Classification of Living Things PDF

Why do we classify living things? There are millions of living things on Earth. How do scientists keep all of these living things organized? Scientists classify living things based on characteristics that living things share. Classification helps scientists answer questions such as: How many kind...

Why do we classify living things? There are millions of living things on Earth. How do scientists keep all of these living things organized? Scientists classify living things based on characteristics that living things share. Classification helps scientists answer questions such as: How many kinds of living things are there? What characteristics define each kind of living thing? What are the relationships among living things? How do scientists know living things are related? If two organisms look similar, are they related? To classify organisms, scientists compare physical characteristics. For example, they may look at size or bone structure. Scientists also compare the chemical characteristics of living things. A) Physical Characteristics: How are chickens similar to dinosaurs? If you compare dinosaur fossils and chicken skeletons, you will see that chickens and dinosaurs share many physical characteristics. Scientists look at physical characteristics, such as skeletal structure. They also study how organisms develop from an egg to an adult. For example, animals with similar skeletons and development may be related. B) Chemical Characteristics: Scientists can identify the relationships among organisms by studying genetic material such as DNA and RNA. They study mutations and genetic similarities to find relationships among organisms. Organisms that have very similar gene sequences or have the same mutations are likely related. Other chemicals, such as proteins and hormones, can also be studied to learn how organisms are related. How are living things named? Early scientists used names as long as 12 words to identify living things, and they also used common names. So, classification was confusing. In the 1700s, a scientist named Carolus Linnaeus (KAR-uh.luhs lih-NEE-uhs) simplified the naming of living things. He gave each kind of living thing a two-part scientific name.  A) Scientific Names: Each species has its own scientific name. A species (SPEE-sheez) is a group of organisms that are very closely related. They can mate and produce fertile offspring. Consider the scientific name for a mountain lion: Puma concolor. The first part, Puma, is the genus name. A genus (JEE-nuhs; plural, genera) includes similar species. The second part, concolor, is the specific, or species, name. No other species is named Puma concolor. A scientific name always includes the genus name followed by the specific name. The first letter of the genus name is capitalized, and the first letter of the specific name is lowercase. The entire scientific name is written either in italics or underlined. What are the levels of classification? Linnaeus's ideas became the basis for modern taxonomy (tak·SAHN·uh·mee). Taxonomy is the science of describing, classifying, and naming living things. At first, many scientists sorted organisms into two groups: plants and animals. But numerous organisms did not fit into either group. Today, scientists use an eight-level system to classify living things. Each level gets more specific. Therefore, it contains fewer kinds of living things than the level above it. Living things in the lower levels are more closely related to each other than they are to organisms in the higher levels. From most general to more specific, the levels of classification are domain, kingdom, phylum (plural, phyla), class, order, family, genus, and species. What are the three domains? Once, kingdoms were the highest level of classification. Scientists used a six- kingdom system. But scientists noticed that organisms in two of the kingdoms differed greatly from organisms in the other four kingdoms. So scientists added a new classification level: domains. A domain represents the largest differences among organisms. The three domains are Bacteria (bak-TIR-ee-uh), Archaea (ar-KEE- uh), and Eukarya (yoo-KAIR-ee-uh).  1) Bacteria: All bacteria belong to Domain Bacteria. Domain Bacteria is made up of prokaryotes that usually have a cell wall and reproduce by cell division. Prokaryotes are single- cell organisms that lack a nucleus in their cells. Bacteria live in almost any environment—soil, water, and even inside the human body! 2) Archaea: Domain Archaea is also made up of prokaryotes. They differ from bacteria in their genetics and in the makeup of their cell walls. Archaea live in harsh environments, such as hot springs and thermal vents, where other organisms could not survive. Some archaea are found in the open ocean and soil. 3) Eukarya: What do algae, mushrooms, trees, and humans have in common? All of these organisms are eukaryotes. Eukaryotes are made up of cells that have a nucleus and membrane-bound organelles. The cells of eukaryotes are more complex than the cells of prokaryotes. For this reason, the cells of eukaryotes are usually larger than the cells of prokaryotes. Some eukaryotes, such as many protists and some fungi, are single-celled. Many eukaryotes are multicellular organisms. Some protists and many fungi, plants, and animals are multicellular eukaryotes. Domain Eukarya is made up of all eukaryotes. What are the four kingdoms in Eukarya? Scientists have classified four types of Eukarya. They ask questions to decide in which kingdom to classify an organism. Is the organism single-celled or multicellular? Does it make its food or get it from the environment? How does it reproduce?  1) Kingdom Protista: Members of the kingdom Protista, called protists, are single-celled or multicellular organisms such as algae and slime molds. Protists are very diverse, with plant-like, animal-like, or fungus- like characteristics. Some protists reproduce sexually, while others reproduce asexually. Algae are autotrophs, which means that they make their own food. Some protists are heterotrophs. They consume other organisms for food. 2) Kingdom Plantae: Kingdom Plantae consists of multicellular organisms that have cell walls, mostly made of cellulose. Most plants make their own food through the process of photosynthesis. Plants are found on land and in water that light can pass through. Some plants reproduce sexually, such as when pollen from one plant fertilizes another plant. Other plants reproduce asexually, such as when potato buds grow into new potato plants. While plants can grow, they cannot move by themselves. 3) Kingdom Fungi: The members of the kingdom Fungi get energy by absorbing materials. They have cells with cell walls but no chloroplasts. Fungi are single-celled or multicellular and include yeasts, molds, and mushrooms. Fungi use digestive juices to break down materials around them for food. Fungi reproduce sexually, asexually, or in both ways, depending on their type. 4) Kingdom Animalia: Kingdom Animalia contains multicellular organisms that lack cell walls. They do not have chloroplasts like plants and algae, so they must get nutrients by consuming other organisms. Therefore, they are heterotrophic. Animals have specialized sense organs, and most animals are able to move around. Birds, fish, reptiles, amphibians, insects, and mammals are just a few examples of animals. Most animals reproduce sexually, but a few types of animals reproduce asexually, such as by budding. How do classification systems change over time? Millions of organisms have been identified, but millions have yet to be named. Many new organisms fit into the existing system. However, scientists often find organisms that don't fit. Not only do scientists identify new species, but sometimes these species do not fit into existing genera or phyla. In fact, many scientists argue that protists are so different from one another that they should be classified into several kingdoms instead of one. Classification continues to change as scientists learn more about living things. How do branching diagrams show classification relationships? How do you organize your closet? What about your books? People organize things in many different ways. Linnaeus' two-name system worked for scientists long ago, but the system does not represent what we know about living things today. Scientists use different tools to organize information about classification. Scientists often use a type of branching diagram called a cladogram (KLAD--uh gram). A cladogram shows relationships among species. Organisms are grouped according to common characteristics. Usually these characteristics are listed along a line. Branches of organisms extend from this line. Organisms on branches above each characteristic have the characteristic. Organisms on branches below lack the characteristic. How can organisms be identified? Imagine walking through the woods. You see an animal sitting on a rock. It has fur, whiskers, and a large, flat tail. How can you find out what kind of animal it is? You can use a dichotomous key. Dichotomous Keys: A dichotomous key (dy·KAHT·uh·muhs KEE) uses a series of paired statements to identify organisms. Each pair of statements is numbered. When identifying an organism, read each pair of statements. Then choose the statement that best describes the organism. Either the chosen statement identifies the organism, or you will be directed to another pair of statements. By working through the key, you can eventually identify the organism.  ********************************************** - Scientists use physical and chemical characteristics to classify organisms. Is that a spider? Look again. It's an ant mimicking a jumping spider! - The flowering plant shown above is called an Indian pipe. It could be mistaken for a fungus. Write down how the plant is similar to and different from other plants you know. - Sharks have fins and gills while dolphins also have fins but not gills. - What characteristics do yellow pansy butterflies have in common with American goldfinches? How do they differ? - The two pandas below share habitats and diets. They look alike, but they have different DNA. - The red panda is a closer relative to a raccoon than it is to a giant panda. - The giant panda is a closer relative to a spectacled bear than it is to a red panda. - How does DNA lead scientists to better classify organisms? - Some living things have many common names. Scientific names prevent confusion when people discuss organisms. - Apply In the scientific names above, circle the genus name and underline the specific name: Felis domesticus - What is true about the number of organisms as they are classified closer to the species level? - How are protists different from plants? - From domain to species, each level of classification contains a smaller group of organisms. - Bacteria from the genus Streptomyces are commonly found in soil. - Archaea from the genus Sulfolobus are found in hot springs. - It may look like a pinecone, but the pangolin is actually an animal from Africa. It is in Domain Eukarya. - What are the differences between Bacteria and Eukarya? - How might the classification of protists change in the future? - How can you use the branching diagram to tell which plants produce seeds? - This branching diagram shows the relationships among the four main groups of plants. - Conifers and flowering plants are listed above this label, so they both produce seeds. Mosses and ferns, listed below the label, do not produce seeds. - How has the classification of living things changed over time? - Branching diagrams and dichotomous keys are used to help classify and identify organisms. - The highest level of classification is the domain. - All species are given a two-part scientific name and classified into eight levels. - Scientists use physical and chemical characteristics to classify organisms. - Many English words have their roots in other languages. Use the Latin suffix below to make an educated guess about the meaning of the word Plantae. - Latin suffix: -ae = Meaning: a group of. Example sentence: Maples are part of the kingdom Plantae. Plantae: - The classification system used today has changed very little since it was introduced (True / False). - To be classified as an animal, an organism must have a backbone (True / False). - Organisms can be classified according to whether they have nuclei in their cells (True / False). - Scientists can study genetic material to classify organisms (True / False). - Organisms that have many physical similarities are always related (True / False). - Scientists compare skeletal structure to classify organisms (True / False). - Scientists study DNA to classify organisms (True / False). - Branching diagrams are used to identify unknown organisms (True / False). - A scientific name consists of domain and kingdom (True / False). - There are more organisms in a genus than there are in a phylum (True / False). - Domains are divided into kingdoms (True / False). - A……………………..contains paired statements that can be used to identify organisms. - The kingdoms of eukaryotes are……………………………., Fungi, Plantae, and Animalia. - Domains ……………….. and……………….…… are made up of prokaryotes. - Describe how scientists choose the kingdom in which a eukaryote belongs. - What two types of evidence are used to classify organisms? - Dichotomous keys and branching diagrams organize different types of information about classification. How are these tools used differently? - Use the figure to answer the following questions. - Which traits do baboons have? - Which animal shares the most traits with humans? - Do both lemurs and humans have the trait listed at point D? Explain. - A scientist finds an organism that cannot move. It has many cells, produces spores, and gets food from its environment. In which kingdom does it belong? Explain. - The photos show two organisms. In the table, place a check mark in the box for each characteristic that the organisms have. Animal & Characteristics Wings Antennae Beak Feathers Yellow pansy butterfly American goldfinch  - Place a check mark in the box for the characteristic that each kingdom displays. Cells Nutrients Reproduction Kingdom Unicellular Multicellular Autotrophic Heterotrophic Sexual Asexual Protista Plantae Fungi Animalia