This Document Contains Chapters 21 to 23 Chapter 21 The Origin and Evolution of Life Contents Part I How Did Life Originate? Early Attempts to Understand the Origin of Life Current Thinking About the Origin of Life Extraterrestrial Or Earth Origin? Meeting Metabolic Needs Summary of Ideas about the Origin of Life Major Events in the Early Evolution of Living Things Reproduction and the Origin of Genetic Material The Development of an Oxidizing Atmosphere The Establishment of Three Major Domains of Life The Endosymbiotic Theory and the Origin of Eukaryotic Cells A Summary of the Early Evolution of Life Part II The Process of Evolution The Development of Evolutionary Thought Evolution and Natural Selection Defining Evolution The Role of the Environment in Evolution Natural Selection Leads to Evolution A Closer Look: The Voyage of the HMS Beagle, 1831-1836 Genetic Diversity is Important for Natural Selection Genetic Diversity Resulting from Mutation Genetic Diversity Resulting from Sexual Reproduction Processes That Drive Natural Selection Differential Survival Differential Reproductive Rates Differential Mate Selection Acquired Characteristics Do Not Influence Natural Selection A Closer Look: The Reemerging of Infectious Diseases Science and Society: Antibiotic Resistance and Human Behavior The Hardy-Weinberg Concept A Closer Look: Human-Designed Organisms Accumulating Evidence of Evolution A Closer Look: Other Mechanisms that Cause Evolution Myths, Mistakes, and Misunderstandings: Common Misconceptions about the Theory of Evolution Part III Speciation Species: A Working Definition How New Species Originate The Role of Geographic Isolation in Speciation The Role of Natural Selection in Speciation Reproductive Isolation Speciation without Isolation The Tentative Nature of the Evolutionary History of Organisms Overview This chapter covers a great deal of material about the origin and evolution of living things. It is divided into three parts. Part I presents material about the origin of life. It begins with some historical background to the thinking about the origin of life before discussing current ideas. There must have been several key steps in the early evolution of life. These include the development of the metabolic processes such as respiration and photosynthesis, the development of genetic material, and the endosymbiotic origin of eukaryotic organisms from prokaryotic organisms. The original Earth probably had an atmosphere that lacked oxygen; therefore, the first organisms would have had to be able to live without oxygen. Oxygen became an important part of the atmosphere after the origin of the process of photosynthesis. A brief discussion of the three domains of life; Bacteria, Archaea, and Eucarya, is presented to help students see how early evolutionary events could have occurred. Part II deals with the process of evolution. The concept of natural selection is explored in depth. The role of genetic diversity is discussed. The significance of differential survival, differential reproductive rates, and sexual selection are explored in detail. Once students recognize that species are populations of organisms and that the individuals are genetically diverse, it is possible to understand why natural selection takes place and that there can be significant change in a species over time. Part III focuses on speciation In order for speciation to occur there is a need for an interruption of the gene flow. Geographic barriers are thought to be a common factor leading to speciation and are easily understood. Once the idea of a geographic barrier is presented, students can better understand other methods of isolation. An understanding of speciation leads to thinking about evolutionary change over long time periods that resulted in the kinds of organisms we see on earth today, but that understanding the specific evolutionary path of an organism is tentative and requires reinterpretation as new information becomes available. For Class Discussions 1. Which of the following is the most likely series of events? a. Earth formed–oxygen in atmosphere–living organisms–ozone b. ozone–living organisms–plants–organic molecules c. organic molecules–ozone–living organisms–oxygen in atmosphere d. organic molecules–living organisms–oxygen in atmosphere–ozone 2. The first organisms most likely lived in a. the ocean. b. glaciers. c. the atmosphere. d. freshwater streams. 3. If an organism is able to make organic molecules from inorganic molecules it a. is a heterotroph b. must have been the first organism on Earth c. must use an external source of energy d. cannot break down organic molecules to inorganic molecules. 4. An oxidizing atmosphere would have a. been present at the origin of the earth. b. developed after eukaryotes were present. c. increased the likelihood of mutation due to ultraviolet radiation. d. been made possible by prokaryotic cells. 5. The endosymbiotic theory is concerned with the development of the cells of a. the Bacteria. b. the Archaea. c. the Eucarya. d. viruses. 6. Which of the following is a likely outcome of the effects of a geographic barrier? a. the same species of birds on island A and island B b. several species of fish in the water between island A and island B c. trees on island A and bushes on island B d. a species of green lizard on island A and a very similar species of brown lizard on island B 7. All of the following would be possible mechanisms of natural selection except a. female mice will mate with males that have a particular odor. b. all of the lizards on an island are killed by a hurricane. c. ultraviolet light from the sun kills some members of a species of plant but not others. d. on an island with little food small lizards have more offspring than large lizards. 8. Animal A can breed with animal D and produce a fertile offspring, animal C. If animal A breeds with animal B, they have a sterile offspring, animal E. The animals that belong to the same species are a. A and E. b. A and B. c. A and C. d. B and E. 9. Evolution a. occurs when an individual mutates. b. occurred in the past but is not happening today. c. causes natural selection. d. is demonstrated by changes in the genetic makeup of populations. 10. All of the following discoveries have supported the concept of evolution except a. the idea that animals develop skills that their offspring inherit. b. the discovery of fossils of extinct organisms. c. the discovery of the structure and function of DNA. d. the ability to examine and make the structure of the DNA of specific species. Answers: 1d, 2a, 3c, 4d, 5c, 6d, 7b, 8c, 9d, 10a Answers to Questions for Thought Part I 1. Sequence of events: Reducing atmosphere first organic molecules living cell oxidizing atmosphere eukaryotes developed 2. Spontaneous generation is the sudden creation of a living thing from nonliving material. Biogenesis is the theory that all life arises from preexisting life. 3. (a) Ozone is formed from O2 and screens out some ultraviolet radiation. (b) Oxygen was made available for use in the more efficient aerobic respiration process found in almost all living organisms. 4. (a) Mitochondria and chloroplasts have DNA. (b) Mitochondria and chloroplasts reproduce. 5. Redi prepared two sets of jars that were identical in every way except one. One set of jars had a gauze covering. The uncovered set was the control group; the covered set was the experimental group. Any differences seen between the control and the experimental groups were the result of a single variable—being covered by gauze. In this manner, Redi concluded that the presence of maggots in meat was due to flies laying their eggs on the meat and not spontaneous generation. Part II 6. Acquired characteristics are those that an individual develops during its life and are not controlled by genes Since these characteristics cannot be transmitted to the next generation through sexual reproduction, they will not influence the gene pool. 7. Natural selection is a process that reduces the frequency of genes for characteristics that are detrimental and increases the frequency of genes that are beneficial within a population of a species. It is accomplished by the death or reduced likelihood of reproduction of those individuals having detrimental genes. 8. Selecting agents include any environmental factor that results in the death or reduced reproduction of individuals within a population. Some examples are: predators that kill certain individuals in a population; low rainfall, which selects those plants and animals that can live with low amounts of water; and low light levels, which selects those individual plants that can live and reproduce in low amounts of light. There are many other examples 9. Lamarck’s theory that acquired characteristics can be passed through reproduction has been disproved by experiment. It is also inconsistent with our modern understanding of the molecular nature of the gene. Lamarck did not understand the genetic forces that determine phenotype. 10. Wallace traveled extensively and, as a result of his travels, came to the same conclusions about natural selection as did Darwin. He was also influenced by Malthus’ ideas, as was Darwin. Although today Wallace is often mentioned as an afterthought, it was his essay concerning his ideas about natural selection that prompted Darwin to publish On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. 11. First of all, evolution only occurs in populations. Populations are groups of organisms of the same species that are able to interbreed and are thus genetically similar. The second point is that genes (specific pieces of DNA) determine the characteristics displayed by organisms. The third point is that the mix of genes (DNA) within populations can change. Thus, evolution involves changes in the genes that are present in a population. By definition, individual organisms are not able to evolve—only populations can. 12. The first involves the phrase “survival of the fittest.” Individual survival is certainly important because those that do not survive will not reproduce. But the more important factor is the number of descendants an organism leaves. An organism that has survived for hundreds of years but has not reproduced has not contributed any of its genes to the next generation and so has been selected against. The key, therefore, is not survival alone but survival and reproduction of the more fit organisms. Second, the phrase “struggle for life” does not necessarily refer to open conflict and fighting. When a resource is in short supply, some individuals survive and reproduce more effectively than others. 13. While sexual reproduction does not generate new genetic information the way mutation does, it generates genetic diversity and allows for the recombination of genes into mixtures that did not occur previously. Each individual entering a population by sexual reproduction carries a unique combination of genes; half are donated by the mother and half are donated by the father. During the formation of sex cells, the activities of chromosomes results in new combinations of genes. This means that there are millions of possible combinations of genes in the sex cells of any individual. When fertilization occurs, one of the millions of possible sperm unites with one of the millions of possible eggs, resulting in a genetically unique individual. Part III 14. Evolution is a fact, because we can observe changes in gene frequency over time and we can detect mutations, which are changes in the genetic material of organisms. However, we cannot, in most cases, state exactly how a specific organisms evolved. We can suggest possible steps in the evolution of organisms but we cannot ever be certain that specific steps were followed. 15. Geographic isolation is necessary for speciation because it prevents interbreeding between two parts of a population. Interbreeding would not permit specific differences to develop. 16. Mules are not capable of breeding and, therefore, do not fit the definition of a species. 17. In order for speciation to occur, the following events are necessary: (a) a geographic barrier dividing a population into two parts, (b) enough time elapses for specific differences to arise by mutation and natural selection, and (c) two distinct populations result. 18. Biologists often use specific observable physical, chemical, or behavioral characteristics as guides to distinguishing species. Structural differences are useful but not foolproof ways to distinguish species. However, we must rely on such indirect ways to identify species because we cannot possibly test every individual by breeding it with another to see if they will have fertile offspring. Furthermore, many kinds of organisms reproduce primarily by asexual means. Because organisms that reproduce exclusively by asexual methods do not exchange genes with any other individuals, they do not fit our biological species definition very well. In addition, the study of fossil species must rely on structural characteristics to make species distinctions since it is impossible to breed extinct organisms. For Further Analysis Part I 1. The simplest of all experiments would be to take horse hairs, clean them thoroughly and put them in water and observe them. Part II 2. Infections obtained while hospitalized are often antibiotic resistant strains. 3. Students will come up with different answers depending on how they decide to rank colors. They should recognize that there is a wide variety of colors, not just black, brown, blond, and red. Therefore, they should conclude that there is a great deal of diversity in this single characteristic. 4. Most cases of racial prejudice are rooted in the supposition that some races are superior to others. Sperm banks that contain sperm from prominent men are based on the assumption that their genes are superior to those of other men. Some life and health insurance companies seek to eliminate certain groups of individuals from their insurance pool. Part III 5. There is a great deal of evidence from fossils, DNA analysis, and other sources that indicates that organisms change over time. There are also current examples of evolution such as the development of antibiotic resistance in bacteria or the “shaping” of domesticated plants and animals by human actions. Evolution is a theory in the scientific sense—it is an accepted generalization that pulls together massive amounts of evidence. The fact that scientists reorganize their thinking about the particular evolutionary path followed by a particular organism is inevitable as new information becomes available. Chapter 22 The History of Life on Earth Contents Part I Kinds of Organisms The Classification of Organisms The Problem with Common Names Taxonomy Phylogeny A Closer Look: Cladistics—A Tool for Taxonomy and Phylogeny A Brief Survey of Biodiversity Domains Bacteria and Archaea Domain Eucarya A Closer Look: The World’s Oldest and Largest Living Organisms Acellular Infectious Particles Viruses Viroids: Infectious RNA Prions: Infectious Proteins Part II The Geologic History of Earth Geologic Time Early Attempts at Earth Dating Modern Techniques for Determining the Age of the Earth Interpreting the Geologic Record Geologic Time and the Fossil Record Early Ideas About Fossils Types of Fossils Using Fossils to Determine the Order of Geologic Events A Closer Look: What Is Carbon-14 Dating? The Geologic Time Scale Paleontology, Archaeology, and Human Evolution A Closer Look: Another Piece of the Human Evolution Puzzle Unearthed? A Closer Look: Neandertals— Homo sapiens neanderthalensis or Homo sapiens sapiens ?? Ardipithecus and Other Early Hominins The Genera Australopithecus and Paranthropus The Genus Homo Where Did It All Start? Overview This chapter looks at the diversity of living things from an evolutionary perspective. Part I begins with a discussion of geologic time and the nature of fossils. Fossils provide a window into the life of the past. In addition to providing evidence of previously existing life, fossils can be arranged in a time sequence based on an interpretation of the layers of rocks in which they are found and they can be compared to the layers above and below. It is important to recognize that fossils are not easily formed and that some kinds of organisms, particularly marine organisms with hard parts, are more easily fossilized than terrestrial organisms or those that lack hard parts. The human fossil record is sparse but it is obvious that there were many kinds of human-like organisms present in the past and that they have only been present in the last few million years. Part II discusses the processes used to classify organisms and put them into a meaningful hierarchy. The hierarchical classification system serves several functions. It organizes organisms into groups that make the vast number of organisms easier to comprehend, it seeks to categorize them into natural evolutionary groups, and it seeks to standardize the naming of organisms on a worldwide basis. Recent studies have clarified the diverse nature of the prokaryotic organisms and they have been reorganized into two major domains; the Bacteria and the Archaea. All of the eukaryotic organisms have been classified into the domain Eucarya. Part II ends with a discussion of particles that show some of the characteristics of life but have not been clearly established as living things: viruses, viroids, and prions. For Class Discussions 1. Fungi are in the domain a. Bacteria b. Archaea c. Eucarya d. None of the above is correct. 2. Single-celled organisms without cell walls are found in the Kingdom a. Protista. b. Animalia. c. Plantae. d. Fungi. 3. The genus Homo has been present on Earth for a. over a million years. b. a few thousand years. c. about a billion years. d. a 100 million years. 4. Which one of the following is the correct way to state the scientific name of humans? a. homo sapiens b. Homo sapiens c. Homo Sapiens d. Homo sapiens 5. A cell’s metabolic pathways can be taken over by the DNA from a a. bacteria. b. fungus. c. virus. d. host. 6. The domain Archaea a. has many species that produce methane b. is older than the domain Bacteria c. consists mostly of organisms that carry on aerobic respirations d. None of the above is correct. 7. The age of the oldest rocks on Earth is about 3.8 billion years. This has been determined by a. examining the fossils they contain. b. comparing the amount of radioactive materials to the amount of products the radioactive materials convert to. c. carbon 14 dating. d. comparing the rocks to the layers above them. 8. The taxonomic subdivisions from largest to smallest are a. domain, kingdom, phylum, class, order, family, genus, species. b. kingdom, domain, class, phylum, order, genus, family, species. c. domain, kingdom, phylum, order, class, family, genus, species. d. domain, kingdom, order, class, phylum, genus, family, species. 9. Which one of the following statements about fossils is true? a. The fossil record probably gives evidence of most of the species of organisms that have existed in the past. b. Fossils that are found in the same layer of rock are about the same age. c. Fossils are easily formed. d. Terrestrial organisms are rarely fossilized. 10. Fossils of the early ancestors of modern humans (australopiths) a. are common. b. are all found in Africa. c. clearly show the steps in the evolution of modern humans. d. indicate they were widespread in Africa, Europe, and Asia. Answers 1c, 2a, 3a, 4b, 5c, 6a, 7b, 8a, 9b, 10b Answers to Questions for Thought Part I 1. Although both Archaea and Bacteria are prokaryotic they differ in their chemical structure and physiology. Bacteria have characteristic molecules in their cell walls that are not present in the cell walls of Archaea. The DNA of Archaea is similar to that of Eucarya. Archaea have a different kind of cell membrane from Bacteria. 2. Taxonomy is valuable in that it helps scientists see the relationships among groups of organisms and seeks to identify organisms in a standard way so that all scientists in the world use the same terminology. 3. Viruses reproduce by entering a cell and taking over the cell’s structures and using them to make more copies of the virus. 4. Latinized forms of words are used in genus and species names for historical reasons and because scientists want to distinguish scientific names for organisms from common names. Since only one scientific name is given to each species it makes it easier to know specifically what species is being discussed. 5. Protista—single celled or colonial; eukaryotic; mostly aquatic Plantae—multicellular; cell wall of cellulose; photosynthesis Fungi—mostly multicellular; cell wall with chitin; heterotrophs Animalia—multicellular; no cell wall; hetertrophs; movement 6. DNA analysis; fossil evidence; life cycle studies; comparative anatomy Part II 7. Because the early Earth would have been a molten mass, igneous rocks would form as the Earth cooled. Rocks thought to be older than 3.8 billion years have been found but there are still questions about the accuracy of aging. Any rocks that were formed 3.8 billion years ago or earlier would have been subjected to erosion and other geologic processes. Therefore, these rocks are not likely to show fossils of the tiny organisms that could have been present at that time. However, the nature of the rocks might provide information about the composition of the atmosphere or other conditions that existed at the time the rocks were formed. 8. The Paleozoic and Mesozoic eras both ended with mass extinctions. It has been proposed that bombardment by meteors could have changed the climate enough to cause these extinctions. Other causes of mass extinctions could have been changes in sea level, volcanic activity, and climate changes. 9. The principle of original horizontality states that any layer of rock that is not horizontal has been subjected to forces that have deformed Earth’s surface. The principle of superposition states that for undeformed rocks, newer rock is layered on top of older rock. Finally, the principle of faunal succession implies that the same types of fossil organisms lived only briefly and should occur only in rocks that are the same age. 10. Actual preservation of remains, alteration or replacement of remains by mineral material, preservation of the shape of an organism in sediments, and preservation of signs of activity in sediments. 11. Correlation–one of the most important uses of fossils is correlating rocks in one location with those in another. Paleoenvironments–the kinds of fossils found at a particular locality can help in determining the former environment of a region. Paleoecology–detailed studies of fossil changes and studies of changes in the type of sediment in which the fossil was found can lead to deductions about how the animal adapted to the environment, its relationship to other organisms, and how ancient communities were structured. Paleogeography–the geographic distribution of fossils also aids in paleogeography studies. From these studies, it is possible to determine the distribution of land and sea areas, paleolatitudes, ancient shorelines, and land connections. Paleoclimates–geologists can also determine the paleoclimate or climates for a given region by studying fossil types. Evidence for evolution–the vertical distribution of fossils provides much support for the idea that living organisms have gradually changed or evolved into their present forms. Evidence for plate tectonics–the distribution of fossils found on continents that are today separated by an ocean provides evidence that the continents were connected at one time. 12. There were several species of early hominins (australopiths) that had small brains, walked upright, and were herbivores. Fossils of these organisms are only found in Africa. More human-like species of the genus Homo developed in Africa as well. These organisms had larger brains and were carnivores or omnivores. More recent species have larger brains and show evidence of tool use. Early species are found only in Africa. Fossils of at least three recently evolved species are also found in Europe and Asia. Homo sapiens is the most recently evolved with a large brain and extensive tool use. H. sapiens may have arisen in Africa or may have arisen simultaneously in Africa, Europe, and Asia from an earlier species of the genus Homo. For Further Analysis Part I 1. How many “kinds” currently exist? The student will need to wrestle with how to define kinds. Does this just mean brands or does it include models? Regardless they should ultimately determine that there are tens to hundreds of kinds. Are there “fossils” that may have been precursors to motor vehicles? Antique cars or old vehicles in junkyards could be considered to be fossils. The wheel and primitive wheeled vehicles could be fossils. What was the ancestor of motor vehicles? Wagons or other wheeled vehicles are ancestors. What was the first motor vehicle? They may have several suggestions for this. What motor vehicles have gone extinct? They should be aware that vehicles like the Edsel, Oldsmobile, Plymouth, and Studebaker are no longer being made. What major evolutionary changes have occurred? There is a long list here: automatic transmissions, disk brakes, improved airflow, electric headlights, etc. What environmental factors shaped the evolution of motor vehicles? Again, there are several possible responses: clean air standards, safety concerns, demand for increased mileage, etc. Part I 2. The student would need to measure the length of the paper then multiply this length by 2, then multiply the resulting number by 2 and continue until 5 operations are completed. For example if the smallest piece of paper was 1 cm long, the student would need to perform the following operations 1 2 = 2, 2 2 = 4, 4 2 = 8, 8 2 = 16,16 2 = 32. 3. Could our early hominin ancestors have seen living dinosaurs? No, dinosaurs were extinct long before humans came on the scene. What did the animals in the Cambrian Period eat? They would have eaten algae or other primitive marine animals. There were no terrestrial organisms. What organisms have dominated most of the history of the earth? Prokaryotic organisms (Bacteria and Archaea) dominated life on earth for nearly 2 billion years. How might viruses and viroids be related? They both consist of small segments of DNA or RNA and may have a common ancestor. Chapter 23 Ecology and Environment Contents A Definition of Environment The Organization of Ecological Systems Energy Flow in Ecosystems Community Interactions Types of Terrestrial Communities Temperate Deciduous Forest Temperate Grassland or Prairie Savanna Desert Boreal Coniferous Forest Mediterranean Shrubland (Chaparral) Temperate Rainforest Tundra Tropical Rainforest Tropical Dry Forest Types of Aquatic Communities Marine Communities Freshwater Communities Estuaries Individual Species Requirements: Habitat and Niche Habitat Niche A Closer Look: The Importance of Habitat Size A Closer Look: Zebra Mussels—Invaders from Europe Kinds of Organism Interactions Predation Parasitism Commensalism Mutualism Competition Competition and Natural Selection The Cycling of Materials in Ecosystems The Carbon Cycle A Closer Look: Carbon Dioxide and Global Warming The Nitrogen Cycle The Phosphorus Cycle Nutrient Cycles and Geologic Time Bioaccumulation and Biomagnification Population Characteristics Genetic Differences Age Structure Sex Ratio Population Density The Population Growth Curve Population-Size Limitation Limiting Factors to Human Population Growth Human Population Growth and the Global Ecosystem Science and Society: Government Policy and Population Control Overview This chapter is designed to present the fundamentals of ecology and emphasize the human being as an animal in a complex ecosystem, the biosphere. Today’s world forces students to make decisions that influence their environment. This means they should be provided with a basis for making wise decisions. The first portion of the chapter provides some basic definitions needed to understand the material that follows. The flow of energy necessary to support life begins with the role of the green plants—the producers—and proceeds through the trophic levels occupied by the various types of consumers. This discussion is followed by a section that describes how organisms interact with one another in food chains. The complexity of a food web and the flow of energy through these food webs serve as an introduction for the explanation of communities and their respective roles in an ecosystem. Included is a discussion of the major types of terrestrial biomes and major types of aquatic ecosystems. The next major section of the text deals with individual organisms interact with their surroundings and including other organisms. It introduces the concepts of habitat, niche predation, parasitism, commensalism, mutualism, and competition. The next major section deals with how materials are cycled through ecosystems and includes detailed descriptions of the carbon, nitrogen, and phosphorus cycles. The chapter ends with a discussion of population biology. It describes how different populations of the same organism can differ in genetic diversity, age structure, sex ratio, and population density. The classic population growth curve is discussed along with the concept of carrying capacity. It introduces the various factors that can act as control mechanisms for growth. These mechanisms include both the external factors of food, energy, predators, and disease, and internal factors such as social behavior and freedom of choice. The ends with a discussion of the implications of population biology to humans and how a growing population affects the world ecosystems. For Class Discussions 1. Which of the following is an example of a biome? a. tundra in Alaska b. the lawn at your college c. sugar cane fields d. Australia 2. The greatest diversity of animals is found in the a. tropical rainforest. b. boreal forest. c. tundra. d. temperate forest. 3. The difference between an ecosystem and a community is that the ecosystem has something a community does not have; the ecosystem has a. producers. b. consumers. c. nonliving parts. d. interacting species. 4. If it were part of a food web a fish could be eaten by a. humans. b. birds. c. cats and dogs. d. All of these answers are true. 5. An example of community is a. this class. b. various kinds of organisms living in the soil. c. bees in a hive. d. goldfish in a jar. 6. Which is a food chain? a. grass-grasshopper-horse b. fish-grasshopper-snake c. light-grass-human d. grass-cow-human 7. Which of the following is not a community? a. a group of different species living in a pond b. a forest c. a population of rabbits d. a pine tree and the organisms that live on it 8. If a habitat is where an organism lives, a niche is a. how the organism functions. b. what happens to the organism. c. what the organism does. d. All of these answers are true. 9. Which one of the following would result in an increase in the rate at which a population grows? a. reduction in the birthrate b. reduction in the number of females c. reduction in the death rate d. reduction in the number of males 10. As the size of a population approaches the carrying capacity a. the number of births and deaths are about equal. b. the population is in the lag phase. c. the population decreases d. the biomass decreases. Answers: 1a, 2a, 3c, 4d, 5b, 6d, 7c, 8d, 9c, 10a Answers to Questions for Thought 1. In most ecosystems photosynthetic producers trap energy and make it available to other organisms. The energy travels from one organism to another, as one organism eats another, with a loss of energy each time it enters another organism. The various organisms represent trophic levels or stages of energy flow. 2. Sunlight is the source of energy. Plants serve to convert light energy into food energy. Second law of thermodynamics—as energy is converted from one form to another useful form, energy is lost. In ecosystems, about 90% of the energy is lost as it flows from one trophic level to the next. Consumers are organisms that obtain energy by eating other organisms. Decomposers obtain energy by breaking down complex organic molecules of dead organisms and organic mater into simple inorganic molecules. Herbivores are animals that eat plants. Carnivores are animals that eat animals. Omnivores are animals that eat both plants and animals. 3. In the flow of energy from the herbivore to the carnivore, there is a loss of usable energy. This loss of energy means that less life can be maintained at the higher trophic level. 4. Predominant abiotic factors are the following: a. Temperate deciduous forest 1. seasonal climate with winter, spring, summer, fall 2. enough rainfall to support trees b. Boreal coniferous forest 1. long, cold winters 2. high altitude or latitude c. Desert 1. low amount of rainfall throughout the year 2. not necessarily hot d. Tundra 1. long, cold winter 2. permafrost e. Tropical rainforest 1. lack of frost 2. high rainfall f. Savanna 1. seasonal rainfall—wet and dry seasons 2. frequent fires 5. No. As energy moves through the ecosystem, some of it is lost in the form of heat. Material can be recycled, but energy cannot be recycled. 6. The students, in describing their niches, might describe the living conditions, job status, type of food, kind of clothes, dependents, health condition, and so on. 7. Parasitism, commensalism, and mutualism all involve a close relationship that is beneficial to one of the members of the association. The difference is that the other member of the association is affected differently in each case. In parasitism, the host is harmed; in commensalism, the host neither benefits nor is harmed; in mutualism, each member benefits. 8. The atom of carbon may be fixed into a carbohydrate by photosynthesis in the plant. If a herbivore eats the plant, the atom of carbon may be changed through digestion and tissue-building processes into a part of the herbivore. This may in turn be taken up by a parasite feeding on the herbivore, and eventually this carbon will be returned as carbon dioxide to the atmosphere by a decomposer breaking down the dead parasite. All organisms (including plants) carry on respiration and release carbon dioxide 9. Bacteria fill the following roles in the nitrogen cycle: Decomposer bacteria break down protein and release ammonia Symbiotic nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia Free-living nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia Nitrite bacteria convert ammonia to nitrite. Nitrate bacteria convert nitrite to nitrate. Denitrifying bacteria convert nitrite to atmospheric nitrogen. 10. Organism that live a long time; have relatively few young; and provide care for their young. 11. Under conditions of intense competition two species of organisms can continue to exist if one of the species migrates to a new location or the organisms evolve to fill slightly different niches. 12. The human population growth curve is currently growing rapidly. It also displays a long lag phase. There is currently no indication that a stationary growth phase is imminent, but it must come eventually. 13. Possible answers: (a) More shade under the bridge; (b) cooler temperatures under the bridge; (c) increased humidity under the bridge. 14. It is possible that their variety will also decrease due to a dramatic change in food types available to other kinds of herbivores. 15. Answer will vary. Students should consider trophic levels when describing their web. For Further Analysis 1. The following are possible plans: Reduce the number of females by trapping or killing them. Sterilize all the females. 2. Plants must take up sulfur from the soil and incorporate it into their proteins. Animals eat plants and other animals and obtain sulfur from the proteins they consume. Decomposers will break down protein and release sulfur to the soil and atmosphere. 3. The following questions are relevant: How much energy does it take to raise the crops? How much land would it take to raise the crops to produce the biofuels? What is the cost of producing these fuels compared to producing, finding, and developing fossil fuel sources? 4. Answers will vary. Several might include: a. Controlling reproduction of endangered species by confinement and controlled breeding. b. Limit hunting or harvesting to allow more young to survive to adulthood. c. Establish reserves where organisms can better survive. 5. mutualism families, any example of teamwork, the buddy system when swimming, etc. parasitism people who copy your homework, panhandlers, people who constantly borrow from you, etc. commensalism a person who eats your leftover food, imitating the successful behavior of a colleague, etc. competition sport teams, economic competition, etc. Instructor Manual for Integrated Science Bill W. Tillery, Eldon D. Enger , Frederick C. Ross 9780073512259
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