Uploaded byLeandro Michael Delos Santos Jr.
Chapters 17 20 ecology
1. The document discusses key concepts in community ecology including species diversity, guilds, food webs, succession, and landscape dynamics. 2. Species diversity is measured by counting species and their relative abundances. A dominant species is most abundant while a keystone species has a large impact relative to its abundance. 3. Landscape features like habitat fragmentation can create patches that impact species diversity depending on patch size and isolation from other habitats.
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Chapters 17 20 ecology
- 1. CHAPTERS 17-20 PRESENTED BY:LEANDRO MICHAEL C. DE LOS SANTOS, JR.
- 2.
- 3. 1. Explain howecologists define species diversity.What data must be collected to determine the diversity of a community?
- 4. Species diversity- ameasurement that relates number and relative abundance of species within a community.This mix of species defines the biological structure of a community. Data needed to determine Species diversity: 1. Count of all species 2. Relative abundance of each species in a community
- 6. 2. Use examplesto illustrate the difference between a dominant species and a keystone species.
- 7. Dominant species- whena single of few species predominate within a community Keystone species- a species that has a disproportionate impact on the community relative to its abundance
- 8.
- 9. 3. Draw adiagram of a simple food web with three trophic levels, and describe the difference between a food chain and a food web
- 10. FoodWeb with 3trophic levels
- 11. Food web- interlockingpattern formed by a series of interconnecting food chain Food chain- an abstract representation of feeding relationships within a community
- 12. 4. Explain thedifference between a guild and a functional type, and discuss why it may be useful for ecologists to classify species in these ways.
- 13. Guilds- subdividing eachtrophic level into groups of species that exploit a common resource in a similar fashion. Ex. Humming birds and other nectar-feeding birds form a guild of species that exploit flowering plants
- 14. Functional type- agroup of species based on their common response to the environment, life history, characteristics, or role within the community. Ex. Plants categorized based on their photosynthetic pathways, shade tolerance or timing of reproductive effort
- 15. Importance of classification: *Simplify the study of communities
- 16. 5. Discuss thephysical structure of either a forest or a lake, and explain how the physical structure affects the biological structure
- 17. Physical structure ofa lake Stratification is determined by light penetration & profiles of temperature and oxygen
- 18. Characteristic organisms inhabiteach available vertical layer in a community. Various types of consumers and decomposers occupy all levels in a community
- 19. 6. Explain whydefining the boundaries of a community can sometimes be very difficult. Do you think this detracts from the usefulness of the concept of community?
- 20. Since community isa spatial concept, defining boundaries between communities can sometimes be difficult because when the species composition and patterns of dominance shift gradually the distinction or boundary between each community will be unclear.
- 21. 7. Explain thedifference between the organismic concept of communities and the individualistic continuum concept.Which of these concepts best describes the majority of communities?
- 22. Organismic concept- clustersor groups of species repeatedly associate together, with each species representing an interacting, integrated component of the whole. Individualistic continuum- relationship among coexisting species is due to the similarities in their requirements and tolerances, not to strong interactions or common evolutionary history.
- 23. 8. Give tworeasons why it is difficult to accurately determine the species diversity of any given community, and suggest how you might go about trying to do so.
- 24. 1. Quantifying thedifference in the set of species from one community to the other 2. How to determine where one community ends and another one begins
- 26. 9. Choose eitherof the two most common indexes of community similarity (Sorenson's coefficient of similarity and percent similarity), and explain how it is calculated. For what purpose might such an index be used?
- 27. Sorensen’s coefficient ofcommunity (CC) - useful when the intended focus is on the presence or absence of species Where: c, number of species common to both communities s1, number of species in community 1 s2, number of species in community 2
- 28. CHAPTER 18 Factors Influencingthe Structure of Communities
- 29. 1. Explain thediffering roles of fundamental niches and species interactions in controlling community structure.
- 30. Fundamental niche- sometimesreferred to as physiological niche, which provides a description of the set of environmental conditions under which a species “can persist’’.
- 31.
- 32. 2. Explain whatan indirect interaction is, and give an example of an indirect interaction that has a strong effect on a specific species in a community.
- 33. Indirect Interactions- occurswhen one species does not interact with a second species directly, but instead influences a third species that does directly interact with the second species
- 34. 3. Explain thedifference between bottom-up and top-down control of community structure. Do you think one or the other is most important, or some combination of both?Why?
- 35. Bottom-up control- productivityand abundance of population at any given trophic levelare controlled by the productivity and abundance of populations in the trophic level below them Competition is strong, predation is weak Top-down control- predator populations can control the abundance of prey species. Predation is strong, competition is weak
- 36. 4. Explain thepotential relationship between the physical structure of a plant community and the diversity of an animal community in the same habitat. Give a real or hypothetical example to support your answer.
- 37. Physical structure ofplant community vs. animal species diversity
- 38. 5. Describe theresponse that plant communities typically exhibit when nutrients are added, and summarize the prevailing hypothesis to explain this response.
- 39. Inversely proportional relationshipbetween soil fertility and species diversity
- 40. Plant species diversityin a control plot and a fertilized plot in the Parkgrass experiment in Rothamstead, England. Fertilized plots have lower species diversity. http://cedarcreek.umn.edu
- 41. 6.What are thepossible explanations for the paradox that diversity in plant communities decreases when nutrient availability increases?
- 42. Low nutrient concentration- species competing below ground (symmetric) - more equal ability of small and large plants to access resources. High nutrient concentration - species competing above-ground (asymmetric) - less equal ability to compete for light
- 43. 7. Explain thedifferences between the rivet model and the redundancy model of ecosystems.Which do you think more accurately described ecosystems?
- 44. Rivet model- anidea that losing a species in an ecosystem is analogous to losing a rivet of an airplane.When loss reaches a certain threshold, major catastrophic effects happen Redundancy model- if a species is lost, other species will fill the gap (“driver” and “passenger”)
- 45.
- 46. 1. Using aspecific example, discuss the ecological differences between early successional species and late successional species within a sere.
- 47.
- 48. In a timberharvested area: Early succession species or pioneer species- shade-intolerant and fast growing plant species predominate the area such as raspberry thickets, pin cherry and pine birch Late succession species- after many years the area will be replaced with shade-tolerant species and species of trees that are larger and longer lived
- 49. 2. Using specificexamples for each, explain the differences between primary and secondary succession
- 50. Primary succession- newlyexposed substrates that have never supported a community Ex. Rock outcrops, cliffs, sand dunes, newly exposed glacial till
- 51. Secondary succession- occursafter disturbances such as old-field succession
- 52. 3. Explain howa chronosequence can be used to understand succession.
- 53. Chronosequence- a groupof sites within the same area that are in different stages of succession
- 54. 4. Using specificexamples for each, describe the differences between autogenic and allogenic environmental changes that drive succession.
- 55. Autogenic environmental change-direct result of the presence and activities of organisms within the community Allogenic environmental change- changes in the environment governed by physical environment rather than biological processes
- 56.
- 57.
- 58. Allogenic change • Elevationon a mountain • Decrease in temperature with depth in a lake or ocean • Change in salinity and water depth
- 59.
- 60. 1. Using anexample, explain how human and natural forces can combine to create habitat patches
- 61. Patch- an areaof habitat that differs from its surroundings and has sufficient resources to allow a population o persist. Factors that create to combine habitat patches: 1. Human activities such as fragmentation of land tracts due to development creates patches of forest, grassland and shrubland 2. Fire- aftermath of forest fires create patches 3. Grazing by herbivores 4. Variations in geology and soil condition
- 62. 2. Discuss themajor ecological differences between edge species and interior species.
- 63. Edge effect- responseof organisms, animals in particular, to environmental conditions created by the edge due to the blending elements of adjacent patches
- 64. EDGE SPECIES INTERIORSPECIES Species restricted exclusively to the edge or border environment Shade-intolerant Can tolerate dry conditions Organisms that require large areas of habitat, even though their home ranges may be small Require environmental conditions characteristic of interior habitats Stays away from abrupt changes in environments
- 66. 3. Discuss thedifferences in diversity between large and small habitat patches.What are the reasons for these differences?
- 67. Large habitat Smallhabitat High diversity of species Low diversity of species Interior species Edge species
- 68. 4. Using agraph, illustrate how the number of species on an island can be affected by its size and distance from a mainland.What are the two important demographic variables that vary with the size of an island and its distance from a mainland?
- 69.
- 70. 2 important demographicvariables: extinction & immigration
- 71. 5. Explain thepotential value of corridors to large-bodied species such as carnivores.
- 72. Corridors- strips ofvegetation similar to the patches they connect but different from the surrounding matrix in which they are set. Source: http://nac.unl.edu
- 73. Characteristics of mammaliancarnivores: • Sensitive to changes in landscape structure • Susceptible to habitat fragmentation • Rarely remain within the boundaries of protected areas that are often too small Potential benefit of corridors to mammalian carnivores: * Help in the facilitation of movement of these animals between protected areas without experiencing high mortality rates due to conflicts with humans thus aiding in their Source: http://esrd.alberta.ca
- 74. 6. Give twoexamples of disturbance, and explain how disturbance can alter a community.
- 75. Disturbance- any relativelydiscrete event- such as fire, windstorm, flood, extremely cold temperatures, drought or epidemic- that disrupts community structure and function
- 76. Spatial &Temporal characteristicsof disturbance • Small scale- makes gaps in the substrate creating patches • Large scale- favor opportunistic species • Severe disturbance- can replace the community altogether
- 77. How disturbance altersan ecosystem: • Results in death of organisms and loss of biomass • Changes geomorphology of an ecosystem such as breaking of barrier dunes by high tides and winds, cutting of banks and course of rivers and streams by floods • Either reduce (eliminates organisms) or foster (favor survival of some) species diversity
Editor's Notes
- #8 Dominance can also be defined based on some combination of characteristics that include both the number and size of the individuals.
- #9 Sea otter: feeds on urchins that which also feed on kelps. Kelps provide habitat for wide variety of species Pisaster starfish- grazing prevents the establishment of dense mussel beds allowing other species to colonize rocks on the pacific coast
- #12 Food chain- series of arrows representing the flow of food energy
- #16 , allowing researchers to focus on more manageable subsets of the community and to ask basic questions about the factors that structure communities
- #18 Epilimnion- well-mixed water layer Metalimnion- characterized by thermocline (steep rapid decline in temp relative to waters above and below) Hypolimnion- deep, cold layer of dense water Photic zone- availability of light supports photosynthesis Aphotic zone- area without light Benthic zone- bottom area where decomposition takes place
- #19 Considerable interchange takes place among the vertical strata
- #21 It does not detract as long as in a particular study a well defined objective and spatial scale is strictly followed. In a sense, the distinction among communities is arbitrary, based on the criteria for classification
- #32 Figure 18.3 species interactions are diffuse Diagram only shows predator-prey relations but there is also competition that happens between predators, mutualism, etc. Removal of single species had little effect Removal of groups of species had stronger effect
- #36 A some combination of these two controls would be most important as a balance between competition and predation is necessary to control a community.
- #38 Changes in the composition of animal species inhabiting various stages of plant succession from old field to conifer forest. Increased vertical structure means more resources and living space and a greater diversity of potential habitats.
- #41 Plant species diversity in a control plot and a fertilized plot in the Parkgrass experiment in Rothamstead, England. Fertilized plots have lower species diversity. The Parkgrass experiment, which began in 1856, is the longest running ecological experiment.
- #45 Rivet- ecological functions of different species overlap so that even if a species is removed, ecological function may persist because of the compensation of other species with similar functions http://digitalcommons.unl.edu/ driver- species that has a strong ecological function that significantly structure the ecosystem Passenger- minor ecological impact
- #48 Succession: temporal change in community structure over a period of time Sere - series of successional stages on a given site that lead to a terminal community
- #49 Early succession species- high growth rates, smaller sizes, high degree of dispersal and high rates of per capita population Late succession species- lower rates of dispersal and colonization, larger and longer lived
- #51 Grasses especially beach grass are the most successful pioneering plants and functions to stabilize the dunes Aspect of primary succession- colonizing species ameliorate the environment, paving the way for invasion of other species
- #52 Decline in the abundance of shortleaf pine and increase in the density of hardwood species
- #54 The peaks in diversity correspond to periods of transition between stages, where species from both stages are present at the site Colonization by new species increases local species richness. Species replacement typically results from competition or an inability of a species to tolerate changing environmental conditions. Species replacement over time acts to decrease species richness.
- #57 Vertical profile of light in a forest is a direct result of the interception and reflection of solar radiation by the trees Light availability decline from canopy to ground level At initial colonization, seedlings are able to establish themselves As plants grow, leaves intercept light, reducing light to shorter plants The reduction in light enables fast growing plants to out compete the other species and dominate the site
- #58 Periods of dominance are correlated with species’ optimal temperature, nutrient, and light requirements all of which systematically change over growing season
- #62 Through successional processes revert back to pre-impact states over a time periods ranging from years to decades.These factors can create or can combine to create habitat patches for opportunistic species
- #70 Immigration or colonization rate declines with increasing species richness while extinction rate increases. The balance between extinction and immigration defines the equilibrium number of species (S) on the island
- #71 Immigration rate are distance related while extinction rate relate to area Islands near a mainland have a higher immigration rate and associated equilibrium species richness than islands distant from a mainland. Extinction rates relate to area and are higher on small islands than on large ones. The equilibrium number of species varies according to island size, and larger islands have greater equilibrium species richness than do smaller islands.