Objectives Classification Notes 8.1 Summarize classification Describe the evidence used to classify organisms. List the seven levels of classification. Describe and list the six kingdoms of living organisms 1 2 Scientists classify millions of species Activity The challenge of classification 400 years ago, scientists classified organisms based on their appearance and behavior. This leads to false connections. For example, caterpillars look like worms. As the discovery of new species increased, scientists needed an easy and universal way to classify organisms. 3 4
Scientists use classification and taxonomy to organize life. Before we move on, we must know the difference between classification and taxonomy. Classification is the process of arranging organisms into groups based on similarities. Taxonomy is the science of naming and classifying organisms. A good system of classification allows you to do three things: 1. Organize a large amount of information so it is easy to find and understand. 2. Provide a tool for comparing very large groups of organisms as well as smaller groups. 3. Allow people to communicate about organisms. 5 6 What is the name of this spider? Before these rules were put into place, several different classification systems existed! The current classification system gives all organisms a name in Latin. While Latin names may be confusing to us, they are much better than the everyday alternative. 7 8
Do you know the name of this common insect? What is the name of this bird? 9 10 What is the name of this bird? As we just saw, the same name can represent a completely different species! Biologists need both a system for organizing and a system for naming. Each name in the system should only refer to one specific type of organism. This way, scientists can use the scientific name and be sure that they are talking about the same organism. 11 12
Scientists use classification to organize life into groups. To classify organisms, scientists use similarities and differences among species. Knowing what is a specie is a very difficult topic to address. Therefore, we shall reduce it ever so sadly to the following A species is any group of similar organisms that are able to reproduce with each other to produce fertile offspring. These differences may be easy to see, such as whether an animal has fur, feathers, or scales. Other times the differences require special lab equipment, such as equipment to study DNA. Therefore, the more similarities two organisms have in common, the closer scientists will classify them. 13 14 Further, the more similarities two organisms have, the more similar their names will be. For example, humans and gorillas have a lot in common. Let s check out our scientific names. Gorilla: Eukarya Animalia Chordata Mammalia Primates Hominidae Gorilla beringei Human: Eukarya Animalia Chordata Mammalia Primates Hominidae Homo sapiens Taxonomists study biological relationships As we learned, scientists need a simple, standard way to arrange all of the different species, including those that are extinct. Taxonomists are scientists who classify and name the organisms based on their similarities and differences into taxons. A taxon is a group of organisms that share certain traits. 15 16
Taxons can be broad, like animals and plants, or more specific, like deer and cats. Taxonomists study the relationship between species in similar taxons because it may reveal a common ancestor. If two organisms have a common ancestor, they can be classified closer together. To find a common ancestor, scientists analyze the traits of organisms. Traits are characteristics or behaviors that can be used to tell two species apart. For example, if an organism is able to produce a web, it may be related to spiders. As taxonomists find more similarities, the taxons can be further narrowed. Just as we saw in comparing our scientific name to that of a gorilla. So, what do taxonomists observe as traits? 17 18 Taxonomists observe two types of evidence to help classify organisms: physical evidence and genetic evidence. Physical Evidence Physical evidence refers to two generals characteristics of an organism: its internal structure and its outward appearance. Examples of physical evidence include an organisms color, size, weight, and how it obtains energy. Physical Evidence (con t) Physical evidence can help scientists see that all living organisms are related by evolution. 19 20
Physical Evidence (con t) Scientists can observe and measure fossilized bones or pieces of bone and compare them to each other. They can also compare bones of species that are extinct with bones of modern species. If they share similarities, they may be related. In this picture we can see how a taxonomist would view the arms of animals. Notice the similarities between our arm and those of a dolphin, cat, and bat. 21 22 Genetic Evidence (Molecular Evidence) In the early 20th century, scientists discovered that organisms inherit their traits through structures called genes. Activity In the mid 1950s, they observed that genes are made of DNA. What is a bat more similar to: a human or a bird? Today, scientists can use lab equipment to catalog each component (gene) of an organism s DNA. 23 24
Genetic Evidence (Con t) Scientists can compare the genes of one organism to the genes of another to see if they are similar. If they are similar, then they are more closely related. Genetic evidence can (sometimes) help prove physical evidence. Image removed due to copyright. 25 26 Linnaeus was the first to develop an advanced classification system A scientist named Carolus Linnaeus developed systems for both naming species and organizing them into groups. All 4,000 species Linnaeus named were plants or animals. He only classified what he could see based on appearance. Today, scientists have named over 1,000,000 species. They have classified over 2.5 million. Biologists use binomial nomenclature to name organisms It is impossible to classify all organisms using just one name. In science, all organisms are given two names to help classify them. The first part of an organism s scientific name is the genus. A genus is a group of species that have similar characteristics. 27 28
The genus name is combined with the species name. This system of naming was invented by Linnaeus and is the basis of modern taxonomy. We call this system binomial nomenclature. This is a fancy name for two names in a list of names. The system provides that you name something uses two names, or two words. Most scientific names are in Latin terms. Linnaeus s system made communication about certain species much easier. When naming an organism, the use of the genus and species name is necessary. Let s see what happens if we only refer to an organism by its species name. 29 30 The species name gracilis which means graceful or slender, can be used to identify several organisms: A flower, a lizard, and a cactus When we use their genus and species, they become separated: Aubrieta gracilus (flower), Chameleo gracilis (lizard), Mammillaria gracilis (cactus) When writing the scientific name of an organism, a few rules must be followed: The scientific name (genus + species) is italicized. The genus always comes first and is capitalized. The species comes second and is not capitalized. 31 32
Organisms are classified into eight levels Activity Classifying organisms using a dichotomous key Genus and species are just part of the scientific name of an organism. Organisms are classified into eight taxons: domain, kingdom, phylum, class, order, family, genus, species. Look in your book on page 33 to see what happens as you progress deeper into the classification system. 33 34 You should notice that fewer organisms appear in each taxon than the one previous to it. The farther you go into the taxons, the fewer organisms are in them. This is because the farther you go into the taxons, the less an organism will have in common with other organisms. In this classification system, the domain is the highest (least specific) taxon. Millions of organisms can be classified into domains. There are three domains: Archaea, unicellular prokaryotes that live in extreme environments Bacteria, unicellular prokaryotes Eukarya, all eukaryotic organisms 35 36
After the domain taxon, we find the kingdom taxon. There are six kingdoms of life: Kingdom Plantae includes plants such as trees, grass, and moss. Kingdom Animalia includes animals such as lions, tigers, and bears to insects and multicellular microbes. Kingdom Protista includes organisms that are uni- or multicellular and share characteristics of other eukaryotes. (Kingdoms continued) Kingdom Fungi include mushrooms, molds, and yeasts. These four kingdoms are part of the Eukarya domain. In the Bacteria domain we find the kingdom bacteria. Kingdom Bacteria are unicellular prokaryotes 37 38 (Kingdoms continued) The sixth kingdom is found in the Archaea domain. Kingdom archaea contains organisms that are similar to bacteria, but have a cell structure so different that it is separately classified. 39