Chapter 1 2 A localized group of organisms that belong to the same species is called a population Organisms interact with their environments exchanging matter and energy For example plant the potential energy of chemical bonds The main source of energy for producers in an ecosystem is light energy Once labor begins in childbirth contractions increase in intensity and frequency until delivery The increasing labor contractions of childbirth are an example of which type of regulation positive feedback When the body s blood glucose level rises the pancreas secretes insulin and as a result the blood glucose level declines When the blood glucose level is low the pancreas secretes glucagon and as a result the blood glucose level rises Such regulation of the blood glucose level is the result of negative feedback Which branch of biology is concerned with the naming and classifying of organisms taxonomy Prokaryotic and eukaryotic cells generally have which of the following features in common ribosomes Prokaryotes are classified as belonging to which two domains bacteria and archaea Which of the following is a correct sequence of levels in life s hierarchy proceeding downward from an individual animal nervous system brain nervous tissue nerve cell Which of the following best demonstrates the unity among all organisms the structure and function of DNA An organism is composed of matter A blank is a substance that cannot be broken down into other substances by chemical reactions element A compound is a substance that consists of two or more elements true About what percent of the 92 naturally occurring elements are essential elements that are necessary for living things 20 25 Humans have 25 essential elements true What elements make up 96 of living matter Oxygen Carbon Hydrogen and Nitrogen Most of the remaining 4 of an organism s weight consists of calcium phosphorus potassium and sulfur Trace elements are required in minute qualities Iodine deficiency results in goiter swelling of the thyroid gland An atom is the smallest unit of matter that still retains the properties of an element Two subatomic particles neutrons and protons are packed together to form a dense core the atomic nucleus at the center of an atom Electrons can be visualized as forming a cloud of negative charge around the nucleus The mass number is the sum of the number of protons and the number of neutrons in the nucleus of an atom Two atoms of the same element that differ in the number of neutrons are called isotopes Most isotopes are stable they do not tend to lose particles Some isotopes are unstable radioactive because they decay spontaneously emitting particles and energy Energy is the ability to cause change by doing work Potential energy is the energy that matter stores because of its structure or location true The different states of potential energy of the electrons of an atom are called electron shells o The first shell closest to the nucleus has the lowest potential energy o Electrons in outer shells have higher potential energy About 25 of the 92 natural elements are known to be essential to life Which four of these 25 elements make up approximately 96 of living matter carbon hydrogen nitrogen oxygen Trace elements are those required by an organism in only minute quantities Which of the following is a trace element that is required by humans and other vertebrates but not by other organisms such as bacteria or plants iodine Which of the following statements is false Virtually all organisms require the same elements in the same quantities What factors are most important in determining which elements are most common in living matter both the relative abundances of the elements and the emergent properties of the compounds made from these elements Why is each element unique and different from other elements in chemical properties each element has a unique number of protons in its nucleus Knowing just the atomic mass of an element allows inferences about which of the following the number of protons plus neutrons in the element In what way are elements in the same column of the periodic table the same they have the same number of electrons in their valence shell The nucleus of a nitrogen atom contains 7 neutrons and 7 protons Which of the following is a correct statement concerning nitrogen the nitrogen atom has a mass number of 14 and an atomic mass of One difference between carbon 12 is that carbon 14 has two more neutrons than carbon 12 Electrons exist only at fixed levels of potential energy However if an atom absorbs sufficient energy a possible result is that an electron may move to an electron shell farther away from the nucleus From its atomic number of 15 it is possible to predict that the phosphorus atom has 15 protons and 15 electrons A covalent chemical bond is one in which outer shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms When two atoms are equally electronegative they will interact to form nonpolar What results from an unequal sharing of electrons between atoms a polar covalent covalent bonds bond A covalent bond is likely to be polar when one of the atoms sharing electrons is much more electronegative than the other atom Which of the following explains most specifically the attraction of water molecules to one another hydrogen bond Van der Waals interactions result when electrons are not symmetrically distributed in a molecule What bonding or interaction is most likely to occur among a broad array of molecules of various types polar nonpolar hydrophilic hydrophobic van der Waals interactions Which of the following is not considered to be a weak molecular interaction a covalent bond Which of the following correctly describes chemical equilibrium Forward and reverse reactions continue with no effect on the concentrations of the reactants and products Which of the following correctly describes any reaction that has reached chemical equilibrium The rate of the forward reaction is equal to the rate of the reverse reaction Refer to the figure above first three rows of the periodic table If life arose on a planet where carbon is absent which element might fill the role of carbon silicon Which drawing in the figure above depicts the electron configuration of an element with chemical properties most similar to Helium 2He E Based on electron configuration which of these elements in the figure above would exhibit a chemical behavior most like that of
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