Biology 1 Exam 1: Chapter 1-2

Describe each of the five characteristics of life, and list several nonliving things that possess at least two of these characteristics.

(1) Life is organized, following a hierarchical pattern from atoms to the biosphere. (2) Organisms acquire and use energy to build cells, repair damage, and reproduce. (3) Organisms maintain homeostasis, so the interiors of cells and living organisms remain within a constant range even if environmental conditions change. (4) Organisms reproduce, meaning they produce offspring that grow and develop into adults that can also reproduce. (5) Life evolves, which means that the genetic makeup of every population changes from generation to generation. The following are examples of nonliving things that possess at least two of life's characteristics: a house is structurally organized and maintains a constant range of temperature; automobiles are organized and require energy; crystal formations are organized and grow; viruses are organized and evolve. (Other answers are also possible.)

A neutral hydrogen atom with a mass number of 1 has ____blank neutrons, ____blank protons, and ____blank electrons. 0; 1; 1 1; 1; 1 0; 1; 0 1; 0; 0

0; 1; 1

How many neutrons does a carbon-14 atom have in its nucleus? 6 7 8 14

8

Why is a cell, and not an atom or a molecule, considered the basic unit of life?

A cell is the basic unit of life because it is the first level of organization that displays all of the characteristics of life. Atoms and molecules do not have all five of life's properties. Furthermore, both living and nonliving things are composed of atoms and molecules, but only living things are composed of cells.

What are the elements of a controlled experiment?

A controlled experiment consists of a control group and one or more experimental groups. The simplest experiments have only one difference between the groups; this difference is the independent variable. The control group is one that is considered "normal" for the variable being tested. It could be a healthy population compared to a diseased population or it could be a population receiving no treatment compared to a population receiving treatment. The dependent variable is the response that the investigator measures. Standardized variables are factors that are the same for all subjects, including the treatment and control groups.

How does electronegativity explain whether a covalent bond is polar or nonpolar?

A polar covalent bond forms between two atoms of different electronegativities (e.g., O and H) because one atom attracts the shared electrons more strongly than the other. In contrast, a nonpolar covalent bond forms between two atoms of nearly equal electronegativities (e.g., C and H) because the electrons are shared equally between the bonded atoms.

Complete and explain the following analogy: a protein is to a knitted sweater as a denatured protein is to a ____.

A protein is to a knitted sweater as a denatured protein is to a tangle of unraveled yarn. A protein is a highly structured chain made of amino acids, just as a sweater is a structured garment made of yarn. When unraveled, a sweater is just a mass of yarn; when denatured, a protein is just a mass of amino acids with no function.

Define solute, solvent, and solution.

A solute is a substance that is dissolved in a solvent. Solutions consist of one or more solutes dissolved in a liquid solvent.

Give an example from everyday life of each of the following properties of water: cohesion, adhesion, ability to dissolve solutes, resistance to temperature change.

A water droplet combining with another droplet on a windshield shows cohesion. A splash of water sticks to the wall with adhesion. Mixing instant coffee into hot water illustrates water's ability to dissolve solutes. Coastal climates are relatively mild because the vast ocean is extremely resistant to temperature change.

Name three examples of emergent properties.

Answers will vary but could include: bonding of atoms into chemically unique molecules; a protein's function emerging when amino acids are linked together; surface tension arising when many water molecules interact; or protein-encoding sequences in DNA.

Imagine two related species of unicellular protists living together in a pond. Write the organizational hierarchy of this ecosystem, starting with "atom" and ending with "ecosystem." Give an example of a structure at each level.

Atom: carbon Molecule: DNA Organelle: one cell's nucleus Cell: single protist Organism: single protist Population: all individuals of one species Community: all individuals of both species (and of other species living in the pond) Ecosystem: all individuals of all species in the pond, plus the surrounding nonliving environment (e.g., water and nutrients)

Besides water, which other molecules are essential to life?

Besides water, life requires organic molecules such as carbohydrates (energy source), proteins (many essential functions), nucleic acids (store and express genetic information), and lipids (energy storage and membrane structure). Oxygen is essential to many but not all organisms.

What type of chemical bond forms during a dehydration synthesis reaction? Covalent Hydrogen Ionic Polymer

Covalent

Other than the brownie example given in the text, name an example of emergent properties from everyday life.

Examples could include anything that incorporates the interactions among multiple simpler parts, such as bricks and mortar coming together to make a house, or a large tub of water creating a swimming pool.

Explain why regulating body temperature is essential to survival.

Excessive heat causes proteins to become denatured, which ruins their shapes. If a protein's shape is destroyed, it can no longer function. Since proteins do nearly all the work in living cells, excessive heat can be deadly.

List each step of the scientific method and explain why it is important.

First, a scientist must observe a phenomenon and question how it works. Without this curiosity, much of what we know about the natural world would never have been discovered. Next, a scientist must use previous knowledge to form a hypothesis, which is a tentative explanation. This is important because it is a testable statement that should help answer the question. The prediction that follows from the hypothesis specifies which results will support or refute the hypothesis. The scientist can then collect data by further observation or experimentation. This step is crucial because it provides the information required to test the hypothesis. The resulting data, when integrated with prior knowledge, leads the scientist to conclude whether or not the hypothesis should be rejected. Finally, peer review ensures that other knowledgeable scientists have evaluated the data before publication in a scientific journal.

Which of the following statements is false? Emergent properties are functions that arise from the interactions between an organism's parts. Two of the three domains contain prokaryotic organisms. When medical researchers test the effectiveness of a new drug, they typically compare the new drug to a placebo. For a scientific study to be considered valid, the researchers must conduct experiments.

For a scientific study to be considered valid, the researchers must conduct experiments.

What is the correct way to write the scientific name for humans? Homo sapiens Homo sapiens Homo Sapiens homo sapiens

Homo sapiens

A scientist has just observed a new phenomenon and wonders how it happens. What is the next step in his or her discovery of the answer? Observe Hypothesize Experiment Peer review

Hypothesize

Describe the main differences between asexual and sexual reproduction. Should changing or unchanging conditions favor each type of reproduction?

In asexual reproduction, all the genetic information comes from one parent, so organisms are almost identical. In sexual reproduction, the genetic information comes from two parents, generating variation. Asexual reproduction produces the least genetic variation, so it should be most adaptive in habitats that are stable. Sexual reproduction allows populations to adapt to changing environmental conditions.

Explain why populations of organisms are typically well adapted to their environment.

In previous generations, members of the population that were best adapted to the environment were most likely to survive and reproduce. Adaptive traits therefore typically become more common in populations over time.

The vitamin biotin contains 10 atoms of carbon, 16 of hydrogen, 3 of oxygen, 2 of nitrogen, and 1 of sulfur. What is its molecular formula?

Its formula is C10H16O3N2S.

Think of an analogy that will help you remember the differences between populations, communities, and ecosystems.

Many analogies are possible. For example, a puzzle is analogous to a population; the collection of the toys in the child's room is analogous to a community; and the child's room is analogous to an ecosystem. All of the pieces of the single puzzle represent individuals of the same species, which make up a population. A puzzle is just one of many types of toys in a child's room, just as many populations make up a community. All of the objects in the child's room, including the toys, furniture, carpet, and air, represent the living and nonliving components of an ecosystem.

Are molecules alive? Can life exist without molecules? Why?

Molecules are not alive. Life cannot exist without molecules, which combine to make larger structures, such as cells, that carry out the functions of life.

What is the relationship between natural selection and evolution?

Natural selection is one of several mechanisms of evolution. For example, certain members of a population might be more likely to reproduce than others because they are stronger, better able to survive environmental stress, more efficient at finding resources, or better at avoiding predation. Because they have greater reproductive success, their adaptations become more common in the next generation of offspring.

Distinguish between nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

Nonpolar covalent bonds are bonds in which both atoms exert approximately equal pull on the shared electrons. In a polar covalent bond, one nucleus exerts a stronger pull on the shared electrons than does the other nucleus. An ionic bond results from the electrical attraction between two ions with opposite charges.

Can nonpolar molecules such as CH4 participate in hydrogen bonds? Why or why not?

Nonpolar molecules cannot form hydrogen bonds because the atoms do not have partial charges.

___ are monomers that form polymers called ___ Nucleotides; nucleic acids Amino acids; nucleic acids Monoglycerides; triglycerides Carbohydrates; monosaccharides

Nucleotides; nucleic acids

Design an experiment to test the following commonly held belief: "Eating chocolate causes zits." Include sample size, independent variable, dependent variable, the most important variables to standardize, and an experimental control.

Overall, the experiment would require dividing a population into two groups, only one of which receives chocolate. Before, during, and after the experiment, the researchers would measure the density of pimples in each group. The independent variable in this experiment is presence or absence of chocolate, and the dependent variable is the density of zits. The experiment should include a large sample size (hundreds of people at minimum). Some variables to standardize include other components of the diet, the age group of the subjects, and the subjects' history of skin problems. The control group would consist of individuals not consuming chocolate.

Consider the following atomic numbers: oxygen (O) = 8; fluorine (F) = 9; neon (Ne) = 10; magnesium (Mg) = 12. Draw the electron shells of each atom, and then predict how many bonds each atom should form

Oxygen: 2 bonds. Fluorine: 1 bond. Neon: 0 bonds (its outermost shell is full). Magnesium: 2 bonds.

Draw and explain the relationships among primary producers, consumers, and decomposers.

Primary producers convert light energy and nutrients into a form that consumers can also use. When organisms die, the decomposers release the nutrients back into the soil to be taken up by the plants.

Give two examples of questions that cannot be answered using the scientific method. Explain your reason for choosing each example.

Science cannot answer questions regarding moral, ethical, aesthetic, and religious issues. Two examples of questions that science cannot answer are "Is a rattlesnake or a peacock more beautiful?" and "Is it wrong to use animals in cosmetics research?" The former is a question of aesthetics and taste, and the latter is a question of ethics.

How is an amino acid's R group analogous to a nucleotide's nitrogenous base?

The R group is the variable portion of an amino acid, just as the nitrogenous base is the variable portion of a nucleotide.

If you dissect and label the parts of an earthworm, are you "doing science"? Why or why not? Give an example of a testable hypothesis that could result from dissecting organisms.

The act of dissecting and identifying the parts of an earthworm is observational, and it provides investigators with the anatomical knowledge needed to ask questions and develop hypotheses. A testable hypothesis resulting from such an activity could address the relationship between the size of an earthworm and the number of segments.

Describe how the number of protons, neutrons, and electrons in an atom affects its atomic number, mass number, and charge.

The atomic number equals the number of protons. The mass number is the number of protons and neutrons added together. If an atom has more electrons than protons, it has a negative charge. If it has more protons than electrons, it has a positive charge.

You eat a sandwich made of starchy bread, ham, and cheese. What types of chemicals are in it?

The bread is mostly starch, although it may also contain some fiber (cellulose) if it is made with whole wheat; both starch and cellulose are polysaccharides. The ham and cheese are composed mainly of protein and fat.

How do hydrogen ions relate to the pH scale?

The concentration of hydrogen ions determines a solution's pH. The higher the concentration, the lower the pH.

Draw from memory a diagram showing the interactions among a few water molecules.

The diagram should resemble components of figure 2.10. Hydrogen atoms should have partial positive charges that are attracted to the partial negative charges on the oxygen atoms of adjacent water molecules.

A man on a very low-fat diet proclaims to his friend, "I'm going to get my cholesterol down to zero!" Why is achieving this goal impossible (and undesirable)?

The liver produces cholesterol from other raw materials, so the man's body would make cholesterol even on an extremely low-fat diet. The goal is undesirable because cholesterol is an essential component of animal cell membranes, and it is a precursor for other essential molecules such as sex hormones.

How are the members of the three domains similar? How are they different?

The members of all three domains are made of at least one cell and contain DNA. Domains Bacteria and Archaea are superficially similar to one another; both consist of prokaryotes and are typically unicellular. However, DNA sequences differ between bacteria and archaea. Domain Eukarya consists of organisms with eukaryotic cells, which have a nucleus.

If oxygen strongly attracts electrons, why is a covalent bond between two oxygen atoms considered nonpolar?

The nucleus of each oxygen atom exerts an equal pull on the shared electrons, so the bond is nonpolar.

Can a theory be proven wrong? No, theories are exactly the same as facts. No, because there is no good way to test a theory. Yes, a new observation or interpretation of data could disprove a theory. Yes, theories are exactly the same as hypotheses.

Yes, a new observation or interpretation of data could disprove a theory.

Which of the following is smaller than an organelle? A. An organ B. A molecule C. A cell D. A tissue

a molecule

A covalent bond forms when electrons are present in a valence shell. a valence electron is removed from one atom and added to another. a pair of valence electrons is shared between two atoms. one atom attracts electrons more strongly than another atom.

a pair of valence electrons is shared between two atoms.

An ionic bond forms when an electrical attraction occurs between two atoms of different charge. a nonpolar attraction is formed between two atoms. a valence electron is shared between two atoms. two atoms have similar attraction for electrons.

an electrical attraction occurs between two atoms of different charge.

Because plants extract nutrients from soil and use sunlight as an energy source, they are considered to be autotrophs. consumers. heterotrophs. decomposers.

autotrophs

A sugar is an example of a ____, whereas DNA is a ____ protein; nucleic acid lipid; protein nucleic acid; lipid carbohydrate; nucleic acid

carbohydrate; nucleic acid

A hydrophilic substance is one that can form covalent bonds with hydrogen. dissolve in water. buffer a solution. mix with nonpolar solvents

dissolve in water.

Water dissolves salts because it is hydrophobic, and salts are also hydrophobic. forms covalent bonds with the atoms of the salt crystal. has partial positive and negative charges. evaporates quickly at room temperature.

has partial positive and negative charges.

The concentration of salts in blood remains relatively steady, regardless of a person's diet. This situation best illustrates homeostasis life's organizational hierarchy autotrophy evolution

homeostasis

In an experiment to test the effect of temperature on the rate of bacterial reproduction, temperature would be the standardized variable. independent variable. dependent variable. control variable.

independent variable.

A hydrogen bond is distinct from ionic and covalent bonds in that it is a weak attraction between two molecules. forms only between two hydrogen atoms. is considerably stronger than the other two types of bonds. occurs more commonly in lipids than in other types of molecules

is a weak attraction between two molecules.

All of the following are characteristics of life EXCEPT evolution reproduction homeostasis multicellularity

multiceullularity

Evolution through natural selection will occur most rapidly for populations of plants that are already well adapted to the environment. live in an unchanging environment. are in the same genus. reproduce sexually and live in an unstable environment.

reproduce sexually and live in an unstable environment.