Chapter: Exploring and Classifying Life

2. Table of Contents Chapter: Exploring and Classifying Life Section 1: What is science? Section 2: Living Things Section 3: Where does life come from? Section 4: How are living thingsclassified?

3. What is science? 1 The Work of Science • Asking questions is one way scientists find out about anything in the world and the universe. • Science is often described as an organized way of studying things and finding answers to questions.

4. What is science? 1 Types of Science • Many types of science exist. • For example, energy and matter have a relationship. That’s a topic for physics. • On the other hand, a life scientist might study any of the millions of difference animals, plants, and other living things on Earth. • Life scientists who study plants are botanists, and those who study animals are zoologists.

5. What is science? 1 Critical Thinking • Suppose your CD player stops playing music. • To figure out what happened, you have to think about it. That’s called critical thinking, and it’s the way you use skills to solve problems. • You separate important information from unimportant information—that’s a skill. • Identifying the problem is another skill you have.

6. What is science? 1 Solving Problems • Besides critical thinking, solving a problem requires organization. • In science, this organization often takes the form of a series of procedures called scientific methods.

7. What is science? 1 Solving Problems

8. What is science? 1 Controls • A controlis the standard to which the outcome of a test is compared. • A variable is something in an experiment that can change. • An experiment should have only one variable.

9. What is science? 1 Report Results • When using scientific methods, it is important to share information. • In science it is important to explain how an experiment can be made better if it is done again.

10. What is science? 1 Developing Theories • After scientists report the results of experiments supporting their hypotheses, the results can be used to propose a scientific theory. • A scientific theory is an explanation of things or events based on scientific knowledge that is the result of many observations and experiments. It is not a guess or someone’s opinion.

11. What is science? 1 Developing Theories • If data collected from several experiments over a period of time all support the hypothesis, it finally can be called a theory.

12. What is science? 1 Developing Theories • A valid theory raises many new questions. • Data or information from new experiments might change conclusions and theories can change.

13. What is science? 1 Laws • A scientific law is a statement about how things work in nature that seems to be true all the time. • They are less likely to change than theories. • Laws tell you what will happen under certain conditions but do not necessarily explain why it happened.

14. What is science? 1 Scientific Methods Help Answer Questions • You can use scientific methods to answer all sorts of questions. • Using scientific methods does not guarantee that you will get an answer. Often scientific methods just lead to more questions and more experiments.

15. What is science? 1 Measuring with Scientific Units • An important part of most scientific investigations is making accurate measurements.

16. What is science? 1 Measuring with Scientific Units • You will use the same standard system of measurement scientists use to communicate and understand each other’s research and results. This system is called the International System of Units, or SI.

17. What is science? 1 Safety First • Laboratory safety is important. • In many states, a student can participate in a laboratory class only when wearing proper eye protection. • Following safety rules will protect you and others from injury during your lab experiences. Click image to view movie.

18. Section Check 1 Question 1 This diagram shows a way to use scientific methods to solve a problem. According to the diagram, if a hypothesis is not supported by data then you should _______.

19. Section Check 1 • change the data so that • they do support the • hypothesis • B. find a different problem to • solve • C. propose a scientific theory • D. revise the hypothesis and • perform new experiments

20. Section Check 1 Answer The correct answer is D. Scientific methods are an organized way to solve a problem in science. This series of procedures involves forming a hypothesis that can be tested.

21. Section Check 1 Question 2 What is the definition of a control in a scientific experiment? Answer A control is the standard to which the outcome of a test will be compared. Controls help you determine how to interpret your data.

22. Section Check 1 Question 3 A statement about how things work in nature that seems to be true all the time is a _______. A. conclusion B. hypothesis C. law D. variable

23. Section Check 1 Answer The correct answer is C. Although laws can be modified as more information becomes known, they are less likely to change than theories.

24. Living Things 2 What are living things like? • What does it mean to be alive? • Any living thing is called an organism. • They have different behaviors and food needs. In spite of these differences, all organisms have similar traits.

25. Living Things 2 Living Things Are Organized • A cellis the smallest unit of an organism that carries on the functions of life. • Cells take in materials from their surroundings and use them in complex ways. Each cell has an orderly structure and contains hereditary material. • The hereditary material contains instructions for cellular organization and function.

26. Living Things 2 Living Things Respond • Living things interact with their surrounds. • Anything that causes some change in an organism is a stimulus (plural, stimuli). • The reaction to a stimulus is a response. • Often that response results in movement.

27. Living Things 2 Living Things Respond • Living things also respond to stimuli that occur inside them. • An organism’s ability to keep the proper conditions inside no matter what is going on outside the organism is called homeostasis. Homeostasis is a trait of all living things.

28. Living Things 2 Living Things Use Energy • The energy used by most organisms comes either directly or indirectly from the Sun. • Plants and some other organisms use the Sun’s energy and the raw materials carbon dioxide and water to make food.

29. Living Things 2 Living Things Use Energy • You and most other organisms can’t use the energy of sunlight directly. Instead, you take in and use food as a source of energy.

30. Living Things 2 Living Things Use Energy • Some bacteria live at the bottom of the oceans and in other areas where sunlight cannot reach. • They can’t use the Sun’s energy to produce food. Instead, the bacteria use energy stored in some chemical compounds and the raw material carbon dioxide to make food.

31. Living Things 2 Living Things Grow and Develop • Growth of many-celled organisms is mostly due to an increase in the number of cells. • In one-celled organisms, growth is due to an increase in the size of the cell. • Organisms change as they grow. • All of the changes that take place during the life of an organism are called development.

32. Living Things 2 Living Things Reproduce • Cats, dogs, alligators, fish, birds, bees, and trees eventually reproduce. • Living things reproduce themselves in many different ways. • Beetles, like most insects, reproduce by laying eggs.

33. Living Things 2 Living Things Reproduce • Without reproduction, living things would not exist to replace those individuals that die. • An individual cat can live its entire life without reproducing. However, if cats never reproduced, all cats soon would disappear.

34. Living Things 2 What do living things need? • To survive, all living things need a place to live and raw materials. • The raw materials that they require and the exact place where they live can vary.

35. Living Things 2 A Place to Live • The environment limits where organisms can live. • Not many kinds of organisms can live in extremely hot or extremely cold environments. • Most cannot live at the bottom of the ocean or on the tops of mountains. • An organism’s surroundings must provide for all of its needs.

36. Living Things 2 Raw Materials • Water is important for all living things. • Plants and animals take in and give off large amounts of water each day. • Most organisms are composed of more than 50 percent water. • You are made of 60 to 70 percent water.

37. Living Things 2 Raw Materials • Living things are made up of substance such as proteins, fats, and sugars. • Animals take in most of these substances from the foods they eat. • Plants and some bacteria make them using raw materials from their surroundings.

38. Living Things 2 Raw Materials • When organisms die, substances in their bodies are broken down and released into the soil or air. • The substances can then be used again by other living organisms.

39. Section Check 2 Question 1 What is the smallest unit in a cat that carries on the functions of life? Answer The cell is the smallest unit. All organisms are composed of cells. Cells take in materials from their surroundings and use them in complex ways.

40. Section Check 2 Question 2 Pulling your hand back when you accidentally touch a hot pan on the stove is an example of what characteristic of living things? A. growth and development B. organization C. reproduction D. response to stimuli

41. Section Check 2 Answer The correct answer is D. The hot pan is an example of a stimulus. Living things can respond to both external and internal stimuli.

42. Section Check 2 Question 3 Give an example of two raw materials that you need to survive. Answer Some possible answers include: water, food, and oxygen. Some bacteria and plants can make food from raw materials in their surroundings.

43. Where does life come from? 3 Life Comes from Life • Before the seventeenth century, some people thought that insects and fish came from mud, that earthworms fell from the sky when it rained, and that mice came from grain. • The idea that living things come from nonliving things is known as spontaneousgeneration. • This idea became a theory that was accepted for several hundred years.

44. Where does life come from? 3 Spontaneous Generation and Biogenesis • From the late seventeenth century through the middle of the eighteenth century, experiments were done to test the theory of spontaneous generation.

45. Where does life come from? 3 Spontaneous Generation and Biogenesis • It was not until the mid 1800s that the work of Louis Pasteur provided enough evidence to disprove the theory of spontaneous generation. • It was replaced with biogenesis (bi oh JE nuh suss), which is the theory that living things come only from other living things.

46. Where does life come from? 3 Life’s Origins • If living things can come only from other living things, how did life on Earth begin? • Some scientists hypothesize that about 5 billion years ago, Earth’s solar system was a whirling mass of gas and dust. • They hypothesize that the Sun and planets were formed from this mass.

47. Where does life come from? 3 Oparin’s Hypothesis • In 1924 Alexander I. Oparin suggested that Earth’s early atmosphere had no oxygen but was made up of the gases ammonia, hydrogen, methane, and water vapor. • Oparin hypothesized that these gases could have combined to form the more complex compounds found in living things.

48. Where does life come from? 3 Oparin’s Hypothesis • American scientists Stanley L. Miller and Harold Urey set up an experiment to test Oparin’s hypothesis in 1953. • Although the Miller-Urey experiment showed that chemicals found in living things could be produced, it did not prove that life began in this way.

49. Section Check 3 Question 1 This diagram shows an experiment Louis Pasteur conducted with boiled broth and S-necked flasks. Why did microbes only grow in the bottom flask?

50. Section Check 3 Answer Microbes from the air settled out at the bottom of the S-neck and only entered the broth when it was tilted so that the broth touched this area. This experiment by Pasteur helped disprove the theory of spontaneous generation.