Exam 4 Study Guide
Exam 4 Study Guide 301
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This page Study Guide was uploaded by Morgan Deal on Wednesday November 18, 2015. The Study Guide belongs to 301 at University of South Carolina taught by Dr. April South in Summer 2015. Since its upload, it has received 54 views. For similar materials see Ecology and Evolution in Biology at University of South Carolina.
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Date Created: 11/18/15
EXAM 4 STUDY GUIDE Chapter 17 Mutualisms Types of mutualisms o Generalists 1 species interacts with many others 0 Specialists 1 species interacts with 1 or a few other closely related species 0 Obligate mutualists 2 species give each other tness bene ts and cannot survive without each other 0 Facultative mutualists 2 species bene t each other but mutualism isn t necessary for survival 0 Mutualisms in plants plants give mycorrhizal fungi products of photosynthesis in exchange for help obtaining nutrients and water 0 Animal mutualisms Gut bacteria help many animals especially humans with digestion Shrimp and goby sh shrimp let sh share their burrow in exchange for warnings of predators from the sh 0 In defense 0 Plants acacia trees provide a habitat for ants while the ants destroy herbivores and competitors for the tree Endophytic fungi help protect from herbivores and increase drought resistance 0 Animals wrasse sh consume parasites on larger sh 0 Pollination many animals feed on the pollen and nectar of plants 0 The animal gets covered in pollen while feeding o Pollen is then distributed later 0 Very speci c mutualism cactus owers are pollinated by bats and have evolved to only open at night for these bats Dispersal many animals eat seeds which pass through the digestive tract unharmed or are carried to other locations to germinate o Ending mutualistic relationships if 1 individual stops bene tting from a mutualistic relationship it turns into predation herbivory or parasitism o Cheating when 1 animal continues to bene t from the relationship without contributing anything in return Favored by natural selection Defenses against cheating also favored by natural selection 0 Effects on communities 0 Species distributions disruption of mutualisms can alter species distribution 0 Communities Altering species diversity removing an organism in a mutualistic relationship can cause a decline in the other species abundance and diversity Chain of reactions mutualistic relationships can affect the community at large not just the participating species 0 Ecosystem functions mutualistic relationships have important roles in helping producers take in nutrients and can increase biomass Chapter 18 Community Structure 0 Community boundaries species composition changes due to changes in what each species can tolerate and their competitive ability 0 Categorizing communities both terrestrial and aquatic communities are characterized by dominant organisms and physical conditionscharacteristics o Ecotone boundary created by sharp changes over short distances accompanied by change in species composition 0 Community diversity 0 Interdependence v independence lnterdependence species depend on each other to exist lndependence species do not depend on each other for survival Which is occurring 0 Use of linetransect surveys Remove speculated interdependent species and observe effects 0 Patterns of species abundance Species richness number of species existing in a community Relative abundance proportion of individuals in a community represented by a species Lognormal distribution bell curve with a log scale on the xaxis Rankabundance curves plots relative abundance of each species in rank order from most to least abundant Species evenness compares relative abundance of each species in community 0 Quantifying community diversity 1 Simpson s index it 1 1 S Shannon s index H Zpilnpi i1 5 species richness Pi relative abundance of each species in decimal form 0 What affects species diversity 0 Resources wide range of patterns between availability of resources and species richness positive negative none u shaped humpshaped Park grass experiment added fertility decreases species richness of plants possibly because it encourages the growth of a few dominant species 0 Habitat diversity communities with high habitat diversity typically have high species richness due to a wider range of potential niches 0 Keystone species species that substantially affects community structure removal could cause community collapse Ecosystem engineers keystone species that in uences habitat structure 0 Intermediate disturbance hypothesis species richness is highest when disturbances happen occasionally Communities with infrequent or very frequent disturbances experience low species richness Food web organization 0 Trophic levels level in food chainweb Primary consumer eats producers Secondary consumer eats primary consumers Tertiary consumer eats secondary consumers o Bottomup effects activities of producers control the abundance of the trophic levels 0 Topdown effects activities of predators control trophic level abundance Community response to disturbance 0 Community stability ability of community to maintain a particular structure 0 Community resistance amount that a community changes when experiencing a disturbance 0 Community resilience time taken for a community to return to its original state after experiencing a disturbance 0 Alternative stable states when a community experiences such a large disturbance that species composition changes and the new community structure is resistant to change Chapter 19 Community Succession 0 Important terminology o Succession species composition of a community changes over time can take weeks months or centuries 0 Pioneer species earliest species to arrive after a disturbance able to disperse long distances 0 Climax community nal stage in succession typically characterized by dominant organisms still subject to change 0 Chronosequence sequence of communities existing over time at a speci c location Observing succession 0 Direct observation is the clearest way to observe however it is not always feasible 0 Indirect observation Examine regional communities that began succession at different times Look at pollen in sediment layers and carbon date it Mechanisms of succession o Terrestrial environments Primary succession habitats initially devoid of plantssoil are colonized by species that require no soil ie moss these early colonizers produce organic matter to generate more hospitable conditions for other organisms Secondary succession disturbed habitat still contains soil but no plants soil contains plant matter allowing for rapid regrowth Sequence of seral stages is variable but can result in the same climax community differences in historic abiotic conditions soil fertility and disturbances can cause variation in chronosequence 0 Animal succession because changes in plant life cause signi cant habitat change succession of plants is usually focused on when studying succession of animals 0 Intertidal communities short generation time of dominant species causes rapid succession o Streams rapid succession organisms move downstream from less disturbed areas or come from outside the ecosystem allochthonous o Ponds and lakes Models suggest slow succession Studies suggest that succession happens in occasional large bursts depending on conditions 0 Changes in species diversity species richness is close to 0 after a disturbance that eliminates most of the species Species richness increases rapidly at rst then plateaus followed by a small decrease during succession o Quantifying community similarity Jaccard s index O O x abx X number of species present in both communities A number of species present ONLY in community A B number of species present ONLY in community B Traits of species In early succession species grow faster reproduce more disperse easily and are more tolerant to harsh conditions In later stages of succession species grow slower reproduce less do not disperse as easily but are better at competing Mechanisms Facilitation 1 species increases the probability of a second species becoming established lnhibition 1 species decreases the probability that another species will become established 0 Competition predation or parasitism Priority e ect arrival of a species affects later colonization of another species Tolerance probability of one species being established depends on dispersal ability and ability to persist in the environment Climax communities still subject to change 0 O O O 0 Environmental conditions change Organisms increase in size Early stages abiotic conditions are rapidly altered Once community contains the largest organisms it can sustain environmental changes more slowly Spatial changes variations in species composition as one moves along environmental gradients Gaps small scale disturbances that allow the growth of non dominant species Transient climax communities not persistent site is frequently disturbed Firemaintained climax community nal stage sustained due to periodic res Grazermaintained climax community nal stage of succession sustained by intense grazing