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Biology. The study of Life. Scientific Method. Observation Question Hypothesis- educated guess that can be tested Experiment-needs to be controlled only manipulating one variable Record and analyze-be accurate and use graphs
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Biology The study of Life
Scientific Method • Observation • Question • Hypothesis- educated guess that can be tested • Experiment-needs to be controlled only manipulating one variable • Record and analyze-be accurate and use graphs • Conclusion-you gain evidence to support hypothesis or disprove hypothesis
Biology “study of life” • Where did life come from? • A mixture of logic and magic • Biosphere • The part of the earth in which organisms live • Land, water, and air • Aristotle (300 BC) and ether • Spontaneous Generation
“Recipes” Bees Dead Bull in Shed Flies Rotting Meat Mice Discarded Rages Geese Mudding River Banks Salamanders Wood & Fire Spontaneous Generation
Francesco Redi’s Experiment • 1668 in Italy • Used cloth cover jars that would not allow maggots to get to meat • Proved flies don’t come from rotting meat • After hundreds of years of debate, biogenesis theory replaced spontaneous generation ideas
Five Properties of Life 1. Organization 2. Energy (metabolism) 3. Growth & Development 4. Reproduction 5. Response & Adaptation Biogenesis- “life comes from life”
Atoms Molecules Cells Tissue Organs Organ system Individual Population Communities Ecosystem Organization
Matter, Mass, and Weight • Matter: An object occupies space and has mass. • Mass: The quantity of matter an object has. • Weight: The pull of gravity on an object’s total mass.
Atomic Theory • All elements are composed of tiny, indivisible particles that we call atoms. • Atoms of the same element are identical while atoms of different elements are different. • Atoms can combine together in whole number ratios. • Atoms can be rearranged into different chemical compounds by chemical reactions. • Atoms of one element can NOT be changed into atoms of different elements.
Atoms Atom: The smallest unit into which an element can be divided and retain its characteristic properties. One unit of an element.
Elements Element: A substance composed only of atoms of the same atomic number. One of more than 100 distinct types of matter that, singly or in combination, compose all materials of the universe.
Atoms: Basic structure Made up of: Protons (+) Neutrons ( ) (Nucleus) Electrons (-) Electrically Neutral if… Protons = Electrons
Atomic Number, Symbol, Mass • Atomic Number: The number of protons found in an atom. • Symbol: The abbreviation for an element. • Atomic Mass: Weight of an atom; approx. the sum of its protons and neutrons.
Periodic Table of the Elements Beryllium 4 Atomic Number: 4 Be Symbol: Be Name Beryllium Atomic Mass: 9.0112 9.0112 .
Periodic Table of the Elements 9 Be 4 Be 4 Mass = Protons + Neutrons What’s wrong with this picture? Beryllium 9.0112
Vertically into Groups Horizontally Into Periods Elements are arranged:
If you looked at one atom of every element in a group you would see…
The group 2 atoms all have 2 electrons in their outer shells Be (Beryllium) Atom Mg (Magnesium) Atom
The number of outer or “valence” electrons in an atom effects the way an atom bonds. • The way an atom bonds determines many properties of the element. • This is why elements within a group usually have similar properties.
If you looked at an atom from each element in a period you would see…
Each atom has the same number of electron holding shells. An example…
The period 4 atoms each have 4 electron containing shells 4th Shell K (Potassium) Atom Kr (Krypton) Atom Fe (Iron) Atom
Isotopes • Neutrons do not equal protons. • More neutrons than protons. • Unstable nucleus. • Radioactive Isotope: Isotopes that give off energy because neutrons peel off their unstable nucleus.
Ions • Protons do not equal electrons. • More protons than electrons = a positive charge. • More electrons than protons = a negative charge. • Na +
Compounds Definition: • Two or more elements in definite proportions that are joined together by a chemical bond. Two Types of Bonds: • Ionic • Covalent
Ionic Bonds • Why do they form? • Octet Rule (Rule of Eight): Atoms tend to establish completely full outer energy levels. (K fills with 2, L and M generally fill with 8.)
Ionic Bonds: an example Chlorine has 17 electrons. Orbital K takes the first 2. Orbital L takes the next 8. Orbital M takes 7. • Sodium has 11 electrons. • Orbital K takes the first 2. • Orbital L takes the next 8. • Orbital M takes 1.
Ionic Bonds: an example Chlorine needs one more electron to fill its outer shell with 8 electrons. (Octet Rule) If sodium gives up one electron it will have eight in its outer level.
Ionic Bonds: an example Chlorine: 17 protons 18 electrons What’s its charge? -1 (negative ion) Sodium: 11 protons 10 electrons What’s its charge? +1 (positive ion) What do you think happens next?
Ionic Bonds: opposites attract The sodium atom and the chloride atoms are attracted toward one another because of their opposite electrical charges. The combination makes sodium-chloride, abbreviated NaCl, commonly known as salt.
Ionic Bonds • Definition: An attraction between ions of opposite charge. • These bonds are relatively weak and will easily dissolve in water.
Covalent Bonds • Definition: A chemical bond formed by the sharing of one or more pairs of electrons. • These bonds can be very strong. • Most of the structures in the body are made using these types of bonds.
Molecules • Definition: A group of elements held together by covalent bonds. • Example: Water Two hydrogens and one oxygen share two pairs of electrons.
Covalent Bonds, cont. • Why do hydrogen and oxygen want to share? • Answer: Each wants to fill its outer shell with electrons. Hydrogen fills with 2. Oxygen fills with 8.
Covalent Bonds Many types of covalent bonds Double covalent: share two pairs. Single covalent: shares one pair. Triple covalent: share three pairs.
Chemical Reactions • Equation: A formula that describes what happens during a chemical reaction. H2 O2 + H2O + O • Balanced Equation: • The elements on the left side of the equation are the same as those on the right. Notice!States of matter (liquid, solid, gas) may change during a reaction.
Chemical Reactions: Terms • Activation Energy (Energy of Activation): The energy needed to make a reaction occur. • Reactant- The chemicals before reaction • Product- The chemicals after reaction
Water The Cradle of Life: • The Universal Solvent. • The Polarity of Water.
Solutions Solution: A homogeneous mixture of the molecules of two or more substances. Ex. Water and glucose mixture.
Solvent Solvent: Medium in which a substance is dissolved (water). Water is known as the universal solvent because most of the chemical reactions necessary for life take place in water (i.e. water is the solvent).
Solutes Solutes: A compound dissolved in some solution. Ex. The glucose in the water glucose mixture.
Polarity For example: • In a water molecule, one oxygen atom shares electrons with two hydrogen atoms. Do they share equally?
Polarity, cont. • Oxygen and Hydrogen do not share electrons equally. • Oxygen is more electronegative (it attracts electrons more heavily) than hydrogen.
Polarity, cont. • The result is that the electrons shared by oxygen and hydrogen actually spend more of their time nearer the oxygen atom. This gives the oxygen a slightly negative charge and leaves hydrogen with a slightly positive charge. + Note: The charges are only partial. (i.e. not as large as a full proton or electron would be. -
The Polarity of Water • Water bonds (hydrogen bonds) to itself. • Water bonds to other molecules. • Water will group non-polar molecules. • Water is a powerful solvent.
Hydrogen Bonds • The positive or negative end of water will be attracted to other polar molecules. • Weak bonds • Usually last only 1/100,000,000,000 sec., but their cumulative effect can be great.
Water Clings Cohesion: Water attracted to water. Adhesion: Water attracted to other polar molecules. Capillary Action – water will “climb” by adhering to a surfaces electrical charges.
