General Ecology Exam Latest Update tested questions and Accurate Answers.

General Ecology Exam Latest Update tested questions and Accurate Answers. What is Ecology? Study of relationships between organisms and their environment, Study of the abundance and distribution of organisms and the interaction with the biotic and abiotic components of their environment. What is NOT ecology? Ecology is not environmentalism, although ecology deals with global climate change, acid rain, habitat loss, and fragmentation. Ecology is not solely observation. What IS ecology? Ecology is quatitative, and relies on the collection and interpretation of data, Use of the scientific method. It is often "messy" data of complex systems with a lot of critters, and with a lot of complex interactions and feedbacks within systems. What else is ecology? INTERDISCIPLINARY. Climatology, organic chemistry, biochemistry, mathematics, statistics, social sciences, evolution, developmental biology, genetics/molecular biology, behavior, physiology, inorganic chem, geology, hydrology. Levels of ecological organization Individuals in populations interacting in communities in ecosystems on landscapes in regions of the Global biosphere. IPI-CEL-RGB Fields of ecology population, evolutionary, community, physiological, behavioral, ecosystem, landscape, global, conservation, restoration. Population population growth, fluctuation, dispersal; birth and death rates Evolutionary natural selection and the evolution of populations and communities Community species interactions in communities; origin, maintenance and consequences of biodiversity in communities Physiological organism responses to environmental conditions Behavioral social interactions of animals in populations and communities Ecosystem study of entire systems; biotic and abiotic Landscape spatial processes that link adjacent communities and ecosystems Global Earth system as a whole Conservation applies ecological principles to the maintenance of populations, communities or biodiversity Restoration applies ecological principles to the restoration and management of perturbed systems Types of Ecological studies: Theoretical, Modeling, Lab experiments, Field studies, Paleoecology, Large-scale Experiments. Theoretical Theoretical predictions of ecological interactions Ex: niche theory, Lotka-Volterra models Modeling Predictive or exploratory models to give insight into factor controlling specific - mathematical food web models; predictive models Lab experiments Highly controlled experiment; eliminate/manipulate specific variables - physiological studies Field studies Collection of field data; "natural" systems; non-manipulative - nutrient budgets, landscape patterns of vegetation distribution Paleoecology Examine long-term fossil records for insights - paleolimnology Paleolimnology Study of ancient lakes from their sediments and fossils Large-scale Experiments Large, system-level manipulations - ELA, Hubbard Brook experimental forest, Limnocorrals ELA Experiment Lakes Area What is a dependent variable? a variable (denoted by y) whose value is dependent on that of another What is an independent variable? a variable (denoted by x) whose variation does not depend on that of another What is directionality? Evolution through what is the unifying theory of modern biology? Natural selection Evolutionary history explains many of the ecological interactions we observe (biotic and abiotic) Also should keep evolutionary history of organisms (selection pressures faced in the past and present) in mind when we try to understand why we see particular ecological phenomena What is evolution? evolution is a process -that changes a population over time -causes change in population phenotypes over time -and change in gene frequencies in a populations gene pool over time What are the causes of evolution? Genetic drift, gene flow, and natural selection What is genetic drift? a random change in gene (allele) frequency in a population; typically associated with smaller populations -founder effect & bottleneck effect What is gene flow? Movement of alleles between local populations due to the migration of individuals; relative gene frequencies are a function of the balance of major migration processes -immigration & emigration What is Natural selection? Differential reproduction and survival of individuals in a population due to the environmental influences The Hardy-Weinberg principle is a mathematical expression that demonstrates genetic equilibrium in populations over time More about Hardy-Weinberg States that In a large population of 1. randomly mating organisms 2. in the absence of evolutionary forces, allele frequencies will remain constant over time process of inheritance itself does not by itself cause changes in gene frequencies -this explains why we don't see disappearance of recessive alleles from a population over time What are Hardy-Weinberg principles? 1. random mating 2. no mutation - no "new" alleles 3. large population size - no genetic drift 4. no immigration or emigration - no loss or gain of alleles 5. no selection - all genotypes have equal probability of surviving and mating How many populations in nature meet these criteria? not the point, demonstrates that evolutionary forces frequently act on sexually reproducing populations Evolution through natural selection Individuals in a population with adaptations that make them more likely to survive and reproduce under the specific environmental conditions will leave more offspring than those individuals that do not have the adaptations What is adaptation? evolutionary process, via natural selection, that changes phenotype (anatomy, physiology or behavior) resulting in an increased ability of individuals to live in a particular environment - different from acclimation Natural selection causes: -Organisms reproduce and make "like" organisms -There is phenotypic variation among individuals (due to mutation) in a population and this variation is heritable -More offspring are produced each generation than can be supported by the environment -Some individuals, due to physical or behavioral traits, have a better chance of surviving and reproducing than other individuals in the population What is Fitness? Measure of the individual ability, due to phenotype, to compete and make a genetic contribution to the subsequent generation (i.e., success at survival and reproduction... and the eventual success of your offspring) What is Selection pressure? an environmental condition (biotic or abiotic) that, given variation in phenotypes in a population of organisms, differentially affects the survival and reproduction of individuals in the population (i.e., affects fitness) Stabilizing selection When selective pressures select against the two extremes of a trait, the population experiences stabilizing selection. For example, plant height might be acted on by stabilizing selection. A plant that is too short may not be able to compete with other plants for sunlight. However, extremely tall plants may be more susceptible to wind damage. Combined, these two selection pressures select to maintain plants of medium height. The number of plants of medium height will increase while the numbers of short and tall plants will decrease. Directional selection In directional selection, one extreme of the trait distribution experiences selection against it. The result is that the population's trait distribution shifts toward the other extreme. In the case of such selection, the mean of the population graph shifts. Using the familiar example of giraffe necks, there was a selection pressure against short necks, since individuals with short necks could not reach as many leaves on which to feed. As a result, the distribution of neck length shifted to favor individuals with long necks. Disruptive selection In disruptive selection, selection pressures act against individuals in the middle of the trait distribution. The result is a bimodal, or two-peaked, curve in which the two extremes of the curve create their own smaller curves. For example, imagine a plant of extremely variable height that is pollinated by three different pollinators, one that was attracted to short plants, another that preferred plants of medium height and a third that visited only the tallest plants. If the pollinator that preferred plants of medium height disappeared from an area, medium height plants would be selected against and the population would tend toward both short and tall, but not medium height plants. Such a population, in which multiple distinct forms or morphs exist is said to be polymorphic. Stabilizing selection 2 Under stabilizing selection, extreme phenotypes in a population have lower rates of reproduction and survival as a consequence, the average phenotype remains the most common from one generation to the next. Directional selection 2 Under directional selection, most phenotypes have lower reproduction and survival compared to exceptional phenotypes as a results, the population average changes in a particular direction over time Disruptive selection 2 under disruptive selection, average phenotypes have lower reproductions and survival compared to the extremes in the population. over time, average phenotypes become less common and the population becomes phenotypically more diverse Critical things to keep in mind Selection works on phenotypes of individuals in a population (careful of "group selection" thinking) Cascades to the genotype, so the genetic information for the phenotype (genotype) is the ultimate recipient of the selection pressure Typically not on single alleles - most phenotypes are controlled by multiples alleles (a gene or gene complex) So called "survival of the fittest" - natural selection should be thought of as selecting against specific phenotypes (thus, genotypes), rather than selecting for phenotypes No "perfect organism" - Evolutionary responses to selection pressures are like trying to hit a moving target AKA Evolution is trying to catch up with the phenotypes being selected against to maintain survival Many cases it is a slow moving one... How are Natural selection and ecology related? population growth and density, predator - prey interactions, beneficial interactions, and competition Population growth and density - Evolutionary responses to high or low population densities Ex: Dispersal under high densities; Schooling/flocking Predator - Prey interactions - Responses of both predator and prey phenotypes to changes in each other's phenotype Ex: Long-term co-evolved stable predator-prey populations; unstable predator-prey dynamics with introduction of a non-native predator Beneficial interactions - One or both organisms benefit from an interaction (commensalism, mutualism) Ex: Leaf cutter ants and "farmed" fungus Competition - Coexisting species exploiting the same resource can face pressure to use alternative resource Ex: Adaptive radiation Speciation generation of "new" species -what about variation within a species? Phenotypic variation among individuals in a population are a result of Genotype and environmental conditions, -Example: plant size of a single species can vary with altitude, but what is the contribution of environmental conditions affecting size and what is the contribution of the local genotype? Ecotypes locally adapted and genetically distinctive populations within a species Changes in environmental conditions lead to what? Phenotypic responses of organisms -Examine the phenotypic responses of a single species Galapagos finches Geospiza spp. Arid island off of South America Large inter-annual variation in rainfall Leads to large inter-annual variation in food availability for finces - seeds -Drought led to high mortality rates of finches -while abundant rains led to high rates of finch population growth Inter-annual occurring or returning once a year Beak size responses during drought During the drought, birds capable of cracking hard seeds survived at higher rate. consequencially the population was dominated by larger birds at the end of the drought Chuckwalla Large, herbivorous (vegetarian), lives in american southwest and northern mexico Chuckwalla ecology Environments vary across the species' range, so expect environmental selection to vary as well... All habitat areas are consistently hot and dry, but range covers large range in altitude (4 - 1166 masl) (1) Do environmental conditions vary with altitude, and (2) if there is a difference in environment, does this affect chuckwalla ecology? Differences in climate associated with elevation Average winter rainfall increased with elevation in these desert mountains Variation in winter rainfall decreased with elevation Relationship between body size and environmental conditions Chuckwallas grow to larger size where winter rainfall is higher Clear phenotypic differences between low and high altitude with chuckwallas Clear phenotypic differences between low and high altitude... Are these differences due to differences in food availability? Or, are they due to genetic differences between populations (i.e. natural selection caused genotypic differences in populations) One way to address this is to collect lizards from different altitudes and raise them under fixed conditions (same temperature, same food amounts) -a common garden experiment Results of the "common garden" experiment Both males and females from higher elevation populations grew to a larger size