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Characteristics of Life- Borton Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required) To access a customizable version of this book, as well as other interactive content, visit www.ck12.org CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based collaborative model termed the FlexBook®, CK-12 intends to pioneer the generation and distribution of high-quality educational content that will serve both as core text as well as provide an adaptive environment for learning, powered through the FlexBook Platform®. Copyright © 2014 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by federal, state, and international laws. Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms. Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons Attribution-Non-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated herein by this reference. Complete terms can be found at http://www.ck12.org/terms. Printed: December 5, 2014 www.ck12.org C HAPTER • • • • • Chapter 1. Characteristics of Life- Borton 1 Characteristics of LifeBorton Define what it means to be living. Know the five characteristics of living organisms. Describe the five characteristics shared by all living organisms. Identify the role of the five characteristics shared by all living organisms. Summarize in detail the role of each characteristic in life. Is fire alive? Fire can grow. Fire needs fuel and oxygen. But fire is not a form of life, although it shares a few traits with some living things. How can you distinguish between non-living and living things? The Characteristics of Life How do you define a living thing? What do mushrooms, daisies, cats, and bacteria have in common? All of these are living things, or organisms. It might seem hard to think of similarities among such different organisms, but they actually have many properties in common. Living organisms are similar to each other because all organisms evolved from the same common ancestor that lived billions of years ago. All living organisms: 1. 2. 3. 4. 5. 6. 7. Need energy to carry out life processes. Are composed of one or more cells. Respond to their environment. Change over many generations. Reproduce. Grow and Develop. Maintain a stable internal environment. 1 www.ck12.org Living Things Need Resources and Energy Why do you eat everyday? To get energy. Energy is the ability to change or do "work". Without energy, you could not do any "work." Though not doing any "work" may sound nice, the "work" fueled by energy includes doing everyday activities, such as walking, writing, thinking and even just existing! But you are not the only one who needs energy. In order to grow and reproduce and carry out the other process of life, all living organisms need energy. But where does this energy come from? The source of energy differs for each type of living thing. In your body, the source of energy is the food you eat. Here is how animals, plants, and fungi obtain their energy: • All animals must eat in order to obtain energy. Animals also eat to obtain building materials. • Plants don’t eat. Instead, they use energy from the sun to make their "food" through the process of photosynthesis. • Mushrooms and other fungi obtain energy from other organisms through decay. That’s why you often see fungi growing on a fallen tree; the rotting tree is their source of energy ( Figure 1.1). • Bacteria can gain energy through various interactions including absorption, photosynthesis, decay etc. FIGURE 1.1 Orange bracket fungi on a rotting log in the Oak Openings Preserve in Ohio. Fungi obtain energy from breaking down dead organisms, such as this rotting log. Living Things Are Made of Cells History of the Cell MEDIA Click image to the left or use the URL below. URL: http://www.ck12.org/flx/render/embeddedobject/142999 Video Reflection Question 1. How did scientists discover cells? 2. How did cells get their name? If you zoom in very close on a leaf of a plant, or on the skin on your hand, or a drop of blood, you will find cells, you will find cells ( Figure 1.2). Cells are the smallest structural and functional unit of living organisms. Most cells are 2 www.ck12.org Chapter 1. Characteristics of Life- Borton so small that they are usually visible only through a microscope. Some organisms, like bacteria, plankton that live in the ocean, or the Paramecium shown in Figure below are made of just one cell. Other organisms have millions, billions, or trillions of cells. All cells share at least some structures. The nucleus is clearly visible in the blood cells ( Figure 1.2). The nucleus can be described as the "information center," containing the instructions ( DNA) for making all the proteins in a cell, as well as how much of each protein to make. The nucleus is also the main distinguishing feature between the two general categories of cell. Although the cells of different organisms are built differently, they all have certain general functions. Every cell must get energy from food, be able to grow and divide, and respond to its environment. More about cell structure and function will be discussed in additional concepts. FIGURE 1.2 These cells show the characteristic nucleus. A few smaller cells are also visible. This image has been magnified 1000 times its real size. Organisms can be composed of many cells ( multicellular) or composed of a single cell ( unicellular). Bacteria are excellent examples of a single celled organisms. Multicellular organisms, like plants and humans, often organize their cells into tissue. Living Organisms Respond to their Environment All living organisms are able to react to their external environment. In fact, organisms constantly respond to their environment when reacting to changes in light, heat, sound, and chemical and mechanical contact. Animals have means for receiving information, such as eyes, ears, taste buds, or other structures. Plants also respond to their environment as seen in the video below. Below is a video of plants responding to light and gravity MEDIA Click image to the left or use the URL below. URL: http://www.ck12.org/flx/render/embeddedobject/142634 3 www.ck12.org Video Reflection Question How does the behavior of the plants support that living things respond to their environment? Living Things Change Over Many Generations For a group or species to maintain life, it must be able to have naturally selected changes over extended periods of time (generations) called adaptations. Adaptations are a result of small changes in DNA (mutations). Some mutations can be positive and thus are an adaptation. For example, over many generations Arctic Hare in the Tundra became overwhelmingly white. This is because the white Arctic Hare were better able to survive in their snowy environment. However, mutations can also be negative making the species less fit and lead to a decrease in the population. Neutral mutations also exist. FIGURE 1.3 Arctic Hare blending into the environment due to adaptations that occurred over many generations. Living Things Reproduce All living things reproduce to make the next generation. Organisms that do not reproduce will go extinct. As a result, there are no species that do not reproduce ( Figure 1.4). Some organisms make identical copies of themselves ( asexual reproduction), especially single-celled organisms. Other organisms reproduce sexually ( sexual reproduction), combining genetic information from two parents to make genetically unique offspring. Living Things Grow and Develop Development is the process of change that occurs within an organism life cycle leading to a more complex organism. Growth is the process that leads to an organism changing is size leading to a demand for more energy to maintain life. Not all organisms will go through both growth and development. For example, bacteria is more likely to engage in a developmental process without much of a growth process. Once organisms have become a mature adult, they are able to reproduce and begin the development and growth process again. The cycle which refers to an organism’s process of growth and development to reproduction is called The Life Cycle. Living Things Maintain Stable Internal Conditions When you are cold, what does your body do to keep warm? You shiver to warm up your body. When you are too warm, you sweat to release heat. When any living organism gets thrown off balance, its body or cells help it return to normal. In other words, living organisms have the ability to keep a stable internal environment. Maintaining a balance inside the body or cells of organisms is known as homeostasis. Like us, many animals have evolved behaviors that control their internal temperature. A lizard may stretch out on a sunny rock to increase its internal temperature, and a bird may fluff its feathers to stay warm ( Figure 1.6). 4 www.ck12.org Chapter 1. Characteristics of Life- Borton FIGURE 1.4 Like all living things, cats reproduce to make a new generation of cats. FIGURE 1.5 Notice the fungal life cycle which depicts a fungus ability to develop from a mere spore to mature adult capable of reproduction. FIGURE 1.6 A bird fluffs its feathers to stay warm and to maintain homeostasis. Summing It All Up Video 5 www.ck12.org MEDIA Click image to the left or use the URL below. URL: http://www.ck12.org/flx/render/embeddedobject/142639 Video Reflection Questions 1. What further information did you learn by watching this video? 2. Why are the characteristics of life essential to the study of biology? Vocabulary • • • • • • • • • • • • • • asexual reproduction: Process of forming a new individual from a single cell or individual. cell: Basic unit of structure and function of a living organism; the basic unit of life. multicellular: Having more than one cell unicellular: Having only one cell deoxyribonucleic acid (DNA): Nucleic acid that is the genetic material of all organisms. energy: Ability to do work. homeostasis: Ability to keep a stable internal environment; ability of the body to maintain a stable internal environment despite a changing environment. generations: the time it takes for an organism to become a mature adult and produce offspring (on average 30 years for human beings) nucleus: Membrane enclosed organelle in eukaryotic cells that contains the DNA; primary distinguishing feature between a eukaryotic and prokaryotic cell; the information center, containing instructions for making all the proteins in a cell, as well as how much of each one to make. organism: Living thing. photosynthesis: Process by which specific organisms (including all plants) use the sun’s energy to make their own food from carbon dioxide and water; process that converts the energy of the sun, or solar energy, into carbohydrates, a type of chemical energy. protein: Organic compound composed of amino acids and includes enzymes, antibodies, and muscle fibers. reproduce: Reproduction; process of forming a new individual. sexual reproduction: Process of forming a new individual from two parents. Summary • Living things are called organisms. • All living organisms need energy to carry out life processes, are composed of one or more cells, respond to their environment, grow, reproduce, and maintain a stable internal environment. Explore More Use the resource below to answer the questions that follow. • Characteristics of Life at http://www.youtube.com/watch?v=gJd65_Xrxs4 (3:15) 6 www.ck12.org 1. 2. 3. 4. Chapter 1. Characteristics of Life- Borton What are cell products? Do you think they should be included in characteristics of life? Why or why not? Are all responses to the environment immediately obvious? Be specific and explain your reasoning. Explain the concept of homeostasis. Give an example. At what level does life evolve? Review 1. 2. 3. 4. Is a crystal alive? Why or why not? What is a cell? How are unicellular organisms and multicellular organisms similar and different? What is homeostasis? What is an example? What are the two forms of reproduction? Describe the examples in your response. References 1. Benny Mazur. Fungi breaking down a rotting log. CC BY 2.0 2. Image copyright Jubal Harshaw, 2014. Nuclei of reptilian blood cells. Used under license from Shutterstock.com 3. Charles Nadeau. Like all living things, cats reproduce to make a new generation of cats. CC BY 2.0 4. Tony Hisgett. A bird fluffs its feathers to stay warm and to maintain homeostasis. CC BY 2.0 7