The Scientific Method 1.Scientists make careful observations of the world around them. 2.They ask questions & form hypotheses. 3.They test their hypotheses, collect, & analyze their data.

Observations vs. Inferences Scientists use observations to gather data (using the 5 senses). Scientists use known data to make inferences (a logical interpretation of the data based on past experiences).

Let’s test your observation skills. Take a good look at this picture:

1.Are there cars parked on the side of the road? 2.What color is the pickup truck driving in the road? 3.Are there any minivans around? 4.What does the blue sign say? 5.What’s the speed limit? 6.Are there pedestrians on the road?

How many did you get correct? 1.Yes 2.Blue 3.Yes 4.Yard Sale 5.35 mph 6.No

Observations vs. Inferences During labs, record your observations, not your inferences. Inferences may be used when writing your conclusion. Your observations can be qualitative or quantitative.

Observations include making measurements & collecting data.

What Scientists Do Using Tools to Collect Data

A wildlife biologist records a description of the alligator mating rituals she observed in her field journal.

A pharmaceutical researcher uses probes & computers to measure the pH of stomach acids.

Though very different, these situations are both examples of observation & the use of tools in scientific investigations.

Tools Used to Gather & Analyze Data Field journals are used to record data. Glassware & hotplates allow scientists to set up experiments. Microscopes enhance the senses. Rulers, balances, & electronic probeware are used to gather quantitative data. Computers are used to calculate & analyze data.

Technology & its Contribution to Science Until the late 1600s, no one knew about the existence of cells or single-celled organisms. Then, the microscope was invented.

Technology as a Tool in Science Microscopes: – Light Microscopes (LM) – Scanning Electron Microscopes (SEM) – Transmission Electron Microscopes (TEM)

Technology as a Tool in Science Medical Imaging An MRI of the knee shows both soft & dense tissues. An x-ray of the knee shows dense tissue (bone).

Technology as a Tool in Science Computer models are used to study systems that cannot be studied directly. – Heart attacks – Effects of medicines on the body – The movement of water in/out of cells – Predictions of how disease will move through a population

Quantitative Observations & Data Quantitative data is collected through measurement, using the metric system. – AKA the SI system (French for Systeme International) – Used by every country in the world, except Liberia, Myanmar, & the USA. In science, we always use the metric system!

The Metric System Based on the number 10, so it’s easy to use – The meter is the distance value. – The gram is the mass value. – The liter is the volume value.

Regardless of the unit, you can use the same prefixes (millimeter, milliliter, etc.). Common prefixes: Kilo = 1000 Centi = 1/100 th Milli = 1/1000 th 1 meter = 100 centimeters = 1000 millimeters

Some Metric Units used in Biology

Conversions If you want to change a larger unit into a smaller unit, move the decimal point to the right. If you want to change a smaller unit to a larger unit, move the decimal point to the left. 100 g = _____ kg kL = _____ L.1 7.4

Scientific Notation Used to make very large or very small numbers easier to read Numbers that are very small have negative exponents. Numbers that are very large have positive exponents.

Scientific Notation Have a single non-zero number (1-9) to the left of the decimal The exponent at the end tells you how many decimal places over & in which direction you would move to get to the original number.

Scientific Notation Only useful if it will make the number shorter! – Keep this in mind when converting.

Scientific Notation kg is easier to read as 1.0 x kg cm is easier to read as x 10 9 cm g = _____________________ cm = _______________________ g = _____________________________ x x

Graphing How a scientist shows patterns in data Several types of graphs – not all of them useful for data communication – Line Graphs – Bar Graphs – Pie Chart

Graphing Line Graph: compares 2 things in which items on 1 axis affect the items on the other axis – If you’re comparing anything to time, it is usually a line graph. – Example: amount of CO2 in the atmosphere over the last 6 decades

Graphing Bar Graph: compares 2 or more values – Example: number of students with red hair in each class

Graphing Pie Chart: effective in showing proportions or percentages of a whole thing – Example: comparing the percentage vote that each candidate received in an election

Graphing Always draw lines with a ruler, use pencil, & use colored pencils when necessary. Graphs must include: – Title: tell what you are comparing or displaying – X-axis: label & give scale – Y-axis: label & give scale – Key: give meanings of symbols & colors used – Data points: clearly marked & label them if there are no grid lines