Study Guide Bio 105 #1
Study Guide Bio 105 #1 Bio 105
UW - L
Popular in General Biology
Popular in Biology
This 17 page Study Guide was uploaded by Megan Milbrath on Wednesday September 30, 2015. The Study Guide belongs to Bio 105 at University of Wisconsin - La Crosse taught by Dr. Mika in Fall 2015. Since its upload, it has received 33 views. For similar materials see General Biology in Biology at University of Wisconsin - La Crosse.
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Study Guide Intro to Biological Concepts and Research 11 What is Life characters of living organisms a life on earth exists at several levels of organization each with its own emergent properties 1 complex biological molecules exist at the lowest level of organization but by themselves the molecules aren t alive a properties of life don t appear until the are arranged into organized chemical system that includes many specialized molecules surrounded by a membrane 2 cells are the lowest level of organization that can survivereproduce 3 emergent properties charac that depend on the level of organization of matter but don t exist at lower levels of organization 4 unicellular organisms single cells bacteria protozoans 5 multicellular organisms plants and animals cells that are so tightly coordinated that they cannot survive on their own 6 population group or organisms of the same kind that live together in the same place 7 community all the populations of different organisms that live in the same place 8 ecosystem includes community and nonliving environmental factors in which it interacts 9 biosphere encompasses all the ecosystems of earth s waters crust and atmosphere b living organisms contain chemical instructions that govern their structure and function 1 deoxyribonucleic acid DNA helical molecule contains instructions for creating a living organism from simpler molecules 2 ribonucleic acid RNA dna copied into molecules of a related substance which then directs the production of different molecules 3 proteins carry out most of the actives of life including production synthesis of all other biological molecules c living organisms engage in metabolic activies 1 metabolism the ability of a cell or organism to extract energy from its surrounding and use it to maintain itself grow and reproduce 2 photosynthesis electromagnetic energy in sunlight is absorbed and converted into chemical energy 3 cellular respiration a metabolic process that store chemical energy d energy flows and matter cycles through living organisms 1 plantsphotosynthetic organisms absorb sun energygt chemical energy used to make complex molecules ex sugar from raw materials like h20 and c02 Photosynthetic organisms are the primary producers of the food on which all other organisms rely 2 consumers animals are this directly or indirectly they feed on the complex molecules manufactured by plants 3 decomposers certain bacteria and fungi feed on remains of dead organisms breaking down complex biological molecules into simpler raw materials 4 cause the transfer of energy from 1 organism to another is not 100 efficient a portion of that energy is lost as heat because it s a fucker who won t stay in it s lane bitch 5 by contrast matter nutrients such as carbon and nitrogen because they have their fucking shit together cycle between living and nonliving components of the biosphere a thus they can be used again and again because they aren t wasteful bitches respect e living organisms compensate for changes in the external environment 1 EVERYTHING responds to changes in the environment duh a only living things can detect environmental changes and fucking compensate for them through controlled responses because of their fucking receptors man 2 homeostasis a steady internal condition maintained by responses that compensate for changes in the external environment ex keep internal temp in a good range so you can fucking live and learn biology and shit f living organisms reproduce and many undergo development 1 reproduction banging for a purpose 2 inheritance the transmission of DNA from 1 generation to the next 3 development a series of programmed changes encoded in DNA through which a well fucked egg divides into many cells that ultimately are transformed into an adult which is itself capable of fucking for a purpose 4 life cycle the stages through which individuals develop grow maintain themselves maybe if they have their fucking shit together and reproduce g populations of living organisms change from one generation to the next 1 biological evolution some organisms have change in their DNA and they pass those modified instructions along to their offspring to make a bigger badder bitch nom sayin 12 Biological Evolution BITCHES a Darwin and Wallace explained how organisms change through time 1 artificial selection fake ass mother fuckers intentional reproduction for desirable traits 2 natural selection basically reproduction for survival the bad ones die out cause they useless fuckers 3 THEIR CONCLUSION a most organisms can produce lots of babies but environmental factors limit that b heritable variations allow some to compete more successfully c the successful mother fuckers somehow pass the good traits to their offspring through black magic or some crazy shit d good traitsmore common in next generation b mutations in DNA are the raw materials that allow evolutionary change 1 genes variability of DNA organized into functional units contains a code for a protein molecule of one of its parts 2 mutations random changes in the structure number or arrangement of DNA molecules 3 most mutations are of no particular value and can be harmful rarely they are beneficial c adaptions enable organisms to survive and reproduce in the environments where they live 1 adaptions characteristics that help an organism survive longer ot reproduce more under certain conditions 2 cryptic coloration camouflage in animals 13 Biodiversity and the Tree of Life aresearchers traditionally defined species and grouped them into successively more inclusive hierarchical categories 1 species group of populations in which the individuals are so similar in structure biochemistry and behavior that they can successfully interbreed 2 genus group of similar species that share recent common ancestry 3 family related genera 4 M related family 45 class related order 5 phylum related class 6 kingdom related phyla 7 domain most inclusive group 8 scientific name first part genus 2nd part species b today biologists identify the trunks branches and twigs on the tree of life 1 phylogenetic trees illustrations of the evolutionary pathways through which species and more inclusive groups appeared for all organisms 2 forks closer to base of tree evolutionary events in past and forks near top more recent evolutionary events c three domains and several kingdoms form the major trunks and branches on the tree of life 1 bacteria and archaea are prokaryotes dna is suspended inside the cell without being separated from other cellular components 2 eukarya comprises organisms that are eukaryotes dan is enclosed in nucleus a separate structure within the cells 3 organelles nucleus and other specialized internal compartments of eukaryotic cells 4 the domain bacteria made up of unicellular organisms that are generally visible only under a microscope a prokaryotes live as producers consumers or decomposers 5 the domain archaea unicellular microscopic organisms that live as producers or decomposers a inhabit extreme environments that others cannot tolerate b distinctive structural molecules and unique photosynthesis to their domain 6 the domain eukarya all of the fucking boss ass organisms on earth including fucking trees and shit and animals including wild stallions YOU are a wild stallion a currently described as protists or some shit and classified as plantea fungi shrooms and animalia dick b protists diverse fucking set of single celled and multicellular eukaryotic species because they don t share a fucking unique common ancestory they do not create a fucking kingdom protozoans are familiar i guess they are consumers and decomposers bc they do whatever the fuck they want c kingdom plantae multicellular organisms carry out photosynthesis and therefore function as producers in ecosystems bc they actually give a fuck d kingdom fungi these motherfuckers are a highly varied group of unicellularAND multicellular species among them the yeasts and molds like what the fuck most fungi are decomposers they don t carry out photosynthesis cause fuck it e kingdom animalia multicellular organisms live as consumers by ingesting protists and organisms from all 3 domains watch the fuck out for these bad ass motherfuckers they can even move actively from one place to another during their life cycles how fucking great 14 Biological Research a biologists confront the unknown by conducting basic and applied research 1 basic research often seek explanations about natural phenomena to satisfy their own curiosity and to advance our collective knowledge 2 applied research goal of solving specific practical problems b scientific method helps researchers crystallize and test their ideas 1scientific method an investigative approach to acquiring knowledge in which scientists make observations about the natural world develop working explanations about what they observe and then test those explanations by collecting more info fuck c biologists conduct research by collecting observational and experimental data 1 observational data basic info on biological structures or the details of biological processes a otherwise known as descriptive science provides info about not yet well studied systems 2 experimental data info that describes the result of a careful manipulation of experimental science often answers why or how systems work as they do d researchers often test hypotheses with controlled experiments 1 hypothesis tentative explanation for an observation that can be tested by further examination 2 null hypothesis statement of what they would see if the hypothesis being tested is wrong 3 falsifiability helps scientists define testable focused hypotheses 4 hypothesis help explain relationship between variables environmental factors that differ among places or characters that differ among individuals 2 hypotheses yield testable predictions statements about what researcher expects to happen to one variable if any other variable changes 3 positive results are consistent with support or confirm a hypothesis 4 alternate hypothesis which a conscientious scientist always considers when designing experiments 5 control represents a null hypothesis tells us what we would see in absence of experimental manipulation 6 experimental variable variable that isn t the control it s experimented fucker 7 replicates multiple subjects that receive either the same experimental treatment of the same control treatment e when controlled experiment are unfeasible researcher employ null hypotheses to evaluate observational date 1 unfeasibleimpractical f biologists often use model organisms to study fundamental biological processes 1 model organisms a widely studied easy to maintain species a bc they have rapid development short life cycles and small adult size 2 research on these small and simple organisms provide insight into biological processes that operate in larger and more complex organisms g molecular techniques have revolutionized biological research 1 biotechnology the manipulation of living organisms to produce useful products Ch 21 Develop Of Evolutionary Thought 1 Recognition of evolutionary change a europeans integrated ideas from ancient greek philosophy into christian doctrine 1 Aristotle first considered student of natural history branch of biology that examines the form and variety of organisms in their natural environments 2 a he believed both inanimate objects and living things had fixed characteristics b created a ladder like classification of nature from simplest to most complex forms minerals at bottom spiritual realm at top 2 natural theology biological research become dominated by this sought to name and catalog all of god s creation everything specially created by god a study of each species would identify its place and purple in the scala naturae or great chain of being aristotle s ladder of life 3 linnaeous developed the science of taxonomy branch of biology that classifies organisms b scientists slowly became aware of change in the natural world 1 francis bacon established importance of observation experimentation and inductive reasoning 2 copernicus galileo galilei descartes isaac newton theories to explain physical events 3 questions about biogeography studies of the world distribution of plants and animals 4 questions about comparative morphology anatomical structure a when comparing morphology discovered interesting similarities and differences b vestigal structures the useless parts we observe today Buffon proposed some animals must have changed since their creation and these structures must have functioned in ancestral organisms 5 questions about fossils fossilisdug up a georges cuvier found of paleobiology study of ancient organisms realized that the layers of fossils represented organisms that hd lived at successive times the past b cuvier and followers developed theory of catastrophism reasoning that each layer of fossils represented the remains of organisms that had died in a local catastrophe c lamarck developed an early theory of biological evolution 1 proposed that a metaphysical perfecting principle caused organisms to bemuse better suited to their environments 2 two mechanisms fostered evolutionary change principle of use and disuse body parts grow in proportion to how much they are used and vise versa inheritance of acquired characteristics changes that an animal acquired during its lifetime are inherited by its o spnng 3 today we know that these proposed mechanisms do not cause evolutionary change BUT 4 lamack made 4 important contributions all species change through time new characteristics are passed from one generation to the next suggested that organisms change in repose to their environments hypothesized the existence of specific mechanisms that fostered evolutionary change d geologists recognized that the earth had changed over time 1 james hutton argued gradualism the view that earth changed slowly over its history which contrasted with caviar s catastrophism 2 uniformitarianism geological processes that sculpted earth s surface over long periods of time are exactly the same as the processes observed today 2 Evolutionary Biology since Darwin 1 the modern synthesis created a united theory of evolution a thomas hunt morgan discerned that genes are carried on chromosomes population genetics recognized the importance of genetic variation as the raw material of evolution b modern synthesis integrated data from biogeography comparative morphology comparative embryology paleontology and taxonomy within an evolutionary framework c microevolution describes the small scale genetic changes that populations undergo often in response to shifting environmental circumstances d macroevolution describes larger scale evolutionary changes observed in species and more inclusive groups 2 research in many field has provided evidence of evolutionary change a adaptation by natural selection b the fossil record 1 biological lineages evolutionary sequences of ancestral organisms and their descendants c historical biogeography study of the geographical distributions of plants and animals in relation to their evolutionary history d comparative morphology analyses of the structure of living and extinct organisms such analyses are based on comparison of homologous traits characteristics that are similar in two species because they inherited the genetic basis of the trait from their common ancestor 3 molecular techniques extend the achievements of the modern synthesis a ex how snakes lost their legs and the woolly mammoth s closest living relative 4 some people misinterpret the theory of evolution a the ancient population or organisms left descendants which now include the living species of apes as well as our own species and that the theory of evolution is an ongoing process b early in the 20th century some scientists embraced the notion of orthogenesi progressive goal oriented evolution 1 suggests that evolution produces new species with the goal of improvement we now know that its an ongoing process not toward any fixed goal Chapter 52 Ecology and the Biosphere 1Biosphere comprises all organisms on earth and the places where they live a Ecology the study of interactions between organisms and their environments 1 all environments have both biotic biological and abiotic nonbiological components b hydrosphere encompasses all the water including oceans and polar ice caps c lithosphere atmosphere includes gases and airborne particles that envelope the planet 2 the science of ecology a the connections between research in ecology and evolution are especially strong bc organisms exhibit evolutionary responses to their ecological relationships and bc ecological relationships change as organisms evolve b basic ecology relates to the distribution and abundance of species and how they interact with each other and with physical environment c applied ecology develops conservation plans and programs to limit repair etc ecological damage caused by human activities d ecologists study levels of organization ranging from individual organisms to the biosphere 1 organismal ecology study the genetic biochemical physiological morphological and behavioral adaptations of organisms to the abiotic environment 2 population ecology focuses on populations study size and other characteristics of populations change in spacetime 3 community ecology examines groups of populations that occur together in one area 4 ecosystem ecology explore the cycling of nutrients and the flow of energy between the biotic components of an ecological community and the abiotic environment e ecologists test hypotheses with observational and experimental data 1 modern ecology born in 1970 german biologist ernst haeckel 2 ecologists create hypotheses about ecological relationships and how they change through time or differ from places 3 often conduct field or lab studies to test predictions of hypotheses 3 environmental diversity of the biosphere a climate weather conditions prevailing over an extended period of time b variations in incoming solar radiation create global climate patterns 1 solar radiation a sunlight strikes earth at 90degrees equator travels shortest distance and falls on smallest possible surface area b oblique angle near poles travels a longer distance and shines on larger area c solar radiation is more concentrated near equator than at high latitudes causing latitudinal variation in temp 2 seasonality a the tilt of the earth 235degrees from the perpendicular plane on which it orbits the sun is permanent b N hemisphere gets max illumination 8 hemisphere its minimum c tropics the latitudes between the tropics of cancer and capricorn only here ever receives solar radiation from directly overhead 3 air circulation a sunlight warms air masses causing them to expand lose pressure and rise in the atmosphere b warm equatorial air masses rise to high altitude before spreading NampS c at low altitude some air masses flow back toward the equator creates winds near the planet s surface d latitudinal variation in the speed of rotation deflects the movement of the rising and sinking air masses from a strictly NS path into belts of E and W winds this defection is called the Coriolis effect 3 winds near equator are called trade winds winds further from equator are called temperate westerlies or easterlies 4 precipitation a warm air holds more water vapor than cool air b air near equator heats up absorbs water warm air masses expand as rise heat energy distributed over large volume temp drops this decrease in temp without actually loss of heat energy is called adiabatic cooling c descending air masses absorb water from land so these latitudes are typically dry 5 ocean currents a latitudinal variations in solar radiation also warm the oceans surface water unevenly b trade wings and temperate westerlies also contribute to the mass flow of water at the ocean surface c oceanic circulation is generally clockwise in N hemisphere and counterclockwise in S c regional and local effects overlay global climate patterns 1 proximity to the ocean a continental climate dry climate hot summers cold winters b maritime climate warm but not hot summers cool but not cold winters narrow annual temperature range c ocean currents affect moisture conditions in coastal climates d monsoon cycles caused by seasonal reversals of wind direction 2 the effects of topography a in N hemisphere S facing slopes are warmer and drier than N facing slopes bc they get more solar radiation b rain shadow after the now dry air crosses the peaks it descends and warms absorbing moisture and forming this c mtns establish regional and local rainfall patterns 3 microclimate the abiotic conditions that immediately surround organisms have greatest effect on survival and reproduction 4 organismal responses to environmental variation and climate change a organisms use homeostatic responses to cope with environmental variation 1 homeostatic responses biochemical behavioral physiological and morpholical enable organisms to maintain a constant condition within their cells and tissues 2 only some responses to environmental variation must always be used 3 the sate of extreme physiological sluggishness called torpor is a facultative response to daily variations in environmental temperature b global climate changes affects the ecology of many organisms 1 rising temps will affect the geographical distributions of populations species and communities 2 global warming will change the timing of important biological events 3 climate warming is also changing the combinations of species that occur together within ecological communities 4 models of climate change predict that distributions of polar species will contact to even higher latitudes ranges of temperate and tropical species will expand or shift word poles and lowland species will move to higher elevations 5 climate change not restricted to terrestrial environments ocean temps are also rising and geographical distributions of species and ecological communities have often changed with climate shifts over evolutionary time ut the rate of global warming has accelerated in our lifetime 5 terrestrial biomes a environmental variation governs the distribution of terrestrial biomes 1 climate is main determinant of biome distributions bc organisms are sensitive to abiotic factors 2 climograph portrays the particular combination of temp and rainfall conditions where each terrestrial biome occurs b tropical forests include earth s most species rich communities 1 tropical forests rainforest deciduous forest and montane forest sweep across the parts of africa asia austraila and central and south american and receive intense solar radiation and heavy rainfall 2 tropical rainforests grow where some rain falls every month mean annual rainfall exceeds 250cm mean annual temp is at least 25degreesC and and humidity is above 80percent 3 tropical deciduous forests occur where winter drought reduces photosynthesis and most trees drop their leaves 4 tropical montane forests cloud forests frequently enveloped in mist densely covered with epiphytes thrive in moisture laden air high altitudes c Savannas grow where moderate rainfall is highly seasonal 1 savanna grasslands with scattered trees grow in areas adjacent to tropical deciduous 2 thorn forests grow at the arid borders of true savanna where large mammals are less abundant grasses scrubby trees highly seasonal d deserts develop where little precipitation falls 1 deserts form where rainfall averages less than 25cm per year descending air masses create very dry conditions e chaparral grows where winters are cool and wet and summers are hot and dry 1 chaparral scrubby mix and short trees and low shrubs dominates narrow sections of coastal lane between 3040degrees latitude where winters and are cool and wet and summers hot and dry f temperate grasslands are subject to periodic disturbance 1 temperate grasslands include the prairies of north america steppes of central asia pampas of south america veldt of southern africa winters cold and snowy and summers are warm and fairly dry g temperate deciduous forests experience seasonal dormancy 1 temperate deciduous forests grow at low to middle altitudes winter low temps reduce photosynthetic rates snow and ice damage leaves forests of ash beech birch chestnut elm and oak h evergreen coniferous forests predominate at high northern latitudes 1 boreal forest or taigacircumpolar expanse of evergreen coniferous tress in europe asia and north america white spruce and balsam fir dominate north americas boreal forest 2 temperate rainforest supported by heavy rain and fog winters mild and wet and summers are cool grow in more southerly coastal lowlands i tundra comprises a vast treeless plain in the northernmost habitats 1 arctic tundra stretches from the boreal forests to the polar ice caps in europe asia and north america windswept and wet winter below freezing 2 month summer so cold a permafrost grown below perpetually frozen more than 500m thick in some areas 2 alpine tundra occurs on high mountaintops 6 freshwater environments a wetlands marshes and swamps may harbor an astounding array of microorganisms algae plants invertebrates and vertebrates often occur at borders of freshwater environments b streams and rivers carry water downhill to a lake or sea 1 riffles shallow fast moving turbulent stretches over a rough bottom of pebbles orrocks 2 pools are deep slow moving areas with a smooth sand or mud bottom 3 m are deep fast moving stretches over smooth bedrock or sand 4 the flow of water affects every aspect of life in streams and rivers c lakes are bodies of standing water that accumulates in basins 1 photic zone the surface water that sunlight penetrates 2 aphotic zone deeper and darker 3 lake zonation a littoral zone shallow water near shore sunlight penetrates to bottom b limnetic zone sunlight water beyond the littoral supports plankton communities c profundal zone perpetually dark water below the limonite zone 4 seasonal changes in temperate lakes a spring overturn mixing surface water with deep water caused by winds blowing across the lake creating vertical currents b epilimnion by midsummer sunlight heats the top layer of the limonite zone c hypolimnion in the deep water of the lake s profundal zone temp remains near 4degreesC d thermocline at the boundary between the epilimnion and the hpolimnion water temps changes abruptly over a narrow depth range e autumn overturn winds mix water vertical once again during this and dissolved gases and nutrients are equalized at all depths 5 trophic nature of lakes a oligotraphic lakes poor in nutrients and organic matter but rich in oxygen b eutrophic lakes rich in nutrients an organic matter 7 marine environments a pelagic province water 1 includes neritic zone shallow water above the continental shelves 2 oceanic zone deep water beyond them b benthic province bottom sediments 1divided into intertidal zone shoreline that is alternately submerged and exposed by tides 2 abyssal zone bottom sediments that lie permanently below deeper water c estuaries form where rivers meet the sea 1 estuaries coastal regions where seawater mixes with freshwater 2 salt marshes tidal wetlands dominated by emergent grasses and reeds many estuaries are bordered by this d rocky and sandy coasts experience cyclic periods of exposure and submergence e light penetrates the shallow water over continental shelves and oceanic banks 1 coral reefs the warm but nutrient poor water above continental shelves if often occupied by this f the open ocean photosynthesis occurs only in the sunlit upper layers 1 nekton consumers that can actively swim against the currents such as squids fishes marine turtles and whales g the benthic province includes the rocks and sediments of the ocean bottom 1 benthos species living in and on the bottom are collectively called this Ch 53 Population Interactions and Community Ecology Ecological Community An assemblage of species living in the same place 1 Population lnteractions usually provide benefits or cause harm to the interacting organisms a coevolution produces reciprocal adaptations in species that interact ecologically 1 coevolution the evolution of genetically based reciprocal adaptations in two or more interacting species a some are simple like interaction between predator vs prey b predation and herbivory define many relationships in ecological communities 1 predation the interaction between predatory animals and the animal pretty they consume 2 herbivory the interaction between herbivorous animals and the plant they eat 3 adaptations for feeding a carnivores sensory systems to locate animal prey herbivores comparable adaptations for locating and processing their food plants b species only eating one type of food are called specialists while eating more types are generalists c optimal foraging theory predict that an animal s diet is a compromise between the costs and benefits associated with different types and sizes of food d food abundance affects food choice 4 defenses against herbivory and predation a plantsampanimals have evolved mechanisms to avoid being eat some plants even increase production of toxic compounds in response to being eaten b cryptic coloration evolved appearance that provides passive defense helps some pretty blend in with their surroundings c aposmematic coloration poisonous or repellant species often advertise their unpalatability with bright contrasting patterns d mimicry in which one species evolves an appearance resembling that of another e batesian mimicry 1 the mimic a harmless species resembles an unpalatable or poisonous one the model f mullerian mimicry two or more unpalatable species share a similar appearance c interspecific competition occurs when different species depends the same limiting resources 1 interspecific competition competition between specifies a interference competition individuals of one species harm individuals of another species directly b exploitative competition two or more populations use the same limiting resource 2 competitive exclusion principle populations of two or more species cannot coexist indefinitely if they rely on the same limiting resources and exploit them in the same way 3 ecological niche a tool for visualizing resource use and the potential for interspecific competition in nature a we define a population s niche by the resources it uses and the environmental conditions it requires over its lifetime b fundamental niche range of conditions and resources that it can possibly tolerate and use from itssssss c realized niche the range of conditions and resources tha tit actually uses in nature 4 evaluating competition in nature a two phenomena provide indirect evidence that interspecific competition in the past probably fostered evolution the first is b resource partitioning the use of different resources in different ways by species living in the same goddamn place c character displacement allopatric populations are morphologically similar and use similar resources but sympatric populations are morphologically different and use different resources d in symbiotic associations the lives of two or more species are closely intertwined 1 symbiosis species with a physically close ecological association there are three types which areeeeeee 2 commensalism one species benefits and the other is unaffected rare in nature 3 mutualism both partners benefit extremely common between plant species and animal species 4 parasitism the parasite using the host in a way that is harmful to the host one feeds on another but not quickly bc a dead host doesn39t have nourishment a endoparasites tapeworms and other parasites that live within a host nasty b ectoparasites leeches and other shitty ass parasites that feed on the exterior of a host c parasitoids the feeding habits of these motherfucking insects fall somewhere between true parasitism an predation 2 the nature of ecological communities a most ecological communities blend into neighboring communities 1 species composition the particular combination of species that occupy the site Clements believed that once a mature ass community was established this was at equilibrium a according to Clement s interactive hypothesis species that typically occupy the same communities should always occur together b according to Gleason s individualistic hypothesis each species is distributed over the section of an environmental gradient to which it is adapted 2 ecotones borders between adjacent communities are often wide transition zones 3 community characteristics a the growth forms of plants establish a terrestrial community s overall appearance b foundation species moderate the abiotic environment within a community 1 foundation species one common species define the nature of a community by creating locally stable environmental conditions c communities differ in species richness and the relative abundance of species 1 species richness the number of species that live within them communities differ greatly in this 2 relative abundance commonness within every community populations differ in this 3 some communities have just one or two dominant species represent a majority of the individuals present 4 species diversity species richness and relative abundance together d feeding relationships within a community determine its trophic structure 1 trophic levels defined by the feeding relationships among its species a primary producers photosynthetic organisms the first trophic levels 1 often described as autotrophs plants are dominant primary producers in terrestrial communities b animals by contrast are consumers c herbivores 2nd trophic leve are primary consumers d carnivores that feed on herbivores are 3rd trophic level secondary consumers e carnivores that feed on OTHER carnivores savage are fourth trophic level tertiary consumers f omnivores feed on several trophic levels g detritivores earthworms and vultures ingest dead organisms digestive wastes and cast off body parts h decomposers small organisms such as bacteria and fungi feed on dead or dying organic material i heterotrophs all the consumers in a community acquire energy and nutrients by eating other organisms or their remains 2 food chains a portrait of who eats whom food web a set of interconnected food chains with multiple links 3 food web analysis acommunity s stability its ability to maintain its species composition and relative abundances when environmental disturbances eliminate some species fro the community 4 effects of population interactions on community characteristics a interspecific competition can reduce species richness within communities 1 bc it can cause the local extinction of species or prevent new species from becoming established in a community b predators can boost species richness by stabilizing competitive interactions among their prey by reducing the populations sizes of their prey 1 a strong interaction qualifies if the interaction between two species affects other species as well 2 keystone species those that have a greater effect on community structure than their numbers might suggest c herbivores may counteract or reinforce competition among their food plants 5 effects of disturbance on community characteristics a frequent disturbances keep some committees in a constant state of flux prevent some communities from ever reaching any kind of equilibrium b moderate levels of disturbance may foster high species richness 1 intermediate disturbance hypothesis composed by Connell in 1978 species richness is greatest in communities that experience fairly frequent disturbances of moderate intensity a communities that have intermediate disturbance contain a rich mixture of species thus recover from disturbances more readily 6 ecological succession responses to disturbance a succession begins after disturbance alters a landscape or changes the species composition of an existing community 1 primary succession begins when organisms first colonize terrestrial habitats without soil 2 climax community relatively stable late successional stage dominant agitation replaces itself and persists until an environmental disturbance eliminates it 3 secondary succession occurs after existing vegetation is destroyed or disturbed by an environmental disturbance such as a fire storm or human activity 4 aquatic succession debris from rivers and run off accumulates in a body of water causing it to fill in at its margins pondswamp inhabited by plants give it enough time may become a meadow or forest b community characteristics change during succession 1first species composition changes rapidly in early stages but slowly in late stages of succession 2 second species richness increases rapidly during the early stages bc new species join the community faster than resident species become extinct 3 third in terrestrial communitites that receive sufficient rainfall the maximum height and total mass of the vegetation increase steadily as large species replace small ones 4 succession can be in plants AND animals c several hypotheses help to explain the processes underlying succession 1 facilitation hypothesis species modify the local environment in ways that make it less suitable for themselves but more suitable for colonization by species typical of the next successional stage 2 inhibition hypothesis new species are prevented from occupying a community by whatever species are already present 3 tolerance hypothesis asserts that succession proceeds because competitively superior species replace competitively inferior ones 4 disclimax community disturbance inhibits successional change establishing a disturbance climax 7 variations in species richness among communities a many types of organisms exhibit latitudinal gradients in species richness 1 for many but not all plant and animal groups species richness follows a latitudinal gradient with most species in the tropics and a steady dalliance in numbers toward the poles 2 hypotheses historical explanations for the origin of high species richness in the tropics focus on ecological explanations for the maintenance of high species richness in tropics b equilibrium theory of island biogeography MacArthur and Wilson sought to explain variations in species richness on islands of different size and different levels of isolation from other landmasses 1 hypothesized that the number of species on any island was governed by the immigration of new species and the extinction of species already there 2 as the number of species on the island incrase so does the rate of extinction bc there are more that can go extint and as species increases competition and predatorprey interactions can reduce population 3 large islands have lower extinction rates because they can support larger populations and provide a greater range of habitats and resources Ch 54 Ecosystems 1 modeling ecosystem processes a biogeochemical cycles virtually all the nutrients that will ever be available for biological systems are already present on earth and they are constantly recycled between the abiotic and biotic components of ecosystems in what ecologists describe as this b food webs illustrate the transfer of energy and nutrients among organisms 1 grazing food web includes the producer herbivore and carnivore trophic levels 2 detrital food web includes detritivores and decomposers c compartment models describe nutrient cycling track the movement of nutrients between food webs and abiotic reservoirs 1 nutrient molecules and ions are either available move rapidly or unavailable move slowly and present in either organic or inorganic material d simulation models predict the effects of perturbations on ecosystem processes to understand how an ecosystem will respond to specific changes 2 energy flow and ecosystem energetics a sunlight provides the energy input for practically all ecosystems 1 gross primary productivity the rate at which producers convert solar energy into chemical energy 2 net primary productivity whatever chemical energy remains after deducting the energy devoted to cellular respiration 3 standing crop biomass the total dry weight of plants present at a given time don t confuse an ecosystem s productivity with this b primary productivity varies greatly on global and local sales 1 limiting nutrient in every ecosystem one nutrient inevitably runs out before the supplies of other nutrients are exhausted the element n short supply is called this because its absence limits productivity 2 productivity is high in near shore ecosystems sunlight can penetrate nutrient rich waters and is low in open waters of large lake or ocean bc sunlight only penetrates upper layers and nutrients sink to bottom c some energy is always lost before it is transferred from one trophic level to the next 1 secondary productivity as energy is transferred from producers to consumers some is stored in new consumer biomass called this 2 ecological efficiency the ratio of net productivity at one trophic level to net productivity at the trophic level below it a harvesting efficiency is the ratio of energy content of food consumed to the energy content of food available b assimilation efficiency is the ratio the energy absorbed from consumed food to the food s total energy content c production efficiency is the ratio of the energy content of new tissue produced to the energy assimilated from food d overall ecological efficient of most organisms is between 5 and 20 percent d ecological pyramids illustrate the effects of energy losses 1 ecological pyramids the inefficiency of energy transfer from one trophic level to the next has profound effects on ecosystem structure and are illustrated in these diagrams 2 pyramids of energy tragically have wide base and narrow tops because each trophic level contains on average only about 10 percent as much energy as the trophic level below it 3 pyramid of biomass the progressive reduction in productivity at higher trophic levels usually establishes this a biomass at each trophic level is proportional to the chemical energy temporarily stored there 4 turnover rates the rate at which the population can grow e consumers sometimes regulate ecosystem processes in a trophic cascade predator prey effects that reverberate through the population interactions at two or more trophic levels 1 consumers may sometimes influence rates of primary productivity especially in ecosystems with low species diversity and relatively few trophic levels 3 nutrient cycling in ecosystems a atmospheric cycles vs sedimentary cycles b the hydrologic cycle the cycling of water recirculates all the water on earth with water molecules moving from the ocean into the atmosphere to the land through freshwater ecosystems and back to the ocean 1 evaporation precipitation reentering to ocean 2 maintains its global balance because totally amount of water that enters atmosphere is equal to about that falls as precipitation c the carbon cycle carbon enters food webs when producers convert CO2 into carbs heterotrophs get carbon by eating other organisms or detritus a common atmospheric pool of CO2 creates this 1 the largest reservoir of carbon is sedimentary rock such as limestone or marble unavailable inorganic compartment d the nitrogen cycle moves nitrogen between the huge atmospheric pool of gaseous N2 and several much smaller pools of nitrogen containing compounds in soils marine and freshwater ecosystems and living organisms and depends on the activity of diverse microorganisms 1 nitrogen fixation molecular N2 is converted into ammonia NH3 and ammonium ions NH4 2 ammonification converts organic nitrogen into NH3 which dissolves into NH4 that plants can assimilate some NH3 escapes into atmosphere as gas 3 nitrification produces NO2 nitrites which are converted by other bacteria to useable NO3 nitrates all of these compounds are water soluble 4 under conditions of low oxygen availability denitrification converts nitrites or nitrates into nitrous oxide N20 and then into N2 e the phosphorus cycle includes a large sedimentary reservoir 1 phosphorus is crucial for construction of nucleic acids 2 phosphorus cycle weathering and erosion carry phosphate ions from rocks to soil and into streams and rivers which eventually transport them to the ocean some enters marine food webs but most of it precipitates out of solutions and accumulates for millions of years as insoluble deposits 4 human disruption of ecosystem processes a our use of combustible energy sources has disrupted the carbon cycle pg 1246 1 greenhouse effect greenhouse gases foster the accumulation of heat in the lower atmosphere a warming action known s this which prevents earth from being cold and lifeless 2 BUT the increase in the atmospheric concentration of CO2 is causing global climate change caused by burning of fossil fuels and wood b human activities have altered the nitrogen cycle 1 primarily through the use of nitrogen containing fertilizers farming and processing of livestock and combustion of fossil fuels
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