1-1 What is Science?

• OBJECTIVES:– Explain what the goal of science is– Explain what a hypothesis is

What Science Is and Is Not

• 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:– Deals only with the natural world– Collects and organizes information carefully– Proposes explanations that can be tested by

examining evidence

Thinking Like a Scientist

• Scientists begin by making observations about events or processes

• The information gathered through observations is called data

• Data can be quantitative (numbers) or qualitative (descriptions)

• Scientists use data to make inferences - logical interpretations based on prior knowledge or experience

Explaining & Interpreting Evidence

• Hypothesis: A scientific explanation for a set of observations

• Hypotheses must be able to be tested with controlled experiments or by gathering more data

Science as a Way of Knowing

• Science is not unchanging knowledge – it is an ongoing process

• Scientific understanding is always changing due to new tools, techniques, and discoveries

• The focus of biologists is on living systems that range in size from the invisibly small to the size of the entire planet

Science & Human Values

• An understanding of science and the scientific approach is is essential in order to make decisions about many current issues– Smoking & lung disease– Cancer– AIDS– Heart Disease– Environmental concerns

1-1 Section Assessment

1. What does science study?

2. What does it mean to describe a scientist as skeptical? Why is skepticism considered a valuable quality in a scientist?

3. What is the main difference between qualitative and quantitative observations?

1-1 Section Assessment

4. What is a scientific hypothesis? In what two ways can a hypothesis be tested?

5. Is a scientific hypothesis accepted if there is no way to demonstrate that the hypothesis is wrong? Explain your answer.

6. Suppose a community proposes a law to require the wearing of seatbelts in all moving vehicles. How could scientific research have an impact on the decision?

1-2: How Scientists Work

• OBJECTIVES:– Describe how scientists test hypotheses– Explain how a scientific theory develops

Designing an Experiment

• Asking Questions

• Forming a hypothesis

• Setting up a controlled experiment– Use only one variable– Control (keep unchanged) all others– Manipulated variable is changed– Responding variable is observed

• Recording & analyzing results

• Drawing conclusions

* Francesco Redi (1668)

• Tested the hypothesis of spontaneous generation (life could arise from nonliving matter)

• Uncovered jars with meat (variable)

• Covered jars with meat (control)

• Maggots only formed in the uncovered jars – spontaneous generation did not occur

Publishing & Repeating Investigations

• Publishing data is important so other can repeat the same experiments

• Needham (1700’s) – used gravy and showed that microorganisms could arise spontaneously under the right conditions

• Spallanzani reviewed Needham’s work and saw that it was flawed - no spontaneous generation

• Pasteur also showed that life can only come from other living things

When Experiments are not Possible

• Field studies can be used for wild creatures

• Testing on humans?

• Try to identify and control as many variables as possible

How a Theory Develops

• A theory develops when a hypothesis becomes well-supported (Ex: Theory of Biogenesis)

• In science, a theory is a well-tested explanation that unifies a broad range of observations

• Theories can be revised or replaced if new evidence is discovered

1-2 Section Assessment

1. Why is Redi’s experiment on spontaneous generation considered a controlled experiment?

2. How does a scientific theory compare with a scientific hypothesis?

3. How do scientists today usually communicate their results and conclusions?

1-2 Section Assessment

• 4. How did the design of Pasteur’s flask help him successfully refute the hypothesis of spontaneous generation?

• 5. Evaluate the impact of Pasteur’s research on both scientific thought and society. What was the effect of Pasteur’s investigations on scientists’ ideas and peoples lives?

1-3: Studying Life

• OBJECTIVES:– What are the characteristics of living things?– How can life be studied at different levels?

• Biology - The study of life -or- the science that seeks to understand the living world

Characteristics of Living Things• Made of cells (enclosed collections of living matter)

• Reproduction (sexual = 2 parents, asexual = 1)

• Based on a genetic code (DNA)

• Growth and development

• Need for materials and energy (metabolism- chem. reactions that build or break down materials)

• Response to the environment (stimulus)

• Maintaining internal balance (Homeostasis- keeping internal conditions constant)

• Evolution (groups of organisms change over time)

Characteristics of Life

Characteristics of Life

Branches of Biology

• Molecules - Groups of atoms

• Cells - Smallest functional unit of life

• Groups of cells - tissues, organs, organ systems

• Organism - Individual living thing

• Population - Groups of organisms of one type

• Community - All populations in an area

• Ecosystem - Community & nonliving surroundings

• Biosphere - Contains all ecosystems

Biology in Everyday Life

• Appreciation of life

• Food and health

• Environmental threats

• Quality of life

1-3 Section Assessment

1. Describe five characteristics of living things

2. What topics might biologists study at the community level of organization?

3. Compare sexual reproduction and asexual reproduction.

4. What biological process includes chemical reactions that break down materials?

1-3 Section Assessment

5. What is homeostasis? Give an example of how it is maintained?

6. Suppose you feel hungry, so you reach for a peach you see in a fruit bowl. Explain how both external and internal stimuli are involved in your action.

1-4: Tools & Procedures

• OBJECTIVES:– What measurement system do most scientists

use?– How are light microscopes and electron

microscopes similar? How are they different?

A Common Measurement System

• Scientists use the metric system which is based on units of 10

• SI is a revised version of the metric system

• Units used include meters (m), kilograms (kg), liters (L), and Celsius degrees (oC)

Analyzing Biological Data

• Tables and graphs make patterns in data easier to recognize and understand

• Computers can be used to organize and collect data

Microscopes

• Two issues – magnification and sharpness

• Light microscopes– Magnify up to 1000 times– Compound uses two lenses

• Electron Microscopes– Use electrons instead of light– 1000 times more detailed than light microscope– SEM vs. TEM

Laboratory Techniques

• Cell Cultures– A single cell is placed in a nutrient solution– The cell produces a group of cells called a cell

culture– Can be used for tests

• Cell Fractionation– Used to separate one part of the cell from the rest of

the cell– Can study one part of the cell– Uses a centrifuge to spin the material

Working Safely in Biology

• Read and understand all procedures before you start an activity

• Follow the teacher’s directions exactly

1-4 Section Assessment

1. Why do scientists use a common system of measurement?

2. What is different in the way light microscopes and electron microscopes produce images?

3. What types of objects can be studied with a light microscope? What types can be studied with an electron microscope?

1-4 Section Assessment

4. Describe the technique and purpose of cell fractionation.

5. It has been said that many great discoveries lie in wait for the tool needed to make them. What does this statement mean to you? If possible, include an example in your answer.