Chordata and chordate may sound similar, but they refer to different taxonomic groups. Chordata is a phylum, while chordate is a term for members belonging to the phylum Chordata. So while they are closely related terms, they have distinct meanings in biology.
What is a Phylum?
In biological classification, a phylum is a high-level taxonomic rank just below kingdom. Organisms within a phylum share basic body structures and developmental pathways. Phyla are then divided into smaller and more specialized groups called classes.
There are over 30 animal phyla, with the most well-known being:
- Chordata – animals with a backbone and neural tube, including vertebrates like mammals, birds, reptiles, amphibians, and fish.
- Arthropoda – invertebrates with segmented bodies and jointed appendages, including insects, spiders, and crustaceans.
- Mollusca – invertebrates like clams, oysters, slugs, and octopuses.
- Annelida – segmented worms like earthworms and leeches.
- Cnidaria – stinging aquatic invertebrates like jellyfish, coral, and sea anemones.
So in summary, a phylum contains organisms sharing broad similarities, but more variety than subsequent taxonomic levels like class, order, family, genus, and species.
Overview of Chordata
Chordata is a phylum of animals distinguished by four key features:
- A notochord – a flexible rod that provides structure and support.
- A dorsal hollow nerve cord – a hollow nerve tube above the notochord.
- Pharyngeal slits or clefts – openings in the pharynx behind the mouth.
- A muscular post-anal tail – extends beyond the anus.
These four characteristics are present at some point during the chordate’s development, but not always in the adult stage. The most familiar chordates are vertebrates like fish, amphibians, reptiles, birds, and mammals.
There are three subphyla of chordates:
- Vertebrata – animals with backbones like fish, amphibians, reptiles, birds, and mammals.
- Tunicata – also called urochordata, these are marine filter feeders like sea squirts.
- Cephalochordata – small fish-like marine invertebrates called lancelets.
So in essence, the phylum Chordata consists of all animals that possess the four key characteristics at some stage of development. It encompasses over 65,000 living species, making it one of the most diverse phyla on Earth.
Definition of Chordate
In contrast to the phylum Chordata, a chordate refers to any individual organism that belongs to the phylum Chordata. So chordates include:
- Vertebrates like mammals, birds, reptiles, amphibians, and fish.
- Tunicates like sea squirts.
- Cephalochordates like lancelets.
Basically, a chordate is an animal that exhibits the distinctive traits of the phylum Chordata at any point in its development: a notochord, dorsal hollow nerve cord, pharyngeal slits, and muscular post-anal tail. All chordates belong to the phylum Chordata, but not all animals in Chordata are vertebrates.
Examples of Chordates
Here are some examples of well-known chordates:
- Mammals: humans, dogs, whales, bats, etc.
- Birds: hawks, chickens, ducks, eagles, etc.
- Reptiles: snakes, lizards, turtles, crocodiles, etc.
- Amphibians: frogs, toads, salamanders, newts, etc.
- Fish: clownfish, sharks, rays, tuna, etc.
- Tunicates: sea squirts, salps, doliolids, etc.
- Cephalochordates: lancelets like Branchiostoma.
As vertebrates, mammals, birds, reptiles, amphibians, and fish all have backbones and clearly fit the chordate body plan. The other two chordate subphyla are less familiar but are still characterized by the chordate features at some life stage.
Comparisons Between Chordata and Chordate
Now that we’ve defined chordate and chordata separately, let’s directly compare and contrast these terms:
Category | Chordata | Chordate |
---|---|---|
Definition | A phylum of animals with four key characteristics: a notochord, dorsal hollow nerve cord, pharyngeal slits, and muscular post-anal tail. | An individual animal that belongs to the phylum Chordata. |
Taxonomic Level | Phylum | Member of the Chordata phylum |
Diversity | Over 65,000 living species in 3 subphyla. | Vertebrates, tunicates, and cephalochordates. |
Examples | Vertebrates, tunicates, cephalochordates. | Humans, fish, lancelets, sea squirts. |
So in summary:
- Chordata is a taxonomic phylum.
- Chordate refers to an individual animal belonging to the Chordata phylum.
- All chordates have the key anatomical features of Chordata.
- Chordata contains over 65,000 chordate species.
Conclusion
While their names sound very similar, chordate and chordata refer to different levels of biological classification. Chordata is a large, diverse phylum of animals that share four key anatomical traits: a notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail. A chordate is an individual animal that belongs to this phylum and exhibits those anatomical traits at some point in its development. Chordates include all vertebrates as well as lesser-known invertebrates like tunicates and lancelets. So in essence, the phylum Chordata contains over 65,000 chordate species that comprise a group of animals with backbones and primitive chordate structures.