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Biology Answers

 This page was last updated on 15-Jun-02
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 1.  DNA  Back

 2.  Reproduction is the process by which parents transmit DNA instructions for duplicating their traits to offspring. Development is the transformation, guided by DNA, of a fertilized egg into a multi-celled adult with cells, tissues and organs specialized for certain tasks.  Development occurs in stages.  Back

 3.  Energy is the capacity to do work.  Metabolism is the capacity to (a) obtain and convert energy from a cell's surroundings; and (b) use the energy to maintain itself, grow and make more cells.  Back

 4.  Receptors are molecules and structures that detect stimuli.  A stimulus is a specific form of energy detected by receptors (i.e., sunlight, heat, etc.).  Homeostasis is the maintenance of an organism's internal operating conditions so they remain within tolerable limits.  Back

 5. In order, from smallest to largest...Subatomic Particle - an electron, proton or neutron (the 3 particles that compose atoms); Atom - the smallest unit of an element still retaining the properties of that element; Molecule - 2 or more atoms, of the same or differing elements, bonded together; Organelle - a membrane-bound sac or compartment, inside all cells except for bacteria, designated for a separate, specialized task; Cell - the smallest unit having the capacity to live and reproduce, independently or as part of a multi-celled organism; Tissue - an organized group of cells and surrounding substances functioning together in a specialized activity; Organ - a structural unit of tissues combined in specific amounts and patterns to perform a common task; Organ System - 2 or more organs interacting chemically, physically or both in ways that contribute to the survival of the whole organism; Multi-Celled Organism - an individual composed of specialized, interdependent cells, most often organized in tissues, organs and organ systems; Population - a group of individuals of the same kind (species) occupying a given area; Community - the populations of all species occupying a given area; Ecosystem - a community and its physical environment; Biosphere - all the regions of the Earth's waters, crust and atmosphere in which organisms can exist.  Back

 6.  Organisms connect with one another by a one-way flow of energy through them and a cycling of materials among them.  Their interconnectedness affects the structure, size and composition of populations, communities, ecosystems and the biosphere.  Energy is transferred from one organism to another; in time, all energy flows back to the environment.  Example of the one-way flow:  
sun ---> producers ---> consumers/decomposers ---> environment
Producers trap, convert and use or store energy from the sun.  Producers and the consumers/decomposers cycle nutrients between each other.  Back

 7.  Archaebacteria - A kingdom of single-celled, prokaryotic bacteria that are found in extreme environments.  Ex:  methanogens, halophiles, thermophiles
Eubacteria - A kingdom of all prokaryotic cells except archaebacteria; Eubacteria are much more successful and prevalent.  Ex:  ?
Protista - An eukaryotic kingdom.  Ex:  water & slime molds, protozoans, algae
Fungi - An eukaryotic kingdom; some are parasites, but most are decomposers.  
Ex:  mushrooms
Plantae - Eukaryotic, multi-celled producers; most all are photosynthetic.  
Ex:  sunflowers
Animalia - Eukaryotic, multi-celled consumers that ingest other organisms.
Ex:  lions & tigers & bears, oh my!  Back

 8.  Mutation - is a molecular change in the DNA.  Mutations are the original source of variations in heritable traits.  Evolution - is a genetically-based change in a line of descent over time.  Natural Selection - is a micro evolutionary process; the outcome of differences in survival and reproduction among individuals of a population that vary in details of heritable traits; typically, adaptive traits are preferred over time, leading to the increased fitness of a species.  This process helps explain evolution.  Back

 9.  A hypothesis is an educated guess about possible answers to questions, or solutions to problems.  It is used as a guideline to develop tests.  A theory is a tested and testable explanation about the cause(s) of a broad range of related phenomena.  It is open to revision and has not been disproved.  Back

 10.  An atom is the smallest particle that retains the properties of an element.  An atom has one or more protons (+) and an equal number of electrons (-).  Except for hydrogen, atoms also have one or more neutrons (no charge).  Atoms have no net charge.  Ex:  hydrogen, oxygen, carbon   Back

 11.  Protons - carry a positive electrical charge (p+).  Protons, along with neutrons, make up the atomic core region (the atomic nucleus).  Electrons carry a negative electrical charge (p-), and zip around the nucleus.  The number of electrons is always equal to the number of protons.  Neutrons carry no net charge.   Back

 12.  Atomic number refers to the number of proteins in an element's atom.  
Ex:  carbon's atomic number is 6 - it has 6 protons.  Mass number refers to the combined number of protons and neutrons in the atomic nucleus of an element's atom.
Ex:  carbon's mass number is 12 - it has 6 protons and 6 neutrons.   Back

 13.  Of an element, and isotope is an atom with more or fewer neutrons than the stoms having the most common number (all atoms of an element have the same number of protons, but not necessarily the same number of neutrons.).
Ex:  carbon has 3 isotopes -
12C (6 protons, 6 neutrons)
13C (6 protons, 7 neutrons)
14C (6 protons, 8 neutrons)   Back

 14.  A chemical bond is a union between the electron structures of atoms.  Atoms with vacancies in their outermost shell will give up, gain or share electrons with other atoms under suitable conditions.  Atoms with no vacancies are "inert" - they show very little tendency to interact with other atoms or enter into chemical reactions.  Atoms with vacancies tend to fill the vacancies by forming bonds with other atoms.   Back

 15.  A molecule is two or more atoms that have bonded together.  Ex:  O2
A compound is a molecule consisting of 2 or more different elements in proportions that never vary.  Ex:  H2O   Back

 16.  These are the 3 important bonds in biological molecules.  Only living organisms put together and use these molecules.  Ionic bonding happens when 2 ions of opposite charge attract each other and stay together.  An ion is an atom that has gained or lost an electron, causing it to have a net positive or negative charge.  Covalent bonding happens when atoms share a pair of electrons.  Covalent bonds are non-polar or polar.  If the atoms share electrons equally, the bond is non-polar.  If the atoms sharing is NOT equal, the bond is polar - slightly positive at one end and slightly negative at the other.  Hydrogen bonding happens when a covalently bound atom showing a slight negative charge weakly interacts with a covalently bound hydrogen atom (which has a slight positive charge).   Back

 17.  A water molecule has no net charge, but it shows polarity (there is a difference in charge between the two ends of the molecule).  Because of this, one water molecule attracts and hydrogen bonds with another.  Cells consist primarily of water and release a great deal of heat energy during metabolism.  Hydrogen bonds in liquid water keep cells from cooking.  Temperature is a measure of the molecular motion of a given substance.  Increased heat absorption = increased vibratory rate.  In water, added energy disrupts hydrogen bonding between molecules, so there is NOT an increase in the motion of molecules.  Hydrogen bonds can buffer large swings in temperature, helping stabilize the temperature of multi-celled organisms and of aquatic habitats.  Additionally, hydrogen bonds in water are constantly breaking and reforming.  Increased energy + increased motion = evaporation, which also stabilizes (evaporation is conversion to a gaseous state).  Cohesion means something has the capacity to resist rupturing when placed under tension.  Hydrogen bonding results in high surface tension (think bug walking on water).  Water has solvent properties - ions and polar molecules easily dissolve into it.   Back

 18.  The ionization of water is the basis of the pH scale.  Ionization occurs when some water molecules break apart into hydrogen ions and hydroxide ions (H= and OH-, respectively).  The pH scale is used to measure the H+ concentration in fluids.  On a scale of 0 to 14, 0=very high H+ and 14=very low H+.  The greater the H+ concentration, the lower the pH number.  Acids donate protons (H+) to other solutes or to water molecules.  Bases accept H+ when dissolved in water (after which OH- is formed).  Acidic solutions release more H+ than OH- (i.e. lemon juice).  Acidic solutions have a pH of 7 or less on the scale.  Alkaline solutions (Base) release more OH- than H+ (i.e. milk of magnesia).  Alkaline solutions have a pH of 7 or more o the scale.  7 is roughly equivalent to spring water.  Human cells are a 7.  NOTE:  a change of 1 on the scale = a tenfold change in the H+ concentration.   Back

 19.  Organic compounds are molecules of one or more elements covalently bonded to carbon atoms.  One element is always hydrogen.  Carbon bonds covalently.  Each carbon atom can share electrons with up to 4 other atoms.  These stable bonds link carbon atoms together in chains, to which hydrogen, oxygen, nitrogen, etc. attach.  This carbon chain is the backbone from which other atoms can project to build 3-dimensional shapes.   Back

 20.  Simple Sugars - monosaccharides (one sugar monomer) are the simplest carbohydrates.  Ex:  glucose, ribose, deoxyribose  Short-Chain Carbohydrates - oligosaccharides (a few sugar monomers) are a short chain of 2 or more sugar monomers bonded covalently.  Ex:  lactose, sucrose, maltose  Complex Carbohydrates - polysaccharides (many sugar monomers) are straight or brached chains of many sugar monomers of the same or different type.  Ex:  cellulose, starch   Back

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