____________Chapter 1Introduction____________

Chapter OutlinesBiologyBiological organizationLiving things are characterized by unity and diversityExobiologyBiology is the science of the 21st centuryThe scientific processInductive and deductive reasoningReview questions

Biology

Biology is the study of life on Earth. Life is defined by enumerating the attributes of living things. These include complexity and cellular composition, acquisition and use of energy and raw materials from the environment, growth and development, locomotion, homeostasis, response to internal and external stimuli, reproduction, adaptation and evolution, and death.

The living things are divided into two groups: the prokaryotes and the eukaryotes. The prokaryotes have no nuclei in their cells, and they include the different types of bacteria. The eukaryotes have nuclei in their cells, and they include the protistans (algae and protozoans), the fungi, the plants, and the animals. The protistans are unicellular eukaryotes, and the fungi, plants and animals are multicellular eukaryotes.

Biological Organization

The levels of biological organization are hierarchical – that is, each level builds on the level below it. They include chemical, biological and ecological organizations in the following hierarchy: subatomic particle (protons, electrons, and neutrons), atom, molecule, organelle, cell, tissue, organ, organ system, organism, population, community, ecosystem, and biosphere. The lowest level that’s considered living is the cell.

Living Things are Characterized by Unity and Diversity

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Living things are characterized by unity and diversity. All living things are assembled from the same kinds of atoms and molecules according to the same laws of chemistry. All living things use energy and store it in the ATP molecule. All living things are composed of cells and use the same genetic code. There is also diversity among living things. Many millions of species exist; many millions more lived in the past and became extinct. The diversity among organisms arises through mutations, changes in the structure of the DNA that may lead to variations in heritable traits.

Exobiology

The science of the study of the possible existence of life on planets other than Earth is called exobiology. The term was first coined by Nobel Prize winning scientist Joshua Lederberg during the early 1960s. Exobiology refers to the search for life elsewhere, Mars, the satellites of Jupiter and in other solar systems.

Biology is the Science of the 21st Century

You are very fortunate to have enrolled in a biology course at this time because we are living in the golden age of biology. Biology is considered the science of the 21 st century because it holds the key to solving some of the most challenging problems facing our times. These problems include feeding a growing population, generating energy, providing health care, and coping with climate changes. Biologists have just completed the Human Genome Project and have gained a growing understanding of how genes and the proteins they produce give rise to biological form and function.

Modern biology is important and inspiring, with exciting breakthroughs changing our very culture. Genetics and cell biology are revolutionizing medicine and agriculture. Molecular biology is providing new tools for anthropology, helping us trace the origins and dispersal of our early ancestors. Neuroscience and evolutionary biology are reshaping psychology and sociology. Ecology is helping us evaluate environmental issues such as the causes and consequences of global warming. Biology is even entering the legal system, as terms such as DNA fingerprinting work their way into our legal system. Biological disciplines are creating new jobs and biology is a magnet for ever increasing research funds.

The Scientific Process

When scientists study a natural phenomenon, they follow the scientific process. The levels of the scientific process include observation, hypothesis, experiment, prediction,

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conclusion, theory, and law (or principle). A hypothesis is an educated guess based on observations and fits the known facts. The scientific process involves the rejection of hypotheses that are inconsistent with experimental results. Hypotheses that are consistent with experimental data are conditionally accepted. A hypothesis that is supported by a great deal of evidence and nobody is able to refute it becomes a theory. Examples of theories include the theory of evolution by natural selection, the theory of relativity, and the theory of electromagnetism. If a theory is universally accepted for a long period of time, and nobody is able to refute it, it becomes a law or principle. Examples of laws include the laws of gravity, the laws of genetics, and the laws of thermodynamics.

Inductive and Deductive Reasoning

When scientists formulate a hypothesis, they follow one of two types of reasoning: induction or deduction. Induction or inductive reasoning is the method of formulating a general principle by examining specific cases, i.e. from specific to general. If you release an apple from your hand (specific case), the apple falls to the ground. Consequently, Isaac Newton inferred that all objects fall toward the center of gravity (general principle). This is inductive reasoning. Deduction or deductive reasoning is the use of a general idea to come up with a specific conclusion, i.e. from general to specific. All living things are composed of cells (general principle); therefore, dinosaurs were composed of cells (specific case). This is deductive reasoning.

Classification of Living Things

Taxonomy is the branch of biology concerned with naming and classifying the diverse forms of life on Earth. The taxonomic categories or taxa used by taxonomists include domain, kingdom, phylum, class, order, family, genus and species. Taxonomists classify living things into the three domains Archaea, Bacteria, and Eukarya based on certain criteria such as rRNA sequences, presence or absence of a cell nucleus, membrane lipids, cell wall composition, and multicellularity. The six kingdoms of life are Archaebacteria, Bacteria, Protista, Plantae, Fungi, and Animalia. Although both protistans and bacteria are unicellular, they are classified in different domains because Protistans have eukaryotic cells and bacteria have prokaryotic cells. Each kingdom is divided into a number of phyla. The correct taxonomic scheme to classify an organism is: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and species. The father of taxonomy is Carl (Carolus) Linnaeus (1707-1787). Review Questions

Multiple-choice Questions: Select the most appropriate answer or statement.

1. Biology is the scientific study of all forms of life on Earth. Living things are characterized by acquisition and use of energy and raw materials from the environment, cellular composition and complexity, growth and development, homeostasis or maintenance of a stable internal

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environment, response to internal and external stimuli, reproduction and inheritance, locomotion, adaptation, evolution, and death. Biology is defined as the scientific study of A. All forms of life on the UniverseB. All forms of life on EarthC. Human life on EarthD. Animals and plantsE. Planet Earth

Answer: B

2. Homeostasis (a Greek word meaning “same state”) is the ability of the body of an organism to maintain relatively stable internal conditions, different from those in the environment. It usually involves some form of feedback self-regulation. Homeostasis is one of the characteristic properties of life. All the organ systems of the body cooperate to maintain homeostasis. Examples of homeostasis include body temperature, heartbeat, respiration rate, blood pH, blood pressure, and blood glucose levels. Which of the following statements about homeostasis is correct?

A. Homeostasis is the maintenance of stable internal conditionsB. The body organ systems cooperate to maintain homeostasisC. Homeostasis is one of the characteristic properties of lifeD. Homeostasis usually involves feedback self-regulationE. All of these are correct

Answer: E

3. Biological sciences play a critical role in society, medicine, agriculture, the environment, and our lives. Biology is considered the science of the 21st century because

A. Biology-based technologies will dramatically affect peoples’ lives for the next 100 yearsB. Many current issues in biotechnology, such as the human genome project, recombinant

DNA technology, stem cell research and human cloning are grounded in a good understanding of biology

C. Biological sciences are helping us evaluate environmental issues, such as the causes and consequences of global warming

D. Many careers in biology are becoming of great demandE. All of these are correct Answer: E

4. Biology is the study of life on Earth. To define life, we list the characteristic attributes of living things. All living things are characterized by cellular composition, complexity, ability to obtain and use energy, maintenance of a stable internal environment, response to internal and external stimuli, reproduction, locomotion, sharing a common evolutionary history, adaptation and change with time, and death. Which of the following is a characteristic property of life on Earth?

A. Maintenance of a stable internal environmentB. Acquisition and use of energy

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C. Cellular compositionD. Response to stimuliE. All of these

Answer: E

5. Organisms develop, grow and change with time. Some of these changes result in increased survival and reproduction. An organism changes as a result of mutations that may alter its characteristics. In addition, a genome may acquire new genes by horizontal gene transfer. The change of populations over the course of time is called

A. GeneticsB. EvolutionC. GenomicsD. ProteomicsE. Development

Answer: B

6. Taxonomists classify living things into the three domains Archaea, Bacteria, and Eukarya based on certain criteria such as rRNA sequences, presence or absence of a cell nucleus, membrane lipids, cell wall composition, and multicellularity. Although both protistans and bacteria are unicellular, they are classified in different domains because Protistans have eukaryotic cells and bacteria have prokaryotic cells

A. Protistans have cellular composition and bacteria lack cellular compositionB. Protistans have eukaryotic cells and bacteria have prokaryotic cellsC. Protistans are autotrophic and bacteria are heterotrophicD. Both A and B are correctE. A, B, and C are correct

Answer: B

7. Taxonomy is the branch of biology concerned with naming and classifying the diverse forms of life on Earth. The taxonomic categories or taxa used by taxonomists include domain, kingdom, phylum, class, order, family, genus and species. Which of the following statements depicts the correct taxonomic scheme to classify the species Ursus americanus, the American black bear?

A. Kingdom – domain – phylum – class – order – family – genus – speciesB. Domain – kingdom – phylum – class – order – family – genus – speciesC. Domain – kingdom – class – phylum – order – family – genus – speciesD. Domain – kingdom – phylum – order – class – family – genus – speciesE. Domain – kingdom – phylum – class – family – order – genus – species

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Answer: B

8. Biology is the study of life on Earth. Living things include bacteria, protists (algae and protozoans), plants, fungi and animals. These living things are divided into prokaryotes (lack cell nucleus) and eukaryotes (have true cell nucleus). Only the bacteria are prokaryotes, and the rest of the living things are eukaryotes. There are two types of bacteria: the archaebacteria (ancient bacteria) and the eubacteria (true bacteria). Which of the following living things are considered eukaryotes?

A. Protozoans, plants, algae, archaebacteria and animalsB. Algae, protozoans, plants, animals, and bacteriaC. Algae, protozoans, plants, fungi and animalsD. Both A and B are correctE. A, B, and C are correct

Answer: C

9. Many scientists are actively searching for the possible existence of life on planets other than Earth. This new field of science is called

A. CytologyB. AnatomyC. PhysiologyD. ExobiologyE. Extraterrestrial biology

Answer: D

10. The term exobiology was coined by Nobel Prize winning scientist Joshua Lederberg during the early 1960s. It refers to the search for life elsewhere, Mars, the satellites of Jupiter and in other solar systems. It is also used to describe studies of the origin of life on Earth, that is, the study of pre-biotic Earth and what chemical reactions might have taken place as the setting for life’s origin. Which of the following is a correct definition of exobiology?

A. The search for the possible existence of life on planets other than EarthB. The study of pre-biotic Earth and life’s originC. The study of the cosmos D. Only A and BE. A, B, and C

Answer: D

11. Life is characterized by both unity and diversity. Descent from a common ancestor explains the unity of life. All living things are composed of cells, their genes are composed of DNA, have the same genetic code, and carry the same metabolic reactions to acquire energy and maintain their organization. Adaptations to different ways of life account for the great diversity of life forms. Many millions of species exist; many millions more lived in the past and became extinct; and many thousands are becoming extinct every year. The number of identified and named species of living things is approximately 1.8 million. Which of the following statements explains the unity of life?

A. All living things are composed of cells6

B. All living things have genes composed of DNA and the same genetic codeC. All living things carry the same metabolic reactions to acquire energy and

materials, and to maintain their organizationD. Only A and B are correctE. A, B, and C are correct

Answer: E

12. Life is characterized by both unity and diversity. Which of the following factors contributes to the great diversity of life on Earth?

A. Mutations, changes in DNA that may lead to variations in heritable traitsB. Adaptation to varying environments and evolution by natural selectionC. Development of the eukaryotic cell D. Development of multicellularityE. all of the above

Answer: E

13. Biologists explore biological organization from the microscopic to the global scale. This includes the study of cells, tissues, organs, organ systems, and organisms. Which of the following is the lowest level of biological organization that can perform all the activities required for life?

A. Organ system, for example the respiratory systemB. Organelle, for example a mitochondrionC. Tissue, for example nervous tissueD. Organism, for example a dogE. Cell, for example a skin cell

Answer: E

14. The study of life extends from the microscopic scale of the molecules and cells that make up organisms to the global scale of the entire living planet. This enormous range can be divided into chemical, biological and ecological organizations. Which of the following statements depicts a correct sequence of the hierarchy of biological organization?

A. Cell – tissue – organ system – organ – organism – populationB. Cell – tissue – organ – organ system – organism – populationC. Cell – organ – tissue – organ system – organism – populationD. Cell – tissue – organ – organ system – population – organismE. Tissue – cell – organ – organ system – organism – population

Answer: B

15. All the different people in your college campus make up a(an)

A. Experimental groupB. Taxonomic domainC. CommunityD. Population E. Ecosystem

Answer: D7

16. If CVCC is a cell, Phenix City is a tissue, Russell County is an organ, and the State of Alabama is an organism system; then the United States of America is a/an

A. PopulationB. CommunityC. OrganismD. EcosystemE. Biosphere

Answer: C

17. An ecosystem refers to all the organisms in a given area as well as the physical environment with which they interact. The dynamics of an ecosystem include the flow of energy from sunlight to producers and then to consumers, and the recycling of chemical nutrients such as minerals. All the ecosystems on planet Earth constitute

A. Life on landB. The UniverseC. The biosphereD. Life in the oceansE. Both A and B are correct

Answer: C

18. In life’s structural hierarchy, the cell has a special place as the lowest level of organization that can perform all activities required for life. Explain why, at the cellular level, plants have more in common with animals than with bacteria.

A. Both plants and animals consist of eukaryotic cells, while the cells of bacteria are prokaryotic

B. Both plant and animal cells have numerous membrane-bound organelles, while bacterial cells lack most organelles

C. Both plants and animals are multicellular, while bacteria are unicellularD. Both A and B are correctE. A, B, and C are correct

Answer: E

19. In order to maintain their organization and carry out metabolic activities, living things need a constant supply of energy. The sun is the ultimate source of energy for life on Earth. Plants capture light energy by the process of photosynthesis and convert it into ATP (adenosine triphosphate) to produce food. When organisms consume food, they extract the energy stored in food, by the process of cell respiration, and use it to grow and do work. Organisms store excess energy in ATP and break down ATP to obtain energy. Thus, ATP is referred to as the “energy currency of the cell.” Which of the following statements depicts a correct pattern of energy flow through living things?

A. Sun – plants – food – ATP – animals B. Sun – animals – ATP – food – plants C. Plants – sun – food – ATP – animals D. Animals – sun – plants – ATP – food

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E. Food – plants – ATP – sun – animals Answer: A

20. In the living world, the whole is greater than the sum of its parts. Each new level of biological organization has emergent properties that are due to the arrangement and interactions of parts as complexity increases. All properties, even emergent properties, are governed by the laws of physics and chemistry. New properties that emerge with each step upward in the hierarchy of life are called

A. Physical propertiesB. Emergent propertiesC. Chemical propertiesD. Biological propertiesE. Shared derived properties

Answer: B

21. The term genome refers to the complete genetic makeup of an organism. Its primary function is to encode the proteome, the entire protein complement of an organism. Proteins are largely responsible for the structure and function of cells. Why is the genome critical to life?

A. Acts as a stable informational unit that stores genetic information B. Provides continuity from generation to generationC. Acts as an instrument of evolutionary changeD. Only A and B are correctE. A, B, and C are correct

Answer: E

22. In their pursuit to study natural phenomena, biologists use the scientific process. This is a hypothesis-based inquiry composed of a series of steps. Based on accumulated data from observations, the scientist poses a casual question and formulates a number of hypotheses as possible answers. The scientist then uses deductive reasoning to make predictions involving the “if, then” logic. Experiments are conducted to test the predictions and to eliminate one or more of the hypotheses. Conclusions are drawn and the most plausible hypothesis is selected. The hypothesis becomes a theory if it is supported by numerous experiments conducted by different scientists. A theory that is universally accepted for a long period of time becomes a principle or law. When biologists use the scientific process to study a natural phenomenon, they follow a sequence of steps. Which of the following depicts a correct sequence of the scientific process?

A. Observations – hypotheses – predictions – experiments – conclusion – theory B. Observations – hypotheses – theory – experiments – predictions – conclusionC. Theory – observations – experiments – hypotheses – predictions – conclusionD. Theory – observations – hypotheses – experiments – predictions – conclusionE. Observations – theory – predictions – experiments – hypotheses – conclusion

Answer: A

23. The scientific process used by scientists to study natural phenomena involves many steps including formulation of hypotheses and theories. Which of the following statements best distinguishes a hypothesis from a theory in science?

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A. A theory is a hypothesis that has been rejectedB. A hypothesis is a guess; a theory is a correct answerC. A theory is proved true in all cases; a hypothesis is usually falsified by testsD. A hypothesis is an educated guess; a theory is supported by a body of evidence E. A theory is relatively narrow in scope; a hypothesis has broad explanatory power

Answer: D

24. In their pursuit to study natural phenomena and to formulate hypotheses, scientists use two types of reasoning: deduction and induction. Deduction or deductive reasoning is the analysis of specific cases using general principles. Induction or inductive reasoning is the method of discovering general principles by careful examination of specific cases. Which of the following statements best describes induction?

A. Through induction, we derive generalizations based on a large number of specific observations, i.e. from specific to general

B. Through induction, we analyze specific cases based on general principles, i.e. from general to specific

C. In induction, the logic flows from the general to the specificD. Both A and B are correctE. A, B, and C are correct

Answer: A

25. Deduction involves taking a general principle and applying it to a specific situation. Which of the following statements illustrates deduction?

A. All living things are made of cells. Therefore, dinosaurs were made of cellsB. If you study your textbook and ask questions, you will pass the comprehensive final

examC. From the incident of an apple falling from a tree, Isaac Newton came up with the laws of

gravity D. Only A and B are correctE. A, B and C are correct

Answer: D

26. The statement “If you study your biology textbook and ask questions, you will pass the mid-term exam” is an example of

A. A statement derived from a hypothesisB. A statement that can be testedC. Deductive reasoningD. A predictionE. All of these are correct

Answer: E

27. Scientists use both inductive and deductive reasoning to formulate hypotheses. A hypothesis is an informed, uncertain, but testable conjecture. Hypotheses are subject to falsification by using experiments. If a hypothesis withstands the test of experiments through time, and is never rejected, it becomes a theory. To scientists, theories are accepted explanations of natural

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phenomena. However, a theory could be proven to be wrong in light of scientific evidence. An informed, uncertain but testable conjecture is a

A. Scientific factB. Natural lawC. HypothesisD. PrincipleE. Theory

Answer: C

28. The process of inductive reasoning

A. Involves the observation of specific occurrences to construct a general hypothesisB. Involves taking a general principle and applying it to a specific situationC. Is not used often in the study of biologyD. Both A and B are correctE. A, B, and C are correct

Answer: A

29. A key explanation for the diversity of organisms is evolution by natural selection. Imagine two girls born; say 6,000 years ago in what is now Finland. Life in this region is precarious for everyone; the winters are long and food is scarce even in warm months. The Northern European lactase mutation appeared about 1,000 years prior to the birth of these girls, which means that only some Northern Europeans now possess this genetic variant. Imagine that one of the girls has inherited this variant but the other hasn’t. This means that from the age of, say, 4, one of these girls can obtain nourishment from cow and goat’s milk while the other cannot. Given this, the girl with the lactase mutation will survive into adulthood, develop a bigger brain and become a mother. The milk and milk products that she consumes will provide her, all year round, with precious calories and calcium. In the environment in which she’s growing up, this girl has been selected to survive by virtue of her genetic makeup. When this process is repeated in one generation after another, the result is the rapid spread of a trait through a population. Today in parts of Northern Europe, 98 percent of the population is believed to be lactase-persistent. In 7,000 years, then, lactase persistence evolved from 0 percent prevalence to 98 percent prevalence in this one part of the world. How strong a force is evolution through natural selection? Which of the following statements about evolution is correct?

A. Members of a population vary in form, function, and behavior; and much of this variation is heritable.

B. Some forms of heritable traits are more adaptive than others; they improve chances of surviving and reproducing. Thus individuals with adaptive traits tend to makeup more of the reproductive base in each new generation.

C. Natural selection is a measure of the difference in survival and reproduction that hasoccurred among individuals that differ from one another in one or more traits.

D. Any population evolves when some forms of traits increase in frequency and othersdecrease or disappear over the generations.

E. All these statements are correctAnswer: E

30. Which of the following statements is NOT correct about a hypothesis?11

A. A hypothesis fits the known factsB. A hypothesis is an intelligent guess that is proven to be trueC. A hypothesis might be rejected in the future in light of new informationD. A hypothesis is a suggested explanation that’s subject to testing by further observation

and by controlled experimentsE. A hypothesis supported by many scientists could become a theory

Answer: B

True/False Questions

31. The scientific study of life on Earth is called exobiology.Answer: False

32. Life is defined by listing the characteristic attributes of living things.Answer: True

33. The theory that life always comes from preexisting life is called biogenesis.Answer: True

34. In the hierarchy of biological organization, tissue precedes (comes before) cell.Answer: False

35. A hypothesis that survives many tests and is very unlikely to be discarded is referred to as a theory.

Answer: True 36. A theory is a well-tested hypothesis, one unlikely to be rejected by future tests.

Answer: True

37. Inductive reasoning derives generalizations from specific cases, and deductive reasoning predicts specific outcomes from general premises.

Answer: True

38. The scientific study of naming and classifying living things is called taxonomy.Answer: True

39. Darwin’s theory of evolution by natural selection is an example of a scientific theory. Answer: True

40. All the different organisms in your college campus make up a population.Answer: False

41. The application of scientific knowledge for some specific purpose is called technology.Answer: True

42. The structure and function of DNA demonstrates the diversity among living things.Answer: False

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43. Organisms are open systems that exchange materials and energy with their surroundings.Answer: True

44. Metabolism is the ability of organisms to obtain and transform energy from the environment and use it during maintenance, growth and reproduction.

Answer: True

45. All the places on Earth where living things are found is the biosphereAnswer: True

46. The capacity to evolve is based on variations in traits, which originally arise through mutation.

Answer: True

47. Metabolism is the process where living things maintain a relatively stable internal environment.

Answer: False

48. In the field of biology, the scientific process (method) is often followed to test the validity of a hypothesis.

Answer: True

Matching Questions: Match the following items with their appropriate definitions

49. __________ biology A. explains origin of mitochondria and chloroplasts

50. __________ community B. life comes from preexisting life

51. __________ deduction C. change of populations over time

52. __________ emergent property D. classifying and naming of organisms

53. __________ homeostasis E. search for live on planets other than Earth

54. __________ induction F. supported by massive body of evidence

55. __________ hypothesis G. scientific study of life on Earth

56. __________ theory H. different populations

57. __________ exobiology I. from general to specific

58. __________ taxonomy J. new property that emerges with each step upward

59. __________ biogenesis K. maintenance of a stable internal environment

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60. __________ evolution L. from specific to general

61. __________ endosymbiosis M. intelligent guess

Answer: 49 – 61: G, H, I, J, K, L, M, F, E, D, B, C, A

Fill-in-the-blank Questions: Use the word bank provided

scientific process exobiology cell taxonomyinduction deduction technology biologyevolution bioinformatics homeostasis species

62. The science of the search for the possible existence of life on planets other than Earth is called __________.

Answer: exobiology

63. The lowest level of biological organization that can perform all the activities required for life is the __________.

Answer: cell

64. The science of __________ is a branch of biology concerned with the naming and classifying of living things.

Answer: taxonomy

65. The method of scientific inquiry that describes natural structures and processes as accurately as possible through careful observation and the analysis of data is known as the __________ __________.

Answer: scientific process

66. Collecting data based on observation is an example of the __________ __________; analyzing the data to reach a conclusion is an example of _________.

Answer: scientific process; induction

67. Application of scientific knowledge for some specific purpose is known as __________.Answer: technology

68. The theory of __________ by means of natural selection was proposed by Charles Darwin in 1859.

Answer: evolution

69. Using computing power, software, and mathematical models to process and integrate biological information from large data sets is called __________.

Answer: bioinformatics

70. The taxonomic category which includes organisms that can interbreed under natural conditions, such as Ursus americanus, is called __________.

Answer: species

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71. __________ means maintaining the body’s internal operating conditions within a tolerable range even when environmental conditions change.

Answer: homeostasis

Short-essay Questions and Answers

72. Define life by listing the characteristic properties of living things.

Life is defined by listing the characteristic properties of living things. These properties include: cellular composition, acquisition and use of energy, growth and development, reproduction and inheritance, response to external and internal stimuli, homeostasis, locomotion, complexity, adaptation and evolution, and death

73. List the levels of biological organization in a correct sequence, starting with cell.

cell – tissue – organ – organ system – organism – population

74. List the steps of the scientific process in the correct sequence.

observations – hypothesis(es) – predictions – experiments – conclusion - theory – law

75. Contrast induction with deduction. When are these two types of reasoning used by scientists?

Induction or inductive reasoning derives generalizations from specific cases; deduction or deductive reasoning predicts specific outcomes from general premises. They are used by scientists to formulate hypotheses.

76. Contrast “theory” with “hypothesis.”

Compared to a hypothesis, a scientific theory is usually more general and more substantiated by an accumulation of evidence. A hypothesis is an intelligent guess based on observations and familiarity with the nature of the problem under study.

77. Apply the principle of emergent properties to explain the relationship of a sentence to the alphabet of letters from which the sentence is constructed.

The meaning of a sentence is a property that emerges from the specific sequence of letters and spaces.

78. List the taxonomic groups from the most inclusive to the least inclusive.

Domain – Kingdom – Phylum – Class – Order – Family – Genus – Species

79. Explain how life is characterized by both unity and diversity.

Decent from a common ancestor explains the unity of life. All living things are composed of cells, their genes are made of DNA, have the same genetic code, and carry the same

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metabolic reactions to acquire energy and maintain their organization. Adaptations to different environments and ways of life account for the great diversity of life forms. Many millions of species exist, many millions more lived in the past and became extinct, and many thousands are becoming extinct every year.

80. Describe the general pattern of energy flow through living things and the universal

role of ATP in all living things.

In order to maintain their organization and carry out metabolic activities, living things need a constant supply of energy. The sun is the ultimate source of energy for life on Earth. Plants capture light energy by the process of photosynthesis and convert it into ATP (adenosine triphosphate) to produce food. When organisms consume food, they extract the energy stored in food, by the process of cell respiration, and use it to grow and do work. Organisms store excess energy in ATP and break down ATP to obtain energy. Thus, ATP is referred to as the “energy currency of the cell.”

81. Why do scientists accept the hypothesis of endosymbiosis, that mitochondria and chloroplasts are the descendants of bacteria, as a theory?

The hypothesis of endosymbiosis was proposed by Lynn Margulis in 1962 to explain the origin of mitochondria in animal and plant cells, and chloroplasts in plant cells. It is not certain that this idea is correct, but the overwhelming weight of evidence supports the hypothesis and most biologists accept it as “proven.” There is no absolute truth in science, however, only varying degrees of uncertainty, and the possibility always remains that future evidence will cause a theory to be revised. A scientist’s acceptance of a theory is always provisional. Mitochondria and chloroplasts are the only cell organelles that contain genes.

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