Classification of Living Things Copyright Houghton Mifflin Harcourt

Classification of Living Things Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things Sorting Things Out! Why do we classify living things? • Scientists classify living things based on characteristics that living things share. • Classification helps scientists answer questions about organisms such as how many kinds there are, their characteristics, and their relationships. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things How do scientists know living things are related? • Physical characteristics, such as skeletal structure, can indicate whether organisms are similar or related. • Scientists also study how organisms develop from an egg to an adult to determine if organisms are related. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things How do scientists know living things are related? • Chemical characteristics can indicate whether organisms are similar or related. • Scientists study genetic material such as DNA and RNA, mutations, and genetic similarities to find relationships among organisms. • Proteins and hormones can also show if organisms are related. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things What’s in a Name? How are living things named? • Carolus Linnaeus simplified the naming of living things with a two-part scientific name. • A species is a group of organisms that are very closely related. • Members of the same species can mate and produce fertile offspring. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things How are living things named? • A genus includes similar species. • A scientific name always includes the genus name followed by the specific name. The first letter is capitalized. The species name is lowercase. • All organisms have a unique two-part scientific name that is italicized or underlined. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things What are the levels of classification? • Taxonomy is the science of describing, classifying, and naming living things. • Scientists use an eight-level system to classify living things. • Each level is more specific than the one above it, and it contains fewer kinds of living things. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things What are the levels of classification? • From most general to more specific, the levels of classification are domain, kingdom, phylum (plural, phyla), class, order, family, genus, and species. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things Triple Play What are three domains? • Scientists once used a six-kingdom classification system, but later added the domain. • A domain represents the largest differences among organisms in classification. • The three domains are Bacteria, Archaea, and Eukarya. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things What are three domains? • Domain Bacteria is made up of prokaryotes that usually have a cell wall and reproduce by cell division. • All bacteria belong to this domain. • Bacteria live in almost any environment: soil, water, and even inside the human body. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things What are three domains? • Domain Archaea is made up of prokaryotes that 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 in soil. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things What are three domains? • Domain Eukarya is made up of all eukaryotes. • Eukaryotes have cells with a nucleus and membrane-bound organelles. • Some eukaryotes, such as protists and some fungi, are single-celled. Other protists—as well as fungi, plants, and animals—are multicellular. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things My Kingdom for a Eukaryote! What are the four kingdoms in Eukarya? • Scientists have classified four types of Eukarya. • Scientists do this by deciding if an organism is unicellular or multicellular, and if it makes its own food, as well as how it reproduces. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things What are the four kingdoms in Eukarya? • Members of the kingdom Protista, called protists, are single-celled or simple multicellular organisms such as algae, protozoans, and slime molds. • Protists are very diverse, with plant-like, animallike, or fungus-like characteristics. • Some protists reproduce sexually, while others reproduce asexually. • Some protists, autotrophs, make their own food. Other protists, heterotrophs, eat other organisms for food. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things What are the four kingdoms in Eukarya? • Members of the kingdom Fungi are single-celled or multicellular organisms such as yeasts, molds, and mushrooms. • Fungi get energy by absorbing materials, and have cells with cell walls but no chloroplasts. • Fungi use digestive juices to break down materials for food. They reproduce asexually or sexually, depending on their type. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things What are the four kingdoms in Eukarya? • Kingdom Plantae consists of multicellular organisms that have cell walls, mostly made of cellulose. • Plants make food through photosynthesis. They are found on land in water that light can pass through, and cannot move by themselves. • Some plants reproduce sexually, when pollen from one plant fertilizes another. Some plants reproduce asexually, when buds grow into plants. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things What are the four kingdoms in Eukarya? • Kingdom Animalia contains multicellular organisms—such as birds, fish, reptiles, insects, amphibians, and mammals—that lack cell walls. • Animals are typically able to move around and have specialized sense organs. They get nutrients by eating other organisms. • Most animals reproduce sexually, but a few types of animals reproduce asexually, such as by budding. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things How do classification systems change over time? • Millions of organisms are not named. • New organisms do not always fit into the existing classification system. • Classification continues to change as scientists learn more about living things. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things How do branching diagrams show classification relationships? • Scientists often use a type of branching diagram called a cladogram, which shows relationships among species. • Organisms are grouped according to common characteristics listed on a line. Branches of organisms extend from this line. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things How do branching diagrams show classification relationships? • Organisms on branches above a particular characteristic have the characteristic. Organisms on branches below the characteristic do not. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things A Class by Themselves • As scientists find more living things to study, they find that they may not have made enough classifications, or that their classifications may not describe organisms well enough. • Some organisms are difficult to classify because they have traits that fall under more than one classification. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things A Class by Themselves • The sea spider is an arthropod because its body has segments and an exoskeleton. • Sea spiders eat by sticking a straw-like structure into sponges and sea slugs and sucking out the juice. No other arthropod eats like this. • To account for this strange mouth, scientists must decide if they need to create a new classification or change an existing one. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 5 Classification of Living Things Keys to Success How can organisms be identified? • A dichotomous key uses a series of paired statements to identify organisms. • Each pair of statements is numbered. • Either you choose the statement that best describes the organism, or you are directed to a new pair of statements. This process happens until you can identify the organism. Copyright © Houghton Mifflin Harcourt Publishing Company