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Department
Biology
Course
BIOL 1010
Professor
gilliangass
Semester
Fall

Description
ecology is the study of relationships -i.e. organism-organism or organism-environment relationships -types of ecology: -population: 1-2 species -community: many species & interactions between them -ecosystem: living and non-living (communities and abiotic environment) landscapes connected to ecosystems -Biomes- ecosystems connected together (largest ecosystem) theory- broader explanation supported by a large body of evidence use theory to solve problems (Evaluate consequences of human activities on species) -wildlife and resources management -pest control -environmental issues skills in ecology -observations in nature -design of experiments -mathematics goals in ecology -to understand how nature works and explain patterns -to use that understanding to solve problems and make predictions what effects/influence distribution and abundance abundance of a species ** i.eSnowshoe hair are generally higher than the lynx -ecologists aim to know why abundances are the way they are -the change in abundance over time is studied by ecologists ** similar distribution- lynx dependant on hare (organism to environment) -need same habitat and similar temperature (prey and predators in same spot) distribution of species ** i.e. barnacles are always found higher than muscles, why? -distribution can be few or many ** i.e. tropical forests have many more species than boreal forests, why? -broadleaf forest have cool winter, and warm hot humid summer -boreal forest have long cold winters and short warm summer (conifers- seeds in a cone-needles stay on all year) -when you know about the climate you can predict the type of plants and animals ecotone- transition zone between biomes -why so few trees? Not too dry, grazing (disturbance) natural process Disturbance (fires keep trees down and grazing) grass is dominant here because it is adapted. Helps new grasses generate quickly explanations -current interactions (species-species or species-environment) 1 -evolutionary history Forest Biomes Northern coniferous-largest terrestrial biome on earth Found-northAmerica and Eurasia Climate-30-70 cm and periodic droughts -cold winters (-50) warm summers (20) main plant type- cone baring trees (prevent too much snow breaking their branches) temperate broad leaf –found- northern hemisphere and aroundAfrica andAustralia climate- rain fall high in all seasons -warmer winters (0) hot summers (35) and humid main plant type- deciduous trees (drops leaves before winter) tropical forest- found- equator climate rain fall highly seasonally with 6-7 dry months -high year round (25-29) main plant type- canopy trees (competition for sunlight) grass biomes temperate grassland - southAfrica climate- dry winter wet summer -cold winters (-10) hot hot summers (30) main plant type- grasses and forbs (grazing) savannah –found- equator climate- rain seasonal 8-9 month dry period -warm year round main plant type found –scatter trees (thorny) dry biomes desert-found north centralAsia climate-low rain fall -vary seasonal (-30-50) main plant type- cacti (deeply rooted shrubs) plants with water storage tundra- found- arctic climate- 20-60 cm rain fall cold winters (-30) cool summers (10) main plant found –herbaceous (mosses grass and forbs) ecological applications -wildlife management – hunting limits -pest control – disease and agriculture -environmental issues – to evaluate the consequences of human activities -conversation – biodiversity, habitat preservation, and species at risk Population growth: -concepts of size, density, distribution -exponential growth model population size changes 2 -no population stays the same size -growth can be positive or negative -there are 200 guanacos in the study area -assume half are females -population size N = 100 -we focus only on females because they are important in output -as long as there are a few males around, ignore them ΔN = change in population size, N population Δt = time interval ΔN/ Δt = change in size per unit time (slope of the graph) -this rate depends on births, deaths, immigrants and emigrants ΔN/ Δt = B – D + I – E -but really, very few I or E, so we simplify to ΔN/ Δt = B - D births b=per capita birth rate b=B/N deaths -D = 20/yr (of females) ΔN/ Δt = B – D ex. = 25 – 20 = 5 -population grew by 5 females this year -next year, N = 105 females per capita birth/death rate -B = 25, N = 100, how many offspring per female? (b) B = b N, so b = 25/100 = 0.25 r- rate of increase ΔN/ Δt = rN Exponential growth equation N = Nte 0 rt r varies with the environment -if there is a high rainfall one year, there is probably better food growth, leading to a higher birth weight and better survival. ▯ higher r b>>m -birth and death depend on environment -negative r means that the population declines -r = 0 means the population stays the same -how long for population to double in size? Ln2= r t distribution -can be uniform, random or clumped (most common) -can influence population growth *** desert locusts have clumped populations 3 -herbivores -eat their own body weight in plants everyday -have caused many problems -most recently crop losses of $2.5 bil in WestAfrica in 2003-2004 -density varies greatly from year to year – not stable at all -what causes outbreak? high population growth rate heavy rainfall ▯ new vegetation (higher r) ▯ clumping (higher local N) / higher survival and births ▯ higher local densities ▯ gregarization low density locusts high density locusts (gregarious) -pale green -stronger colours -fly alone at night -fly in swarms during the day -do not like to associate with other locusts -smaller -develop faster How does gregarization work? Mechanical stimulation -if young locusts are poked, they think they are being jostled and change -behaviour can change within hours -colour change at next moult -transmitted to offspring why is gregarization bad? -gregarious juveniles form hopper bands and move across countryside -eat everything in their wake, destroying vegetation gregarization ▯ higher mobility ▯ more food ▯ higher r ▯ even higher N what ends the outbreak? -no more food -rains end, no new vegetation, or locusts have eaten everything -low N: locusts return to solitary form -r becomes negative -now aided by human control effects, i.e. pesticide spraying Limits to population growth Why does population growth slow down? -food/space is limited -resources set the limit -the limit to the number of individuals an environment can support is the carrying capacity, represented by K -intraspecific competition (between individuals of different species) -with a few individuals and lots of resources ▯ fast pop growth -w many individuals and not enough resources ▯ pop growth slows Logistic Growth model dN/dt = rmax(K-N)/K where the (K-N)/K part is the effect of competition -starts as exponential but levels off at K (carrying capacity) -russian sea otter population has stopped growing -thin mothers have high pup mortality 4 effect of competition -if N ~ 0, (K-N)/K ~ 1, acts like exponential growth -if N ~ K, (K-N)/K = 0 and population is not growing -if N > K, population growth is negative -as K increases, final pop size can increase -if r is increased, growth rate increases but still levels off at K -what determines K? -resources (food, water, space) density-dependent population regulation (birth rate) -growth is fast at low densities, slows at high densities, levels off at K (N=K) -birth rate could be declining at density increases -density dependent growth rate: females have more offspring on average when there are more resources available -density dependent death rate: death rate is higher when population is larger because of fewer resources available -population at eqbm when birth rate = death rate (r=0) – intersection of birth rate and death rate graphs modeling for density dependent growth dN/dt= rN (K-N)/K Life History Patterns -organisms vary in fecundity (potential reproductive capability) -species vary in rmax– it depends on # of offspring and generation time - why such variation? Different evolutionary strategies to maximize fitness (contribution an individual makes to the gene pool of next generation) -does this maximize the number of offspring? Only if the offspring are likely to survive and reproduce life history strategy -way of maximizing fitness -organism cant have both quality and quantity – energy is limited -organisms end up having many low quality offspring (r-strategy) or few high quality offspring (K-strategy) r-strategists K-strategists -strategy is to maximize # of offspring -strategy is to maximize offspring survival by -reproduce while young, and grow/mature fast providing food and defence -small offspring -reproduce later in life -no parental care -large offspring -tend to be invaders/colonists, and poor -provide parental care competitors -tend to be good competitors -survivorship curve - concave up (III) -survivorship curve – concave down (I) -found in unpredictable environments -found in stable environments Type I survival curve -k strategy -produce few offspring and most young survive Type II survival curve -linear -same probability of dying no matter how old you are -i.e. songbirds 5 Type III -r strategy -produce many offspring most die early Demography -in an age structure pyramid different ages are represented -certain age groups have higher probabilities of reproduction (25-35) -certain age groups have higher probabilities of dying human population growth -boomers (echo babies from boomers) -invention of agriculture caused a little bump -population explosion in the last few years (faster than exponential) -projected 9.4 billion by 2050 (growth rate of 1.2%/yr expected to slow) world statistics from 2002 -N = 6000 million, B = 133 million/yr, D = 56 million/yr -delta N = 133 – 56 = 77 million/year -per capita rates: b = 0.021, d = 0.09, r = 0.012 (pop increased by 1.2%/yr) how do we stop growth? -make b = d -birth rate depends on age structure: more females of reproductive age, more babies, higher b -to balance deaths, each female should have 2.1 children (TFR=total fertility rate) (but pop in Canada is still growing because of immigration) -what if world achieved 2.1 now? would keep growing for awhile and then level off, because all of the children (lots in some countries) now would have to have their 2.1 children before the age structure stabilizes -in the last 20 years Canada has had low birth rate w few young -in contrast Zimbabwe has had a high birth rate caused by past births -world population growth is slowing -but population still growing because r > 0, and young age structure from the text: Global Carrying Capacity (p. 1155 – 1156) -how many humans can the world support? Is there a K for humans -average estimate of carrying capacity is 10-15 billion -determined by logistic curves, generalizations from existing areas of high density multiplied by total habitable land, limiting factors such as food – all estimates require many assumptions ecological footprint -land & water area needed by each nation to produce all resources it consumes and to absorb all wastes produced -types of ecological production areas: arable, pasture, forest, ocean, built-up land, fossil energy land -about 2 ha per person – conserving some land for parks etc, more like 1.7 -when graphed, it shows that countries vary greatly in their individual footprint size and available ecological capacity – US over carry capacity, New Zealand below carrying capacity -when study conducted, world was already in ecological deficit -we are now at or slightly above carrying capacity 6 what will limit us in the future? -food? Environments can support herbivores better than meat-eaters -suitable space? -non-renewable resources? Metals, fossil fuels, water -capacity of environment to absorb wastes -technology will not allow us to grow indefinitely Aquatic biomes Depth matters-light place to attach and temperature Photic (top layer) Pelagic (over laps with photic and goes down deep in ocean) Benthic (under the pelagic) Thermocline- zone of rapid temperature change -water max density at 4degrees summer and winter have a thermocline fall and spring it circulates Types: Competition (-/-), Predation (+/-), mutualism (+/+), commensalism (+/0) Interspecific competition (- -) -between different species -occurs over a resource in short supply -resource shortage results in lower birth rate, slower growth, higher death rate – overall, effect of competition is a slower population growth -can lower densities and limit distributions -can eventually eliminate a species ** i.e. intertidal barnacles -barnacles close up until tide comes in, have free-swimming larvae -two types: balanus (large), chthalamus (small) -chthamalus is only found in higher region (excluded from lower shore by interspecific competition) -balanus is only found in lower region (excluded from upper shore from physical factors) -when they are young, there is an overlap in regions – something must happen between where they are as young and where they settle -removal experiment was performed 1 -in the lower (bal) region, all the bal was removed, and chthamalus was successfully settled there -when bal was present in that region and chth was introduced, all the chth disappeared after some time -conclusion can be made that bal excludes chth from lower shore 2 -in the higher (chth) region, bal died both when chth was present and when it was removed -this points to a physical reason for bal being excluded from upper shore -this is because chth can close up very tightly, so it can be out of water for a longer period of time, whereas bal cant ** i.e. coral reefs (found in clear shallow tropical waters –few nutrients) -corals in decline because they are in competition with algae for space 7 -algae overgrows coral and kills it why is algae winning now? -nutrient addition: sewage, erosion – nutrients favour algae -warming: increase in coral disease (white syndrome, black band disease), coral bleaching – these give advantage to algae, warm water temperatures -fishing: fish stocks greatly reduced, and fish prey on algae -symbiosis –living together (coral polyps feed on plankton) -zooxanthellae inside coral cells (outer layer) –corals die without it -zooxanthellae help coral by producing organic molecules -coral help zooxanthellae by providing safe place to live, chemicals used by zoox and coral gets rid of harmful oxygen food webs show trophic interactions (humans on top now whales used to be) -have 3-5 chain lengths marine have longer food chains energetic, dynamic stability, carnivore size predation / other (+/-) interactions -predators: (animals) eat more than one prey, kill prey -herbivores: eat parts of plant, don’t kill the plant -parasitoids: (insects) have one host, consume entire host and kill it (evil) -parasites: (plants/animals) have one ore few hosts, consume part of host without killing it (not so evil) predators can -reduce prey densities -change prey behaviour -indirectly affect other species ** i.e. gray wolf -prey on mammals: large (deer/elk/moose), small (rabbits/beavers) -eliminated from much of former range by bounties, poisoning, etc -in 1926, the last wolf in Yellowstone National Park was shot -1995/96, 31 Cdn. Wolves introduced into YNP, ~30 introduced into Idaho -wolf abundance grew over the next years research was done on elk abundance -they were destroying the park -elk numbers are lower since wolves were introduced -recent analysis: wolves didn’t reduce # of elk on their own, also hunting and drought effect on aspens and willows (+) -pre-wolf: aspen groves eaten and trampled, vegetation beside streams destroyed by elk populations -post-wolf: vegetation is recovering -these effects are probably going back to the natural way it was before wolves were killed off from YNP 8 -wolves are a “keystone” species with very large impact on community structure despite low numbers species with a large impact dominant species -most abundant species or species with highest biomass -powerful control over other species -why does one species become dominant? could be most competitive, or most successful at avoiding predation or disease keystone species -not necessarily abundant in a community -exert control over other species bc of their ecological roles/niches -impact can be determined by removal experiments – i.e. mussels (mytilius californius) are dominant species, but presence of sea stars (pisaster ochraceous) removes competitive edge, allowing for other species to occur – without sea stars, biodiversity drops dramatically -another i.e. – sea otters allows kelp forests to survive by preying on the predator of kelp (sea urchins) – decline in otter population due to whales decreases kelp population and increases sea urchin population – otters are keystone species foundation species/ecosystem “engineers” -some species cause physical changes in the environment that affect the structure of the community, either through behaviour or biomass -i.e. beavers transform landscapes by felling and dam building -foundation species act as “facilitators” with + effects on survival and reproduction of other species trophic cascade- top predator influences abundance of lower tropic levels topdown control –higher trophic levels control lower levels bottom up control-lower tropic levels control higher level/abundance biomass Why do animals behave the way they do? What is advantageous of certain types of behaviours? -behaviour is a product of evolution and natural selection -those with appropriate behaviour pass on more genes -we explain it in terms of costs (fitness decreases) and benefits (fitness increases) types of social behaviours -cooperative (++) – defence, hunting, breeding -selfish (+-) – territoriality -altruistic (-+) – alarm calls, increases risk o self -spiteful (--) – wasteful killing (only in humans) evolution of behaviour -behaviour must have a fitness advantage where benefit > cost -obviously true in cooperative and selfish 9 evolution of altruism inclusive fitness -total effect on # of genes passed on due to both: -actual production of offspring by self -offspring produced by relatives thanks to your aid kin selection -selection for act that enhances reproductive success of relative Hamilton’s rule -C is the cost to altruist (lost reproduction) -B is the benefit to the recipient (increased reproduction) -r is relatedness (# of shared genes) -natural selection will favour an altruistic act if rB > C -siblings share, on average, half their genes (r=0.5) grand mother to grand daughter (r=1/4) example of Hamilton’s rule: saving drowning brother -you’re 20 years old, you/your bro will each eventually have 2 children, your bro is drowning, risk of you dying is 5% – do you save him? -B = 2 children, r = 0.5, C = risk x lost reproduction – (0.05)(2) = 0.1 -rB > C ? ▯ (0.5)(2) > (0.1)? yes. If there was a trait for saving drowning brothers, it should evolve -but if the rescuer is a poor swimmer with an 80% of drowning, rB < C, trait should not evolve -depends on relatedness (r) : full siblings r = ½, first cousins r = 1/8 -net benefit has to be higher for cousins -also depends on expected benefit – i.e. should a grown adult try to save their own parents, who aren’t going to have anymore children, and are no longer providing paternal care? Science says no. -there may be some unmeasured emotional/social benefits Animal Societies -First social interaction: gamete exchange (necessary) -Social groups: organized, fitness of individual influenced by group -Eusociality: most social groups, i.e. ants and bees living in groups -benefits: cooperating hunting and defence and breeding -costs: disease/parasites increased, competition for food, lower reproduction for some individuals (i.e. in wolf packs where only the dominant male and female reproduce) -group living will evolve where benefits > costs social Societies -only some reproduce -overlapping generations (diff ages at same time) -cooperative care of young i.e. wasps (some species), ants, bees, termites army ants (a eusocial insect) -group predators -division of labour: reproductive queen, reproductive males 10 -sterile female workers: defence, foraging, brood care, prey/brood transport Florida scrub jay (eusocial vertebrate) -live in scrub oak habitat which is fragmented & little left -territorial family groups -the helpers are mainly male, because they get territory if father dies, territory partitioned, or a neighbouring male dies -females only get territory by dispersing -dominance hierarchy: breeding pair, then male offspring by age, then female offspring -in Florida there is a limited habitat, this is why they become eusocial -the benefit from helping each other out > benefit from looking for territory naked mole-rat (eusocial vertebrate) -lives in arid habitats in the horn ofAfrica -colonies in underground burrows -in the workers, reproduction is suppressed by the queen – they are bullied, and queen produces chemicals that suppress it -most mole-rats are not eusocial -naked mole-rat habitat is dry with scarce food -individuals cannot survive alone – better to help than to leave -eusocial societies are the most developed, while not necessarily the best -found in environments where inclusive fitness for helping is greater than independent reproduction monogamous- with one for life polygamous- having multiple mates promiscuous- casual sexual relations environment influences social behaviour i.e. weaverbirds inAfrica have two habitat types: savannah and forest -in the savannah there are conspicuous nests close together, and they feed in flocks on seeds – more social – males have bright plumage, are polygamous and don’t care for their young -in the forest they are territorial (live in pairs), feed alone by hunting for insects, and hide their nests – males are dull coloured and they help care for the young - due to different environments -in savannah there is an abundance of seeds so less competition allows them feed together – females need no help feeding young so males put more energy into finding mates -in the forest there is sparse food, so territories need to be defended, and females need help to feed their young competitive exclusion principle -if species compete for one resource, better competitor eliminates other -two species cannot occupy the same niche indefinitely niches -ecological position in community -each of Macarthur’s warblers occupies a different niche -two types of niches -fundamental: where it can survive and reproduce, i.e. the range of temperatures in which a species can survive 11 -realized: where it is actually found in nature, smaller than fundamental -in barnacles, bal has equal sized realized and fundamental niches, while chth has a smaller realized than fundamental (more common) -why is the realized niche smaller? because of competition -we cannot have more species than niches -#niches limits #species in community biodiversity -species richness is equal to the number of species in a region -more niches means a higher level of biodiversity -diversity is not evenly distributed – clumps in areas called hotspots, mostly around the equatorial region -hotspot: small land area with large number of endemic or endangered -endemic species: found nowhere else in the world, i.e. beetle on Sable -in all types of species, the diversity decreases as you go north biodiversity issues -explaining patterns: why do some areas have more species? -describing unknown species Succession -sequence of changes in species after disturbance -primary succession: starts with no life -secondary succession: starts with some life primary succession -early colonists are good disperses, tolerate harshness, and change conditions by improving the soil (lichen and moss) -later colonists depend on the improved conditions -plants alter conditions for later plants -changes in soil quality most important -early species grow in poor soil, later species require better soil human disturbance -agricultural development -logging and clearing from development, mining and farming -when forests are clear-cut, weedy/shrubby vegetation can colonize the area and dominate for many years -also rainforests,Africa etc. ecological succession -something like glacier or volcanic eruption can strip away vegetation -in primary succession, only life left behind are autotrophic prokayotes -secondary succession happens when disturbance leaves soil behind -early arrivals can facilitate appearance of later species by making the environment more favourable -early species can also inhibit establishment of later species, so that when they do arrive it is in spite of the early species -or early species are completely independent of later species -when glacier first retreats soil is basic – as vegetation arrives, pH falls – especially spruce which reduces pH from 7 to 4 12 secondary succession -begins with disturbance leaving some life -forest regenerates by three mechanisms 1- colonize from outside (grasses, goldenrod) 2- germinate from seed bank (raspberry, cherry) 3- re-sprout from surviving root systems (white birch, red maple) early succession -shade intolerant species -i.e. white birch, red maple, shrubs, herbs and grasses -good dispersers, or can tolerate disturbance -fast growth, weak competitors mid-succession -red maple can’t grow in shade and can’t replace itself late succession -shade-tolerant species -i.e. sugar maple, yellow birch, beech -out compete early species by shading them -can replace themselves -poorer dispersers -slower growth -strong competitors (can tolerate shade) secondary succession species interactions -shade-tolerance causes competition for light -early species start quickly and grow, but can’t grow in their own shade -later species are stronger competitors Ecosystem -set of components that process energy and nutrients -ecosystem dynamics: flow of energy and nutrients -primary producers ▯ consumers ▯ decomposers ▯ primary producers -energy: used to produce and transform organism material • Energy gets lost in the form of heat because of metabolic activity energy capture -primary producers (autotrophs) : capture radiant/chemical energy, use it to make organic molecules -consumers & decomposers (heterotrophs) : energy from other organisms energy storage -biomass: quantity of organic material (kg/ha) -productivity: rate at which biomass is produced (kg/ha/yr) -primary – autotrophs, secondary – heterotrophs energy flow -open, one way 13 -sun ▯ primary producers ▯ herbivores ▯ carnivores ▯ detritus ▯ decomposers (with energy lost as heat at each trophic level) -energy is lost in transfer between trophic levels -i.e. caterpillar eats plant w/ 200 J – 100 to feces, 67 to respiration – 33 go to growth and is passed on to next trophic level (~17%) -some is not used at all, i.e. 17% of radiation that hits surface actually gets used -decomposition release of energy and nutrients from detritus (dead organic matter) -detritivores (decomposers) pulling nutrients back into system production efficiency -percent of consumed food converted to biomass -some taxa are more efficient – insects most at 40%, mammals least 1-3% (consumers aren’t very efficient) -trophic efficiency: percent of stored energy transferred to next trophic level pyramids -abundance pyramid: shows number of individuals (#/ha) at each trophic level – can sometimes be inverted, like when one tree feeds many insects2 -biomass pyramid: shows amount of matter (g/m ) at each level -energy pyramid: never inverted, reflects trophic efficiencies primary production -what limits? Nutrients -determined energy availabl22in ecosystem -total energy from sun (10 J/day) -varies across ecosystems (i.e. tropical forest, reefs, oceans) -difference limiting factors -terrestrial: temperature, moisture, nutrients (N) tropics very active -aquatic: light, nutrients (N, Fe in marine – P in freshwater) -engine of the ecosystem -variation is related to the environment Physical and Chemical factors limit primary production in ecosystems -amount of light energy converted to chem energy by autotrophs during a given time period is an ecosystems primary production -amount of solar radiation ultimately reaching surface of globe limits the photosynthetic output of ecosystems -only small fraction actually strikes autotrophs, only some wavelengths -of the light that reaches only about 1% is converted by photosyn -gross primary production (GPP) – total primary production in an ecosystem -net primary production (NPP) = GPP – energy used for respiration by producers (R) -NPP of more interest to ecologists -in forests NPP can be ¼ of GPP -NPP is amount of NEW biomass added in given period of time -tropical rainforests are the most productive -estuaries and coral reefs also have high NPPs but v. small area -broad leaf produce quicker than confiers biogeochemical cycles 14 -movement of nutrients through organisms and physical reservoirs -nitrogen, and sulphur -nutrients stay within ecosystems generalized schemes -abiotic reservoir where nutrients unavailable ▯ available nutrients ▯ producers ▯ consumers ▯ decomposers ▯ avail. nutrients/reservoir Nitrogen Cycle -atmosphere is a reservoir for N , w2ich is unusable in that form + -N-fixing bacteria change N ▯ N2 which 4s partly used by plants and converted to “organic N” -nitrifying bacteria change NH to 4O and NO 2 3- -plants can also use these nitrates and nitrites + -plants broken down by decomposers and the N is reverted back to NH 4 -some NO and2NO is cha3ged ▯ N by denitri2ying bacteria global N budget -115 Tg of N fixed is from pristine sources (microbes, lightning) -160 Tg of N fixed is from human input -legume crops : enhance microbial activity (N from reservoir) -fertilizers : chem process to make NO3 from N2 (N from reservoir) -fossil fuels : burning coal/oil produced NOx (from new reservoir: stored organic matter more on human input -the extra NO c2eated by fossil fuel burning is released into the atmosphere and falls back into the ecosystem or through rain -deposits back on land -fertilizers and legumes impact cropland and freshwater -fossil fuel burning impacts atmos, all ecosystems through NO depositixn -run off of nitrates from the ground takes cations like Ca and Mg along (adding to soil) -assimilation by plants uses H+ ions experiment on N-addition to fertilizer -higher N input changed the N-cycle (nitrification > assimilation) -plant growth initially increased -the soil became acidified and nutrients were lost -in the end, plant growth was lowered -eutrophication excessive growth of algae due to overload of nutrients Pristine N-cycle High N-input -NH4 system -NOx system -N is limited -N abundant, plant growth increase -tight cycling -leaky, nutrient loss, water contamination Sulphur Cycle Reservoirs -earth’s crust (in form of gypsum, CaSO4) -ocean water, soil water (SO4-2, H2S) -atmosphere (SO4-2, H2S, H2SO4) 15 Human Impact -in the atmosphere, H2S ▯ So2 ▯ H2SO4 -fossil fuels contribute more SO2 -earth crust and decomposers contribute more H2S -eventually the H2SO4 returns to water and soil by way of acid rain -this SO4-2 is returned to plants -H2S –(oxidizes)-> SO2 –(dissolves)-> H2SO4 –(photosynthesis)-> proteins –(decomposition)-> H2S -(proteins also go back to SO2) -SO2 + H2O ▯ H2SO4 (acid rain) Acid Rain -pure rain pH ~5.6 due to carbonic acid formed by CO2 -our rain pH ~ 4.5 which is much more acidic -due to SO4-2 from coal burning and NOx from cars and electricity Effect ofAcid Rain -bigger effect of acid rain is in lakes and rivers where fish, crustaceans, and aquatic insects are killed (@ Clyde river salmon are extinct) Recovery of Freshwater Ecosystems [email protected] Keji SO4 is down, pH is the same, organic acids are up -why no recovery? Less is going in but there’s still too much -also the buffering capacity is gone bc calcium is gone from ecosystem -how do we save salmon?Add lime to raise the pH Conservation Biology -use of ecological theory in conservation guidelines -the goal is a scientific basis for conservation -the target is the biodiversity crisis (we are losing species at high rate) two approaches to conserving species diversity -community/ecosystem approach – focus on habitat in hotspots (threatened habitats) -species approach – what causes species to go extinct? Genetic- maintain large populations Government -takes species approach -COSEWIC (committee on status of endangered wildlife in Canada) -extinct: gone everywhere -extirpated: gone in Canada but found elsewhere -endangered: immediate extirpation -threatened: could soon be endangered -rare: few or restricted range, but not in danger now historic extinctions -there have been three periods of mass extinction -caused by major disturbances (climate, volcanoes, asteroids) 16 -causes: the major disturbance has been humans, through habitat change, introduced species or exploitation benefits of diversity -new foods, new medicines, and new products for industry, ecosystem services habitat destruction -greatest threat right now -reduces population size by reducing habitat amount and quality (edges of a habitat are not as good as the interior of the habitat) -lower K -new declines (habitat loss, disturbance, and predation) Small PopulationApproach extinction vortex -small pop prone to positive feedback loops of inbreeding and genetic drift that draw them down a vortex toward smaller pop sizes -loss of generic variation drives this vortex -focus on small population size (k) and population growth (b and m rates) effective population size -based on breeding potential of population and not only numbers -Ne = 4NfNm / (Nf+Nm) -always some fraction of total population -need to protect reproductively active individuals small population sizes -smaller the population, higher the risk of extinction -how small is too small? Minimum viable population (MVP) -MVP is smallest population that will persist, time and probability -how do they find this? They have an average r value and a variance value – they run 10000 random graphs and see what the chance is -low variable growth rate introduced species -can cause extinctions due to predation -higher mortality rate, lower growth rate -displaced from habitat lower K overexploitation responsible for many past extinctions -higher mortality rate, lower growth rate stochastic events -population size varies from year to year BIO NOTES Cells- single cells is the lowest to be able to live Tissues- cells grouped into tissue -groups of cells similar in structure and function 17 epithelial tissue- layers of densely packed cells that sit on a base membrane -found – lining of organs and skin - helps people prevent injury - helps us retain moisture - fights off pathogens connective tissue- cells are sparsely distributed -fibers within the cells -they sit in an extr
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