Phylum

Scientists sort living things into groups.

One big group is called a phylum. This group sits below a kingdom.

Animals have many of these groups. There are about 32 groups for animals. Plants also have many groups. There are about 14 groups for plants. Some fungi have about eight groups. These groups help us see how life is related. It is like sorting toys into bins. We can see which things belong together.

Scientists use groups to sort all living things. One important group is called a phylum.

A phylum sits below a kingdom. It sits above a class.

There are many different phyla. The animal kingdom has about 32 phyla. The plant kingdom has about 14 phyla. The fungus kingdom has about eight phyla.

How do we pick which things belong in a phylum? There are two main ways. One way looks at how things are built. This is called a phenetic definition. It looks at the body plan of an animal.

Another way looks at family history. This is called a phylogenetic definition. It shows how living things are related by their genes.

These groups can change over time. New studies help us learn more. Sometimes two groups merge into one. Other times, one group splits into two. This happens when we find new data. We use molecular studies to see these links. This helps us understand the history of life.

Scientists use special groups to organize all life on Earth. One very important level of this organization is called a phylum.

A phylum sits below a kingdom but above a class. This helps researchers sort through the millions of different living things. There are many different phyla in the world. The animal kingdom contains about 32 phyla. The plant kingdom has about 14 phyla. The fungus kingdom contains about eight phyla.

There are two main ways to define a phylum. One way is the phenetic definition. This looks at the body plan or how an organism is built. It asks if different creatures share similar shapes or parts. The other way is the phylogenetic definition. This looks at evolutionary relatedness. It asks how closely related organisms are through their history.

Scientists use these methods to see how successful different body plans have been. They want to know how living things grew and changed over time.

People have been studying these groups for a long time. Ernst Haeckel coined the term phylum in 1866. He used a word from Greek that means "race" or "stock." He noticed that species evolved from common original forms. For example, all vertebrates belong to one big group. In 1883, August W. Eichler used the term "division" for plants. This term is still used for plants, algae, and fungi today.

Phyla can change as we learn more about science. Scientists use molecular studies to look at tiny details in genes. If they find two groups are actually close relatives, they merge them. For instance, bearded worms were once their own phylum called Pogonophora. Later, research showed they were actually part of the annelid family. Sometimes, one phylum is split into two smaller ones. This happened to the phylum Mesozoa when scientists studied its members.

Understanding phyla helps us see how everything is connected. You might know about common animals like insects or worms. Insects belong to the phylum Arthropoda, which means "jointed foot." Many worms belong to the phylum Annelida, which means "little ring." Even the plants in your garden belong to specific phyla. By grouping things, we can see the big picture of life. It turns a messy world into an organized map of discovery.

In biology, a phylum is a major level of classification used to organize life. This taxonomic rank sits below the kingdom level but above the class level.

Scientists use these groups to make sense of the vast diversity on Earth. The animal kingdom, or Animalia, contains approximately 32 different phyla. The plant kingdom, known as Plantae, includes about 14 phyla. The fungus kingdom, or Fungi, contains roughly eight phyla. In botany, researchers often use the term "division" instead of phylum. However, the International Code of Nomenclature for algae, fungi, and plants now accepts both terms as equivalent.

There are two primary ways to define what makes a phylum. The first is the phenetic definition, which focuses on morphological similarity. This means scientists look at the physical body plan and shared structural features. The second is the phylogenetic definition, which focuses on evolutionary relatedness. This approach looks at how closely organisms are related through their shared ancestry.

While the phylogenetic method is considered more important, the phenetic method is very useful. It helps researchers understand how successful different body plans have been throughout history.

Scientists also use a definition based on shared characters among living representatives. This approach was proposed by paleontologists Graham Budd and Sören Jensen. It defines a phylum by a specific set of traits shared by all its current members.

This method is helpful when studying the fossil record. It allows scientists to classify extinct organisms into "stem groups." A stem group is an organism that bears a strong resemblance to a phylum. However, this method can be difficult. It is hard to prove a fossil belongs to a "crown group," which is a specific subset of a phylum. This is because a stem group might have the general body plan without all the necessary specific traits.

History shows that our understanding of these groups is always changing. The term "phylum" was coined in 1866 by Ernst Haeckel. He took the word from the Greek term for "race" or "stock." Haeckel observed that species evolve into new species while retaining certain consistent features. He believed a phylum represented an aggregate of species evolved from one common original form. For example, all vertebrates belong to such a group. In 1883, August W. Eichler used the term "division" to classify plants into five groups. This terminology remains common in plant taxonomy today.

Modern technology, especially molecular studies, causes phyla to be merged or split. Scientists look at genetic data to see how closely organisms are actually related. If new data shows two groups are close relatives, they are merged. For example, the bearded worms were once a separate phylum called Pogonophora. About fifty years after their description, molecular work proved they were actually annelids. Consequently, they were moved into the annelid family. Conversely, some phyla are split apart. The parasitic phylum Mesozoa was divided into two phyla, Orthonectida and Rhombozoa. This happened because scientists discovered one group was likely a deuterostome and the other a protostome.

The sheer number of species within phyla can be massive and difficult to count. For instance, the phylum Nematoda, or roundworms, has about 25,000 to 27,000 described species. However, published estimates for the total number of nematode species vary wildly. Some scientists estimate there are 500,000 species, while others suggest there could be 10 million or even 100 million.

This variation happens because some counts are based only on described species. Other counts use mathematical extrapolations to guess the number of species humans have not yet found.

Understanding phyla helps us see the connections between different biological systems. We can see how specific traits define entire groups of life. For example, the phylum Arthropoda is characterized by jointed feet and segmented bodies. The phylum Chordata is defined by having a hollow dorsal nerve cord and a notochord.

Even extinct groups like the Ediacaran Petalonamae help us map the history of life. By studying these ranks, biologists can trace the complex relationships within larger clades. This research continues to uncover how life is organized across the entire planet.