Week 11: Communities and Ecosystems Flashcards
Communities, ecosystems and biomes (22 cards)
Relate the methods used to assess biodiversity, and the benefits/drawbacks of each method
Classical techniques: (quadrats, focal walks, trapping, camaras)
+ provide relative abundance
- may be biased/ labour intensive/ may need specialist
Molecular techniques: (sample soil/pond for DNA, amplify by PCR, sequence through NGS and reference known data bases)
+ Very broad sampling very quick
- may have taxa biases, only works in some env, not quantitative, requires tech base and experience
Understand, calculate and interpret summary statistics for alpha, beta and gamma diversity.
Alpha: number of species in site
Beta: variation between sites
Gamma: number of species in landscape
Relate the different forms of consumption and non-consumption interactions in a community
- C: associated with energy transfers (herbivory, predation, parasitism, decomposition), shown in food webs can be quantitative by size of arrows
specialist: eat one thing (often parasites, lock and key, tolerance/detox to plant defences)
Generalist: eat many - NC: Direct evolved interactions (symbiosis/ mutualism, mimicry, allelopathy, territorial exclusion) can modulate consumptive interactions, produce dependencies. Also indirectly allows the passing of info between species.
Define and provide examples of ecosystem engineers and keystone species.
Ecosystem engineers: creates habitat biodiversity for others through action (could be a keystone species but not always as sometimes not too rare or there is another species with a greater impact)
Keystone species: one who’s removal has in impact on community composition that exceeds its abundance (can also be EE but need to be rare also, if not they may just be the top predator)
State the filters that determine how a community forms, and relate why assembly may not be predictable
How:
- local reset events (tree falling creates new env OR human interference)
- Geophysical reset (e.g. ice age, rainfall patterns)
-Geological (tectonics, volcanic activity, glaciation)
Filters:
1. Dispersal filter: can they arrive? determines community structure
2. Environmental filter: can they live in the conditions? determines fundamental niches
3. Ecological niche: can they coexist? determines realised niche
Unpredictable:
-specific mutualist/symbiont
-altering environment
-established dominance
-narrowing realised niche
Outline, with case studies, how an understanding of community ecology underpins conservation efforts
alpha: shows regions of high value
- beta: importance of maintaining multiple sites
- gamma: both a and b help conserve g
- keystone and ecosystem engineers are more important to protect (e.g. sea otters, excess hunting caused more sea urchins causing collapse of kelp forests)
- critical limits of species loss due to loss of functional diversity
- management of rewilding to aid succession
Relate how community ecology understanding underpins microbiome dynamics and therapies based on microbiome engineering.
microbiome in human gut is a community.
bacteria interactions/bacteria phage interactions mimic predator-prey cycle
Understand concepts used to describe and explain energy fluxes in ecosystems
Ecosystem: community of organisms and the physical environment they inhabit
Includes flows and stocks of E from E transfers and nutrient cycles
organism -> population -> community -> ecosystem
Properties emerge from the level below
99% solar energy absorbed as heat
1% primary producers (respiration lost, decomposers get energy through there faeces and dead matter)
This carries on down the trophic levels
Explain energy fluxes through ecosystems
Energy captured by primary producers flows to heterotrophs but losses through respiration
Secondary Productivity – rate of production of energy or biomass or C by heterotrophs per unit area per unit time
Net Ecosystem Production
NEP = GPP – Rtotal
where Rtotal is the respiration of all organisms in the ecosystem
NEP = NPP – Rhet
where Rhet is respiration of heterotrophs
Understand the ecological and energetic basis of some current environmental problems and crises
major environmental challenges stem from perturbations to ecosystems and their processes:
climate change, food security, acid rain, eutrophication, habitat destruction
Understand how different factors limit rates of net primary productivity both on land and in water
TERRESTRIAL: (temp, water supply, soil age)
-suitable space with favourable conditions: not temp or pH
-Solar radiation: needed to control O2 and CO2 movement in and out of a plant (stomata)
- Seasonal and latitudinal variation: effects temp and solar radiation
-seasonal changes
AQUATIC: (nutrients and light)
- high NPP near surface for phytoplankton growth reduces light penetration below surface
-in summer surface water is warm and light so photosyn
-Nutrition limitation in water: Phosphate more likely to be limited than Nitrogen
Describe the fate of ingested energy using equations for assimilation efficiency, gross and net growth efficiency
TROPHIC LEVELS:
Sun -> primary producers -> Herbivores -> primary carnivores -> secondary carnivores
Detritivores: receive energy from all
Assimilation Efficiency = [(E ingested – E defaecated)/E ingested] x 100
Describe the main features of the C, N, P and S cycles and their key differences
Carbon: CO2 in atm -> photosynthesis in plant/ algae converts to carbon <-> exchange of CO2 between water and atm dissolved as HCO3- -> passed on though t and a food chains so carbon in animals -> lost in respiration and dead organic matter but can be reused not lost <- microbial respiration returns it to atm <- carbon in fossil fuels which combustion of such returns <- release of methane and its oxidation releases CO2 back to atm
Nitrogen (aquatic and terrestrial): N2 in atm ->nitrogen fixation by aquatic/soil cyanobacteria -> dissolved NH3 and NO3- -> nitrogen in tissues of algae and plants (through roots) -> food chains cause N in animals -> secrete as NH3 -> activity of denitrifying microbes return N2 to atm
Phosphate: soluble phosphates in soil (lost in drainage so then dissolve in solutions) -> phosphates in sediment -> uptake by roots then into plant tissue -> food chain so phosphates in animal tissues <- excretion and decomp returns to solution/soil
Sulphur: release of SO to atm from burning FF/ sea spray aerosols/ anaerobic respiration by sulphate-reducing bacteria/ volcanic activity
Understand the potential for biota to regulate environmental conditions by cycling elements
Understand how humans have affected the abundance and distribution of different nutrients
Understand the ecological impacts of these human-induced perturbations of ecosystem processes
- Agriculture, huge rise in livestock so more biomass and therefore more nitrogen contents in the soil
- Eutrophication (over enrichment with nutrients): fertiliser run off cause algae growth blocking off sunlight so aquatic plants die and dead matter provide food for microbes which compete for O2 and water becomes deoxidised so fish die.
- greenhouse gases: CO2 from fossil fuel consumption, methane formation from incomplete combustion. Greenhouse effect: GHGs absorb and reemit infrared radiation which heats the earth’s atm
Recognize characteristics and general distribution of biomes and key factors influencing their spatial coverage
Main determinant: CLIMATE
affects plant growth and disruption as organisms are adapted to the physical env of their biomes.
Terr: temp and moisture
Aqu: wind and currents are important
Whittaker Biome Distribution Theory: boundaries between biomes are often indistinct and wide with the main factors being ppt and temps well as other factors such as topography and soil
Describe various biome/life zone types (globally and locally)
- Tundra 8% : very little ppt, short GS as less than 0oC most the year. circumpolar treeless biome, harsh cold winters and short cool summers. Nutrient poor soil due to low organic matter and permafrost. Adp: migratory, thick fur, small leaves, low growing.
- Taiga/ Boreal forest: slightly more ppt, short GS, Avr temp still below 0. Coniferous biome, N Hem S of Tundra, Low PP due to poor acidic soil and slow decomp of organic matter and low species richness. Adp: drought tolerant evergreens, migratory, hibernation, plants have needles for less water loss
- Temperate Rainforest: quire high ppt, long GS as Avr temp above 0. nutrient poor soil with high organic matter but slow decomp, large evergreens allow high species richness so moderate PP but has been exploited for timber. Adp: plants adapted to low light under canopy.
- Deciduous Forest:
higher ppt and 15oC avr temp so long GS. Soil rich in dead organic matter and higher nutrients allows higher species richness and moderate PP. Adp: early plant flowering ground fauna as shade shade tolerance.
-Temperate Grassland:
less ppt, long growing season, moderate Avr temp. Low ppt means cannot support trees, seasonal hot summers and moderately cool winters. Herbaceous plants mean high species richness. Adp: grazing and drought tolerant plants
-Mediterranean:
moderate ppt and Avr temp and fires regulate this biome. Nutrient poor and thin soil so low PP but dense evergreen shrubs provide high species richness. Adp: nocturnal to live in low water
-Desert:
very low ppt very high Avr temp and marginal GS. lack of ppt limits growth meaning nutrient poor soil, sparse veg so very low PP. Avr: very small animals often nocturnal, succulent plants reduced leaves with deep roots and hairy protection.
-Savanna:
moderate ppt with a wet/dry season dependent GS. Fire and grazing are consumer controls. Nutrient poor soil due to leaching but grassland allows high species richness low/moderate PP
Tropical Rainforest:
very high ppt and often constant GS. Highest species richness so very high PP. Ancient nutrient poor soil as tied up in vegetation.
Understand spatial variation (gradients) in forest types (e.g., elevation, latitude, disturbance, temperature, precipitation)
Identify factors that control the ecological functioning of fresh water and oceanic biomes
Marine:
-Intertidal Zone: area between high and low tides, sandy or rocky. Large changes in temp, O2 and salinity so animals (muscles etc) are adapted to short timescale changes.
- Benthic Zone: Ocean floor from tidal to deep sea trenches. substrate often mud which supports burrowing and ecosystem engineers : SEA GRASS BEDS (10m deep and provide habitat and food in temperate/tropical waters), KELP FORESTS: (60m on rocky shores, productive and dynamic so supports diversity that rivals reefs. Arctic water), CORAL REEFS: (most diverse mainly in shallow tropical waters)
- Pelagic environment: open ocean water. NERCTIC PROVINCE (200m) organisms are floaters or swimmers, and OCEANIC PROVINCE (>200) 75% ocean and organisms depend on organic snow.
Oligotrophic: deep, clear, nutrient poor water
Eutrophic: shallower murky nutrient rich fresh water
Mesotrophic: intermediate level of nutrients
Explain how differential heating of the Earth’s surface by the sun leads to large-scale movement of air in the atmosphere and water in the oceans, helping to define the Earth’s climate
- Differential heating: Earth’s surface illuminated unevenly so different tropics/ even poles/varies with seasons. Hot at E and earth’s tilt cause variation in light and temp towards poles
- Uneven solar radiation influences wind patterns: at E ascending moist air releases moisture, away means descending dry air absorbs moisture causing desert
Ocean currents: global wind patterns and earth’s rotation shape climate on neighbouring continents
Understand how differences in climate across the globe determine which biome occurs
Holdridge life zone systems:
takes into account annual ppt, humidity, potential evapotranspiration (water that does not fall/ cannot be used) as well as latitudinal and altitudinal belts which affects temp
