Unit 1 Part 1: the Scientific Method

UNIT 1 PART 1: THE SCIENTIFIC METHOD

The SCIENTIFIC METHOD uses a series of steps to solve problems.

All scientists try to solve problems in the same way.

This allows experiments to be repeated and verified.

If your experiment can’t be repeated with the same results, it is not valid.

A Good Experiment…

•Can be repeated with the same results.

•Has a large sample size.

•Is performed for a long time.

•Tests only one variable. It has a control.

•Is peer reviewed – looked at by others.

•Does not have to agree with the hypothesis.

•Is objective; not based on opinion; unbiased.

DESIGNING AN EXPERIMENT

Form a hypothesis
Define the variables
Describe the materials and conditions
Perform the experiment
Collect data
Interpret the data
Draw a conclusion

STEP 1: FORM A HYPOTHESIS

•A hypothesis is an educated guess, or prediction, of what you think might happen.

•It must be a statement, NOT a question.

•It must be testable – a yes or no type statement, or an if…then statement. For example:

–Plants need light to grow.

–If plants do not have light then they will not grow as tall.

STEP 2: DEFINE THE VARIABLES

•The INDEPENDENT variable is what is being tested, Ex. The amount of light. This is what YOU change in the experiment. On a graph, it is always on the X axis.

•The DEPENDENT variable is what is measured when the independent variable is changed,

Ex. Height of the plants.

On a graph it is always

on the Y axis.

Draw a graph with the axes labeled:

STEP 3: MATERIALS AND CONDITIONS

•What is needed for the experiment?

–Plants, soil, pots, water

•What conditions must be kept the same?

–Amount of water, type of plants, type of soil, size of pots, temperature

•What will be changed (independent)?

–Amount of light

•What will be measured (dependent)?

–Height of plant

STEP 4: PERFORM THE EXPERIMENT

•Collect what is needed and set up as many identical experimental setups that are required. All experiments have at least 2.

•The experimental group(s) are being tested. They will have different amounts of the independent variable. (light)

•The control group is “normal” and usually has none of what is being tested. (kept in dark)

STEP 5: COLLECT DATA

•As the experiment is performed, make observations and measurements. (height of plants)

•These may include temperature readings, height, weight, amounts of variables, etc.

•Data is often organized into tables to make it easier to read and graph. These usually go in increasing or decreasing order of the independent variable in the first column with the dependent variable in the second column. (make a table for our example)

STEP 6: INTERPRET THE DATA

•Compare your experimental data to the control data

•Make a graph and/or drawing

•Are there any trends in the data?

•Were there any problems during the experiment?

•For our example:

–Draw a graph

–Label each axis

–Make a scale

STEP 7: DRAW A CONCLUSION

•Does your data support your hypothesis?

•If not you must reject your hypothesis.

•Explain your results either way. This means you must describe WHY your hypothesis is supported or rejected.

•If your hypothesis is rejected, how could you change it?

UNIT 1 PART 2: CLASSIFICATION OF LIVING THINGS

•All living things are put into groups, or classified. They are organized.

•This makes them easier to study and easier to find.

•The branch of biology that deals with classifying and naming organisms is called taxonomy.

Taxonomic Categories

•Largest group: Kingdom

•Phylum

•Class

•Order

•Family

•Genus

•Smallest group: species

•Only one type of organism is in a species.

Each kind of organism has a two word Latin name made up of its genus and species names. This is its scientific name and is always written in italics.

Kingdom / Animal / Animal / Animal / Animal
Phylum / Chordate / Chordate / Chordate / Chordate
Class / Mammal / Mammal / Mammal / Mammal
Order / Carnivora / Carnivora / Carnivora / Primate
Family / Canine / Canine / Felidae / Homidae
Genus / Canus / Canus / Felis / Homo
species / familiarus / lupis / domesticus / sapiens
Common / Dog / Wolf / Cat / Human

The scientific name of a human is Homo sapiens.

The Six Kingdoms

Today, with the use of DNA, taxonomists put organisms into one of six kingdoms.

Archaebacteria

•Live in extremely hostile environments :

–Volcanic hot springs

–Salt lakes or seas

–Bottom of swamps

•Most live without oxygen

•Unicellular

•Prokaryotic

Eubacteria

•Includes most bacteria, those that cause disease, and cyanobacteria

•Unicellular

•Prokaryotic

Protista

•Mostly unicellular and eukaryotic

•Protozoa are animal-like and eat food.

•Algae are plant-like and use photosynthesis.

Fungi

•Mushrooms, yeasts, molds

•Eukaryotic

•Cell walls are different than plants.

•No chlorophyll so no photosynthesis. They do not make their own food.

Plantae

•Mosses, liverworts, ferns, and seed plants

•Can not move on their own

•Multicellular, cells have cell walls

•Eukaryotic

•Have chlorophyll and use photosynthesis

Animalia

•Mammals, insects, birds, sponges

•Can move on their own

•Multicellular, cells do not have cell walls

•Eukaryotic

•Must get food from the environment

Taxonomic Keys

•A tool used to identify organisms already classified.

•Most are dichotomous. That is, there are only two choices at each step that describe some characteristic of the organism.

•Using the characteristics shown above, please make a dichotomous key for the 13 triangular critters at the left. Some characteristics may be used more than once. You may use their assigned numbers for names.

UNIT 1 PART 3: CHEMICAL COMPOUNDS OF LIFE

•The most common elements in living things are:

–Carbon (C)

–Hydrogen (H)

–Oxygen (O)

–Nitrogen (N)

2 Types of Chemical Compounds

Inorganic compounds DO NOT contain carbon and hydrogen,

Ex: O2, H2O, NaCl, CO2, HCl, H2SO4

Organic compounds contain both carbon and hydrogen.

Ex: C6H12O6, NH2C4H8COOH, C17H35COOH

Organic Compounds

•Organic Compounds always contain Carbon and Hydrogen.

•The 4 biologically important types are:

–Carbohydrates

–Lipids

–Proteins

–Nucleic acids

Carbohydrates: Sugars & Starches

Contain C, H & O

•The H’s & O’s are in a 2:1 ratio as in C6H12O6

•Usually end in –ose

•Usually have a 5 or 6 sided ring structure.

•Used for Energy

•Most common one is glucose, C6H12O6.

Types of Carbohydrates

•Simple sugars, (glucose, fructose,ribose)

• Found in fruits, used as quick energy because they digest quickly

Draw a picture of one:

•Double sugars, (maltose, lactose, sucrose)

• 2 simple sugars combined to form one molecule. They are table sugars, and also found in fruits and vegetables.

Draw a picture of one:

•Starches, (glycogen, cellulose-plant cell walls)

• String of many simple sugars combined in repeating chains They are used as storage for large sources of energy and are found in pastas, cereals, breads, vegetables

Draw a picture of one:

Dehydration synthesis

Dehydration synthesis is the joining of molecules with the release of water (Dehydration) in a process that forms a bigger molecule. (Synthesis = To make or build)

2 simple sugars into a double sugar (draw them in)

C6H12O6 + C6H12O6  C12H22O11 + H2O

Hydrolysis - Digestion

Hydrolysis – is the opposite of dehydration synthesis. This is the breaking apart of complex molecules into simpler ones, by adding water. This is part of digestion.

Changing starches back to simple sugars. (draw them in)

C18H32O16 + 2H2O  3 C6H12O6

Lipids: fats, oils, and waxes

Contain C, H & O but not a 2:1 hydrogen and oxygen ratio (H2O), they have many H’s & few O’s (C51H98O6)

The basic structure of the lipid is 3 fatty acids and a glycerol molecule.

Lipids are used as long term energy sources because they have about twice as much energy (calories) as carbohydrates.

They are used as part of membrane structures in cells.

Types of lipids:

1. oils- liquid at room temperature and come from plants usually, ex: corn oil

2. fats- semisolid at room temperature, and come from animals usually, ex: butter

3. waxes- solid at room temperature

4. steroids- hormones (chemical messengers)

They are also formed by dehydration synthesis.

NUCLEIC ACIDS: DNA AND RNA

•Contain N and P as well as C, H, and O

•Controls all cell activities

•Building blocks are nucleotides:

PROTEINS

Proteins always containC,H,O, N and sometime S

a.Amino Acids are the building blocks of protein.

b. An amino acidis made of

1. a carboxyl group (acid) (COOH)

2. an amino group (NH2)

3. a side group, ( R )

c. The R group makes each amino acid different

Dehydration synthesis of Proteins

•Dehydration synthesis combines many amino acids together to form a protein molecule.

–The bond between amino acids is called a peptide bond

–A dipeptide contains 2 amino acids, a polypeptide, many

–Proteins are one or more polypeptides bonded together

***SHAPE = FUNCTION***

•Amino acids can be joined in any order.

•Every sequence makes a different protein.

•These chains can twist and fold into many different shapes.

•The sequence of amino acids determines the shape of each protein.

•The shape of the protein determines its function.

Important Proteins

Proteins are used as:

Hormones - chemical messengers

2. Antibodies - fight diseases

3. Receptor molecules – cellular communication

4. Enzymes - control chemical reactions in cell

Characteristics of Enzymes

•Enzymes are Specific (do 1 reaction).

•Enzymes help reactions to occur Faster

•Enzymes are used over and over

•Enzymes are not changed by reactions

•Enzyme reactions are reversible.

•Enzyme names end in –ase. (protease, lipase)

•Enzymes are helped by coenzymes (vitamins).

•Enzymes are affected by temperature, pH, & concentration.

Lock and Key Theory

Each chemical reaction requires a specific enzyme, shaped in a specific way.

The substrate is the substance acted upon by the enzyme.

The enzyme molecule joins temporarily with the substrate (forming an enzyme-substrate complex)

The enzyme helps a reaction to take place in the substrate.

Upon completion of the reaction, the enzyme releases the new products.

Effect of temperature on enzymes

•Every enzyme works best at a specific temperature (called optimum temperature).

•An enzyme isdenatured at high temperatures (loses its shape) and will not work

•At low temperatures the enzyme lacks the energy to work, but its shape is not denatured.

Effects of pH on enzymes

•Enzymes work best at a specific pH level.

–Stomach enzymes work best at low pH 2 levels.

–In your intestine, enzymes work at pH 8.

•Outside of the optimum pH the enzyme is denatured, (loses its shape) and will not work

Effect of Concentration on Enzyme Action

•If the amount of enzyme remains constant and you add substrate, the rate of reaction will increase.

•Eventually all of the enzyme is being used so the reaction rate will level off.

•If the amount of substrate remains constant and you add enzyme, the rate of reaction will increase.

•Eventually all of the substrate is being used so the reaction rate will level off.