Phylum: Characteristics & Classification

Phylum: Characteristics & Classification
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  • 0:30 Definition
  • 1:35 Binomial Nomenclature
  • 2:29 Example Phylum: Chordata
  • 3:42 Example Phylum: Arthropoda
  • 4:32 Example Phylum: Echinodermata
  • 5:35 Plant Phyla
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Lesson Transcript
Instructor: Jeffrey Sack

Jeff is a Biology teacher and has a Doctorate in Educational Leadership

This lesson will describe the characteristics of the term 'phylum.' It will show how it relates to other taxonomic classifications, as well as describing some of the major phyla used to place living things into groups.

What Is a Phylum?

The living world is very diverse. There are millions of different organisms that have been discovered, and it is estimated there are millions more yet to be found. If science did not have some kind of organized way of keeping track of all these critters, it would be very difficult to conduct any research, and information about particular creatures would never pass around the scientific community.

Just like books in the library, living things are grouped according to similar characteristics. These may be physical, behavioral, or genetic. Phylum is one of the eight major categories that can be used to organize the relationships between organisms. In order, they are: domain, kingdom, phylum, class, order, family, genus, and species.

In Ancient Greece, a man named Aristotle was one of the first to classify organisms. He put all living things within two main groups - plants and animals. He then put each of these into a smaller group depending upon where the creature lived.

It wasn't until the 18th century, when a botanist named Carl von Linné developed a system still used today. He was frustrated by the fact that some organisms had several descriptive names and others had none. He also realized that certain organisms are found all over the world, which caused them to have multiple common names. So Linné designed a system using Latin names that removed the confusion. He assigned a hierarchical classification scheme for all living things that gave each organism a two-word Latin name that was unique to it. This system of classification is called binomial nomenclature.

Taxonomy is the classification of organisms. The advent of genetic technology and DNA fingerprinting has allowed for a much more accurate and complete analysis of how organisms are related. Modern taxonomists have found that organisms that were once thought to be related are not connected at all, and others that show no external similarities are actually very similar genetically.

There are over 30 animal phyla. Let's go over some examples.

Example Phylum: Chordata

You are a member of a phylum Chordata. It contains all of the vertebrate animals (fish, birds, reptiles, amphibians, and mammals), as well as a couple of invertebrate ones. All members of this phylum have certain structures, though sometimes they only show up during the embryo phase.

These structures include: pharyngeal slits- a series of openings in the throat connecting to the outside of the 'neck'. These are often, but not always, used as gills.

A dorsal nerve cord- a bundle of nerve fibers that runs down the top of the animal. It connects the brain with the muscles and other organs.

A notochord- a cartilaginous rod running underneath and supporting the nerve cord.

A post-anal tail- an extension of the body past the anal opening.

Ancestral Chordate
Ancient Chordate

There are a couple of organisms in this phylum that are invertebrates. One such creature is called the sea squirt, marine organisms that are very good at filtering water. They create a current of water using a tube called a siphon. Inside of the animal's body is mesh-like tissue that filters out plankton.

Sea Squirt
Sea squirt

Example Phylum: Arthopoda

The phylum Arthropoda is the largest animal phylum. It contains all the insects, crabs, lobsters, spiders, and scorpions. It is believed there are more than one million types of insects alone on the planet, with many of them yet undiscovered.

General characteristics of arthropods include jointed legs and an exoskeleton. The exoskeleton offers protection to the animal but does not grow with it. When the animal gets too large for the exoskeleton, it needs to shed it and then grow a new one. As it climbs out of its old shell, its body is very soft. It will harden up over time. The exoskeleton breaking is the crunching sound you hear when you step on a bug or crack open a lobster.

Lobster - Phylum Arthropoda
Lobster meal

Example Phylum: Echinodermata

The phylum Echinodermata contains those animals with a 'spiny skin.' The animals in this phylum are the sea stars, sea urchins, bristle stars, sand dollars, and sea cucumbers.

Sea Cucumber - Phylum Echinodermata
Sea Cucumber

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