Nature of Science Unit Notes

-Scientific Method-Measurement

-Graphing-Safety

-Characteristics of Life-Microscope

The Scientific Method

-Organized common sense approach to asking an answering

questions.

-A way to address a problem and reach a solution to the problem.

Step 1: Observe and state a problem or question

• Will my BioBird twirl more times if it …

• Will my BioBird twirl fewer times if it…

Step 1.5: Research

• Learn something about your topic so that you can make predictions about the outcomes of experiments based in facts, not guesses!

Step 2: Form a hypothesis

• Hypothesis - a proposed, scientifically testable explanation for an observed phenomenon.

• Can be dis-proven (rejected) but never proven (only can be supported).

• Is an “If… Then…” statement!

Hypotheses must be measurable and compared to

a control • Bad:

– If a small biobird is dropped, then it will twirl differently.

• Good:– If a small biobird is dropped, then it will

twirl 3x as many times as a control bird.– If a large biobird is dropped, then it will twirl

half as many times as a control bird.

Step 3: Test the hypothesis

• Must use a controlled experiment.– Allows researcher to test the effects of a

single factor, or experimental variable.

Step 3: Test the hypothesis

• A controlled experiment uses two set-ups to ensure any differences are due to the experimental variable:– Control setup – kept constant– Experimental setup --contains the variable

• Independent variable - “I control” - plot on X axis• Dependent variable - “Data collected” - plot on Y axis

Step 4: Record and analyze data

• Data - observations and information collected during an experiment.– Data Tables - where the numerical data

you collect is placed.

• Graphs- easy to interpret, visual representations of data in tables.

Quantitative vs. qualitative data

• Quantitative data is measurable, numerical information collected in an experiment.– Examples: length, height, volume, mass

• Qualitative data can be observed but not measured.– Examples: color, smell, taste, appearance

Direct vs. indirect evidence

• Direct evidence (observations) – information about a situation that is definite and based on observations.– The boy is typing.

• Indirect evidence (inferences) – the result of a mental process where information is assumed or inferred about a situation.– The boy is writing an essay.– The boy is updating his Facebook page.

Accurate vs. precise data

• Accurate – closeness of measurements of a quantity to the quantity’s actual value.

• Precise – the degree to which repeated measurements under unchanged conditions show the same results (a measure of reproducibility).

Step 5: Form a conclusion

• Support or reject your hypothesis.– Cannot be proven!

• **Not all hypotheses are correct!**

Step 6: Replicate the work• By repeating several times yourself or by others or by using

more samples.• A hypothesis becomes a scientific theory when it is tested

and confirmed often enough that it is unlikely to be disproved in future tests.– Scientific theory - provides a system of assumptions, accepted

principles, and rules of procedure devised to analyze, predict, or otherwise explain the nature or behavior of a specific set of phenomena.

• A theory becomes a scientific law when it can’t be disproved.– Scientific law - generalizes a body of observations. At the time it is

made, no exceptions have been found to a law.  It explains things but does not describe them; serves as the basis of scientific principles.  

• Remember, there is no “absolute truth” or proof in science!

Metric Conversions Ladder Method

The metric system• Decimal based system - scaled on multiples of 10• AKA the International System of Units, or SI• Two ways to solve conversion problems:

– Ladder method– Dimensional Analysis

KILO1000Units

HECTO100

Units

DEKA10

UnitsDECI

0.1Unit

CENTI0.01Unit

MILLI0.001Unit

MetersLitersGrams

Ladder Method

How do you use the “ladder” method?

1st – Determine your starting point.

2nd – Count the “jumps” to your ending point.

3rd – Move the decimal the same number of jumps in the same direction.

4 km = _________ m

12

3

How many jumps does it take?

Starting Point Ending Point

4.1

__.2

__.3

__. = 4000 m

Metric Conversions - Dimensional Analysis

Question: 8400mg = ___?___g

Steps:

1. Know the conversion factor (there are 1000mg in 1g).

2. Set up a multiplication problem and cancel out units on the top and bottom of the fractions.

3. Do the math to find the answer (8.4g).

Graphing• Graph- pictoral representation of the

information recorded in a data table.

• Two common types:– Line graph– Bar graph

Graphs must have…

• A title

• Properly located and labeled X and Y axes

• Units on X and Y axes

• Legends

Science Lab Safety

Lab Safety Video:http://www.flinnsci.com/teacher-resources/teacher-resource-videos/best-practices-for-teaching-chemistry/safety/laboratory-safety-challenge/

Safety Symbols

Flame

Poison

Dangerous Fumes

Wear Safety Goggles

Electrical Shock

Safety Rule #1

Never perform any unauthorized experiments or use any equipment or instruments without proper instruction.

Always follow all directions given by your teacher!

Safety Rule #2

Do not begin working on your lab unless your teacher is present!

Safety Rule #3

When required, proper eye protection must be worn during the entire class period!

Safety Rule #4

When something breaks or spills, you must notify your teacher so it can be cleaned up properly.

DO NOT TRY TO DO THIS YOURSELF!

Safety Rule #5

When working on a lab, dangling jewelry should be removed and long hair should be tied back.

Safety Rule #6

Do not eat or drink anything in the lab at any time.

Safety Rule #7

Consider every material used in the lab as dangerous.

Avoid inhaling fumes, tasting, touching, or smelling any chemical unless your teacher instructs you otherwise.

Rinse anything that spills on your skin with water immediately.

Safety Rule #8

Nothing is to be taken from the laboratory unless checked out to you in writing by your teacher.

Safety Rule #9

Never become involved in horseplay or practical jokes in the lab.

Use maturity at all times when working in the lab.

Safety Rule #10

Never point a test tube toward yourself or anyone else.

Safety Rule #11

Do not put anything in the sink or garbage can unless instructed by your teacher.

Always clean up according to the lab and teacher’s instructions.

Safety Rule #12

Note the location of the safety equipment in and around the classroom.

Always wash your hands with soap and water before leaving the lab.

• Sample size – the number of observations or replicates in an experiment.

• Scientific mechanism – the combination of components and processes that serve a common function.

• Scientific principle – a concept based on scientific laws, believe to be true and present, where general agreement is present.

• Bias – a particular preference or point of view that is personal rather than scientific.

• Science – a body of evidence-based knowledge gained through observation and experimentation.

• Biology – the scientific study of life.• Organism - a form of life; an animal, plant, fungus, protist,

or bacterium.

• Characteristics of living organisms include…– Made of cells– Based on a universal genetic code– Obtain and use energy– Grow and develop– Reproduce– Respond to their environment– Maintain homeostasis– Change over time

Living things are made of cells

• Unicellular – made up of a single cell.

• Multicellular – made up of more than one cell; cells work together.

• Cells are not found in non-living matter unless it was once alive.

Reproduction is necessary for the survival of a species

• Sexual reproduction – requires two cells from different individuals to unite.

• Asexual reproduction – single organism can reproduce alone.

Living organisms grow and develop

• Growth – adding new material or matter to add to or replace existing parts that wear out.

• Development – cycle of changes that eventually lead to aging.

Metabolism is the way organisms obtain and use

energy• Must get energy from their environment or

surroundings.• Must use energy to grow, develop, &

reproduce.• Plants-obtain energy from the sun during

photosynthesis.• Animals-take in energy in the form of food.

– Use oxygen to make the sugars in food into energy, releasing carbon dioxide and water.

Ways to obtain and use energy

• Anabolism-process of a living organism synthesizing complex substances from simpler substances.– Often powered by ATP (uses energy).– Used to build bone, muscle, etc.

• Catabolism-breakdown of complex substances into simpler ones resulting in the release of energy.– Way you acquire energy from food.

• Metabolism-sum of all chemical reactions in the body (anabolism + catabolism).

Living organisms respond to their environment

• Can be rapid (changes in behavior) or can be slow (changes in metabolism or growth).

• Stimulus-anything in the environment that causes and organisms to react.– Light– Temperature– Odor– Sound– Heat – Pressure

Responding to the environment

• Irritability-ability of living things to react to stimuli.– Both plants and animals exhibit this behavior.

• Homeostasis-the process by which organisms respond to stimuli in ways that keep conditions in their bodies suitable for life.– Ability to maintain constant/stable conditions

necessary for survival.– Ex. thermostat

Other characteristics of living organisms include…

• Evolutionary change – over many generations, groups of organisms evolve or change over time.

• Universal genetic code – all organisms store the information they need to live, grow, and reproduce in a genetic code written in a molecule of DNA.

Electron Microscopes• Used to observe VERY small objects that

require going beyond the limit of resolution of a compound light microscope. – Transmission electron microscopes (TEMs)-

shine beam of electrons at sample and magnify the image.

– Scanning electron microscopes (SEMs)-beam of electrons scan across surface of object; electrons that bounce off specimen are detected to generate the image.

MitochondriaCapillary

Plant cellTEM images

Hypodermic Needle Velcro

Bedbug

Cobweb

Red blood cells

SEM images

Compound Light Microscopes• Frequently used tools of biologists.• Magnify organisms too small to be

seen with the unaided eye.• To use:

– Sandwich specimen between transparent slide and thin, transparent coverslip.

– Shine light through specimen into lenses of microscope.

• Lens closest to object is objective lens.• Lens closest to your eye is the ocular lens.

• The image viewed through a compound light microscope is formed by the projection of light through a mounted specimen on a slide.

How does a compound light microscope work?

• Video tutorial

Diaphragm

Base

Always carry a microscope with one hand holding the arm and one hand under the base.

Eyepiece/ ocular lens

Arm

Stage Coarse Adjustment

Fine Adjustment

Positioning knobs

Light Source

Stage Clips

Nosepiece

Objectives/ objective lens

Diaphragm

Magnification

• The process of enlarging something in appearance, not actual physical size.

What’s my power?

To calculate the power of magnification or total magnification, multiply the power of the ocular lens by the power of the objective.

Power of Ocular lens X power of Objective 10 X 40 = 400

Comparing Powers of Magnification

We can see better details with higher the powers of magnification, but we cannot see as much of the image.

Which of these images would be viewed at a

higher power of magnification?

Resolution

• The shortest distance between two points on a specimen that can still be distinguished as two points.

Limit of resolution

• As magnifying power increases, we see more detail.

• The point where we can see no more detail is the limit of resolution.– Beyond the limit of resolution, objects get

blurry and detail is lost.– Use electron microscopes to reveal detail

beyond the limit of resolution of a compound light microscope!

Field of view

• The diameter of the circle of view when you look down the microscope.

What happens to the size of the field of view as you increase magnification?

Proper handling technique

1. Carry microscopes with one hand on the arm and one supporting the base.

2. Carry microscopes vertically.

3. Use proper focusing techniques at all times!

Proper focusing technique1. Check that the lighting is on.2. Make sure the objective lens is on low power.3. Place the slide on the center of the stage.4. Keep both eyes open.5. Without looking through the ocular lens, move the

stage using the coarse adjustment knob to bring the slide as close to the low power objective lens as possible.

6. Look through the eyepiece & FOCUS DOWN by turning the coarse adjustment knob away from you until the specimen is in focus.

7. Fine tune the focus with the fine adjustment knob.- do not use the coarse adjustment knob after this point!

Proper focusing technique, contd.

8. To magnify the specimen, move the objective lens to medium power. The specimen may appear cloudy when viewed. Use the fine adjustment knob to refocus.

9. To further magnify the specimen, move the revolving nosepiece to medium. If you focused properly, you will not hit the slide! Use the fine focus knob to refocus.

10. When finished with the slide, wash the slide right away. Move the objective from high to medium power and from medium power to low power.

11. Once low power is locked in place, lower the stage using the coarse adjustment knob.

12. Remove the slide from the stage.13. Properly store the microscope.

Proper clean up technique

1. Clean up right away

2. Go back to low power

3. Lower the stage

4. Remove the slide

5. Proper storage1. Check the stage

2. Check the objective

3. Wind the cord

4. Dust cover it

Proper storage technique

1. The stage must be all the way down.

2. The low power objective must be in place.

3. The slide must be removed.

4. The cord must be wound around the base.

5. The dust cover must be replaced.

How to make a wet-mount slide …

1 – Get a clean slide and coverslip.

2 – Place ONE drop of water or stain in the middle of the slide. Don’t use too much or the liquid will run off the edge! Place the specimen in the drop.

3 – Place the edge of the cover slip on one side of the liquid drop.

4-Hold the coverslip at a 45-degree angle in the edge of the puddle.

5 – Remove bubbles by gently tapping. Dry the bottom and sides of the slide.

6 - Place the slide on the stage and view it first with the low power objective. Wash and dry the coverslip and slide when finished.

5 - Slowly lower the cover slip on top of the drop with fingers or forceps. Cover

SlipLower slowly

You do not need to use the stage clips when viewing wet-mount slides!