Download 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…
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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
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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.
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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)
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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
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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?
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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
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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.
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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
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Protista
• Mostly unicellular and eukaryotic
• Protozoa are animal-like and eat food.
• Algae are plant-like and use photosynthesis.
Fungi
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Mushrooms, yeasts, molds
Eukaryotic
Cell walls are different than plants.
No chlorophyll so no photosynthesis. They do not make their own
food.
Plantae
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Mosses, liverworts, ferns, and seed plants
Can not move on their own
Multicellular, cells have cell walls
Eukaryotic
Have chlorophyll and use photosynthesis
Animalia
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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.
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• 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.
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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
A. Inorganic compounds DO NOT contain carbon and hydrogen,
Ex: O2, H2O, NaCl, CO2, HCl, H2SO4
B. 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.
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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
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C12H22O11 + H2O
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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
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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
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• Contain N and P as well as C, H, and O
• Controls all cell activities
• Building blocks are nucleotides:
PROTEINS
Proteins always contain C,H,O, N and sometime S
a. Amino Acids are the building blocks of protein.
b. An amino acid is 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***
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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:
1. Hormones - chemical messengers
2. Antibodies - fight diseases
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3. Receptor molecules – cellular communication
4. Enzymes - control chemical reactions in cell
Characteristics of Enzymes
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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.
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Effect of temperature on enzymes
• Every enzyme works best at a specific temperature (called
optimum temperature).
• An enzyme is denatured 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
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• 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.
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