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reductionism
a method that is so named because it reduces complex systems to simpler components that are more manageable to study
inquiry
a search for information and explanations of natural phenomena
data
recorded observations. items of information on which scientific inquiry is based.
inductive reasoning
we collect and analyze observations which can lead to important conclusions. Our conclusions are based on this type of logic.
hypothesis
an explanation, based on observations and assumptions, that leads to a testable prediction.
experiment
a scientific test, carried out under controlled conditions
deductive reasoning
involves logic that flows from the general to the specific. From general premises, we extrapolate to the specific results we should expect if the premises are true. In the scientific process, deductions usually take the form of predictions of results that will be found if a particular hypothesis (premise) is correct.
What must a scientific hypothesis be?
Testable. There must be some observation or experiment that could reveal if such an idea is likely to be true or false.
controlled experiment
designed to compare an experimental group with a control group.
variables
a feature or quantity that varies in an experiment.
independent variable
the factor being manipulated by the researchers.
dependent variable
the factor being measured that is predicted to be affected by the independent variable
theory
much broader in scope than a hypothesis. general enough to spin off many new, testable hypotheses. compared to any one hypothesis, a theory is generally supported by a much greater body of evidence.
model organism
a species that is easy to grow in the lab and lends itself particularly well to the questions being investigated. Scientists often use this organism when they are cooperating.
What is the difference between science and technology?
The goal of science is to understand natural phenomena, while that of technology is to apply scientific knowledge for some specific purpose.
matter
anything that takes up space and has mass
element
a substance that cannot be broken down to other substances by chemical reactions
compound
a substance consisting of two or more different elements combined in a fixed ratio
essential elements
elements that an organism needs to live a healthy life and reproduce
trace elements
required by an organism in only minute quantities
atom
the smallest unit of matter that still retains the properties of an element
subatomic particles
smaller parts of an atom
protons
a subatomic particle that is electrically charged and has one unit of positive charge
electrons
a subatomic particle that is electrically charged and has one unit of negative charge
neutrons
a subatomic particle that is electrically neutral
atomic nucleus
a dense core at the center of an atom
dalton
a unit of measurement used to describe the mass of minuscule objects such as neutrons and protons
atomic number
number of protons in the nuclei of a particular element
mass number
total number of protons and neutrons in the nucleus of an atom. From this number we can deduce the number of neutrons
atomic mass
the total mass of an atom. The mass number is close to, but slightly different from the atomic mass.
isotopes
different atomic forms of the same element. This happens because some atoms of the same element have more neutrons than others.
radioactive isotope
an isotope in which the nucleus decays spontaneously, giving off particles and energy
half-life (of an isotope)
the time it takes for 50% of the parent isotope to decay
radiometric dating
the process scientists use to measure the ratio of different isotopes and calculate how many half-lives have passed since an organism was fossilized or a rock was formed
energy
the capacity to cause change
potential energy
the energy that matter possesses because of its location or structure
What electron shell does the chemical behavior of an atom depend mostly on?
the outermost shell
valence electrons
the electrons in the outermost, or valence, shell
inert
chemically unreactive
orbital
the three-dimensional space where an electron is found 90% of the time
chemical bonds
attractions that hold atoms close together
covalent bond
the sharing of a pair of valence electrons by two atoms
molecule
two or more atoms held together by covalent bonds
single bond
a pair of shared electrons
double bond
two pairs of shared valence electrons
electronegativity
the attraction of a particular atom for the electrons of a covalent bond
non polar covalent bond
when electrons are shared equally because the two atoms have the same electronegativity
polar covalent bond
when an atom is bonded to a more electronegative atom and the electrons of the bond are not shared equally
ions
when two atoms are so unequal in their attraction for valence electrons the more electronegative atom strips an electron completely away from its partner and creates two oppositely charged atoms called this
cation
a positively charged ion
anion
a negatively charged ion
ionic bond
the attraction between cations and anions
ionic compounds (salts)
compounds formed by ionic bonds
hydrogen bond
the attraction between a hydrogen and an electronegative atom. When a hydrogen atom is covalently bonded to an electronegative atom, the hydrogen atom has a partial positive charge that allows it to be attracted to a different electronegative atom nearby.
van der Waals interactions
when electrons accumulate by chance in one part of a molecule or another. This results in ever-changing regions of positive and negative charge that enable all atoms and molecules to stick to one another.
polar molecule
when a molecule’s overall charge is unevenly distributed. There is an unequal sharing of electrons
What are four emerging properties of water that contribute to water’s suitability as an environment for life?
Cohesive behavior
Ability to moderate temperature
Expansion upon freezing
Versatility as a solvent
cohesion
the phenomenon that describes when hydrogen bonds hold the substance of water together
adhesion
the clinging of one substance to another. This plays a role in water transfer by countering the downward pull of gravity
surface tension
a measure of how difficult it is to stretch or break the surface of a liquid
kinetic energy
the energy of motion
thermal energy
the kinetic energy associated with the random movement of atoms or molecules. The thermal energy of a body of matter reflects the total kinetic energy, and thus depends on the matters volume
temperature
the average kinetic energy of the molecules in a body of matter, regardless of volume
heat
thermal energy in transfer from one body of matter to another
calorie
the amount of heat it takes to raise the temperature of 1 g of water by 1 degree celsius. conversely, a calorie is also the amount of heat that 1 g of water releases when it cools by 1 degree celsius
kilocalorie
(1,000 calories) the quantity of heat required to raise the temperature of 1 kilogram of water by 1 degree celsius
specific heat (of a substance)
the amount of heat that must be absorbed or lost for 1g of that substance to change its temperature by 1 degree celsius. Can be thought of as a measure of how well a substance resists changing its temperature when it absorbs or releases heat.
heat of vaporization
the quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state
solution
a liquid that is a completely homogeneous mixture of two or more substances
solvent
the dissolving agent of a solution
solute
the substance that is dissolved in a solution
hydration shell
the sphere of water molecules around each dissolved ion
hydrophilic
any substance that has an affinity for water
hydrophobic
substances that do not have an affinity for water. Substances that are nonionic and nonpolar actually seem to repel water.
molecular mass
the sum of the masses of all the atoms in a molecule
mole (mol)
represents an exact number of objects (6.02 x 10^23). We measure substances in moles because we can’t weigh out small numbers of molecules
molarity
the number of moles of solute per liter of solution
acid
a substance that increases the hydrogen ion concentration of a solution
base
a substance that reduces the hydrogen ion concentration of a solution
pH (of a solution)
the negative logarithm (base 10) of the hydrogen ion concentration
buffer
a substance that minimizes changes in the concentrations of the hydrogen ions and hydroxide ions in a solution. It does so by accepting hydrogen ions from the solution when they are in excess and donating hydrogen ions to the solution when they have been depleted.
ocean acidification
When carbon dioxide dissolves in seawater and reacts with water to form carbonic acid and in turn lowers ocean pH. This process alters the delicate balance of conditions for life in the oceans
valence (of an atom)
the number of covalent bonds an atom can form. This will be equal to the number of unpaired electrons in the valence shell.
hydrocarbons
organic molecules consisting of only carbon and hydrogen
isomers
compounds that have the same number of atoms of the same elements but different structures and hence different properties
structural isomers
isomers that differ in the covalent arrangements of their atoms
cis-trans isomers
isomers where carbons have covalent bonds to the same atoms, but these atoms differ in their spatial arrangements due to the inflexibility of double bonds.
enantiomers
isomers that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon, one that is attached to four different atoms or groups of atoms.
polymer
long molecule consisting of many similar or identical building blocks linked by covalent bonds, much as a train consists of a chain of cars.
monomers
the repeating units that serve as the building blocks of a polymer
enzymes
specialized macromolecules that speed up chemical reacotions
dehydration reaction
a reaction in which two molecules are covalently bonded to each other with the loss of a water molecule
hydrolysis
a process that is essentially the reverse of the dehydration reaction. This is how polymers are disassembled to monomers.
What are the four main classes of large biological molecules?
carbohydrates, lipids, proteins, and nucleic acids
carbohydrates
these molecules include sugars and polymers of sugars. They serve as fuel and building material.
monosaccharides
a type of carbohydrate that generally has a molecular formula that is some multiple of the unit CH2O.
disaccharide
consists of two monosaccharides joined by a glycosidic linkage, a covalent bond formed between two monosaccharides by a dehydration reaction
polysaccharides
macromolecules, polymers with a few hundred to few thousand monosaccharides joined by glycosidic linkages
starch
a polymer of glucose monomers
glycogen
polysaccharide. a polymer of glucose that is like amylopectin but more extensively branched.
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