Taxonomy of the Animal Kingdom

Nau mai hoki mai! Welcome to Module 4 – Animal Form and Function. This course will equip you with the skills to be able to talk about common companion animals based on their physical features. You will also be able to explain how physical features in animals often provide clues about how to provide care for them when kept as companions, and why we need to do so. You will know your companion animals inside and out by the time this module is completed. Me tīmata tātou, let’s begin!

What's in a Name?

Have you ever wondered why things are named the way they are? In science there is often a direct relationship between how an animal looks, how its body functions, the places that it lives and how it is named. In science systems of naming things are known as classification and the map or structure of a particular classification is called a taxonomy. 

Knowing this information can help human carers of animals have detailed discussions about the animals that we care for and help us make good decisions for their health and wellbeing.

In this module we are going to look at how animals are named, using scientific taxonomy. We will then look at the physical features of each animal, and different breed types. We’ll talk briefly about identification methods for pets, before finishing with the relationship between the external environment, how the animal looks on the outside and how its body functions on the inside. You’ll feel like a beginner animal scientist as you move through the content!

Credits	15
Learning Hours	150
Learning Outcome	LO4.1 Identify and describe the characteristics of companion animals commonly found in New Zealand LO4.2 Explain the functions of companion animals commonly found in New Zealand
Assessment	ANML04A1

You are free to plan your studies in the way that works best for you, but we know that guidance on how to do this is also helpful. We suggest following way to navigate through the learning content over the next few weeks:

Week 1	Topic One - Classification Systems
Week 2	Topic Two - Cats
Week 3	Topic Three - Dogs
Week 4	Topic Three - Dogs
Week 5	Topic Four - Rabbits
Week 6	Topic Five - Pocket Pets
Week 7	Topic Six - Birds
Week 8	Topic Seven - Permanent ID Methods Topic 8 Eight - Animal Form and Function
Week 9	Topic Nine - SDL Tasks, Revision and Work on Assessment 04A1
Week 10	Topic Nine - SDL Tasks, Revision and Work on Assessment 04A1

We’re going to start at the beginning… 

All life on earth began around 3.7 billion years ago from simple organisms that evolved to turn sunlight (by photosynthesis) into sugar to make food for themselves, like plants still do today. From those simple organisms, more complex organisms evolved, eventually leading to the astounding variety of life forms we have on the planet today. According to Wikipedia “around 2.16 million living animal species have been described”. (Ref: Animal - Wikipedia) This number does not include the many more types of plant, bacteria and fungi life forms. And yet all of these life-forms are regarded by scientists as resulting from the same tiny organism. The way we classify life-forms on planet Earth reflects this.

Humans have always attempted to classify the living things we see around us to make sense of them. The classification system that we use currently is called the ‘Linnaean System’, which was developed by a Swedish botanist named Carolus Linnaeus in the 1700s. He in turn borrowed from the works of the Greek philosopher Aristotle, almost 2000 years before him.

The process of classifying things according to scientific method is called taxonomy, from the Greek words taxis (arrangement) + -nomia (distribution). Each level, or taxa, of the hierarchy has more detail than the one before it. The purpose of taxonomy is to recognise, characterise, classify, and name all living species based on their physical properties. As our scientific understanding of the world has increased, many revisions have been made to the original taxonomy created by Linnaeus.

In modern taxonomy the levels are:

1. Domain
2. Kingdom
3. Phylum
4. Class
5. Order
6. Suborder
7. Family
8. Genus
9. Species

It’s often presented in diagrammatic form to show the relationships between levels in the hierarchy. 

Now let’s see how this looks for companion animals and birds – birds are on a slightly different branch of the taxonomy than animals so we will look at them separately.

1. Domain

The original simple organism that all life descended from over long periods of time evolved into three distinct groupings of lifeforms:

1. Bacteria
2. Archaea
3. Eukarya

Hopefully, you are familiar with the term bacteria – which are very tiny single cell life forms that thrive everywhere on the planet, including at the bottom of the sea, and in the digestive systems of insects, humans and other animals. There are millions of types of bacteria, and potentially still more to be discovered and named.

Archaea were once thought to be a type of bacteria but since the 1970s are now regarded as distinct from them. Like bacteria, they are very small. However, they are structurally and genetically very different from bacteria. Many types of archaea live in extreme environments where other organisms would not be found.

Eukarya is the remaining group. All plants, fungi, and animals (including dogs, cats, rabbits, rodents and birds) are in this group. A eukaryote is an organism whose cells contain a nucleus with a membrane. The DNA for the organism is inside the nucleus. This is different to bacteria where the DNA strand is not separated from the rest of the cell. Eukaryotes can be small single-celled organisms, or multi-celled organisms like trees or chimpanzees.

Eukaryote cells vary in structure depending on the type of organism. The example below is of a plant cell: a human or animal cell would be a little different.

2. Kingdom

The three domain taxa/levels branch into six kingdoms, as shown below. As you can appreciate, there are branches each time we move to a new level, making the taxonomic tree increasingly more difficult to map. From this point onwards, we are only going to follow along the branches that relate to our companion animals.

There are four Eukarya ‘kingdoms’. These are:

• Animalia
• Plantae
• Fungi
• Protista

You can probably guess what the first three are (animals, plants, fungi). The fourth, Protista, is a widely varying group of single-celled organisms that don’t share characteristics with the other three kinds of eukaryotes. 

In this course, the learning content will follow the Animalia branch. We will not discuss the other three kingdoms past this point.

3. Phylum

The next level on the hierarchy from kingdom is phylum. Things start to get more complex here: depending on where you look, the animalia kingdom has between nine (9) and forty (40) different phylum. Each phylum is regarded as both physically (by arrangement of body plans) and genetically different from the others. An easy example of body plan difference is between those life forms known as vertebrates (have back bones like humans) and invertebrates that do not have backbones (like snails or slugs).

The phylum that our companion animals belong to is called Chordata. This body plan is distinguished from other phylum by having a nerve cord, pharyngeal gill slits, and post-anal tail at some stage during their development. In human embryos, the nerve cord develops inside the spine, but the pharyngeal gill slits and post-anal tail develop into our ears and tail-bone. In vertebrate fish, the pharyngeal gills slits develop into gills to help fish breathe under water, and in monkeys the post-anal tail develops into a strong limb that helps with climbing and balance.

4. Class

We are now going to use a term that should be more familiar to you: the class that relates to our four-legged companion animals is Mammalia. In plain English we use the term mammals, which means animals that produce milk to feed their young. This is a good example of a ‘body plan’ as there are other classes of animals that do not have the body parts to produce milk.

5. Order

So far our four-legged companion animals have all belonged to the same path of the taxonomy but at the ‘order’ taxa is where they split out into different branches. These are:

• Carnivora (cats and dogs)
• Lagomorpha (rabbits)
• Rodentia (rats and mice)

Carnivora is similar to the word ‘carnivore’ and means meat-eating. Rodentia comes from the Latin word meaning ‘to gnaw’ and refers to the continuously growing teeth of rats and mice that require them to constantly chew on hard items to keep their teeth short. Lagomorpha comes from the Greek word that means ‘hare-shaped’. A hare is a wild animal that looks like a rabbit but is bigger. You can see them in country-side around New Zealand sometimes.

6. Suborder

Scientific knowledge is constantly being revised as humans learn new things about the world. Not all animals have a sub-order, and this is the case for rabbits, whose path on the taxonomy goes from Order to Family. We have three Sub-orders that our companion animals belong to, and these are:

• Caniformia (from the Latin word for dog, ‘canis’)
• Feliformia (from the Latin word for cat, ‘felis’)
• Myomorpha (from the Latin word for mouse, ‘muris’)

7. Family

The Family names for our companion animals are similar to their Order and Suborder names:

• Canidae
• Felidae 
• Muridae (rats and mice)
• Leporidae (rabbits)

If we were to look at all of the taxonomic branches we would see that at this point there are many other Family members for our companion animals. For example:

• The Canidae family includes domestic dogs, wolves, coyotes, foxes, jackals, and dingoes.
• The Felidae family  includes cheetahs, the caracal, the lion, the tiger, and the snow leopard.
• The very large Muridae family includes rats, mice, gerbils, whistling rats and quite a few others.
• The Leporidae family includes rabbits and hares.

8. Genus

At the genus level of the taxonomy there are so many relatives of dogs, cats, rabbits, mice and rats that we are not going to list them here. What is interesting to note is that the Genus level is usually is frequently used in science to refer to the names of our companion animals. We look at the naming system in a moment.

9. Species

A species is a distinct group of animals that is capable of having babies with each other. Sometimes, but not often, species that are related at the genus level can reproduce such as when donkeys and horses mate to produce mules (look up the word ‘liger’ as well).

Naming Animals

When we refer to the scientific names of life forms on the planet, we use the Genus and Species levels of the taxonomy. The Genus name is usually capitalised, and the species name is usually in lower case. For example, humans are Homo sapiens.

But what about the term breed? Why isn’t that included in the taxonomy? The reason is that two different breeds of the same animal are able to reproduce with each other and are considered to be genetically the same kind of animal. ‘Breed’ is important for this course, and we will be covering this in the next couple of topics.

Activity

How much did you already know about the naming of companion animals before starting this module? You might have heard of their names before starting this course. In this activity you will match the genus name with the species name. There are some clues in the actual names that will help you.

Activity

For this activity you will complete a worksheet, describing the taxonomy for a range of animals.

Click on this link to open the worksheet.

Let’s take a look at our feathered friends now. Birds follow the same pathway through the taxonomy as our four-legged companion animals until the Class level, where the branch splits into the Mammalia and Aves branches. The word ‘Aves’ comes from the Latin word for bird.

1. Order

There are more than thirty different orders for birds under Linnaean taxonomy. However, most of the birds that make up common companion birds fall into one of the following two bird body plans:

• Passeriformes (birds that perch)
• Psittaciformes (parrots)

According to the IOC Bird list, there are 403 types of parrots and 6533 types of perching birds! 

2. Family

Like rabbits, the information on suborders varies depending on the source, so the learning content for this course takes the approach that there is no agreed upon Suborder for companion birds and that the next level of the taxonomy is Family.

We won’t list all of the families here, because as you can see from the information above there are hundreds of types of parrot and thousands of perching birds.

3. Genus and Species 

Birds are named the same way that animals are: Genus and species, with the species name always in lower case. Sometimes the species name is double to distinguish the domestic variety with the wild variety that can still reproduce with each other. For example, domestic mice (Mus musculus domestica) are the same mice as the wild variety Mus musculus, but they have been bred to have traits that make them easy to keep as pets, which is where the extra ‘domestica’ part of the name comes from.

We’ll talk more about bird breeds in another section of this module. Let’s complete a similar activity for birds as you did for our other companion animals.

Activity

For this activity you will complete a worksheet, describing the taxonomy for two types of birds.

Click on this link to open the worksheet.

Summary

The pathway that we have taken through the taxonomy for companion animals looks like this:

This section has been a little bit of a science and history lesson. If you are interested in becoming a veterinary nurse or veterinarian, then the knowledge we have just covered on classification and taxonomy is a good starting point for your career. In the next couple of topics we will look at the breeds of different companion animals. Hoake tātou – let’s go!