Scientists devised experiments to shed light on whether different fish species of the same genus compete in their natural habitat. They constructed 12 ponds, identical in chemical composition and physical characteristics. Then they released the following individuals into each pond:

Ponds 1,2,3Species A 300 per pondPonds 4,5,6Species B 300 per pondPonds 7,8,9Species C 300 per pondPonds 10,11,12 Species A,B,C 300 of each

per pond

Does this experimental design take into consideration all factors that can affect the outcome? If not, how would you modify it?

Chemistry of Life

Elements of LifeCarbonHydrogenOxygenNitrogen

} 96% of life

Atom Structure Review

Atomic Number = Number of protons

Mass Number = Number of protons + Number of neutrons

Isotopes – Variant forms of elementsIsotopes occur because of variations in

neutron number (proton number is always the same)

RadioisotopesSpontaneous decay of nucleusEmits energy Used as radioactive tags

http://www.buzzle.com/articles/radioactive-isotopes-in-medicine.html

Electrons and Energy LevelsLocated in energy levels (shells)

Shells closest to nucleus are lower energy levels

Shells farther away are higher energy levels

Electrons and Energy LevelsChemical properties depend on the number of

valence electrons

OrbitalsOnly 2 electrons per orbital

Chemical BondingIons = charged particles

Cations = +Anions = -

Ionic bondingCations and anions attractForms salts

http://bcs.whfreeman.com/thelifewire/content/chp02/02020.html

Chemical BondingCovalent bonds

Atoms share valence electrons

http://bcs.whfreeman.com/thelifewire/content/chp02/02020.html

Chemical BondingPolar and Nonpolar Covalent Bonding

Polar – electrons are shared unequallyCharge difference

Chemical BondingPolar and Nonpolar Covalent Bonding

Nonpolar – electrons are shared equallyNo charge difference

Weak attraction between H and electronegative atomFound in:

H2OProteinsNucleic Acids

Easily Broken

Hydrogen Bonding

http://www.stolaf.edu/people/giannini/biological%20anamations.html

Properties of WaterCohesion (water molecules cling to each

other)Causes surface tension

Adhesion (water molecules cling to other molecules)Allows for “capillarity”

Water travels upward through vascular tissue

Properties of Water

Properties of WaterTemperature Stabilization

heat does not immediately change temperature

Evaporative coolingAs H2O evaporates, remaining liquid area is

coolerMolecules with more heat energy leave as

vapor

Properties of Water

Properties of WaterSolvent properties

Polarity allows water to “tear apart” molecules

Water dissociation

Acids, Bases and Buffers

Water has neutral pH because of equilibrium between H+ and OH-

Acids – proton (H+) donorsBases (alkaline fluids) – proton acceptors

(OH-)

Acids, Bases and Buffers

Buffers – regulate pH by countering slight changesAccept H+ when it is in excessDonate H+ when they are depleted

Acids, Bases and Buffers

http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/buffer12.swf

Explain, with reference to its properties, the significance of water as a coolant, a means of transport and as a habitat.