a Order b Regulation
c Growth and development d Energy utilization
THE SCOPE OF LIFE The Properties of Life
e Response to the environment
f Reproduction
g Evolution
THE SCOPE OF LIFE The Properties of Life
– Biologists explore life at levels ranging from the biosphere to the molecules that make up cells.
Life at Its Many Levels
BiosphereEcosystems
Communities
Populations
Organisms
Organ Systemsand Organs
Tissues
Cells
OrganellesMolecules and Atoms
Atom
Nucleus
Life in Its Diverse Forms– Diversity is the hallmark of life.
• The diversity of known life includes 1.8 million species.• Estimates of the total diversity range from 10 million to over
100 million species.
Grouping Species– Biodiversity can be beautiful but overwhelming.– Taxonomy is the branch of biology that names and
classifies species.
The Three Domains of Life• The three domains of life are
– Bacteria
– Archaea
– Eukarya
Chemistry of Life– Matter is anything that occupies space and has mass.– Matter is found on the Earth in three physical states:
• Solid • Liquid• Gas
– Matter is composed of chemical elements.• Elements are substances that cannot be broken down
into other substances.
Chemistry of Life
Change the number of PROTONS in the nucleus and you change the ELEMENT
Atoms
Nucleus
Protons
Neutrons
Electrons
Nucleus
Cloud of negativecharge 2 electrons
2
2
2
– Each element consists of one kind of atom.• An atom is the smallest unit of matter that still retains the
properties of an element.
– Elements differ in the number of subatomic particles in their atoms.• The number of protons, the atomic number, determines which
element it is.• An atom’s mass number is the sum of the number of protons
and neutrons.• Mass is a measure of the amount of matter in an object.
Chemistry of Life
Periodic Table of the Elements
Atomic number = number of protons within the nucleus
Other nonmetals Halogens
Noble gases
Other metals
Rare earth metals Transition metals
Alkali earth metals
Alkali metals
Synthetic
Gas
Liquid
Solid
Legend
Chemistry of Life
Carbon C: 18.5%
Hydrogen H:9.5%
Nitrogen N:3.3%
Calcium Ca: 1.5%
Trace elements: less than 0.01%
Boron B Manganese Mn
Oxygen O:65.0%
Magnesium Mg: 0.1%
Phosphorus P: 1.0%
Potassium K: 0.4%
Sulfur S: 0.3%
Sodium Na: 0.2%
Chlorine Cl: 0.2%
Cobalt CoChromium Cr
Iron FeIodine IFluorine FCopper Cu Silicon Si
Zinc ZnVanadium VTin Sn
Molybdenum MoSelenium Se
– Twenty-five elements are essential to life.– Four elements make up about 96% of the weight of
the human body:• Oxygen• Carbon• Hydrogen• Nitrogen
First electron shellcan hold 2 electrons
Outer electron shellcan hold 8 electrons
Hydrogen HAtomic number = 1
Carbon CAtomic number = 6
Nitrogen NAtomic number = 7
Oxygen OAtomic number = 8
Electron
Chemical Properties of Atoms– Electrons determine how an atom behaves when it encounters
other atoms.
© 2010 Pearson Education, Inc.
Covalent Bonds– A covalent bond forms when two atoms share one or
more pairs of outer-shell electrons.– Atoms held together by covalent bonds form a
molecule.
Namemolecular formula
Hydrogen gas H2
Oxygen gas O2
Methane CH4
Electron configuration Structural formula Space-filling model Ball-and-stick model
Single bonda pair of shared electrons
Double bondtwo pairs of shared electrons
Ionic Bonds– When an atom loses or gains electrons, it becomes
electrically charged.• Charged atoms are called ions.• Ionic bonds are formed between oppositely charged ions.
Outer shellhas 1 electron
Outer shellhas 7 electrons
The outer electron is strippedfrom sodium and completesthe chlorine atom’s outer shell
NaSodium atom
ClChlorine atom
Completeouter shells
The attractionbetween theions—an ionicbond—holdsthem together
Na
Sodium ionCl
Chlorine ion
Sodium chloride (NaCl)
Hydrogen Bonds– Water is a compound in which the electrons in its
covalent bonds are shared unequally.• This causes water to be a polar molecule, one with opposite
charges on opposite ends.
H H
O
slightly slightly
slightly –
Hydrogen bonding• Weak bonds formed
between hydrogen and another atom – Surface tension of water
• Important as intramolecular bonds, giving shape to proteins and other biomolecules