have completely different cell types, molecular cells, and reproduce. Signup and view all the answers

Why do scientists today rely on molecular and genetic similarities to classify organisms?

Physical differences do not separate molecular similarities, and molecular and genetic similarities are a more reliable organization. Signup and view all the answers

What is taxonomy the science of?

Naming and classifying organisms. Signup and view all the answers

What is used in binomial nomenclature?

Words from the Latin language. Signup and view all the answers

In the binomial nomenclature naming system, what is each species given?

A scientific name that includes a genus name and a species descriptor. Signup and view all the answers

What is modern classification based on?

Evolutionary relationships. Signup and view all the answers

What does the term phylogeny refer to?

The evolutionary history for a group of species. Signup and view all the answers

What does cladistics classify organisms based on?

Evolutionary relationships, or common ancestry. Signup and view all the answers

What is a cladogram?

An evolutionary tree that suggests how species may be related. Signup and view all the answers

What are traits that are shared by some species but not by others called?

Derived characters. Signup and view all the answers

What is phylogeny?

The evolutionary history for a group of species. Signup and view all the answers

How can phylogeny be shown?

They can be shown as branching tree diagrams. Signup and view all the answers

Describe the main goal of cladistics.

To classify organisms based on evolutionary relationships, or common ancestry. Signup and view all the answers

What is a clade?

A group of organisms that share certain traits derived from a common ancestor. Signup and view all the answers

How are derived characters used in marking a cladogram?

They show the sharing of evolutionary relationships between organisms. Signup and view all the answers

On a cladogram, what is a node and what does it represent?

A place where a branch on a cladogram splits. It represents a common ancestor for all species above that point. Signup and view all the answers

Give two examples of molecular evidence that can be used to help determine species relatedness.

Similar protein sequences and similar DNA sequences. Signup and view all the answers

Why are evolutionary trees often changed?

New evidence can lead scientists to change an evolutionary tree. Signup and view all the answers

What can be concluded if the genes of two species are found to be nearly identical?

They have the same DNA sequence. Signup and view all the answers

What do the Greek roots of phylogeny mean?

Phylogeny organizes organisms in classes based on their origins. Signup and view all the answers

Study Notes

Organism Classification

Organisms are classified based on physical similarities.
Taxonomy is the science of naming and classifying organisms.
A taxon is a group of organisms in a classification system.

Naming Species

Binomial nomenclature is a system that assigns each species a two-part scientific name using Latin words.
Each species is identified by a genus name and a species descriptor.

Linnaean Taxonomy

Linnaean taxonomy classifies organisms into groups called taxa based on traits.
The seven levels of Linnaean classification are: kingdom, phylum, class, order, family, genus, and species.

Taxonomic Trends

As you move from kingdom to species, the taxa groups get progressively smaller.
Linnaeus focused on physical characteristics due to the lack of technology for molecular and genetic analysis.

Limitations of Physical Similarities

Physical similarities don’t always indicate close relationships; traits may evolve similarly in different species due to environmental factors.
Molecular and genetic similarities offer a more reliable classification, as physical differences do not separate molecular traits.

Modern Classification

Modern classification prioritizes evolutionary relationships and phylogeny, which is the evolutionary history of a group of species.
Cladistics classifies organisms based on evolutionary relationships and common ancestry.

Cladograms and Clades

A cladogram is an evolutionary tree that suggests relationships among species.
A clade is a group sharing derived traits from a common ancestor.
Derived characters indicate shared evolutionary relationships and are used to construct cladograms.
A node on a cladogram represents a point where a branch splits, indicating a common ancestor for the species above it.

Molecular Evidence in Classification

Similar protein sequences and DNA sequences serve as molecular evidence to determine species relatedness.
Evolutionary trees are adjusted when new evidence arises, reflecting updated understanding of relationships.
Nearly identical genes between two species imply they have a similar DNA sequence.

Phylogeny Definition

Phylogeny, derived from Greek meanings class (phylo-) and origin (geny), organizes organisms based on their historical backgrounds and relationships.

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Explore the Linnaean System of Classification through interactive flashcards. Learn about the key concepts such as taxonomy, taxons, and binomial nomenclature, which are essential for understanding how organisms are classified. Perfect for students and enthusiasts of biology.