Study Guide for Exam 1
Study Guide for Exam 1 BIOL 4410
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This 17 page Study Guide was uploaded by Matthew Wieters on Monday August 8, 2016. The Study Guide belongs to BIOL 4410 at Clemson University taught by Dr. David Tonkyn in Fall 2016. Since its upload, it has received 41 views. For similar materials see Ecology in Biology at Clemson University.
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Date Created: 08/08/16
Exam 1 will cover the following chapters: Chapter 1 -- The Web of Life (pages 2-20) Chapter 6 -- Evolution and Ecology (pages 136-159) Chapter 4 -- Coping with Environmental Variation: Temperature and Water (pages 84-98, 100-108) Chapter 2 -- The Physical Environment (pages 22-44, 46-49) Chapter 3 -- The Biosphere (pages 50-71, 80-83) Chapter 1: The Web of life ● Concepts ○ 1.1 -- Events in the natural world are interconnected ■ Laboratory and field experiments on the effects of parasites on amphibian deformities illustrate how events in nature can be connected with one another ■ Because events in the natural world are interconnects, any action can have unanticipated side effects ■ People both depend on and affect the natural environment ○ 1.2 -- Ecology is the scientific study of interaction between organisms and their environment ■ Ecology is a scientific discipline that is related to, but differs from, disciplines such as environmental science ■ Public and professional ideas about ecology often differ ■ Ecology is broad in scope and encompasses studies at many levels of biological organization ■ All ecological studies address events on some spatial and temporal scales while ignoring events at other scales ○ 1.3 -- Ecologists evaluate competing hypotheses about natural systems with observations, experiments, and models ■ In an ecological experiment, an investigator alters one or more features of the environment and observes the effect of that change on natural processes ■ Some features of the natural world are best investigated with a combination of field observation, experiments, and quantitative models ■ Experiments are designed and analyzed in consistent ways: ■ Typically, each treatment, including the control, is replicated ■ Treatments are assigned at random ■ Statistical methods are used to analyze the results ■ The information in this book is a static body of knowledge; what we know about ecology is always changing ● Summary from book ○ Concept 1.1 notes ■ Immediate cause of amphibian deformities is often infection by Ribeiroia parasites ■ Pesticides may decrease amphibians' ability to fight off infection ■ Deformities are more likely in environments that contain pesticides ■ Addition of nutrients can cause algal blooms, which is a food source for snails that harbor Ribeiroia parasites ■ When people alter one aspect of the environment, we can cause other changes that we do not intend or anticipate ○ Concept 1.2 notes ■ Ecology -- the scientific study of interactions between organisms and their environment ■ Environmental science -- focused more specifically on how people affect the environment and how we can address environmental problems ■ Ecologist might examine pollution as one of several factors that influence the reproductive success of wetland plants, where as an environmental scientist might focus on how economic and political systems could be used to reduce pollution ■ Ecologists now recognize: ■ That natural systems do not necessarily return to their original state after a disturbance ■ That seemingly random perturbations often play an important role in nature ■ Overall, although the natural world may not be as predictable or as tightly woven as early ecologists may have thought, species are connected to one another ■ Ecological studies at the population and community levels often examine both biotic and abiotic factors ■ Population or community ecologist --> concerned about features of the abiotic environment ■ Temperature, precipitation or nutrients influence the fertility of individuals or relative abundance so of the different species found in a community ■ Ecosystems ecologist --> concerned about how ecosystems work ■ Rate at which a chemical (such as nitrogen from fertilizers) enters a particular community, as well as how the species living there affect what happens to the chemical once it enters the community ○ Concept 1.3 notes ■ Scientists can use results from observational studies and experiments to develop quantitative models that predict how the geographic ranges of species will change depending on how much the planet actually warms in the future ■ Studies have also suggested that a range of factors can cause amphibian abundances to drop. Such factors include: ■ Habitat loss ■ Parasites and diseases ■ Pollution ■ Over exploitation ■ Climate change ■ Introduced species ■ UV light Chapter 6: Evolution and Ecology (pages 136-159) ● Concepts ○ 6.1 -- Evolution can be viewed as genetic change over time or as a process of descent with modification ■ Biologists often define evolution in a relatively narrow sense as change over time in the frequencies of alleles in a population ■ Evolution can also be viewed as descent with modification, a process in which populations accumulate differences over time and hence differ from their ancestors ■ Natural selection modifies populations by favoring individuals with some heritable traits over others ■ Although natural selection acts on individuals, an individual does not evolve--it either has a favored trait or it does not. Only populations evolve ○ 6.2 -- Natural selection, genetic drift, and gene flow can cause allele frequencies in a population to change over time ■ Mutation and recombination are the sources of new alleles and new combination of alleles thereby providing the genetic variation on which evolution depends ■ Natural selection occurs when individuals with certain heritable phenotypic traits survive and reproduce more successfully than individuals with other traits ■ Genetic drift, which occurs when chance events determine which alleles are passed from one generation to the next, can have negative effects on small populations ■ Gene flow, the transfer of alleles between populations, makes populations more similar to one another genetically and can introduce new allies into populations ○ 6.3 -- Natural selection is the only evolutionary mechanism that consistently causes adaptive evolution ■ By consistently favoring individuals that have advantageous alleles over individuals that have other alleles, natural selection can cause adaptive evolution, in which the frequency of an advantageous trait in a population increases over time ■ Natural selection can increase the frequency of advantageous traits rapidly--in days to years, depending on the organism and the selection pressure ■ Gene flow can limit the extent to which a population is adapted to its local environment ■ Constraints on adaptive evolution result from factors such as lack of genetic variation, evolutionary history, and ecological trade-offs ○ 6.4 -- Long-term patterns of evolution are shaped by large-scale processes such as speciation, mass extinction, and adaptive radiation ■ The genetic divergence of populations over time can lead to speciation, the process by which one species splits into two or more species. Speciation between populations ■ The number of species in a group of organisms increases when more species are produced by speciation than are lost to extinction, and decreases when the reverse is true. The outcome of this process can be visualized with an evolutionary tree ■ Biological communities can lose much of their diversity in mass extinctions, global events in which large proportions of Earth's species are driven to extinction in a relatively short time ■ Adaptive radiations can be promoted by factors such as the removal of competitor groups by a mass extinction in a relatively short time ■ An adaptive radiation occurs when a group of organisms gives rise to many new species that expand into new habitat or fill new ecological roles ■ Adaptive radiations can be promoted by factors such as the removal of competitor groups by a mass extinction or by the evolution of a major new adaptation ○ 6.5 -- Ecological interactions and evolution exert a profound influence on one another ■ Ecological interactions amount organisms and between organisms and their environment can cause evolutionary changes, ranging from allele frequency changes in populations to the formation of a new species ■ Similarly, evolutionary change can alter the outcome of ecological interactions, thus having a large influence on biological communities ● Summary from book ○ Concept 6.1 notes ■ Biological evolution is change in organisms over time ■ Evolution includes the relatively small fluctuations that occur continually within populations, as when the genetic makeup of a population changes from one year to the next ■ Can also refer to the larger changes that occur as species gradually become increasingly different from their ancestors ■ Evolution ■ Change over time in the frequencies (proportions) of different alleles in a population ■ Descent with modification-- populations accumulate inferences over time, and hence, when a new species forms, it differs from its ancestors ■ Darwin proposed that populations accumulate differences over time primarily by natural selection, the process by which individuals with certain heritable characteristics survive and reproduce more successfully than other individuals because of those characteristics ■ By favoring individuals with different heritable characteristics in different populations, natural selection can cause populations to diverge genetically from one another over time; that is, each population will accumulate more and more genetic differences. Thus, natural selection can be responsible for the "modification" part of "descent with modification" ■ Natural selection acts as a sorting process, favoring individuals with some heritable traits (e.g., those with small horns) over others (e.g., those with large horns) ■ Individuals in the population do not evolve--they either have the traits favored by selection or they don’t ○ Concept 6.2 notes ■ Mutation is the source of the new alleles on which all the of evolution depends, while natural selection, genetic drift, and gene flow are the main mechanisms that cause allele frequencies to change over time ■ Individuals in populations differ from one another in their observable characteristics, or phenotype ■ Phenotype--physical features, metabolism, growth rate, susceptibility to disease, and behavior, are influenced by its genes ■ Different alleles arise by mutation, a change in the DNA of a gene ■ Individuals in a population can differ genetically not only because of mutation, but also because of recombination, the production of offspring that have combinations of alleles that differ from those in either of their parents ■ We can think of mutation as providing the raw material (new alleles) on which evolution is based, and recombination as rearranging that raw material into unique new combinations ■ Overall, in terms of its direct effects, mutation is a weak agent of allele frequency change ■ Natural selection occurs when individuals with particular heritable traits consistently leave more offspring than do individuals with other heritable traits ■ Natural selection into three types ■ Directional selection--occurs when individuals with one extreme of a heritable phenotypic train (for example, large size) are favored over other individuals (small and medium-sized individuals) ■ Stabilizing selection--individuals with an intermediate phenotype (for example, medium- sized individuals) are favored ■ Disruptive selection--individuals with a phenotype at either extreme are favored (for example, small and large individuals have an advantage over medium-sized individuals) ■ When chance events affect which alleles are passed from one generation to the next, genetic drift is said to occur ■ Genetic drift has four related effects on evolution in small populations: ■ Because it acts by chance alone, genetic drift can cause allele frequencies to fluctuate randomly in small populations over time ■ Event ually some alleles disappear from the population, while others reach fixation ■ Reduces the genetic variation of the population ■ Increase the frequency of a harmful allele ■ Increase genetic difference between populations ■ Gene flow occurs then alleles are transferred from one population to another via the movement of individuals or gametes ■ Two important effects: ■ By transferring alleles between populations, it tends to make populations more similar to one another genetically ■ This homogenizing effect of gene flow is one reason why individuals in different populations of the same species resemble one another ■ A lleles are exchanged often enough that relatively few differences accumulate between the populations ■ Second, gene flow can introduce new alleles into a population ■ gene flow acts in a manner similar to mutation (although mutation remains the original source of new alleles) ■ T his effect of gene flow can have considerable consequences for human health ○ Concept 6.3 notes ■ By consistently favoring individuals with some alleles over individuals with other alleles, natural selection causes adaptive evolution (sometimes called simply adaptation) ■ A process of change in which traits that confer survival or reproductive advantages tend to increase in frequency over time ■ Gene flow is one of the factors that can limit the extent to which a population is adapted to its local environment ■ For example, some plant species have tolerant genotype a that can grow on soils at former mine sites containing high concentrations of heavy metals; such soils are toxic to intolerant genotypes. On normal soils, the tolerant genotypes grow poorly compared with the intolerant genotypes ■ In general, whenever alleles are transferred between populations that live in different environments, the extent to which adaptive evolution occurs in each population depends on whether natural selection is strong enough to overcome the effects of ongoing gene flow ■ In addition, organisms face a number of constraints on adaptive evolution: ■ Lack of genetic variation ■ If none of the individuals in a population has a beneficial allele of a particular gene that influences survival and reproduction, adaptive evolution cannot occur at that gene ■ Evolutionary history ■ Natural selection does not craft the adaptations of an organism from scratch. Instead, if the necessary genetic variation is present, it works by modifying the traits already present in an organism ■ Ecological trade-offs ■ To survive and reproduce, organisms must perform many essential functions, such as acquiring food, escaping predators, warding off disease, and finding mates ■ Natural selection, and the adaptive evolution that results, is driven by the interactions of organisms with one another and with their environment ○ Concept 6.4 notes ■ Such reproductive barriers arise when a population accumulates so many genetic differences from the parental species that its members rarely produce viable, fertile offspring if they mate with member of the parental species ■ As a result, like natural selection, genetic drift can ultimately lead to the evolution of reproductive barriers and hence to the formation of new species ■ Gene flow, on the other hand, typically acts to slow down or prevent speciation because populations that exchange many alleles tend to remain genetically similar to one another, making it less likely that reproductive barriers will evolve ■ What can we learn about ecology and evolution from mass extinctions ■ Biological communities are devastated by mass extinctions events ■ After a mass extinction occurs, it takes millions of years for adaptive radiations to increase the diversity of life to the levels seen prior to the mass extinction ○ Concept 6.5 notes ■ As we've seen, actions such as trophy hunting, antibiotic use, and commercial fishing are themselves a powerful source of selection ■ Other human actions, such as emissions of pollutants or introductions of invasive species, change aspects of the abiotic or biotic environment ● Review questions Chapter 4:Coping with Environmental Variation: Temperature and Water (pages 84- 98, 100-108) ● Concepts 1. 4.1 -- Each species has a range of environmental tolerances that determines its potential geographic distribution 1. The physical environment affects an organism's ability to obtain energy and resources, thereby determining its growth and reproduction and, more immediately, it's ability to survive the extremes of that environment. The physical environment is therefore the ultimate constraint on a species' geographic distribution 2. Individual organisms can respond to environmental change through acclimatization, a short-term adjustment of the organism's physiology, morphology, or behavior that lessens the effect of the change and minimizes the associated stress 3. A population may respond to unique environmental conditions through natural selection for physiological, morphological, and behavioral traits, known as adaptations, that enhance individuals' survival, growth, and reproduction under those conditions 2. 4.2 -- The temperature of an organism is determined by exchanges of energy with the external environment 1. Temperature controls physiological processes through its effects on enzymes and membranes 2. Gains of energy from and losses of energy in the external environment determine an organism's temperature. Modifying this exchange of energy with the environment allows an organism to control its temperature 3. Terrestrial plants may modify their energy balance by controlling transpiration, increasing or decreasing absorption of solar radiation, or adjusting the effectiveness of convective heat loss 4. Animals modify their energy balance mainly through behavior and morphology to adjust heat losses and gains, and in the case of endothermic animals, metabolic heat generation and insulation to lower heat loss 3. 4.3 -- The water balance of an organism is determined by exchanges of water and salutes with the external environment 1. Water flows along energy gradients determined by solute concentration (osmotic potential), pressure or tension (pressure potential), and the attractive force of surfaces (matrix potential) 2. Plants and microorganisms can influence water potential by adjusting the solute concentration in their cells (osmotic adjustment) 3. Aquatic animals that are hypo osmotic to the surrounding water must expend energy to excrete salts against an osmotic gradient. On the other hand, aquatic animals that are hyper osmotic to their environment must take up salutes from the environment to compensate for solute losses to the surrounding water 4. Terrestrial organism's can alter their gains or losses of water by adjusting their resistance to water movement, as by the opening or closing of stomates in plants or adaptations of the skin in animals ● Summary from book ● Review questions 1. Organisms exhibit different degrees of tolerance for environmental stresses. How does tolerance for variation in body temperature vary among plants, ectothermic animals, and endothermic animals? What factors influence the differences in tolerance among these groups? Can plants exhibit avoidance of temperature extremes? 2. Arctic foxes exhibit large seasonal changes in the thickness of their fur, while the African bat-eared foxes lack this response. Use this example to describe the concepts of acclimatization and adaptation. Assume that the bat-eared fox evolved earlier than the arctic fox 3. Organismal adaptations to environmental conditions often affect multiple ecological functions, leading to associated trade-offs. The following are two different trade-offs to consider: 1. Plants transpire water through their stomates. What effects does transpiration have on temperature regulation in leaves? What is the trade-off with transpiration all temperature regulation in terms of leaf physiological function? 2. Animals can more effectively warm their bodies by absorbing solar radiation if they are a dark color. Many animals, however, are not dark-colored, but instead have a coloration close to that of their habitat (camouflage, as in the case of the basking lizard in Figure 4.15). What is the trade-off between animal coloration and heat exchange? 4. List several ways in which plants and animals in terrestrial environments influence their resistance to water loss to the atmosphere Chapter The Physical Environment (pages 22-44, 46-49) ● Concepts 1. 2.1 -- Climate is the most fundamental characteristic of the physical environment ■ Weather refers to the current conditions of temperature, precipitation, humidity, wind, and cloud cover. Climate is the long-term average weather at a given location ■ Climate determines the geographic distribution and physiological functioning of organisms ■ The climate system is driven by the balance between energy gains from solar radiation and re-radiation by the atmosphere and energy losses due to infrared radiation from Earth's surface, latent heat flux, and sensible heat flux 2. 2.2 -- Winds and ocean currents result from differences in solar radiation across Earth's surface ■ Latitudinal differences in the intensity of solar radiation at Earth's surface establish atmospheric circulation cells ■ The Coriolis effect and the difference in heat capacity between the oceans and the continents act on atmospheric circulation cells to determine the pattern of prevailing winds at Earth's surface ■ Ocean currents are driven by surface winds and by differences in water temperature and salinity ■ Winds and ocean currents transfer energy from the tropics to higher latitudes 3. 2.3 -- Large-scale atmospheric and oceanic circulation patterns establish global patterns of temperature and precipitation ■ Global temperature patterns are determined by latitudinal variation in solar radiation, but they are also influenced by oceanic circulation patterns and by the distribution of continents ■ Temperature decreases as the elevation of the land surface increases ■ Global patterns of terrestrial precipitation are determined by atmospheric circulation cells, but are also influenced by semi-permanent pressure cells 4. 2.4 -- Regional climates reflect the influence of oceans and continents, mountains, and vegetation ■ Seasonal variation in temperature is greater in the middle of a continent than on the coast because ocean water has a higher heat capacity than land ■ Mountains force air masses passing over them to rise and drop most of their moisture as precipitation, resulting in moister environments on windward slopes and drier environments on leeward slopes ■ Vegetation influences regional climates through its effects on energy exchange associated with albedo, evapotranspiration (latent heat transfer), and surface winds (sensible heat transfer) 5.2.5 -- Seasonal and long-term climate variation are associated with changes in Earth's position relative to the sun ■ The tilt of Earth's axis as it orbits the sun causes seasonal temperature changes in temperate and polar regions, and in precipitation in tropical regions ■ Temperature-induced differences in water density result in non-mixing layer of water in oceans and lakes. In temperate-zone lakes, these layer break down in fall and spring, allowing the movement of oxygen and nutrients 6.2.6 -- Salinity, acidity, and oxygen concentrations are major determinants of the chemical environment ■ The salinity of Earth's waters, including water in soils, is determined by the balance between inputs of salts and gains (by precipitation) and losses (by evaporation) of water ■ The pH of soils and surface waters is determined by inputs of salts from the breakdown of rock minerals, organic acids from plants, and acidic pollutants ■ Oxygen concentrations are stable in most terrestrial ecosystems, but oxygen availability decreases as elevation increases. Concentrations of oxygen in aquatic ecosystems are low where its consumption by organisms exceeds its slow rate of diffusion into water ● Summary from book ● Review Questions 1. Why is the variability of physical conditions potentially more important than average conditions as a determinant of ecological patterns, such as species distributions? 2. Describe the factors that determine the major latitudinal climate zones (the tropic, temperate, and polar zones) 3. How do mountains affect regional terrestrial climates? How do oceans affect terrestrial climates? 4. Why are deserts more prone to salinization from irrigation than area with greater precipitation? Chapter The Biosphere (pages 50-71, 80-83) ● Concepts 1.3.1 -- Terrestrial biomes are characterized by the growth forms of the dominant vegetation ■ Terrestrial biomes are characterized by plant growth forms. These biomes reflect global patterns of precipitation and temperature ■ The potential and actual distributions of terrestrial biomes differ due to human activities, particularly conversion of land for agriculture, forestry, and grazing ■ There are nine major terrestrial biomes: tropical rainforests, tropical seasonal forests and savannas, and hot deserts in tropical and subtropical zones; grasslands, shrublands and woodlands, deciduous forests, and evergreen forests in the temperate zone, and boreal forests and tundra in polar regions ■ Biological communities in mountains occur in elevational bands associated with climate gradients 2.3.2 -- Biological zones in freshwater ecosystems are associated with the velocity, depth, temperature, clarity, and chemistry of the water ■ Biological communities in streams and rivers vary with stream order and location within the stream channel ■ Biological communities in lakes vary with depth and light penetration 3.3.3 -- Marine biological zones are determined by ocean depth, light availability, and the stability of the bottom substrate ■ Estuaries, salt marshes, and mangrove forests occur in shallow zones at the margins between terrestrial and marine ecosystems. They are influenced by inputs of fresh water and sediments from nearby rivers ■ Biological communities at the shoreline reflect the influence of tides and the stability of the substrate (sandy versus rocky) ■ Coral reefs and kelp and seagrass beds are productive communities with high diversity associated with habitat complexity provided by their photosynthesizers ■ Biological communities of the open ocean and deep benthic zones contain sparse population of organisms, whose distributions are determined by light availability and proximity to the bottom ● Summary from book ● Review Questions 1. Why are terrestrial biomes characterized using the growth forms of the dominant plants that occupy them? 2. Describe the close association between the distribution of biomes and the major climate zones described in Chapter 2. In particular, consider how seasonality of both temperature and precipitation influence biome distribution 3. As streams flow from their source to the oceans, what physical changes occur that affect the distribution of their biological communities? 4. Why do ocean depth and the stability of the substrate play important roles in determining the composition of marine biological communities?
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