Classification What features do biologists use to group living things? You know that most plants are green and do not more around. You also know that most animals are not green and do move around. The tubeworm pictured in A to the left lives in the water attached to one spot. It is not green. Is the tubeworm a plant or an animal? The euglena in B is green and moves around in the water. Is it a plant or an animal, or does it belong to some other group? Biologists have a system for grouping living things. Each living thing has a specific name that biologists all over the world understand. In this unit, you will learn why we group living things and about the system used to group them. Why Things are Grouped How often do you classify things? You probably classify things more often than you think. To classify means to group things together based on things they have in common. Many things in our daily lives have been grouped for us. Think about how food is grouped in a grocery store. Frozen foods, meats, produce, bakery items, and canned foods are found in separate areas. What subjects are you taking this year? Don t you group your courses? Spanish, French, and German are language courses. Algebra, Geometry, and Calculus are math courses. How Grouping helps us There are several reasons to classify things. 1. One reason is to put things in order so that they become easier to find. Your school library must have thousands of books. They are arranged by a system of numbering that makes it easier to find a certain book. Think of trying to find a classroom with the numbers out of order. Could you find a phone number in a phone book if the names were not in alphabetical order? 2. The second reason we classify things is to show that they share certain traits. A trait is a feature that a thing has. In a library, you see biographies grouped together. What trait do they share? 3. The third reason is that is makes it easier to name new species when we discover them. You look for traits that are similar to something that is already named. Biologists classify living things. Doing so put organisms in order. It also shows how they are alike. There are over 1.5 million known kinds of living things. It would be impossible to find information about them if they were not grouped in some way. 1 Methods of Classification For hundreds of years, people have been grouping living things. The job has not been easy. What makes the job of classifying hard is that scientists do not always agree on how to group living things.
2 Early Classification Over 2000 years ago, a Greek scientist named Aristotle (pictured to the right) was one of the first people to classify living things. He noticed that living things fit into two main groups: green and did move. Aristotle next divided all animals into three groups. He based his groups on where the animals lived. Animals that lived in water went in one group. Animals that lived on land went into a second group. Animals that lived in the air and could fly made up a third group. Aristotle then worked out a system for grouping plants. He based it on size and pattern of growth. He divided plants into 3 smaller groups. Tall plants with one trunk were put into the tree group. Medium plants with many trunks were put into a shrub group. A burning bush that turns bright red when exposed to frost in the autumn is an example of a shru Small plants with soft stems went into an herb group. Herbs include grasses and wildflowers. The beginning of Modern Classification Scientists used Aristotle s system of classification for hundreds of years. However, as scientists found more and more living things, Aristotle s system became less useful. Many of the newly discovered living things did not fit into his system. In 1735, Carolus Linnaeus (pictured to the left) came up with a new classification system. Linnaeus pput living things with similar traits into the same group and called this group a species. He used very specific traits for his groups. For example, he used flower parts to group plant species. He places similar species into a larger group called a genus. Through his work, Linnaeus made a number of important changes in Aristotle s system. 1. He classified plant and animals into more groups. 2. He based his system on specific traits. 3. He gave organisms names that described their traits. These names had two parts. All living things still have two-part names today. Today, there are seven groups for classifying organism kingdom, phylum, class, order, family, genus, and species. The kingdom is still the largest group of living things. Kingdoms are divided into groups called phyla (singular phylum). A phylum is the largest group within a kingdom. Phyla are divided into even smaller groups called classes. A class is the largest group within a phylum. Classes can be divided into groups called orders. An order is the largest group within a class. Orders are divided into families. A family is the largest group within an order. The largest group within a family is a genus. The smallest group of living things is a species.
3 How Scientist Classify Today How do scientists know to which groups an organism belongs? They look at many traits. They compare the traits of one organism with those of another. Scientists also compare organism living today with those that lived long ago. Let s look at how scientists classify living things. Classifying based on how organism are related Living things that are closely related are in many of the same classification groups. For example, if two plants are closely related, they will be in almost all of the same groups. If they are not closely related, they will not be in very many of the same groups. The table below shows a list of groups to which a house cat belongs. It also shows the traits for each group. You may recognize some of the group names. Many are from the Greek or Latin language. House cat classification Group Group Name Group Trait Kingdom Animal Has many cells, eats food Phylum Chordate Rod-like structure along the back for support Class Mammal Nurses young, has hair Order Carnivore Eats flesh, has large teeth Family Felidae Sharp claws, large eyes Genus Felis Small cats Species Catus tame The table below compares the classification of two members of the cat family, the house cat and the lion. Comparing the Classifications of House Cat and Lion Group House Cat Lion Comparison Kingdom Animal Animal Same Kingdom Phylum Chordate Chordate Same Phylum Class Mammal Mammal Same Class Order Carnivore Carnivore Same Order Family Felidae Felidae Same family Genus Felis Panthera Different genus Species Catus Leo Different species The table above shows that five of the seven groups for these two animals are the same. Only the genus and species groups are different. The lion and the house cat are very similar. They have many of the same traits. Look at the table on the next page to compare the classifications of two animals that are more different. The table compares the classification of a house cat with that of a deer.
Comparing the Classifications of House Cat and Lion Group House Cat Deer Comparison Kingdom Animal Animal Same Kingdom Phylum Chordate Chordate Same Phylum Class Mammal Mammal Same Class Order Carnivore Artiodactyla Different Order Family Felidae Cervidae Different family Genus Felis Odocoileus Different genus Species Catus virginianus Different species 4 Other evidence used in classifying There are several other pieces of evidence that help scientists classify organisms they are 1. Classification can be based on a living thing s ancestors. An ancestor is a related organism that lived some time in the past. For example, horses and donkeys have many of the same ancestors. They have more of the same ancestors than horses and goats do. Horses and goats have more of the same ancestors than horses and fish do. Of these pairs, horses and donkeys have the most ancestors in common and are the most related. 2. Similar body structures often show that living things have common ancestors. This is important in classification. You can see from the picture below that the front limbs of various animals and a human. Notice the limbs are all similar in their bone structures. These similarities show a common ancestor. All the limbs are similar even though they do different things. They have similar bones arranged in similar patterns. 3. Another way to group living things is by body chemistry. A good example is the horseshoe cra At first, the horseshoe crab was thought to be like other crabs. The blood of the horseshoe crab, however, is more like that of a spider. As a result, the horseshoe crab is now grouped with spiders. For many years scientists have debated about how to classify the giant pand Some classified it with raccoons, while others classified it with bears. Now its body chemistry shows it to be more closely related to bears.
Name: Date Classification Review Part 1 1. Name one place you come in contact with classification in your daily life. 5 2. What is the term used to mean grouping organisms or orbjects based on things they have in common? 3. Who was the first person to classify living things? 4. What are the three things Linneaus improved about Aristotle s system? 5. What were Aristotle s kingdoms? 6. Name three pieces of evidence scientists use to classify living organisms.
7. How many classification groups do a lion and a house cat have in common? 6 Match the classification level with its definition. Classification level 8. Class 9. Family 10. Genus 11. Kingdom 12. Order 13. Phylum 14. Species Definition largest group within an order smallest group of living things the largest group within a phylum d. the largest group within a kingdom e. the largest group of living things f. the largest group within a class g. largest group within a family 15. Name the levels of classification from largest to smallest.
Scientific names come from classification The scientific name for a house cat is felis catus. The name comes from the genus Felis and the species catus. Notice that the genus is always capitalized and the species is not. Both the genus and species are in italics. A wolf s scientific name is Canis lupus. The name includes the genus Canis and species lupus. The scientific name for humans is Homo sapiens. What are the genus and the species to which humans belong? Have you ever called a plant or an animal by its scientific name? You have, but you may not have realized it. The table below shows a list of some living things that you know about. It gives a list of their scientific names. You probably have used parts of these scientific names many times. Scientific Names of some plants and animals Scientific Name Name you probably use Pinus sylvestris Scotch pine Rosa Carolina Rose Elephas maximus Asian elephant Gorilla gorilla Gorilla Giraffa camelopardalis giraffe Why Scientific Names are used You call a robin, seal, apple tree, and house cat by their common names. Common names are names used in everyday language. Scientists prefer to use scientific names. There are several reasons for using scientific names instead of common names. 1. No mistake can be made about which living thing is being described. That s because two different living things don t have the same scientific name. Two different living things, however, may have the same common name. For example, hawk is the common name for several kinds of birds. Only one kind of hawk, however, is named Buteo jamaicensis. This hawk has broad wings and a reddish tail. You may know it as the red-tailed hawk. 2. Scientific names seldom change. 3. Scientific names are written in the same language around the world. Using scientific names allows scientists to communicate no matter what their everyday language is. The language in which scientific names are written is Latin. Latin is used because it does not change. Kingdoms: 5 or 6? Depends on who you talk to. Remember that early scientists grouped living things into two kingdoms plant and animal. As scientists learned about more living things, they found that some living things did not fit into either kingdom. A new system of classification was needed to group all the living things being discovered. Today most scientists use the 6 kindgom system. These are the 6 kingdoms with the characteristics of those kingdoms. 7
1. Kingdom Archaebacteria- very simple one celled organisms that are prokaryotes (do not have a nucleus) They are all producers and live in very weird places like your intestine, at the bottom of the ocean, in very salty environments like the great salt lake. They have a cell wall and a little circular piece of DNA. An example of an Archaebacteria is a methanogen. 2. Kingdom Eubacteria very simple single celled that are prokaryotes. They can be producers or consumers. They have a cell wall and a little circular piece of DNA like the Archaebacteri They do not live in weird places. An example from this kingdom is the streptococcus. They are the bacteria that cause strep throat. 3. Kingdom Protista This is the catch all kingdom. It contains the organisms that don t fit into the other kingdoms. All members of the Protista Kingdom are eukaryotes (have a nucleus and membrane bound organelles). They can be microscopic or meters long. They can be producers or consumers. They can be single celled or multicelled. None of them have a cell wall. A couple of examples from the protist kingdom is a paramecium (pictured to the right) and sea weed. 4. Kingdom Fungi all are eukaryotes. They have cell walls and are all consumers (decomposers). Most of them are multicellular but a few are single celled. An example from this kingdom is a mushroom. 5. Kingdom Plantae all are eukaryotes. They have cell walls and are all producers. They are all multicellular. No plants are able to move from place to place by themselves. An example is a fern plant. 6. Kingdom Animalia all are eukaryotes. They do not have cell walls. They are all consumers and multicellular. They have complex body organization by having tissues and organ systems. These organisms are able to move from place to place at some time in their lives. You are an example of the Animal kingdom. Scientists who still use the 5 Kingdom system put all the bacteria in one kingdom and call it the Monera Kingdom. 8
Name: Date: Classification Review 2 1. Name 3 characteristics of the Protist kingdom. 2. If you find a new species, what are two pieces of information you need to know about it to put it in the correct kingdom? 3. Name 3 characteristics of the fungi kingdom. 4. How is the 5 kingdom system different from the 6 kingdom system besides the 6 kingdom system has one more kingdom? 9 5. Name 3 characteristics of the Eubacteria kingdom. 6. If two organisms are in the same family, what other levels are classification do they have in common? d.
10 7. List the seven levels of classification from the level that has the most members to the member that has the fewest members. d. e. f. g. 8. Name 3 characteristics of the Animal kingdom. 9. Name 3 characteristics of the Plant Kingdom. 10. Name the 6 kingdoms of life. d. e. f.