Classification of Living Things: Definition, Examples, and Practice

For centuries, there were only two ways to classify living things; either as a plant or an animal. Today, thanks to the classification of living things, we can gain a better understanding of all living organisms. Learn more about the classification of living things and some tips for remembering the classification.

Classification of Living Things: Definition, Examples, and Practice

From an early age, we all learned the difference between plants and animals, and it probably wasn’t until a few years later when we learned that there are different types of animals and plants; even though they share some similarities, they are entirely different. 

Centuries ago, living things were classified as either plants or animals. Today, the classification of living things helps us gain a better understanding of the world we live in, our relation to living things, and understanding Biology better overall. Let’s take a closer look at the classification, a little bit of its history, and some tips for learning how to use it when exploring a living organism.

What Is The Classification Of Living Things? 

Taxonomic Ranks diagram

You might already know a little about the classification of living things, which is also referred to as taxonomy. Many students learn the basics of taxonomy in elementary school, but unless you spend a lot of time focused on Biology, the details may have become a bit fuzzy over the years.

Classification of all living things got its start with Swedish Botanist, Carl Linnaeus. Due to his interest in plants and animals, his first classification guide, Systema Naturae, was published in 1735.

Linnaeus, who is often considered to be the “Father of Taxonomy,” and his classification system is still in use today. While the classification system continues to grow, Linnaeus will always remain an integral part of how we name, rank, and classify plants and animals. 

The classification system starts out by sorting living organisms into groups based on basic and shared characteristics (such as a plant or animal). Then each group is broken down further into more specific classifications; it might be helpful to think of a classification system like a family tree.

Next, we’ll take a closer look at the eight levels of the taxonomy, depending on your resource, you may see seven levels discussed.


The first or top level of the classification system is the domain. A domain has the most number of individuals in the group since it’s the broadest level. The domain level helps to distinguish between cell types. Currently, there are three types of domains, which include Bacteria, Archaea, and Eukarya.



Kingdoms are levels which are broken down from the domains. There are six kingdoms which include Eubacteria, Archaebacteria, Plantae, Animalia, Fungi, and Protista. While kingdoms are a little more specific, it should still be relatively easy to categorize a living organism based on the kingdom.

The Plantae Kingdom is broken down even further to include divisions. The following divisions include:

  • Bryophyta: mosses, liverworts, and hornworts
  • Psilotophyta: whisk ferns
  • Lycophyta: club mosses and quillworts
  • Sphenophyta: horsetails
  • Polypodiophyta: ferns
  • Coniferophyta: pines, spruces, redwoods
  • Ginkgophyta: ginkgoes
  • Cycadophyta: cycads
  • Gnetophyta: gnetophytes
  • Magnoliophyta: flowering plants

Learning the kingdoms can be a little tricky, and if you don’t get the kingdoms right from the beginning, you may have a difficult time classifying something correctly. Check out this checklist for figuring out which kingdom that an organism belongs to.


jelly fish

The phylum is the next level in the classification system and is used to group living organisms together based on some common features. A good example to consider is when you sort your laundry by items of clothes. Your socks aren’t all the same, you most likely group them together and put them in the same dresser drawer.

Consider the animal kingdom, there is a phylum group called “chordates,” and it refers to all animals with a spinal column. As humans, we are also part of the chordate phylum. Like the Plantae Kingdom, phyla is broken down into divisions: 

  • Porifera: sponges
  • Coelenterata: jellyfish, hydras, and corals
  • Platyhelminthes: flatworms
  • Nematoda: roundworms
  • Annelida: segmented worms
  • Arthropoda: arthropods like insects
  • Mollusca: mollusks like clams
  • Echinodermata: sea urchins
  • Chordata: chordates


The class level is another way to group together organisms that are alike, but it becomes even more specific than phylum. There are more than 100 classes, but some of the more common ones that you’ll likely use on a regular basis in Biology class includes the vertebrates, invertebrates, dicots, or monocots.


As you might guess, the order is just another way to break down the class of plants and animals. Think of it as “refining your search.” Some orders include carnivores, primates, rodents, fagales, and pinales.


The next level in the classification of living organisms is categorized much like the group of people that we call family. We are all different, but we share enough similarities that we belong in the same family; the same applies to all living things.


The genus is the first part of a living thing’s scientific name, also known as binomial nomenclature. Let’s look at lions and tigers, for example, the scientific name for a lion is Panthera leo, and the tiger is Panthera tigris; Panthera is the genus.


The species is the final and most specific level of the classification system. The best way to describe a species is a group of organisms that are best suited for breeding healthy offspring, which can also continue to reproduce.

Some Examples of Classification

Classifying living things takes a lot of practice, and while it may take you a long time to familiarize yourself with the scientific names in a domain or phylum, it’s best to learn and memorize the levels of classification as soon as you can. Forgetting about the phylum or order can make the classification process even more difficult.

Many people use a mnemonic device to remember the order of the levels of taxonomy. Some people use "Dear King Phillip Came Over For Good Soup,” but you can come up with whatever and works best for you.

Let’s take a look at a few in-depth examples. We’ll start out by classifying humans.

Classification of Humans

children taking bath

The Domain is Eukarya because we have a nucleus and organelles. The Kingdom is Animalia because we ingest food, are multicellular, and have no cell walls. The Phylum is Chordata because we have spinal cords (our subphylum is vertebrata because we have a segmented backbone).

The Class is Mammalia because we nurse our offspring and the Order is Primates due to our higher level of intelligence. The Family is Hominidae because we are bipedal (walk upright). The Genus is Homo for Human, and the Species is H. sapiens, which means modern human.

The result is Homo Sapiens, which as we all know translates to today’s human beings.

Classification of a Fruit Fly

fruit flies

Everyone will agree that fruit flies can be a nuisance, but they can be a fascinating organism to study. Here’s how we can classify a fruit fly.

The Domain is Eukarya because it has a nucleus and organelles. The Kingdom is Animalia because it ingests food, is multicellular, and has no cell wall. The Phylum is Arthropoda due to the hard exoskeleton, paired legs, and a segmented body. The Class is Insecta because it is terrestrial, has six legs, and antennae. The Order is Diptera due to having two-wings.

The Family is Drosophilidae, the Genus is Drosophila, Species is D. melanogaster; also known as the common fruit fly. As you looked at the different levels of classification, can you see where we’re related to the annoying and small insect?

Classification of a Maple Tree

maple tree

We can get syrup from a maple tree, and it has stunning foliage in the fall, but you probably haven’t thought much beyond that. Here’s the classification of a red maple tree. 

The Domain is Eukarya because it has a nucleus and organelles and the Kingdom is Plantae since it makes its own food and has a multicellular cell wall. Immediately, we can see that a maple is nothing like a human.

The Phylum is Tracheophyta due to the tissue-level organization, and the Class is Angiospermae because it flowers. The Order is Sapindales because it produces sap and the Family is Aceraceae. The Genus is Acer, the Species is A. rubrum, and we end up with a red maple.

Classification of a Dandelion


People either love or hate dandelions but like other organisms, they are a living thing, and they have a complex level of classification. Let’s see if you can guess the Domain, Kingdom, and Phylum. Did you guess Eukarya, Plantae, and Angiosperms? Then, you’re right.

The Class is Magnoliopsida, the Order is Asterales, Family is Asteraceae, the Genus is Taraxacum, and the Species is T. officinale; your result is the dandelion.

The more time you spend classifying living things, the easier it becomes, and even in these quick examples, you probably started to see some similarities.

Tips and Advice on Growing Plants in Aquariums – What You Need to Know

We all know plants require sunlight, micro nutrients, macro nutrients and CO2 to grow healthy. However, very few know that there is an optimum amount for each to ensure a healthy growth for plants. If one is far less than the others, while growth may occur, it certainly wouldn’t be the healthiest way. Balance is the key here. If you’re planning to have plants in your aquarium to provide the best environment you can for your fishes, then you need to know more about this. Let’s break down these important factors:


Light is an essential factor needed for chemical reactions to occur in plants without which, they wouldn’t be able to produce any food. The absence of light leads to the certain death for plants. To ensure the best possible growth for your plant, you need to know the correct spectrum of light that is required. Plants utilize light in the blue and red spectrum best for growth. However, as far as aesthetics are concerned, the full spectrum of light is what makes everything visually pop.

Plants Aquarium

While sunlight is optimal for plants on land, it might not be the best for plants in aquariums. While the full spectrum of sunlight may make your aquarium look good, most purists or hobbyists see it as having many disadvantages. The amount of light would either be too weak for the plants or short. It can also be very bad for fishes and plants alike if there are significant fluctuations in the light. Algae growth is yet another bad consequence of incorrect amount of light in aquariums. Considering all these facts, it is far more efficient and effective to use artificial lights for aquariums.

Full spectrum fluorescent light is one of the best ways to light up your aquarium. The amount of light required for optimum plant growth differs according to the density of plants in the aquarium. If the aquarium is sparely planted, then about 1.5w of light per every gallon of water is the recommended amount. If however, your aquarium is densely planted, then 3w to 5w per gallon would be optimum. In both cases, 10 to 12 hours of light supply is essential for encouraging and allowing healthy and efficient plant growth.


Carbon Dioxide

Co2 is another essential element required for plants to create food. During the process of photosynthesis, co2 is transformed into carbohydrate and used for plant growth. Aquariums that don’t have a good co2 source have about 1-3ppm of the gas but most plants flourish when there is about 10-20 ppm of co2 in the water. Co2 supplementation is very important for having an effective planted aquarium.

There are two different types of co2 setups for aquariums namely, a co2 tank and the DIY co2 reactor. The co2 tank is quite simple to use and it’s better for large aquariums, although it will get expensive in the long run. The DIY co2 reactor is made for smaller aquariums by combining yeast, sugar and water.

Macro Nutrients

Plants also require various nutrients in large amounts for their growth like Nitrogen, Potassium and Phosphorus.Excessive amounts of these nutrients will result in an undesirable growth of algae in the tank. So when providing nutrients to plants in your aquarium, remember moderation is the key. These elements also exist organically. For instance, Nitrogen is easily available and present in the form of ammonium from fish waste. Ammonium is actually very good for the plants because it actually takes less energy to use. Potassium and phosphorous on the other hand can be provided from external sources like fish food. Certain fertilizers also contain potassium and they can be added in small quantities.

Macro nutrients should be supplemented if your aquarium is densely planted or if you are growing medium and hard category plants since they require more nutrients.

neon tetra

Micro Nutrients

M nutrients like iron, copper, zinc, sulphur, calcium and magnesium are some of the other essential ingredients needed. While iron is usually present in tap water, it usually gets oxidized to the limit where it becomes unusable for plants. One way to prevent it from happening is to use chelated iron mixtures which prevents the iron from oxidizing. The amount of iron in the water should be less than 0.2 ppm. Calcium and magnesium can also be found in tap water but it’s usually not enough so they should be added externally in small amounts. One very important thing to remember as far as micro nutrients are concerned is that they should be added only in very small amounts. Too much if it can lead to high toxicity in the water which will be very detrimental to the plant’s growth in the aquarium.

The final point in setting up an effective planted aquarium is to change water each week. This will not only remove extra fish waste but also get rid of any unwanted nutrients. Doing so will not only promote better growth but it also suppress algae growth. By informing yourself of key factors such as these, you will have no problem in maintaining a healthy environment for your fishes and plants.

Plant Classification Study Guide


1. There are more than ________________ different plant species.

2. Plants share Four Characteristics:




3. In their characteristics plants are most similar to the ________________________.

4. Plants and Green Algae Have these Characteristics in Common:




5. There are also some important Difference:




6. All plants are photosynthetic, multicellular, __________________________ organisms, and can _________________________  _________________________.

7.  A ____________________ is a ripen ovary that surrounds the seeds of angiosperms.

8. All plants probably evolved from ______________________   __________________.

9. One of the greatest problems that encountered by the first land plants was the need for

10.   How does water aid the fertilization of some organisms? ______________________

11.   _________________________ of _______________________ means that there are TWO
phases in the life cycle of plants:

    A.  The first phase: ___________________  ______________________ phase that produces ________________________ and _______________________.

    B. The second phase: ___________________  _____________________ phase that produces ________________________.

12.  Sexual reproduction ensures there will be __________________________  ______________________ in plants.

13.  The type of vascular tissue that transports organic compounds is ____________________________.

14.   The _____________________ is a waxy, waterproof layer that coats the parts of a plant
exposed to air.

15.   The earliest plants were probably __________________, and had NO true ___________,
____________________, or ______________________.

16.   __________________ is a hard compound that strengthens cell walls, enabling cells to support additional weight.

17.  The 12 Phyla of plants can be divided into two groups based on the presence of __________________________  ___________________________.

18. One adaptation that help land plants to slow the evaporation of water was a

19. The type of vascular tissue that transports water is _________________________.

20. This type of angiosperm has parallel leaf venation __________________________.

21. The waxy covering on plant surfaces is called _____________________________.

22.  The plant material in peat bogs decomposes very ________________________ because the bogs are ____________________________.

23. How many plant phyla produce seeds? _____________________

24. What type of gymnosperm produces fleshy seeds? ____________________________

25. What is the photosynthetic phase of a moss called? ______________________________

26.  Bryophytes, instead of roots, they have long, thin strands of cells called ____________________ that attach the plant to the soil.

27.   Vascular plants absorb water from the soil through underground structures called
_____________________.  They also provide a plant with ___________________.

28.  Non-woody plants are usually called ___________________________.

29.  _____________________ carries organic compounds in any direction depending on the plant’s needs.

30.   In order to reproduce, a nonvascular plant must have ________________________.

31.   Rhizoids are long, thin strands of cells that resemble ________________________.

32.   The roots of vascular plants absorb water and _________________________  _________________________.

33. What is the non-photosynthetic phase of a moss called ____________________________.

34. Gymnosperms produce “_____________________” seeds, while angiosperms produce _______________________ protected inside a _____________________________.

35. This type of angiosperm has net leaf venation __________________________.

36. The _________________________ allow for the exchange of carbon dioxide and oxygen.

37. Sphagnum is often used to ______________________ soil and help it ____________________  __________________________.

38.   A ___________________ is a protective structure that contains a plant
__________________, and _________________  __________________.

39.   A __________________ is a structure that develops in plants with flowers and contains the

40.  Nonvascular plants are distinguished by the absence of ______________________ and ____________________________.

41. All nonvascular plants are collectively called _______________________________.

42.   Vascular plants are classified into one of Two Types: _______________________ or
________________________________ plants.

43.   What are the Four Phyla of Seedless Vascular Plants? ________________________,
________________________, ______________________, ________________________.

44.   What are the Five Phyla of Seed Vascular Plants? _______________________,
_________________________, _________________________,
________________________, and  ______________________________.

45.  Vascular seed plants are subdivided into TWO general categories according to the type of seeds they produce: _________________________________ and

46. A ____________________________ is a special reproductive structure composed of hard scales, that produces seeds without a fruit.

47.   ____________________ are vascular plants that produce seeds lacking a protective
_______________________.  They are often called _______________  _________.

48.  A seed is a _________________________ embryo inside a __________________________  _____________________.

49.   The _____________________ are vascular plants that produce seeds enclosed and
__________________ by a __________________.

50.   All angiosperms produce _________________ and _________________.

51.   The protective structure that contains the seed or seeds of an angiosperm is the

52. One way of distinguishing among the many types of angiosperms is by counting the number of seed leaves or ________________________.

53.  Angiosperms with only ONE cotyledon are called _______________________________  or simply  _____________________.

54.  An angiosperm whose embryo has TWO cotyledons are called __________________________________ or simply _______________________.

56.   Plants that produce seed protected by a fruit are called _______________________________.

57.   A dicot is an angiosperm whose embryo has Two _______________________.

58. Plants remove carbon dioxide from the air by the process of ________________________.

59. Bryophytes are _______________-growing plants that live in _____________________  ________________________________.

60. All vascular plants have __________________________ tissues and _____________________________ of _________________________________.

61. True roots, stems, and leaves are characteristics of all ______________________  _________________________.

62. What are the primary functions of spores and seeds?

63. In what ways do green algae differ from plants?

64. Why do nonvascular plants have to live in moist environments?

65. Name three bryophytes, and identify their common characteristics.

66. Which plant phylum contains the tallest and most massive plants?  Is this a phylum of nonvascular, seedless vascular, or seed plants?

67.  Conifers are often found living at high elevations in locations with cold, dry winters.  What characteristic enables them to retain their leaves in these conditions?