3.1 Types of Living Things

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1 CHAPTER 3 CLASSIFYING LIVING THINGS 3.1 Types of Living Things Look around you. What types of living things do you see? You probably see plants and animals. What would you see if you could shrink down to the size of a cell? At this size, you might see dust mites crawling across the floor (Figure 3.1). You would definitely see bacteria, a microscopic life form that lives just about everywhere. What are the different types of life and how do we classify them? Classifying life A trip to the grocery store The importance of classification Kingdoms Ryan was cooking chicken and rice for his family. He looked in the cupboard and found that they were out of rice. He had to get some quick so he ran to the grocery store. The huge store contained thousands of products. He located the aisle marked pasta, beans, and rice and quickly found exactly what he was looking for. Grocery stores are organized so you can find things easily. Products are grouped in aisles according to their similarities. You wouldn t look in the dairy aisle if you wanted to find canned pineapple! In a similar way, living things are classified by similar characteristics. Each different type of organism is called a species. It is estimated that there are over 10 million different species on Earth. Can you see why it is important to classify living things? One system of classification groups all living things into one of six kingdoms: Archaebacteria, Eubacteria, Protista, Fungi, Plantae, or Animalia. To classify a living thing into one of the kingdoms, scientists often ask three questions (Figure 3.2): Do its cells have a structure called a nucleus? Is it single-celled or multicellular? Does it get energy by making its own food (a producer) or by getting food from other organisms (a consumer)? Figure 3.1: Dust mites are tiny organisms that live in your home. Figure 3.2: Three questions asked when classifying an organism into a kingdom. 44 UNIT 1 LIVING SYSTEMS

2 CLASSIFYING LIVING THINGS CHAPTER 3 Bacteria, Kingdom Protista, and Kingdom Fungi Two Kingdoms of bacteria Kingdom Protista Kingdom Fungi Bacteria are the simplest of all living things. They are single-celled organisms and their cells do not have a nucleus. Some bacteria can produce their own food while others break down food and absorb it. Primitive bacteria have been found living in hot springs and deep sea vents (Figure 3.3). Because of this discovery, many scientists divide bacteria into two kingdoms. Under this system, Kingdom Archaebacteria are the primitive bacteria and Kingdom Eubacteria are the true bacteria. Bacteria are discussed in Chapter 9. Members of the Kingdom Protista are called protists. Protists are an odd group of organisms. They are mostly single-celled, though there are some multicellular protists. The cells of protists have a nucleus. Some protists can produce their own food while others get their energy by eating other organisms. Figure 3.4 shows some examples of protists. Protists are discussed in Chapter 9. Kingdom Fungi includes the fungi, mushrooms, molds, and yeasts. You may have seen members of this kingdom growing on rotting logs in the woods. Fungi are important because they break down rotting things and return the nutrients to the soil. Fungi cells have a nucleus and most (except yeasts) are multicellular. They get their energy by breaking down and absorbing dead organisms like rotting logs. You ll learn more about fungi in Chapter 15. Figure 3.3: These bacteria were found living in a hot spring. Figure 3.4: These are just a few members of Kingdom Protista. 3.1 TYPES OF LIVING THINGS 45

3 CHAPTER 3 CLASSIFYING LIVING THINGS Kingdoms Plantae and Animalia Kingdom Plantae The Kingdom Plantae is made up of multicellular organisms whose cells have a nucleus. In a process called photosynthesis, plants convert energy from the Sun and store it in the form of molecules. When animals eat the plants, they use those molecules as energy to survive. Examples of plants include mosses, ferns, trees, and flowering plants. Figure 3.5 shows the characteristics of a typical plant. Plants are discussed in Chapter 16. Figure 3.5: The characteristics of a typical plant. Kingdom Animalia Like plants, animals are multicellular organisms with cells that have a nucleus. Unlike plants, members of the Kingdom Animalia need to eat other organisms to get their energy. Beetles, worms, snakes, and birds are animals. You are also an animal. Figure 3.6 shows the characteristics of a typical animal. Animals are discussed in Chapter 17. Figure 3.6: The characteristics of a typical animal. 46 UNIT 1 LIVING SYSTEMS

4 CLASSIFYING LIVING THINGS CHAPTER 3 Levels of classification Taxonomy Levels of classification Taxonomy is the process of identifying and classifying living things. The Swedish scientist Carolus Linnaeus ( ) developed this system for identifying and classifying living things. Taxonomy is based on the characteristics of organisms. Organisms with shared characteristics are grouped together. For animals, the levels of classification are kingdom, phylum, class, order, family, genus, and species. For animals, the levels of classification are kingdom, phylum, class, order, family, genus, and species. Organisms belonging to the same kingdom are not necessarily very similar. As levels get smaller, organisms share more characteristics. Organisms in the same order share more characteristics than organisms in the same class. Organisms belonging to the same species are very similar and can produce offspring together. Table 3.1 shows the classification of some animals. taxonomy - the process of identifying and classifying living things. species - a group of similar organisms that can produce offspring. How many different species of organisms can you identify in your backyard or local park? Visit a local park or your backyard. List all of the different species of organisms you see. Table 3.1: Classification of some common animals Level Human Wolf Bull frog Brine shrimp Kingdom Animalia Animalia Animalia Animalia Phylum Chordata Chordata Chordata Arthropoda Class Mammalia Mammalia Amphibia Crustacea Order Primates Carnivora Anura Brachiopoda Family Homonidae Canidae Ranidae Anostraca Genus Homo Canis Rana Artemia Species Homo sapiens Canis lupus Rana catesbeiana Artemia gracillus 3.1 TYPES OF LIVING THINGS 47

5 CHAPTER 3 CLASSIFYING LIVING THINGS Scientific names What is a scientific name? Where do scientific names come from? The meaning of scientific names The importance of scientific names Have you ever heard of an animal called a Felis domesticus? Sure you have, it s a house cat! When organisms are classified, scientists assign them a scientific name. A scientific name is the two-part, scientifically recognized name given to an organism, consisting of its genus and species. Scientific names are internationally recognized names given to organisms based on the system developed by Carolus Linnaeus. The first person to describe a new species gives it a scientific name. If the species belongs to an established genus, then the first part of the name is not new. If the organism cannot be placed into an existing genus, a new genus name must be given. Genus names are usually nouns. Species names are usually adjectives. There are many different sources for the species name including appearance, behavior, habitat, location where it was found, or the name of the person who discovered it. You may have a difficult time understanding scientific names because they are usually in Latin or Greek. However, scientific names do have meanings. In our cat example (Figure 3.7), Felis is Latin for cat and domesticus is Latin for domesticated. The scientific name is usually printed in italics, with the genus capitalized. A scientific name is incomplete without both the genus and species names. There are many different languages in the world. For example, a house cat is called a gato in Mexico. Different common names could cause confusion among scientists from around the world. Therefore, all scientists refer to each species by its scientific name. All known living things have a two-part scientific name. Do you know your scientific name? It s Homo sapiens! scientific name - the two-part, scientifically recognized name given to an organism, consisting of its genus and species. Figure 3.7: The scientific name for the house cat. 48 UNIT 1 LIVING SYSTEMS

6 CLASSIFYING LIVING THINGS CHAPTER Section Review 1. Why is it important to classify living things? 2. Complete the following table. Kingdom Eubacteria Protista Fungi Plantae Animalia Prokaryotic or eukaryotic cells? Single-celled or multicellular? Producers or consumers? 3. For each organism below, (a) name the kingdom and (b) give a reason for your answer. What is this? Euglenas are one-celled, eukaryotic organisms that live in ponds. They have the following characteristics: They are green and can make their own food. They have whip-like structures called a flagella that they use to move around. They sometimes find food instead of making their own. Answer the following questions: 1. To which kingdom do Euglenas belong? 2. Before the invention of the microscope, scientists classified all organisms as either animals or plants. Explain why they needed to invent a new Kingdom when they discovered Euglenas. 4. Which scientific name is written correctly? a. felis Domesticus b. Felis domesticus c. Felis Domesticus d. felis domesticus 3.1 TYPES OF LIVING THINGS 49