THE SCOPE OF LIFE The Properties of Life a Order b Regulation c Growth and development d Energy utilization

THE SCOPE OF LIFE The Properties of Life f Reproduction e Response to the environment g Evolution

Life at Its Many Levels Biologists explore life at levels ranging from the biosphere to the molecules that make up cells. Biosphere Ecosystems Communities Populations Organisms Organ Systems and Organs Tissues Cells Organelles Molecules 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

Chemistry of Life Matter is composed of chemical elements. Elements are substances that cannot be broken down into other substances. Change the number of PROTONS in the nucleus and you change the ELEMENT

Atoms Each element consists of one kind of atom. An atom is the smallest unit of matter that still retains the properties of an element. Nucleus Protons Neutrons Electrons Cloud of negative charge 2 electrons 2

Chemistry of Life 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.

Periodic Table of the Elements Other nonmetals     Halogens Noble gases Other metals Rare earth metals Transition metals Alkali earth metals Alkali metals Synthetic       Gas      Liquid Solid Legend Atomic number = number of protons within the nucleus

Chemistry of Life Twenty-five elements are essential to life. Four elements make up about 96% of the weight of the human body: Oxygen Carbon Hydrogen Nitrogen 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 Co Chromium Cr Iron Fe Iodine I Fluorine F Copper Cu Silicon Si Zinc Zn Vanadium V Tin Sn Molybdenum Mo Selenium Se

Chemical Properties of Atoms Electrons determine how an atom behaves when it encounters other atoms. First electron shell can hold 2 electrons Outer electron shell can hold 8 electrons Hydrogen H Atomic number = 1 Carbon C Atomic number = 6 Nitrogen N Atomic number = 7 Oxygen O Atomic number = 8 Electron © 2010 Pearson Education, Inc.

a pair of shared electrons two pairs of shared electrons 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. Name molecular formula Hydrogen gas H2 Oxygen gas O2 Methane CH4 Electron configuration Structural formula Space-filling model Ball-and-stick model Single bond a pair of shared electrons Double bond two pairs of shared electrons

Sodium chloride (NaCl) 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 shell has 1 electron has 7 electrons The outer electron is stripped from sodium and completes the chlorine atom’s outer shell Na Sodium atom Cl Chlorine atom Complete outer shells The attraction between the ions—an ionic bond—holds them together Na Sodium ion Cl 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. slightly  slightly  H H O 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