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Intro to Biology and Basic Chemistry
Ch. 1,2,3
We are living in a golden age of biology
Biology is woven into the fabric of society as never beforeKnowledge of biological concepts is more important than ever
Biology is the scientific study of lifeTHE SCOPE OF BIOLOGY
Biology’s scope stretches across the enormous diversity of life on Earth
Biologists explore life at levels ranging from the biosphere to the molecules that make up cells
Figure 1.2.2
Cells Nucleus within cell
Cells in squirrel
DNA
The Unity of Life
Amoebas, molds, trees, and people are all made from similar cellsAll organisms share a common chemical language for their genetic material, DNA
Diversity is the hallmark of lifeLife in Its Diverse Forms
•The diversity of known life includes 1.7 million species•Estimates of the total diversity range from 5 million to over 30 million species
Biodiversity can be both beautiful and overwhelming
Grouping Species: The Basic Concept
Taxonomy is the branch of biology that names and classifies species
It formalizes the hierarchical ordering of organisms
Figure 1.7
The three domains of life are
The Three Domains of Life
Bacteria Archaea Eukarya
Figure 1.8.1
Domain Bacteria Domain Archaea
Domain Eukarya
Kingdom Protista Kingdom Plantae
Kingdom Fungi Kingdom Animalia
Bacteria and Archaea are both prokaryotic domains
Figure 1.8.2
Domain Bacteria Domain Archaea
Eukarya includes at least four kingdoms
ProtistaPlantaeFungiAnimalia
Figure 1.8.3
Domain Eukarya
Kingdom Protista Kingdom Plantae
Kingdom Fungi Kingdom Animalia
Quick Think
What are the 2 classifications of prokaryotes?
All eukaryotes belong to which group?
Can you list the characteristics of the prokaryotic domain Archaea?
Underlying the diversity of life is a striking unity, especially at the lower levels of structure
Unity in the Diversity of Life
Example: the universal genetic language of DNA
Evolution accounts for this combination of unity and diversity
The universal architecture of eukaryotic cilia
Figure 1.9
(a) Paramecium (b) Cells from fallopian
tube
(c) Cross section of cilium
Think-Pair-Share
What is studied under the scope of biology?
Think/Write 30 seconds Pair 1 minute Share with class when
asked to
The history of life is a saga of a restless Earth billions of years old
EVOLUTION: BIOLOGY’S UNIFYING THEME
Fossils document this history
Figure 1.10
Life evolves
Each species is one twig of a branching tree of life extending back in time
Figure 1.11
Giantpanda
Spectacledbear
Slothbear
Sunbear
Americanblack bear
Asiaticblack bear
Polarbear
Brown bear
Ancestral bear
The evolutionary view of life came into focus in 1859 when Charles Darwin published The Origin of Species
The Darwinian View of Life
Figure 1.12
Darwin’s book developed two main points
Descent with modificationNatural selection
Darwin was struck by the diversity of animals on the Galápagos Islands
Natural Selection
He thought of adaptation to the environment and the origin of new species as closely related processes
As populations separated by a geographic barrier adapted to local environments, they became separate species
Fourteenspecies of Galápagos finches have beak shapes adapted to suit their environments
Mediumgroundfinch
Cactusgroundfinch
Smalltree finch
Mediumtree finch
Woodpeckerfinch
Largegroundfinch
Smallgroundfinch
Large cactusground finch
Vegetarianfinch
Largetree finch
Mangrovefinch
Greenwarbler
finch
Graywarbler
finch
Sharp-beakedground finch
Seed-eaters Cactus-flower-eaters
Bud-eater Insect-eaters
Ground finches Tree finches Warbler finches
Common ancestor fromSouth American mainland Figure 1.13
Darwin synthesized the concept of natural selection from two observations that were neither profound nor original
Darwin’s Inescapable Conclusion
Others had the pieces of the puzzle, but Darwin could see how they fit together
Darwin & Wallace
Fact 1: Overproduction and struggle for existence
Fact 2: Individual variation
The inescapable conclusion: Unequal reproductive successIt is this unequal reproductive success that Darwin called natural selectionThe product of natural selection is adaptation
Natural selection is the mechanism of evolution
Figure 1.14
Population with varied inherited traits
Elimination of individuals with certain traits
Reproduction of survivors
Increasing frequency of traits that enhance survival and reproductive success
1
2
3
4
Artificial selection is the selective breeding of domesticated plants and animal by humans
Observing Artificial Selection
Figure 1.15
There are many examples of natural selection in action
Observing Natural Selection
The development of antibiotic-resistant bacteria is one
Figure 1.16
Darwin’s publication of The Origin of Species fueled an explosion in biological research
Evolution is one of biology’s best demonstrated, most comprehensive, and longest lasting theoriesEvolution is the unifying theme of biology
Think-Pair-Share
How would you explain evolution and natural selection to someone (briefly)?
Atoms & Molecules
The Chemistry of Life
Take any biological system apart and you eventually end up at the chemical level
Ecosystem African savanna
CommunityAll organisms in savanna
PopulationHerd of zebrasOrganism Zebra
Organ systemCirculatory system
OrganHeart
CellHeart muscle cell
TissueHeart muscletissue
MoleculeDNA
AtomOxygen atom
Building Blocks of Matter
Matter is the amount of material in an object; it is measured using mass (not weight!)
Matter is composed of chemical elements
There are 92 naturally occuring elements
25 are essential to life Four of these make up ~ 96% of the
weight of the human body Trace elements occur in smaller
amounts
Trace elements are also essential for life Trace elements are
required for all organisms in very small amounts
Iron is essential to all organisms
Iodine is essential to vertebrates
An iodine deficiency causes goiter
Atoms: smallest unit of matter that retains its characteristics-ex. H, C, Na Nucleus = protons
and neutrons
Electrons = in clouds around the nucleus, at varying energy levels
The type of atom is determined by the number of protons in its nucleus.
Atomic Number •the number of protons in the nucleus
What is the atomic number of carbon?
Mass Number• the sum of the protons and neutrons
What is the mass number of carbon?
Atomic Elements
Isotopes are alternate mass forms of an element
Isotopes
They have the same number of protons and electrons But they have a different number of neutronsChange in # of neutrons changes the mass number
Radioactive isotopes
The nucleus decays, giving off particles and energyRadioactive isotopes have many uses in research and medicine
Example: PET scans
Electrons determine how an atom behaves when it encounters other atoms
The properties of an atom are determined by the configuration of its outer electrons (aka valence electrons)
Electron Arrangement and the Chemical Properties of Atoms
Stable Electron Configuration
The most stable electron configuration is 8 in the outer shell (2 for H and He)All elements will try to gain, lose or share outer electrons in order to reach this configuration.
Electrons tend to exist at the lowest state of potential energy - the lowest shell
1st shell - holds 2 electrons max
2nd shell - holds up to 8 electrons
3rd shell - holds up to 8 electrons
Shell Relationships
Elements with the same number of valence electrons tend to behave similarly
Atoms of the four elements most abundant in life
Figure 2.7
Electron
Firstelectron shell(can hold2 electrons)
Outermostelectron shell(can hold8 electrons)
Carbon (C)Atomic number = 6
Nitrogen (N)Atomic number = 7
Oxygen (O)Atomic number = 8
Hydrogen (H)Atomic number = 1
Energy EmissionEnergy may hit an electron and raise it to a higher level
This is an unstable condition
The electron emits energy as it drops down to original level
Think-Pair-Share
What is an atom, what are the parts of an atom, and which of these parts is most important to reactivity and why?
Chemical Bonding and Molecules
Chemical reactions enable atoms to give up or acquire electrons in order to complete their outer shells These interactions usually result in atoms staying
close together The atoms are held together by chemical bonds
When an atom loses or gains electrons, it becomes electrically charged
Ionic Bonds
Charged atoms are called ions
Cations - positive charge
Anions - negative charge
Sodium atom (Na) Chlorine atom (Cl)
Completeouter shells
Sodium ion (Na) Chloride ion (Cl)
Sodium chloride (NaCl)
Opposites attract
Ionic Bonds Ionic bonds are formed
between oppositely charged ions
Ionic compounds are salts Salts do not consist of
individual molecules• They are just an
aggregate of cations and anions
A covalent bond forms when two atoms share one or more pairs of outer-shell electrons
Covalent Bonds
Cells constantly rearrange molecules by breaking existing chemical bonds and forming new ones
Chemical Reactions
Such changes in the chemical composition of matter are called chemical reactions
Hydrogen gas Oxygen gas Water
Reactants Products
Chemical reactions can be symbolized with equations
On the left side of the equation are the reactants, the starting materialsOn the right side of the equation are the products, the end materials
Balancing Equations Amount of matter on both sides of a chemical reaction
must stay the same
Matter cannot be created or destroyed
Numbers (coefficients) are added in front of chemical formulas to BALANCE equations.
2NaOH + H2SO4 2H2O + Na2SO4
Molecules
Formed from atoms that “share” their electrons (covalent bonding)
Together they have a neutral charge
Often contain carbon and are then known as “organic” molecules
Can have single, double or triple bonding
Inorganic Molecules
Organic Molecules
Must include Carbon atom(s)
Organic Molecules
Think-Pair-Share
Why do we say that matter cannot be created or destroyed?
Chemical Properties of Water
Your Objective
Be able to state at least 1 property of water that helps support life
AND
Be able to explain how the chemical nature of water gives
rise to that property
Water and Life
Life on Earth began in water and evolved there for 3 billion years.
Modern life still remains tied to water
Cells are composed of 70%-95% water
•Water is found Water is found
as a liquid over as a liquid over
71% of the 71% of the
earthearth•The abundance The abundance
of water is a of water is a
major reason major reason
Earth is Earth is
habitablehabitable
Studied in isolation, the water molecule is deceptively simple Its two hydrogen atoms are joined to one
oxygen atom by single covalent bonds
The structure of water
H
O
H
But the electrons of the covalent bonds are not shared equally between oxygen and hydrogen
This unequal sharing makes water a polar moleculeOxygen is more electronegative than hydrogen, so it has a greater pull on the electrons
() ()
() ()
The polarity of water results in weak electrical attractions between neighboring water molecules
These interactions are called hydrogen bonds
(b)
()
Hydrogen bond()
()()
()
()
()
()
Polar Structure
Electronegativity of H20
Quick Think Why is a molecule
of water said to have polar covalent bonds?
What kind of bonds hold individual water molecules together?
Water’s Life Supporting Properties
The polarity of water molecules and the hydrogen bonding that results explain most of water’s life-supporting properties Water’s cohesive nature Water’s ability to moderate temperature Floating ice Versatility of water as a solvent
Water molecules stick together as a result of hydrogen bonding
The Cohesion of Water
This is called cohesionCohesion is vital for water transport in plants
Microscopic tubes
Surface tension is the measure of how difficult it is to stretch or break the surface of a liquid
Hydrogen bonds give water an unusually high surface tension Cohesion between water molecules form a skin-like surface
Can support animals like “water Can support animals like “water striders” in pondsstriders” in ponds
Surface Tension
Water drops are round because all the molecules on the edge are pulled to the middle.
Adhesion
Water will also adhere to other polar substances
This is called adhesion
It is due to the polar nature of the water molecule
Caused by adhesion the water runs along the glass and does not fall straight.
Capillary Action
Glass has polar molecules.
Glass can hydrogen bond.
Attracts the water molecules.
Some of the pull is up.
Meniscus
Water curves up along the side.
This makes the meniscus.
Quick Think
How are adhesion and cohesion similar and different?
Give an example of how these properties help support life.
Water moderates temperature
Because of hydrogen bonding, water has a strong resistance to temperature change
Water moderates temperature
Heat and temperature are related, but different Heat is a measure of the amount of kinetic
energy in the atoms and molecules in something
Temperature measures the intensity of the heat
Whenever 2 objects meet, the cooler object absorbs heat from the warmer object until they are the same temperature
Water moderates temperature
Water has a high specific heat Specific heat = the amount of heat that must Specific heat = the amount of heat that must
be absorbed or lost to change the be absorbed or lost to change the temperature of 1g of the substance 1°Ctemperature of 1g of the substance 1°C
Water moderates temperature Since water has a high specific heat, it
will not change temperature much when it absorbs or loses heat
This is because much of the absorbed heat is used to break hydrogen bonds, not increase the kinetic energy of the molecules
Water moderates temperature
So water can absorb and store large amounts of heat while only changing a few degrees in temperature
Large bodies of water help to moderate temperature
Earth’s giant water supply causes temperatures to stay within limits that permit life
Evaporative cooling removes heat from the Earth and from organisms
How water moderates temperature
Water also has:Water also has:
High heat of fusionHigh heat of fusion• The temp at which liquid turns solidThe temp at which liquid turns solid
High heat of vaporizationHigh heat of vaporization• The temp at which liquid turns to gasThe temp at which liquid turns to gas
When water molecules get cold, they move apart, forming ice
The Biological Significance of Ice Floating
A chunk of ice has fewer molecules than an equal volume of liquid water
IceLiquid water
The density of ice is lower than liquid water This is why ice floats
Figure 2.15
Hydrogen bond
Liquid water
Hydrogen bondsconstantly break and re-form
Ice
Stable hydrogen bonds
Change of State
Dipole Structure
Ice floats in water because all ice molecules are held in hexagons
Center is open space, making ice 8% less dense than water.
Since ice floats, ponds, lakes, and even the oceans do not freeze solid
Marine life could not survive if bodies of water froze solid
Floating ice insulates water below, preventing freezing: critical for ocean animals
Maximum density: 3.98oC
Below this temp, form hexagonal polymers and decrease density
Above this, molecules are energetic, water behaves like other liquids - expanding when warm and contracting when cool
A solution is a liquid consisting of two or more substances evenly mixed
Water as the Solvent of Life
The dissolving agent is called the solventThe dissolved substance is called the solute
Ion in solutionSalt crystal
When water is the solvent, the result is called an aqueous solution
Water is a good solvent because it is polar
Ionic (salts) and polar (sugars) compounds dissolve readily in water
Solvent Properties Water dissolves salts by surrounding the atoms in the
salt molecule and neutralizing the ionic bond holding the molecule together
Quick Think
What are some unique properties of water that allow it to support life and how is this related to its polar nature?
Acids, Bases &
Buffers
Acid
Acids, Bases, and pH
A chemical compound that donates H+ ions to solutionsBase
A compound that accepts H+ ions and removes them from solution or a compound that dissociates in water to form hydroxide ions
Basicsolution
Neutralsolution
Acidicsolution
Oven cleaner
Household bleach
Household ammonia
Milk of magnesia
Seawater
Human bloodPure water
Urine
Tomato juice
Grapefruit juice
Lemon juice;gastric juice
pH scale
To describe the acidity of a solution, we use the pH scale
pH scale (log scale)
Each number on the scale is 10x difference from the number next to it
• pH 1 is 10x more acidic than pH 2, 100x more acidic than pH 3, 1000x more acidic that pH 4, and so on
pH - Percent Hydronium
A measure of the percent of hydronium ions in the solution
The greater the percent hydronium ions, the more acidic the solution is
HH22COCO33 -------------> H -------------> H++ + + HCOHCO33 - -
CARBONIC ACIDCARBONIC ACID HYDRONIUM BICARBONATE HYDRONIUM BICARBONATE
ION ION IONION
Measuring Acidity
Buffers are substances that resist pH change
They accept H+ ions when they are in excessThey donate H+ ions when they are depleted
Buffering is not foolproof
Example: acid precipitation
normal rain water (pH of 5-6) pH of acid rain is between 3-4
Buffers
Dissolved CO2 in water acts as a buffer, a substance that prevents large shifts in pH.
Buffers help keep pool and spa water clean
Buffer Systems
CO2 + H2O H2CO3 H+ + HCO3- H+ + CO3
-2
H2CO3 is carbonic acid,
H+ is the hydronium ion
HCO3- is the bicarbonate ion
CO3-2 is the carbonate ion
Buffer Systems
CO2 + H2O H2CO3 H+ + HCO3-H+ + CO3
-2
Adding CO2 shifts the reaction to the right and produces more H+ ions making the water more acid.
Buffer Systems
CO2 + H2O H2CO3 H+ + HCO3- H+ + CO3
-2
Removing CO2 shifts the reaction to the left, combining H+ ions with carbonate and bicarbonate ions reducing the acidity.
Ocean Buffers