CambridgeBiology
Chapter 1: Evolution and the Foundations of Biology
1.1 The study of life reveals common themes
Theme: Organization this is an add on - The hierarchy of life unfolds as follows: biosphere > ecosystem > community > population > organism > organ system > organ > tissue > cell > organelle > molecule > atom. With each step up, new properties emerge (emergent properties) as a result of interactions among components at the lower levels. - Structure and function are correlated at levels of biological organization. The cell is the lowest level of organization that can perform all activities required for life. Cells are either prokaryotic or eukaryotic. Eukaryotic cells have a DNA- containing the nucleus and other membrane-enclosed organelles. Prokaryotic cells lack such organelles. Theme: Information
- Genetic information is encoded in the nucleotide sequences of DNA. It is DNA that transmits heritable information from parents to offspring. DNA sequences (called genes) program a cell’s protein production by being transcribed into mRNA and then translated into specific proteins, a process called gene expression. Gene expression also produces RNAs that are not translated into proteins but serve other important functions. Theme: Energy and Matter
- Energy flows through an ecosystem. All organisms must perform work, which requires energy. Producers convert energy from sunlight to chemical energy, some of which is then passed on to consumers (the rest is lost from the ecosystem as heat). Chemicals cycle between organisms and the environment. Theme: Interactions
- Organisms interact continuously with physical factors. Plants take up nutrients from the soil and chemicals from the air and use energy from the sun. Interactions among plants, animals, and other organisms affect the participants in varying ways. Core Theme: Evolution
- Evolution accounts for the unity and diversity of life and also for the match of organisms to their environments.
1.2 The Core Theme: Evolution accounts for the unity and diversity of life
- Biologists classify species according to a system of broader and broader groups. Domain Bacteria and domain Archaea consist of prokaryotes. Domain Eukarya, the eukaryotes, includes various groups of protists as well as plants, fungi, and animals. As diverse as life is, there is also evidence of remarkable unity, which is revealed in the similarities between different kinds of organisms.
- Darwin proposed natural selection as the mechanism for the evolutionary adaptation of populations to their environments. Natural selection is the evolutionary process that occurs when a population is exposed to environmental factors that consistently cause individuals with certain heritable traits to have greater reproductive success than individuals with other heritable traits.
- Each species is one twig of a branching tree of life extending back in time through more and more remote ancestral species. All of life is connected through its long evolutionary history.
1.3 In studying nature, scientists form and test hypotheses
- In scientific inquiry, scientists make and record observations (collect data) and use inductive reasoning to draw a general conclusion, which can be developed into a testable hypothesis. Deductive reasoning makes predictions that can be used to test hypotheses. Scientific hypotheses must be testable.
- Controlled experiments, such as the investigation of coat color in mouse populations, are designed to demonstrate the effect of one variable by testing control groups and experimental groups differing in only that one variable.
- A scientific theory is broad in scope, generates new hypotheses, and is supported by a large body of evidence.
- Observations and experiments must be repeatable, and hypotheses must be testable. Biologists approach questions at different levels; their approaches complement each other. Technology is a method or device that applies scientific knowledge for some specific purpose that affects society as well as for scientific research. Diversity among scientists promotes progress in science.
Chapter 2:The Chemical Context of Life
2.1 Matter consists of chemical elements in pure form and in combinations called compounds
- Elements cannot be broken down chemically to other substances. A compound contains two or more different elements in a fixed ratio. Oxygen, carbon, hydrogen, and nitrogen make up approximately 96% of living matter.
2.2 An element’s properties depend on the structure of its atoms
- An atom, the smallest unit of an element, has the following components:
- An electrically neutral atom has equal numbers of electrons and protons; the number of protons determines the atomic number. Isotopes of an element differ from each other in neutron number and therefore mass. Unstable isotopes give off particles and energy as radioactivity.
- In an atom, electrons occupy specific electron shells; the electrons in a shell have a characteristic energy level. Electron distribution in shells determines the chemical behavior of an atom. An atom that has an incomplete outer shell, the valence shell, is reactive.
2.3 The formation and function of molecules depend on chemical bonding between atoms
- Chemical bonds form when atoms interact and complete their valence shells. Covalent bonds form when pairs of electrons are shared. H2 has a single bond: H¬H. A double bond is the sharing of two pairs of electrons, as in O“O.
- Molecules consist of two or more covalently bonded atoms. The attraction of an atom for the electrons of a covalent bond is its electronegativity. Electrons of a polar covalent bond are pulled closer to the more electronegative atom, such as the oxygen in H2O.
- An ion forms when an atom or molecule gains or loses an electron and becomes charged. An ionic bond is an attraction between two oppositely charged ions, such as Na+ and Cl−.
- Weak bonds reinforce the shapes of large molecules and help molecules adhere to each other. A hydrogen bond is an attraction between a hydrogen atom carrying a partial positive charge (δ+) and an electronegative atom (δ−). Van der Waals interactions occur between transiently positive and negative regions of molecules.
- The molecular shape is usually the basis for the recognition of one biological molecule by another.
2.4 Chemical reactions make and break chemical bonds
- Chemical reactions change reactants into products while conserving matter. All chemical reactions are theoretically reversible.
- Chemical equilibrium is reached when the forward and reverse reaction rates are equal.
2.5 Hydrogen bonding gives water properties that help make life possible on Earth
- A hydrogen bond forms when the slightly negatively charged oxygen of one water molecule is attracted to the slightly positively charged hydrogen of a nearby water molecule. Hydrogen bonding between water molecules is the basis for water’s properties.
- Hydrogen bonding keeps water molecules close to each other, giving water cohesion. Hydrogen bonding is also responsible for water’s surface tension.
- Water has a high specific heat: Heat is absorbed when hydrogen bonds break and is released when hydrogen bonds form. This helps keep temperatures relatively steady, within limits that permit life. Evaporative cooling is based on water’s high heat of vaporization. The evaporative loss of the most energetic water molecules cools a surface.
- Ice floats because it is less dense than liquid water. This property allows life to exist under the frozen surfaces of lakes and seas.
- Water is an unusually versatile solvent because its polar molecules are attracted to ions and polar substances that can form hydrogen bonds. Hydrophilic substances have an affinity for water; hydrophobic substances do not. Molarity, the number of moles of solute per liter of solution, is used as a measure of solute concentration in solutions. A mole is a certain number of molecules of a substance. The mass of a mole of a substance in grams is the same as the molecular mass in daltons.
- A water molecule can transfer an H+ to another water molecule to form H3O+ (represented simply by H+) and OH−.
- The concentration of H+ is expressed as pH; pH = −log [H+]. A buffer consists of an acid-base pair that combines reversibly with hydrogen ions, allowing it to resist pH changes.
- The burning of fossil fuels increases the amount of CO2 in the atmosphere. Some CO2 dissolves in the oceans, causing ocean acidification, which has potentially grave consequences for coral reefs.
Chapter 3: Carbon and the Molecular Diversity of Life
3.1 Carbon atoms can form diverse molecules by bonding to four other atoms
- Carbon, with a valence of 4, can bond to various other atoms, including O, H, and N. Carbon can also bond to other carbon atoms, forming the carbon skeletons of organic compounds. These skeletons vary in length and shape. Hydrocarbons consist of carbon and hydrogen. Isomers have the same molecular formula but different structures and properties.
- Chemical groups attached to the carbon skeletons of organic molecules participate in chemical reactions (as functional groups) or contribute to function by affecting molecular shape.
- ATP (adenosine triphosphate) can react with water, releasing energy that can be used by the
3.2 Macromolecules are polymers, built from monomers
- Large carbohydrates (polysaccharides), proteins, and nucleic acids are polymers, which are chains of monomers. The components of lipids vary. Monomers form larger molecules by dehydration reactions, in which water molecules are released. Polymers can disassemble by the reverse process, hydrolysis. An immense variety of polymers can be built from a small set of monomers.
3.3 Carbohydrates serve as fuel and building material
3.4 Lipids are a diverse group of hydrophobic molecules
3.5 Proteins include a diversity of structures, resulting in a wide range of functions
3.6 Nucleic acids store, transmit, and help express hereditary information
3.7 Genomics and proteomics have transformed biological inquiry and applications
- Recent technological advances in DNA sequencing have given rise to genomics, an approach that analyzes large sets of genes or whole genomes, and proteomics, a similar approach for large sets of proteins. Bioinformatics is the use of computational tools and computer software to analyze these large data sets.
- Recent technological advances in DNA sequencing have given rise to genomics, an approach that analyzes large sets of genes or whole genomes, and proteomics, a similar approach for large sets of proteins. Bioinformatics is the use of computational tools and computer software to analyze these large data sets.