chapter 26 outline
chapter 26 outline BIOL 1110
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This 6 page Class Notes was uploaded by Caitrín Hall on Tuesday January 26, 2016. The Class Notes belongs to BIOL 1110 at University of Connecticut taught by Bernard Goffinet in Summer 2015. Since its upload, it has received 8 views. For similar materials see Introduction to Botany in Biology at University of Connecticut.
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Date Created: 01/26/16
Principles of Ecology and the Biosphere 26.1 Ecology focuses on populations, communities, ecosystems, biomes, and the biosphere Ecology – “knowledge of the house”; stud of organisms and their interactions with each other and with the physical and chemical components of their environment Population – all individual organisms of single species in defined area (range) Community – all organisms of different species in particular area Ecosystem – community plus its physical environment Biomes – ecosystems with similar climates Biosphere contains all organisms on Earth 26.2 Populations show patterns of distribution and age structure, grow and decline, occupy specific niches, and interact with other populations Local distribution of individuals Random – uniform conditions, little interspecific interactions (competition) or dependency, steady resources (ex: dandelions growing in park); least common Uniform – dominance of a species that may be outcompeting others, such as grasses in grasslands, conifers in boreal forests compete for space with other mature trees to generate a uniform distribution of trees in forest Clumped – strong dependency on specific habitat (if moss species grows on dung), resources are often clumped in nature most common Age distribution & survivorship curves Graphs show #s or proportions of individuals of different ages in the population; age structure of population can be characterized Survivorship curves show how death rate in population changes with age of individuals o Type I – death rate is low for young and middle-aged but increases sharply for older individuals o Type II – constant death rate with age o Type III – death rate is high for young Patterns of growth Population growth rate = net growth rate R = b – d Negative if death rate exceeds birth rate; positive if birth rate exceeds death rate Flask example a) As resources are used, population decreases b) If resources are periodically added to compensate for those lost, carrying capacity—growth rate approaches zero as population reaches maximum size—of population fluctuates c) If richer resources are provided, population reaches higher carrying capacity Abiotic factors Determine the area the population occupies Include physical and chemical features of the environment such as light, temperature, moisture, pH, salinity, winds, water currents, disturbances like flooding and fire Limiting abiotic factors: moisture and temperature for land plants Interactions between populations of different species Mutualism – two populations exchange benefits Parasitism – parasite lives in/on members of host and feed upon it without killing it right away Herbivory – animals eat plant parts without fatal consequences to the plant; plants develop physical and chemical (quantitative or qualitative) defenses Predation – one population benefits while other suffers death; carnivorous plants Competition – individuals or populations attempt to use same limiting resource; may lead to extinction and replacement of species o Allelopathy – plants compete by releasing chemicals into environment to inhibit growth of other individuals of same or different species; black walnut 26.3 Communities are composed of individuals of many different species Communities are characterized by species diversity o Not equally or randomly distributed depends on climate o Species diversity includes richness and evenness Species richness - # of species present in a community; decreases with altitude (most at equator); highest in southeast U. S. Evenness – distribution of individual organisms among species o Possible reasons for more species in an area 1. Favorable climate 2. Habitat diversity 3. Herbivory 4. Age of region **unglaciated land more species** Ecological succession is the change in community composition over time o Primary = areas not previously occupied by organisms; bare soil; bryophytes, lichens, and cyanobacteria o Secondary = areas where a community has been removed o Change is continuous but rate of change gradually decreases o Climax community – theory with final and stable stage; no longer accepted o Restoration ecology – aims to understand process of ecological succession and to use that understanding to restore natural communities that have been disturbed by human activity 26.4 Ecosystem studies focus on trophic structure and energy flow Flow of energy through food chain is linear o Food chain – trophic structure that organizes functional categories o Solar energy primary producers primary consumers secondary consumers tertiary consumers decomposers o Energy in organic molecules remains in wastes and dead bodies, passes to decomposers, finally dissipated as heat o Food web – all the different populations at different trophic levels Small fraction of energy passes between trophic levels o Photosynthesis captures only 1-3% of light energy chemical energy o Much of energy in plant biomass is lost as heat or waste o 10% of trophic level biomass is converted into next level o Restraints: Food chains – limited to 3 or 4 links because amount of energy left at the end is too little to support population of high consumers Top consumer must be large enough to attack/kill consumer below o Keystone species have far-reaching effects, called trophic cascades, on entire systems o Chemical pollutants can become concentrated as they pass through levels 26.5 Global climatic patterns determine the distribution of biomes Global patterns of atmospheric circulation Solar energy received at surface varies with latitude north or south of equator Same amount of energy is spread over much larger land area in polar regions Tilted axis (23.5 degrees) causes seasons Differences in atmospheric heating create winds and drive global patterns of atmospheric circulation Continentality, ocean currents, and mountain ranges Continentality – some landmasses are so large that interior areas are located too far from oceans to receive moist winds (aka drier than their latitude would predict) Wind patterns and Earth’s rotation create ocean currents As moist air flows up slopes of mountain ranges, air cools (1 degree C per 100m) 26.6 Matter moves between biomes and the physical environment in large-scale biogeochemical cycles Water cycles through oceans, atmosphere, lands, and organisms – hydrosphere Water is the medium for all biochemical reactions Nitrogen is a macronutrient largely controlled by microorganisms Bacteria and cyanobacteria use nitrogenase in the absence of oxygen to fix N2 into oxidized or reduced form for other organisms 1. Nitrogen fixation – conversion of gaseous nitrogen into ammonia 2. Nitrification – aerobic bacteria convert ammonia into nitrate 3. Assimilation 4. Ammonification 5. Denitrification – nitrogen re-enters atmosphere CO2 cycles between atmosphere and biosphere o Bulk of carbon is locked up in limestone rock (unavailable to all organisms) Cycling of carbon between limestone by weathering and back to rock by sedimentation is long-term o All organisms must have carbon because organic molecules essential for life are built of carbon o Carbon fixation – photosynthesis removes CO2 from atmosphere and fixes it into organic molecules o Carbon release – respiration & burning fossil fuels return CO2 to atmosphere o Rate of carbon fixation SHOULD EQUAL rate of carbon release Chapter Wrap-up Examine and Discuss Self Test 1. Classify each of the following as a population, community, ecosystem, or biome, based on definitions given in this chapter. a. The Joshua trees (Yucca brevifolia) in Joshua Tree National Park, California: _______. b. The desert of Death Valley National Park, California: _______. c. The plants and animals of the Okefenokee Swamp in southern Georgia and northern Florida: _______. d. The cattails of the Okefenokee Swamp: _______. e. The alpine tundra in Rocky Mountain National Park, Colorado: _______. f. The tundras of the world: _______. g. The life in Lake Ponchartrain, Louisiana: _______. 2. You are conducting a study of the fish populations in a lake. Based on net data and mark-recapture studies, you estimate the population biomass of piscivorous fish (tertiary consumers that eat smaller fish) in the lake at 300 kg. You could therefore predict the biomass of the secondary consumers (fish that eat zooplankton) at ______ based on the efficiency of energy transfer between trophic levels. a. 150 kgb. 300 kgc. 1000 kg d. 3000 kg e. 30,000 kg 3. Which of the following globe-girdling air cells are responsible for delivering moisture to the temperate forest and grassland biomes in the northern and southern hemispheres of the Earth? a. Hadley cellsb. Amundsen cells c. Ferrel cells d. Polar cells e. Byrd cells 4. Which of the following best describes the nitrogen cycle process of nitrification? a. Aerobic bacteria in soil and water convert ammonia into nitrate. b. Plants take up ammonia or nitrate from soil. c. Bacteria and cyanobacteria in soil and water convert gaseous nitrogen into ammonia. d. Bacteria in soil and water reduce organic nitrogen com- pounds to ammonia. e. Anaerobic bacteria in water-logged soils and sewage reduce nitrate to gaseous nitrogen. 5. Which of the following processes is not part of the nitrogen cycle? a. nitrification b. nitrogen fixation c. ammonification d. assimilatione. sedimentation 6. Which of the following is the main reservoir of carbon on Earth? a. peatlands b. limestone rock c. forestsd. soile. bones and shells Applying Concepts 1. In “Dinosaur Renaissance” (Scientific American, 1975, 232:58– 78), paleontologist Robert Bakker argues that dinosaurs were not cold-blooded ectotherms but rather warm-blooded endotherms. One line of evidence he presents is that in Mesozoic dinosaur communities, predator-prey biomass ratios (as gleaned from fossil data) were typically from 1 to 3% (that is, 30– 100 times as much prey biomass as predator biomass). Why are predator- prey biomass ratios correlated with predator ectothermy/endothermy status? How would you expect these numbers to change if dinosaurs were ectotherms? 3. If the birth rate and the death rate of a population are equal, what happens to the growth rate? What if the birth rate is slightly lower than the death rate?
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