science

Taxonomy of fish

Taxonomy of fish is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Taxonomy of fish rather than just read about it. In short: Fishes are a paraphyletic group and for this reason, the class Pisces seen in older reference works is no longer used in formal taxonomy. Traditional classification divides fish into three extant classes (Agnatha, Chondrichthyes, and Osteichthyes), and with extinct forms sometimes classified within those groups, sometimes as their own classes: Fish account for more than half of vertebrate species.

Key takeaways

Taxonomy of fish belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Taxonomy of fish to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Taxonomy of fish from memory before moving on to harder problems.

Reference excerpt

Fishes are a paraphyletic group and for this reason, the class Pisces seen in older reference works is no longer used in formal taxonomy. Traditional classification divides fish into three extant classes (Agnatha, Chondrichthyes, and Osteichthyes), and with extinct forms sometimes classified within those groups, sometimes as their own classes: Fish account for more than half of vertebrate species. As of 2016, there are over 32,000 described species of bony fish, over 1,100 species of cartilaginous fish, and over 100 hagfish and lampreys. A third of these fall within the nine largest families; from largest to smallest, these are Cyprinidae, Gobiidae, Cichlidae, Characidae, Loricariidae, Balitoridae, Serranidae, Labridae, and Scorpaenidae. About 64 families are monotypic, containing only one species.

Class "Agnatha" (jawless fish, paraphyletic) Subclass Cyclostomata (hagfish and lampreys) Subclass †"Ostracodermi" (armoured jawless fish, paraphyletic) Class Chondrichthyes (cartilaginous fish) Subclass Elasmobranchii (sharks and rays) Subclass Holocephali (chimaeras and extinct relatives) Class †"Placodermi" (armoured fish, paraphyletic) Class †"Acanthodii" ("spiny sharks", sometimes classified under Actinopterygii and paraphyletic) Superclass Osteichthyes (bony fish) Class Actinopterygii (ray-finned fish) Clade Sarcopterygii (lobe-finned fish and tetrapods) The above scheme is the one most commonly encountered in non-specialist and general works. Many of the above groups are paraphyletic, in that they have given rise to successive groups: Agnatha are ancestral to Placodermi, who again have given rise to Osteichthyes, as well as to Acanthodii, the ancestors of Chondrichthyes. With the arrival of phylogenetic nomenclature, the fishes has been split up into a more detailed scheme, with the following major groups:

Class Myxini (hagfish) Class †Pteraspidomorphi (early jawless fish) Class †Thelodonti Class †Anaspida Class Petromyzontida or Hyperoartia Family Petromyzontidae (lampreys) Class †Conodonta (conodonts) Class †Cephalaspidomorphi (early jawless fish) Clade †Galeaspida Clade †Pituriaspida Clade †Osteostraci Infraphylum Gnathostomata (jawed vertebrates) Class †"Placodermi" (armoured fish, paraphyletic) Class Chondrichthyes (cartilaginous fish) Class †"Acanthodii" (spiny sharks, paraphyletic) Superclass Osteichthyes (bony fish) Class Actinopterygii (ray-finned fish) Subclass Chondrostei Order Acipenseriformes (sturgeons and paddlefishes) Order Polypteriformes (reedfishes and bichirs). Subclass Neopterygii Infraclass Holostei (gars and bowfins) Infraclass Teleostei (many orders of common fish) Class Sarcopterygii (lobe-finned fish and tetrapods) Subclass Actinistia (coelacanths) Subclass Dipnoi (lungfish, sister group to the tetrapods) † – indicates extinct taxonSome palaeontologists contend that because Conodonta are chordates, they are primitive fish. For a fuller treatment of this taxonomy, see the vertebrate article. The position of hagfish in the phylum Chordata is not settled. Phylogenetic research in 1998 and 1999 supported the idea that the hagfish and the lampreys form a natural group, the Cyclostomata, that is a sister group of the Gnathostomata.

References

Worked examples

Example 1 — a first encounter with Taxonomy of fish

Start with the simplest possible case. Write down what Taxonomy of fish claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Taxonomy of fish before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Taxonomy of fish ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Taxonomy of fish

In research: Taxonomy of fish appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Taxonomy of fish in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Taxonomy of fish is common in secondary-school and first-year university syllabi. It links to neighbouring topics Fish taxonomy, Vertebrate taxonomy, so understanding it makes those chapters shorter.
In everyday life: Look for Taxonomy of fish outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Taxonomy of fish in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Taxonomy of fish means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Taxonomy of fish out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Taxonomy of fish in simple terms?

Why does Taxonomy of fish matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Taxonomy of fish?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Taxonomy of fish.