Chapter 1. The Science of Biology. h+p://

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1 Chapter 1 The Science of Biology h+p://

2 Section 1: What is Science? The goal of science is to investigate and understand the natural world, to explain events in the natural world, and to use those explanations to make useful predictions. Science - is an organized way of using evidence to learn about the natural world.

3 Thinking Like A Scientist Why won t the car start?

4 Thinking Like a Scientist Observation - The process of gathering information about events or processes in a careful, orderly way. (Usually involves the senses, particularly sight and hearing.) Data - Information gathered from observations. o Quantitative - Expressed as numbers o Qualitative - Expressed as characteristics

5 Thinking Like a Scientist Inference - A logical interpretation based on prior knowledge or experiences.

6 Explaining and Interpreting the Evidence After the initial observation, scientists will propose one or more hypothesis. Hypothesis - A proposed scientific explanation for a set of observations o Often referred to as an educated guess o Only useful if it can be tested Scientists generate hypotheses using prior knowledge, (what they already know); logical inference; and informed, creative imagination.

7 Explaining and Interpreting the Evidence Scientists often collaborate in teams to work on complex questions or problems.

8 Science is a way of knowing Science is a never ending process. New tools, techniques, and discoveries can lead to new scientific understandings. Look at the picture below What might a scientist do with such a discovery?

9 Science and Human Values Today, scientists contribute information to discussions about health and disease, and about the relationship between human beings and the living and nonliving environment.

10 Notebook #1 1. What does science study? 2. What is the difference between qualitative and quantitative data? 3. What is a hypothesis? 4. When trying to solve complex problems, how do scientists often work?

11 Section 2: How Scientists Work For thousands of years, people have noticed that living things have magically appeared from non-living things. o Maggots appear on dead animals or rotting meat. o Mice appear on piles of grain. o Beatles appear on cow dung. Scholars from that era called this phenomenon Spontaneous Generation.

12 Designing an Experiment The maggot theory lasted until 1668 when an Italian physician, Francesco Redi, designed an experiment to test his hypothesis. Redi believed that maggots were the larva form of house flies. To test this hypothesis, Redi designed the following experiment.

13 Designing an Experiment

14 A Controlled Experiment Whenever possible, a hypothesis should be tested by an experiment in which only one variable is changed at a time. All other variables should be kept unchanged, or controlled. This is called a controlled experiment. Independent Variable (Manipulated Variable) - the variable that is deliberately changed (Gauze). Dependent Variable (Responding Variable) - the variable that is observed (Maggots appear).

15 Recording and Analyzing Results Scientists must keep written records of their observations, or data, that occur during their experiment. In the past, most results were written in notebooks or journals. They also could have drawn pictures like the following. Today, records can be kept with computers, tablets, and other electronic devices.

16 Drawing a Conclusion Scientists use the data from an experiment to evaluate the hypothesis and draw a valid conclusion. Was the hypothesis supported or not supported by the results?

17 The Scientific Method

18 Repeating Investigations Many times after a scientist publishes their work, other scientist will retest their ideas. In the mid 1700 s, an English scientist named John Needham tested Redi s ideas using another organism called animalcules (Discovered by Anton van Leeuwenhoek). Needham believed spontaneous generation could occur under the right conditions. He sealed a bottle containing gravy and heated to kill any living thing. Several days later, he examined the bottle and saw it was filled with activity. He inferred these little animals can only have come from the gravy. h+p:// method

19 Spallanzani s Test Lazzaro Spallanzani read Redi and Needham s work. He believed Needham did not heat the gravy enough and decided to do the following experiment.

20 Fige 1-10 Spallanzani s Experiment Gravy is boiled. Flask is open. Gravy is teeming with microorganisms. Gravy is boiled. Flask is sealed. Gravy is free of microorganisms.

21 Pasteur s Test Another scientist named Louis Pasteur wanted to disprove spontaneous generation. He stated that Spallanzani s experiment wasn t valid because living things need air to survive. The sealed bottle of gravy prevented that. Pasteur used a flask that had a curved neck which allowed air in but kept microorganisms out.

22 Figure 1-11 Pasteur s Experiment Broth is boiled. Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms.

23 Notebook #2 1. What is spontaneous generation? Is it a scientific explanation that is well supported today? 2. What is a controlled experiment? 3. What is the difference between the independent variable and the dependent variable in an experiment? 4. Why is it important to repeat experiments?

24 Section 3: Studying Life Interest Grabber Shells and Snowflakes How can we distinguish between living and nonliving things, such as a radiolarian (left) and a snowflake (right)? A radiolarian is a tiny living thing that is covered with a glasslike shell and lives in the ocean. A snowflake is a crystal made of frozen water.

25 Interest Grabber (continued) Work with a partner to answer the following questions. 1. What are some similarities between the snowflake and the glass shell of the radiolarian? 2. What are some differences between the snowflake and the glass shell? 3. Would you classify the shell as a living thing or a nonliving thing? Explain your answer.

26 Characteristics of Living Things Living things 1. Are made up of units called cells 2. Reproduce 3. Are based on a universal genetic code 4. Grow and develop 5. Obtain and use materials and energy 6. Respond to their environment 7. Maintain a stable internal environment (homeostasis) 8. Change over time

27 Characteristics of Living Things Characteristic Living things are made up of units called cells. Living things reproduce. Living things are based on a universal genetic code. Living things grow and develop. Living things obtain and use materials and energy. Living things respond to their environment. Living things maintain a stable internal environment. Taken as a group, living things change over time. Examples Many microorganisms consist of only a single cell. Animals and trees are multicellular. Maple trees reproduce sexually. A hydra can reproduce asexually by budding. Flies produce flies. Dogs produce dogs. Seeds from maple trees produce maple trees. Flies begin life as eggs, then become maggots, and then become adult flies. Plants obtain their energy from sunlight. Animals obtain their energy from the food they eat. Leaves and stems of plants grow toward light. Despite changes in the temperature of the environment, a robin maintains a constant body temperature. Plants that live in the desert survive because they have become adapted to the conditions of the desert.

28 Characteristics of Living Things Cell collection of living matter enclosed by a barrier that separates the cell from its surroundings Sexual reproduction cells from two parents unite to produce the first cell of the new organism Asexual reproduction process by which a single parent reproduces by itself Metabolism combination of chemical reactions through which an organism builds up or breaks down materials Stimulus signal to which an organism responds Homeostasis process by which organisms maintain a relatively stable internal environment Evolution change in a kind of organism over time

29 Figure 1-21 Levels of Organization Levels of Organization Biosphere Ecosystem The part of Earth that contains all ecosystems Community and its nonliving surroundings Biosphere Community Populations that live together in a defined area Hawk, snake, bison, prairie dog, grass, stream, rocks, air Population Group of organisms of one type that live in the same area Hawk, snake, bison, prairie dog, grass Bison herd

30 Figure 1-21 Levels of Organization continued Organism Individual living thing Bison Groups of Cells Tissues, organs, and organ systems Nervous tissue Brain Nervous system Cells Smallest functional unit of life Nerve cell Molecules Groups of atoms; smallest unit of most chemical compounds Water DNA

31 Notebook #3 1. What are the 8 characteristics of living things? 2. What is a cell? 3. What is the difference between sexual and asexual reproduction? 4. What is metabolism? 5. What is homeostasis?

32 Section 4: Tools and Procedures A Common Measurement System Most scientists use the metric system when collecting data and performing experiments. Metric system decimal system of measurement based on certain physical standards and on multiples of 10

33 Metric System

34 Microscopes Light microscopes produce magnified images by focusing visible light rays o Compound light microscope uses two lenses to form an image Electron microscopes produce magnified images by focusing beams of electrons o Transmission electron microscope (TEM) shines a beam of electrons through a soecimen o Scanning electron microscope (SEM) scan a narrow beam of electrons back and forth across the surface of the specimen

35 Laboratory Techniques Cell culture group of cells grown in a nutrient solution from a single, original cell Cell fractionation technique in which cells are broken into pieces and the different cell parts are separated

36 Notebook #4 1. What is the metric system and why have scientists around the world agreed to use it? 2. What is the difference between a light microscope and an electron microscope? 3. What is a cell culture? 4. What is cell fractionation?