Biology in the 21st century Chapter 1

Characteristics of Science for Biology design and conduct scientific investigations (GPS, ACT) (SCBI_A2005-1) apply standard safety practices for all classroom laboratory and field investigations (GPS) (SCBI_A2005-2) use technology to collect, observe, measure, and manipulate data and findings (GPS, ACT) (SCBI_A2005-3) use valid critical assumptions and evidence to draw conclusions (GPS, ACT) (SCBI_A2005-4) apply computation and skills necessary for analyzing data and developing conclusions (GPS) (SCBI_A2005-5) communicate scientific information, ideas, and arguments clearly (GPS) (SCBI_A2005-6) read scientific materials to establish context for subject matter, develop vocabulary, and to be aware of current research (GPS) (SCBI_A2005-7) discuss the importance of curiosity, honesty, openness, and skepticism in science and exhibit these traits in efforts to understand how the world works (GPS)

Studying Life The word biology means the study of life. A biologist is a scientist who uses a scientific method to study the living world. All living things and all places they are found on Earth make up the biosphere. Biodiversity is the variety of life within an area. Bio=life Logy=study of

Interactive Review: Life http://www.classzone.com/cz/books/bio_07/resourc es/htmls/interactive_review/bio_intrev.html Complete this interactive review using your virtual textbook at home. Concept maps are an excellent way to organize your thoughts and review material!

Characteristics of Living Things Living things share several characteristics: Made up of units called cells Reproduce Based on a universal genetic code Grow and develop Obtain and use materials and energy Respond to their environment Maintain a stable internal environment Change over time Group activity: Try to determine whether or not the following things are living or non-living – beetle, fire, grass, virus, clouds, water, mushrooms (explain your classification method, i.e. what do the living things have in common, the non living things)?

Reproduction All organisms produce new organisms through a process called reproduction: Sexual: two cells from different parents unite to produce the first cell of the new organism Asexual: the new organism has a single parent What might be some advantages of sexual reproduction? Of asexual reproduction?

Based on a Universal Genetic Code With minor exceptions, the DNA genetic code determines the inherited traits of every organism on Earth. Deoxyribonucleic acid With asexual reproduction, offspring and their parents have the same traits With sexual reproduction, offspring differ from their parents in some ways Explaining how organisms inherit traits is one of the greatest achievements of modern biology.

Growth and Development Every type of organism has a distinctive life cycle – a particular pattern of growth and change occurring over the organism’s lifetime: Growth (increase in size) Development (cells in an organism not only increase in number but also become different) All organisms grow during at least one part of their life

Need for Materials & Energy Organisms use energy and a constant supply of materials to grow, develop, and reproduce Materials & energy are also needed just for an organism to stay alive Metabolism is the combination of chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes The way organisms take in selected materials from their surroundings varies. Sunlight: plants, some bacteria, and most algae Herbivores Carnivores Decomposers Omnivores

Response to the Environment Organisms live in constantly changing environments Amount of light and temperature can vary from day to day Nearby living and nonliving things can change Organisms can make changes to their environment Each organism responds to environmental changes in its own way Examples: Plants tend to grow in a direction toward a source of light (phototropism). Birds fly south for the winter. Examples: needs of a plant seed, leaf growth toward light, plants provide shelter for insects, death of organisms.

Maintaining Internal Balance The process by which organisms keep their internal conditions relatively stable is called homeostasis This condition is constantly being threatened by changes in the environment If homeostasis is disrupted in a major way, an organism cannot survive What are some examples of disruption of homeostasis that can lead to death in humans?

Evolution As a group, any given kind of organism can evolve, or change over time Changes are not generally significant over a few generations, but over thousands or millions of years, changes can be dramatic The ability of a group of organisms to change over time is invaluable for survival in a world that is always changing

Living things may be studied on many different levels Living things may be studied on many different levels. The largest and most complex level is the biosphere. Class Activity: Try to think of a nonliving thing that satisfies each characteristic of living things. Does any nonliving thing have all the characteristics of life? KEY WORDS: biology, cell, sexual reproduction, asexual reproduction, metabolism, homeostasis, evolve KEY CONCEPTS: What are some characteristics of living things? What topics might biologists study at the different levels of organization? Compare sexual/asexual reproduction.

Critical Thinking: Connecting Concepts Plants generally grow in the direction of a light source. This phenomenon is called phototropism. What characteristic of life does this illustrate? Many desert animals, such as rabbits, have large ears that provide a large surface area for heat to escape. What characteristic of life does this illustrate? What are the advantages and disadvantages sexual and asexual reproduction? Phototropism illustrates response to the environment. Having large ears for heat escape illustrates evolution. Sexual provides genetic variation, but is costly in terms of energy/metabolism. Asexual is quick and relatively inexpensive, but provides no genetic variation.

Interactive Review: Biological Themes http://www.classzone.com/cz/books/bio_07/resourc es/htmls/interactive_review/bio_intrev.html Complete this interactive review using your virtual textbook at home. Concept maps are an excellent way to organize your thoughts and review material!

What is Science? How is science different from other human endeavors? Deals only with the natural world Scientists collect and organize information in an orderly way in search of patterns & connections between events Scientists propose explanations that can be tested by examining evidence What is the goal of science? To investigate and understand nature, to explain events in nature, and to use those explanations to make useful predictions. What does it mean to say “science deals with only the natural world”? Why is it important that explanations of phenomena be testable? Science is an organized way of using evidence to learn about the natural world.

The Scientific Process: Observation The first step in the scientific process is making observations Involves using one or more of the senses to gather information The information gathered is called evidence, or data It is important when making observations to be objective and avoid bias Observations can be classified into 2 types: Quantitative (involves numbers & measuring) Qualitative (involves characteristics not easily measured or counted) Senses: sight, hearing, touch, smell and taste Quantitative: involves numbers (counting or measuring objects) – EX: there are seven birds at the feeder Qualitative: involves characteristics that cannot be easily measured or counted (color or texture) – EX: one of the birds has a red head Why does the scientific process not stop with observation? Observation alone has little meaning – since the goal is to understand what is observed.

The Scientific Process: Question or Inference Observations are usually followed with questions or inferences. Question: who, what, why, where, when, how… regarding phenomena observed Inference: a logical interpretation based on prior knowledge and experience

The Scientific Process: Hypothesis A hypothesis is a possible general explanation for a set of observations or an answer to a scientific question In science, a hypothesis is useful only if it can be tested Hypotheses must be falsifiable Hypotheses may arise from prior knowledge, logical inferences, or educated guesses Hypotheses are tested via controlled experiments Why are only testable hypotheses useful? There must be some way to check the validity of the idea. There must be some observation or experiment that could reveal if such an idea is actually not true.

The Scientific Process: Predictions Following a general hypothesis, a specific prediction is usually made. Like hypotheses, predictions must also be testable and falsifiable Example: Hypothesize that there is a difference in the age of the trees between the north side of the hill and the south side of the hill. Specifically predict that the trees on the north side are older. Example: Hypothesize that there is a difference in the age of the trees between the north side of the hill and the south side of the hill. Specifically predict that the trees on the north side are older.

The Scientific Process: Experiment Scientists usually test hypotheses and predictions with unbiased, controlled experiments Controlled experiments test ONLY ONE variable at a time The experiment may support or refute the hypothesis No matter the outcome, a tested hypothesis has value in science because it helps researchers advance scientific knowledge

The Scientific Process: Concept Map Class Activity: Flashlight/electronic device experiment! IMPORTANT NOTE: Science is an ongoing process, not the discovery of an unchanging, absolute truth. Scientific findings are always subject to revision as new evidence is developed. KEY WORDS: science, observation, data, inference, hypothesis KEY CONCEPT: what is the goal of science?

How Scientists Work: Setting Up 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 type of experiment is called a controlled experiment Manipulated variable (independent) Responding variable (dependent) A control group should always be specified – this is the group to which you will compare your experimental group The variable that is deliberately changed is called the manipulated, or independent variable. The variable that is observed and that changes in responses to the manipulated variable is called the responding, or dependent variable.

How Scientists Work: Drawing a Conclusion Scientists use the data from an experiment to evaluate the hypothesis and draw a solid conclusion They use evidence to determine whether or not a hypothesis was supported or refuted

How a Theory Develops As evidence from numerous investigations builds up, a particular hypothesis may become so well supported that scientists consider it a theory In science, the word theory applies to a well-tested explanation that unifies a broad range of observations in the natural world A useful theory may become the dominant view among the majority of scientists, but no theory is considered absolute truth. As new evidence is uncovered, a theory may be revised or replaced by a more useful explanation.

Scientific Laws & Theories Scientific laws describe what nature does under certain conditions, and will predict what will happen as long as those conditions are met Often mathematically defined Scientific theories explain how nature works Are generally non-mathematical All scientists agree that a theory is NOT a “transitory law, or a law in waiting”. There is NO hierarchy being implied by scientists who use the words theory and law. A law is neither better than nor above a theory, and vise-versa. Class Activity: Analyze experiments performed by Redi, Spallanzani, and Pasteur. KEY WORDS: controlled experiment, manipulated variable, responding variable, theory, law KEY CONCEPTS: How do scientists test hypotheses? How does a scientific theory differ from a law or a hypothesis?

Scientific Laws & Theories Commonalities between a scientific law and theory: BOTH are based on tested hypotheses BOTH are supported by a large body of empirical data BOTH help unify a particular field BOTH are widely accepted by the vast majority of scientists within a discipline BOTH could be shown wrong at some time if there are data to suggest so DISCUSSION: Theory misused in everyday conversation: i.e. just a theory. What is the difference between a scientific law and theory.

Data Analysis: Qualitative & Quantitative

Critical Thinking: Connecting Concepts Why is the statement “all life is made of cells” an example of a theory. Explain. When first proposed, the idea that all life is made of cells changed the way scientists thought about what defines an organism. Not only did it encompass all accumulated evidence, but it also provided a framework for new investigations.

Interactive Review: Scientific Thinking http://www.classzone.com/cz/books/bio_07/resourc es/htmls/interactive_review/bio_intrev.html Complete this interactive review using your virtual textbook at home. Concept maps are an excellent way to organize your thoughts and review material!