Volume 6 Issue 2
Science by Laurisa
THE TREE OF LIFE
When one begins to contemplate the vast amount of life inhabiting our Earth, the task can become overwhelming very quickly. Estimates for the number of individual species that exist today vary anywhere from 1.5 million to 200 million. In other words, we really don't know for sure just how many different kinds of species there are. From the largest animal that ever lived, the Blue Whale, to the tiniest microscopic one-celled organism, mankind is in constant pursuit of discovering and categorizing life in all its variety.
The Father of Classification
This quest to catalog all living things began about four hundred years ago when two botanists attempted to classify plants according to their fruit and the shape of their leaves. Their methods were rudimentary at best and far from fail-proof. Additionally, the system of naming organisms at the time was complicated and disorderly.
In the early 1700's, a Swedish medical student by the name of Carl Linnaeus developed a simple and ordered way to name organisms. He chose what he called a binomial nomenclature, a two name system, that consisted of an organism's genus and species. All scientific names were in Latin, the common language of science, so that there would be no confusion from one culture to the next. Linnaeus also revolutionized the system of classifying flowers by distinguishing them not by their leaves, but by their pistils and stamens, a system that proved much more dependable than preceding approaches. Linnaeus spent a good deal of his time exploring various lands, collecting specimens, then classifying and naming them. If a word he wanted to use in a name did not exist, he simply created a new word by adding a Latin ending to it. He did this frequently when naming organisms after friends and family. Though Linnaeus' system had its faults and has since been improved, his discoveries and designs laid the foundation for the modern system of classifying living organisms.
Linnaeus eventually became a professor of botany at the University of Uppsala in Sweden and was knighted by the king of Sweden in 1762. During his lifetime his accomplishments included classifying whales as mammals, developing a method for inducing mussels to create pearls by placing limestone inside their shells, and publishing descriptions for over 700 species from North America.
A Place for Every Living Thing
The study of all groups of living things is called Taxonomy. Taxonomists identify organisms and assign each one a name and a place in the classification system. Currently, scientists are attempting to catalog every creature that lives or has ever lived on Earth. This is an enormous undertaking and will take many years to accomplish.
The basic system of classifying organisms consists of seven levels. All living things are placed into one of five kingdoms: Animal, Plant, Fungus, Protista, which includes protozoans (one-celled, animal-like organisms) and algae (except blue-green algae), and Monera, which includes bacteria and blue-green algae. These kingdoms are each broken down into phyla (plural for phylum). Phyla are divided into classes, classes into orders, orders into families, families into genera (plural for genus), and genera into species. Species are a group of organisms that are capable of interbreeding. In other words, one species cannot breed with another species. Each species perpetuates only its own kind.
For example, Humans are part of the animal kingdom. Our phylum is Vertebrata (note: some texts refer to this phylum as Chordata.), a group which consists of all animals with backbones. Other phyla include echinoderms (sea urchins, starfish, etc.), Cnidaria (jellyfish, coral, etc.), Cephalopoda (octopus, squids, etc.) and Anthropoda (insects & spiders). Each phylum is divided into many classes. Humans are in the Class Mammalia along with all other mammals. Other vertebrate classes include birds, fish, amphibians, reptiles and dinosaurs. These classes are broken down into orders. Humans are of the order of Primate along with monkeys and apes. The Primate order is divided into families. Humans are included in the Hominidae family. Our genus is Homo. Our species is Sapiens. The binomial nomenclature (scientific name) for humans is Homo Sapiens. Below is a chart comparing the classification of humans to that of the Blue Whale.
Humans Blue Whale
Homo Sapiens Balaenoptra Musculus
Kingdom Animal Kingdom Animal
Phylum Vertebrata Plylum Vertebrata
Class Mammalia Class Mammalia
Order Primates Order Cetacea
Family Hominidae Family Mysticeti (baleen whales)
Genus Homo Genus Balaenopteridae
Species Sapiens Species Musculus
Like most sciences, taxonomy is not as simple as first appearances may seem. In most elementary and even high school level texts, the explanation of the classification of living organisms ends here. However, this seven level system is only the tip of the iceberg, so to speak. In reality, each group of organisms are often divided in much more specific and discriminating groups. For example, in more advanced scientific circles the class Mammalia is first divided into Monotremata (platypus, etc.), Marsupials (kangaroos, opossums, ect.) and Eutheria (all animals which bear young in a placenta.) Only then can Eutheria be broken down into orders including Primates. This and many other similar examples only illustrate just how diverse life on this planet really is and how difficult it is to place each creature in a neat and tidy compartment.
A good resource to study the relationships between these divisions is at
If you have difficulty accessing this website, log onto www.all-species.org and click onto Tree of Life under their Links section. This website offers an in depth library of hundreds of thousands of species both living and extinct. Laid out like a family tree, species are linked together according to their evolutionary history (called phylogeny). Since many people, including myself, do not accept the theory of evolution as the key to the genesis of all life, it may be necessary to overlook certain statements made in their texts. However, the information provided is of great value in studying the connections between different levels of classification.
The classification of organisms can stimulate the minds of all ages. Young children can develop their skills in grouping according to a variety of characteristics. Let them cut out pictures of animals or insects from magazines. Help them divide the animals into groups by asking them what characteristics about them are the same. Glue the pictures onto poster board and label each group according to its class (bird, mammal, reptile, etc.)
The zoo is a great place for learning about the classification of animals. The placards beside each animalís enclosure usually list the animalís binomial nomenclature, or Latin name. Older children and teens can search for animals whose "first name" is the same, or that come from the same genus. This can also be done at botanical gardens with plants. Have them list these names in a notebook along with the speciesí common name. Check out a Latin dictionary and look up the meaning for the names. Why did scientists choose the name for that particular species?
Finally, encourage your children to start their own specimen collections. Carl Linnaeusí collection at the time of his death included about 14,000 plants and 3,200 insects. Press flowers between sheets of blotting paper and glue them into a notebook or laminate them. A collection of dried flowers and plants is called an herbarium. You can collect living plants, as well. During nature walks, bring some paper cups and a small shovel. Dig up small samples of plants and take them home to plant in your garden. Use a field guide to look up the species name.
Examples of Common Binomial Nomenclatures
(Names followed by a capital L. indicate organisms named by Carl Linneaus.)
Common Name Species Name Literal Meaning
Banana Musa paradisiaca (L.) fruit of paradise
Broccoli Brassica oleracea (L.) cabbage, smelly
Cucumber Cucumi sativus (L.) cucumber, cultivated
Daisy Chrysanthemum leucanthemum (L.) gold flower, white flower
Poison Ivy Rhus toxicodendron (L.) sumac, poison leaves
Violet Viola sororia (L.) violet, of sister
White Pine Pinus strobus (L.) pine, pinecone
Cat Felis domesticus cat, domestic
Dog Canis familiaris (L.) hound, domestic
Frog Rana pipiens frog, chirping
Gray Wolf Canis lupus (L.) hound, wolf
Honey Bee Apis mellifera (L.) bee, honey-bearing
Horse Equus caballus (L.) horse, packhorse
Salmon (Atlantic) Salmo salar (L.) salmon, salty
Taxonomy The science of classifying organisms according to common characteristics
Phylogeny The evolutionary development of an animal or plant species
Kingdom A general category for living organisms
Species A classification of organisms capable of interbreeding
Binomial Nomenclature The scientific name for organisms
Herbarium A collection of dried plants for use in scientific studyCopyright © 2006 Modern Media