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Ecology Biol 121

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University of British Columbia
BIOL 121
Carol Pollock

Thinking Like A Biologist January-08-14 1:31 PM Ch 1. 1.5 Doing Biology • Theories good b/c explain fundamental aspects of nature • Considered correct b/c withstand extensive testing Introduction to Hypothesis Testing • Two step process 1. State hypothesis clearly and list predictions it makes 2. Design observational/experimentalstudy capable of testing prediction • Food CompetitionHypothesis ○ Longer neck giraffe can reach food unavailable to other species + short neck giraffe ○ Resulted in longest-neckedpopulation to survive better and produce more young ○ Long necks are adaptions, increase fitness of giraffes during food competition ○ Natural selectionoccurred long enough to change population as a whole ○ Prediction:  Neck length variable among giraffes: studies confirm  Neck length heritable: not testable, accepted assumption  Giraffes feed high in trees, more in dry season when threat of starvation high: both male and female spend most of time eating from 60% of full height • Sexual CompetitionHypothesis ○ Based on idea that longer-necked giraffes ale to strike harder blows during combat (for mating purposes) ○ If neck length inherited,average length should increase over time due to sexual competition ○ Long neck are adaptions,increase fitness of males during competition for females ○ Studies shown long-necked males more successful in fighting • Both hypothesiscould be correct, but must be tested rigorously Introductionto Experimental Design • Experimental design allow researchers to test effect of single, well-defined factor on particular phenomenon • Good scientific hypothesis make testable predictions(can be supported/rejectedby collecting and analyzing data) • Null hypothesis: what we should observe when hypothesis is incorrect • Pedometer Hypothesis ○ Use leg movement to gage distance from nest by tacking number of steps taken and stride length  Taking into account angles and stride length ○ To test: 1. 3 test groups w/ 25 ants 1. 3 test groups w/ 25 ants a. Stumps (cutting lower legs of some) b. Normal (normal legs) c. Stilts (gluing pig bristles onto legs) 2. Recorded travel distance before ants make 180° turn back 3. Results a. Stumps: 5m short b. Normal: 10m correct c. Stilts: 5m too far • Second test done to control for possibility that manipulation itself (not leg length) affected behaviour of stilts and stumps ants Important Characteristics of Good Experimental Design • Control groups ○ To check for other factors that might influence outcome ○ Typically 2 groups: a. Normal (unmanipulated) b. Manipulated • Experimental conditions must be constant or equivalent as possible • Essential to repeat tests ○ Larger sample sizes, testing many individuals ○ Reduces outliers/unusual circumstances in data • Biologist practice evidence-baseddecision making using experimental/observation evidence to decide which hypothesis supportedby data Introduction to Ecology January-10-14 7:45 PM Ch. 50 50.1 Levels of Ecological Study • To understand why organisms live where they do and in what numbers • For main levels of Ecology 1. Organisms 2. Populations 3. Communities 4. Ecosystems Organismal Ecology • Exploring morphological,physiological, behavioural adaptions that allow survival in an area • How individuals interact w/ physical surrounding and other organisms • How cope with transitions, which get best nests/lay most eggs/ most successful in fertilizing Population Ecology • Focus on how number of individuals in population change over time • Population:group of individuals of same species living in same area at same time • Factors affecting population size help assess impact of dams, climate changes, harvest levels, or other protection efforts CommunityEcology • Nature of interaction between species and consequences of interactions • Community:species that interact w/ other species within particular level • Predation, parasitism, competition,groups response to fires/flood/disturbances EcosystemEcology • How nutrients and energy move among organisms and through surrounding atmosphereand soil or water • Ecosystemconsists of all organisms in region w/ abiotic components. • Ex. Impact of pollution and increase temperature on distribution and abundance of species How do Ecologyand Conservation Efforts Interact? • Conversationbiology: effort to study, preserve, and restorethreatened population, communities,and ecosystems • Ecologist:how interactions between organisms and environmentsresult in particular species found in particular area at particular population size Research 50.1 Future of Canada's Lakes and Wetlands • "Current protectionapproach relies too much on recoveryand treats problems in isolation", David Schindler • Eutrophication:result of over-fertilizationof lake waters leading to excessivegrowth of phytoplankton and aquatic plants, depletion of oxygen in deep waters, neg changes in animal population • Divide lake into 2 ○ Lake 1: Fertilized w/ nitrate, sucrose, no phosphate Result: unchanged   Result: unchanged ○ Lake 2: Fertilized w/ nitrate, phosphate, and sucrose  Result: became highly eutrophic • Retested experiment ○ Added nitrate, phosphate, and sucrose which caused algae bloom ○ Reduced phosphate levels and lake recovered • Slight decrease in pH can decrease lake biodiversity Ch. 50.5. Biogeography: Why are Organisms Found Where They Are? • Biogeography:study of how organisms distributed geographically Abiotic Factors • Due to fitness trade-offs, organisms are adapted to limited sets of physical conditions (temp, moisture,etc) • Biologist examine historical and biotic factors in addition to physical conditions present ○ Temperatureincrease The Role of History • Dispersal: movementof an individual from place of origin to where lives and breeds as an adult ○ Method of studying species range ○ Missing species in particular areas may be due to physical barrier (glacier, mountain, etc) • Wallace Line: Barriers to dispersal ○ Biogeographical demarcation which separates species w/ Asian and Australian affinities despite similar biome ○ Caused by deep trench in ocean, landforms on either side isolated • Humans as Dispersal Agents ○ Airplane passengers ○ Transportation of thousands of plants, birds, insects, and others • Exotic and Invasive Species ○ Exotic species becomesinvasive species if introduced and spreads rapidly, eliminating native species. Biotic Factors • Distribution of species limited by biotic factors • Biotic factors: interactions w/ other organisms ○ Ex. Townsend's warblers attack hermit warblers and evict from breeding territories ○ Moth laying eggs only in yucca plants so not exist outside of yucca range Biotic and Abiotic Factors Interact • Role of Fire in Cheatgrass's Spread ○ Fire abiotic factor that kills shurbs allowing cheatgrass to grow ○ Fire doesn't affect cheatgrass 1. Cheatgrass annual, no living tissue exposed once growing season is over 2. Seeds sprout readily in soil depleted of organic matterby fire • Roll of Overgrazing in Cheatgrass's Spread ○ Grazed on bunchgrass until died, stomped on blacksoil so no nitrogen ○ Cheatgrass shades out black soil crust organisms, decreasing nitrogen to bunchgrass ○ Can competewith bunchgrass successfully Cheatgrass palatable and nutritious for shorter periods, so detrimentalto herbivores ○ Cheatgrass palatable and nutritious for shorter periods, so detrimentalto herbivores ○ Expansion of cheatgrass increase frequency and severity of fires Research 50.1. Insect Outbreaks Contribute to Climate Change? • Mountain pine beetle, Dendroctonus ponderosae, attack lodgepole pine tress • Bluestain fungus used by MPB invade tree's phloem and xylem and kill/damage trees • Due to global warming, cold winters and forest fires are unable to limit population of MPB; hot, dry summers weaken trees • Forest will change from carbon sink to greenhouse gases due to increase of CO2 Biome and Abiotic Environment January-13-14 8:46 PM Ch. 50.3. Types of Terrestrial Ecosystems • Biomes: Major groupings of plant and animal communitiesdefined by dominant vegetation type • Dependant on climate and weather ○ Temperaturecritical with enzyme optimal efficiency (narrow range) + moisture availability ○ Moisture necessary for life ○ Sunlight required for photosynthesis ○ Wind to exacerbates effects of temp and moisture+ physical impact by pushes birds + insects around • Biomes developmentgoverned by: 1. Average annual temp and ppt 2. Annual temp and ppt variation i. Amount of variability of head and ppt structures as much as water depth and flow rate structure aquatic environment • Net primary productivity(NPP): total amount of carbon fixed per year minus amount oxidized during cellular respiration ○ Represents organic matter available for food for organisms ○ NPP maximizedon land when temps warm and wet ○ Stomata:pores found in epidermis of leaves open for CO2 • Biomass:fixed carbon consumed for energy not growth produces biomass • Above-ground biomass: total mass of living plants, excluding roots Arctic Tundra • Throughout arctic regions of Northern Hemisphere and Antarctica (not covered in ice) • Low species diversity, low productivity, low above-ground biomass • Soil in permafrost (perennially frozen state), covered with plants/lichens, insect abundance can be high • Temperature:growing season 10-12 weeks at most, below freezing throughout rest (5- -30°C) • Precipitation:extremelylow. Due to low evaporationrates, artic soil saturated year-round (Average 3cm~) • Vegetation:treeless due to short growing season. Woody shrubs (willows,birch, blueberries) Subtropical Deserts • 2 distinct locations: 30° latitude from equator, south and north • Temperature:vary significantly but never fall below freezing (35-11°C) • PPT: low ppt (7.5cm average) • Vegetation:widely spread plants (competitionfor water) ○ Growing at low rate year-round/breakdormancy and rapid growth during rainfall Ch. 50.4. Role of Climate and Consequences of Climate Change • Climate change: Due to rising [CO2] Global Patterns in Climate • Why are the tropics wet? ○ Hadley cell: major cycle in global air circulation responsible for making Amazon River basin wet and Sahara Desert dry  Air rises above equator. Adiabatic cooling occurs  As rising air cools, water retention ability decreases. Water vapour cools, water condenses  Cycle continues, as old air gets pushed poleward  Gets cool enough to sink eventually, and as absorbs moreand more solar radiation as it sinks  Warmer air has higher water-holding capacity so 30° away from equator is dry and warm Why are Tropics Warn and Poles Cold? • Regions at or near equator receive much more sunlight per area thus much more energy of heat • Angle of sun directly overhead of equator and at angle as movetowards poleward • Result of earth's spherical shape What Causes Seasonality in Weather? • Seasons: regular, annual fluctuations in temp, ppt, or both • Incline due to earth tilting affects facing of sun Mountains and Oceans: Physical Features have Regional Effects on Climate • Br
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