Chapter 1 Introduction: Themes in the Study of Life

Levels of Biological Organization u Biosphere ---to--- molecule

Diversity and Unity u Diversity u Taxonomy u 3 Domains Unity Evolution Example: cillia

What are Themes? u General principles or ideas that occur over and over. u “Themes” are not a test item, but they are a framework to organize the study of Biology.

Unifying Themes in the Study of Life 1. The living world is a hierarchy. Emergent Properties emerge-with each step in life’s hierarchy.

2. The Cell Is the “basic unit” of Life

. u Life on Earth uses the nucleic acid and code for Heritable Information. 3. The continuity of life is based on DNA

Growth & Development u Organisms increase in size and complexity.

u Organisms reproduce their own kind.

4. Structure and function are correlated at all levels of biological organization.

. u Structure and Function are related at all levels.

u 5. Organisms are “open” systems, they must continually take in energy. u Energy to do work u Sun is ultimate source

6 Regulation Feedback mechanisms: Positive and Negative Organisms maintain their internal environment within tolerable limits.

Homeostasis u “homeo” = same “stasis” = state

. u Structure and Function are related at all levels.

7. Unity in Diversity u The three Domains of Life The 6 Kingdoms

u 8.Evolution—THE CORE THEME-explains unity and diversity.

u 9. Scientific Inquiry u Observation-based u Hypothesis-based

u 10.Integrating Science & Technology for society. u Marriage of u Understanding natural phenomena u Apply this knowledge for a specific purpose

Evolutionary Adaptation u Organisms change over time as they adapt to their environment.

u Organisms must adapt, move, or die!

1. Order u Living things are highly organized in structure and function.

u Analyzing a biological structure gives us clues about what it does and how it works

u Growth - increase in size. Development - increase in complexity. u Life - grows by internal changes. u.u.

4. Energy Utilization u Organisms take in energy and transform it to do work.

5. Response To Environment u Organisms respond to changes or stimuli in their environment.

u The speed of the response may be “fast” or “slow”.

6. Homeostasis u “homeo” = same “stasis” = state

Science is: u A process. u A way of “knowing”.

Science is based on: u Observations u Experiments u Deductive Reasoning

Observations: u Are the “keystone” to Science. u If it can’t be “observed”, it can’t be studied by the Scientific Method. u Can be made through your senses or through the use of tools.

Scientific Method: u A formal process of inquiry. u Obtains “evidence” through the use of experiments. u Hypothetico-deductive reasoning. u Use deductive logic to test a hypothesis.

Scientific Method Steps 1. Identify the problem. 2. What is already known? 3. Formulate a hypothesis. If- (this is what you test)-then (this is your expected result) statement 4. Conduct an experiment.

Scientific Method Steps 5. Collect data. 6.Compare data to hypothesis. 7. Conclusions and new hypothesis.

Theories vs. Laws u Theory: u A comprehensive explanation of a natural phenonemon suppported by much interrelated research. u Applicable to a particular situation and time.

u Laws: True anywhere in the universe, anytime

Summary u We will see the “themes” at various times throughout the course. u AP Biology students must be able to design an experiment to test a hypothesis. u Why? This is a national exam test item.

Matter u Anything that has mass and occupies space.

Element u Matter made up of only one type of atom. u 92 natural elements. u Each element has a symbol.

Atoms u Smallest particle of elements.

Compound u Elements combined in fixed ratios. u A compound has characteristics beyond those of its combined elements.

Question? u What Elements are necessary For Life? u Life requires about 25 chemical elements.

Macroelements u Elements needed in large amounts or quantities. u Examples: C HOPKNS CaFe Mg NaCl

ControlMinus Nitrogen

Microelements u Elements needed in very small quantities. u Also known as Trace Elements. u Examples: I, Cu, Fl, Zn, Mo, Mn

Goiter – minus Iodine

Atoms and Molecules u Atomic structure determines the behavior of an element.

Atomic Particles u Protons + charge, 1 Dalton mass u Neutrons no charge, 1 Dalton mass u Electrons - charge, essentially no mass

Atomic Model

u Atomic Number u Atomic Mass

Isotopes u Atoms of the same element u with different atomic mass. u caused by changes in the number of neutrons. u Used as “tracers”.

Types of Isotopes 1. Radioactive - where the nucleus decays spontaneously, giving off particles and energy. 2. Heavy - has a stable nucleus, but masses more than the standard isotope for the element.

Energy & Electrons

Energy u The ability to do work.

Potential Energy u Is the energy that matter stores u Electrons have potential energy because of their position relative to the nucleus.

Electron Energy Levels (shells) u Energy levels around the nucleus of an atom. u 1st level can have 2 electrons and has the lowest potential energy. u Other levels can hold more than 2 electrons and have higher energy levels.

Electron Orbitals u The three dimensional space where an electron is found 90% of the time. u Different orbitals have different shapes. u Each orbital can hold only 2 electrons.

Electron Orbitals

Chemical Behavior Of An Atom u Based on the number and location of electrons in valence shell. u Reactivity arises from the presence of unpaired electrons in valence shell.

Valence Electrons u Electrons in the outermost energy level. u Electrons available chemical bonds.

Octet Rule u The most stable condition is to have an outer level of 8 electrons. u Exception - 1st level is stable with only 2 electrons. u When stable - no chemical reactions will take place. Ex: Ne, He, (Noble gases)

Electrons of the first elements

Chemical Bonds-Forming Molecules. u Forces that join atoms together to form molecules. u Usually caused by sharing or transferring valence electrons. u Bond Formation Depends On: u The number of valence electrons that must be gained, lost, or shared to reach the stable condition.

Chemical Bond Types u Nonpolar Covalent u Polar Covalent u Ionic u Hydrogen

Nonpolar Covalent u When electrons are shared equally between atoms. u Very strong bond. u Important in many molecules found in living things. u Ex: carbon to hydrogen

Nonpolar Covalent u Can be single, double, or triple between two atoms. O=O u Each nonpolar covalent bond involves a pair of electrons.

Polar Covalent u When electrons are shared unequally between atoms. u Results in “polar” molecules that have charged areas. Ex: Water, H to O bonds

Ionic Bonds u Formed when electrons are transferred from one atom to another and ions are formed.

Types of Ions u Cations - have lost electrons (p+ > e-) giving them a positive charge. u A n ions - have gained electrons (p+ < e-) giving them a negative charge.

Ionic Bonds u Formed when cations and anions attract each other. u Weak chemical bond.

Ionic Bonds

Types of Bonding Between Molecules or within large molecules u Hydrogen Bonds u Van der Waals

Hydrogen Bonds u When a hydrogen atom bonded to one molecule is attracted to the slightly negative area (often N or O) of another molecule. u Very weak individual bond. u Can be a “strong” force if there are many H bonds.

Hydrogen Bonds

Molecular Shape u Determined by the positions of the atom’s orbitals.

Molecular Shape u Crucial in Biology : determines how most molecules of life recognize and respond to one another.

Chemical Reactions u The making and breaking of chemical bonds. u Reactions do not destroy matter, they only rearrange it.

Chemical Equations u A way to represent what is happening in a chemical reaction. Ex: 2 H 2 + O 2 2 H 2 O

Parts of the Equation u Reactants: - the starting materials. u Products: - the ending materials. u Note - all atoms of the reactants must be accounted for in the products. 2 H 2 + O 2 2 H 2 O

Chemical Equilibrium u When the conversion of reactants to products is balanced to the reverse reaction. Ex: 3 H 2 + N 2 2 NH 3

Summary u We will now put elements together to form molecules and build the next level in the hierarchy.