Lecture 2 Outline of Last Lecture I. Levels of organization II. Living things and their environments III. Cells are fundamental units of life IV. All forms of life have common features V. Evolution explains the unity and diversity of life a. Natural selection VI. Hypothesis-based science poses and tests hypotheses a. Falsifiable b. Theories VII.Biology is all around us everyday Outline of Current Lecture I. Hierarchy exists at all levels II. How to build a universe III. How to build a galaxy IV. How to build a solar system V. How to build an Earth VI. Elements of life VII. Subatomic particles VIII. Differences in elements IX. Isotopes BIOL 1543 Custom Edition These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best !used as a supplement to your own notes, not as a substitute. !X. Electron arrangement XI. Chemical bonding a. covalent bonds XII.Unequal electron sharing creates polar molecules XIII.Hydrogen bonds are “weak” but important XIV.Cohesion of water XV. Water’s hydrogen bonds regulate temperature a. water stores heat efficiently XVI.Ice is less dense than liquid water XVII.Water is the solvent of life Current Lecture I. Hierarchy exists at all levels a. Universe, Galaxy, Solar System, Planets, Moons II. How to build a universe a. What do we know about the origin of the universe? i. The Big Bang is the term used to describe the beginning of the universe, probably about 14 billion years ago. The universe expanded rapidly from a single point and gradually cooled. This led to the formation of atoms and, eventually, galaxies and stars.(hypothesis) b. What do stars have to do with biology? i. Most of the substance of Earth, its ocean, and all living things were formed by stars. Every chemical element heavier than hydrogen, helium, and lithium was manufactured and released into space by stars. III. How to build a galaxy a. A giant star collapses and compacts densely. Then it explodes into a supernova, releasing enough heat and energy to form heavier elements.i. a supernova is the explosive death of a massive star. It must be at least 8 times bigger than our sun to count as a supernova. b. These explosions leave behind nebula clouds. Parts of these clouds can condense to form new solar systems. i. Nebula clouds are an immense interstellar cloud of dust and gas, mainly hydrogen IV. How to build a solar system a. The cloud begins to spin and flatten into a disk. The center of the disk forms the sun. The rest of the disk condenses into the planets. V. How to build an Earth a. Earth grew by the aggregation of particles. Meteors and asteroids bombarded the surface, heating the new planet and adding to its growing mass. b. Gravity pulled all the material together.. High temperatures in the interior turned the inner Earth into a semisolid mass; dense iron fell toward the center to form the core. Friction generated by this movement heated Earth even more. c. The result of density stratification is evident in the formation of an inner and outer core, a mantle, and the crust (thinnest @ 3-4 miles thick). d. Volcanic activity released most of the water on Earth. Vapor in the atmosphere eventually condensed into clouds and millions of years later, cooled enough to rain. Comets and other objects from space may have added additional water. VI. Elements of life a. Living organisms are composed of about 25 chemical elements i. About 25 different chemical elements are essential to life. ii. Carbon, hydrogen, oxygen, and nitrogen make up (96%) the bulk of living matter. iii.Tr ac e elem e n ts a r e esse n tial t o lif e , but o ccur i n min u t e am o u nts. (fluoride prevents caries = tooth decay) iv. Some trace elements are essential to human health and may be added to food or water. (like sodium)b. Atoms consist of protons (+), neutrons (=), and electrons (-). The smallest particle of matter that still retains the properties of an element is an atom. VII. Subatomic particles a. An atom is made up of protons and neutrons, located in a central nucleus. The nucleus is surrounded by electrons, arranged in electron shells.i. the number of protons = the atomic number ii. the number of electrons = the number of protons which = atomic number iii.the mass number = the number of p+ plus the number of n= iv. the number of neutrons = the mass number minus the atomic number VIII. Differences in elements a. Atoms of each element are distinguished by a specific number of protons. IX. Isotopes a. The number of neutrons in an atom may vary i. Variant forms of an element are called isotopes ii. Some isotopes are radioactive (continuously emits particles from the nucleus) X. Electron arrangement a. Electrons are arranged in shells, which may contain different numbers of electrons. The arrangement determines the chemical properties of an atom. b. Atoms whose shells are not full tend to interact with other atoms and gain, lose, or share electronsc. These interactions form chemical bonds XI. Chemical bonding a. Covalent bonds join atoms into molecules through electron sharing. b. In covalent bonds, two atoms share one or more pairs of outer shell electrons, forming molecules. c. Molecules can be represented in many ways. XII.Unequal electron sharing creates polar molecules a. A molecule is nonpolar if its covalently bonded atoms share electrons equally. (like H2O, having a positive side and negative side) b. In a polar covalent bond, electrons are shared unequally between atoms, creating a polar molecule. XIII.Hydrogen bonds are “weak” but important a. The charged regions on water molecules are attracted to the oppositely charged regions on nearby molecules b. This attraction forms weak bonds called hydrogen bonds. c. This makes water “sticky” (“cohesive”) - a very important feature for most living things. XIV.Cohesion of water a. Cohesion is the intermolecular attraction between like molecules b. Cohesion will impart the characteristics of surface tensioni. Surface tension is the effect of the surface of the liquid which makes it behave as though a thin elastic film covers the surface XV.Water’s hydrogen bonds regulate temperature a. water stores heat efficiently i. basketball player using the evaporation of sweat to cool down b. Water’s ability to store heat moderates body temperature and regional climate. c. It takes a lot of energy to disrupt hydrogen bonds, so water is able to absorb a