biotic - living abiotic - non living. ecosystems, communities, populations, individuals. usueful for - managing resources, managing diseases, conserving biodiversity, inderstanding global warming, understanding human population growth. Things that determine distribution and abundance of species - geological & climatic history of a place, tolerance to enviromnental conditions, required resources, reproduction and death, dispersal, interactions with other organisms.
1. geological &climatic history of place determines species distrubution - the world land splitting 150mya.
2. tolerance to environmental conditions - abiotic components of environmental environments that arent consumed e.g temp, humidity, pH, salinity, heavy metals & toxins and disturbances. no competition for these. temp changes with altitude, latitude, microclimates, isoclines. activity of organisms limited by temp - diff enzymes involved in metabolic processes respond diff to temp - intermediate toxic products build up. organisms dehyrate at low and high temps: osmoregulatory problems at low, evaporation and transpiration in hot. indirect effects of temp: effects on interacting species, effects on dissolved gasses (in aquatic, low 02 conc in hot h20, effects on humidity.
correlation may be due to third factor. e.g temp - humidity - distribution range. Biomes: global variation with temp and precipitation results show distinct associations of vegetation and animals.
pH change - direct - damage cells. indirect - change availability of nutrients and conc of toxins.
salinity change - osmoregularity problems, dehydration. toxin change e.g heavy metals and toxic by-products of human activity.
abiotic factors may stimulate onset of activity e.g - period of chilling to break seed dormancy. certain temp onset reproduction, diapause and migration.
resources - biotic/abiotic components that organisms consume causing competition e.g light, water, mineral nutrients, co2, o2 and other organisms. exponential growth dN/dt = rN. abiotic challenges limit species range. available resources limit growth within suitable abiotic conditions.
autotrophs: assimilate inorganic resources and produce proteins, carbs etc e.g green plants, certain bacteria. heterotrophs : unable to manufacture own food therefore consume other organims e.g decomposers, parisites and predators
saprotrophs: derive nuitrition from dead organic matter - decomposers (bacteria and fungi) and detritivores (animal consumers of dead matter). Parasites: derive nutrition from host, but rarely kill them.
o2 availabilty depends on medium and temp. O2 conc vary in aquatic, low in slow moving water high in fast moving water. water is a key factor in influencing species distriubtion - migration or adaption.
ecological niche - n-dimensional hypervolume within which it can maintain a viable population. fundamental ecological niche - describes the overall potential of a species. realised ecological niche - descrbes part of the fundamental niche that an organism can use in the presence of competitors and predators.
exponential growth - growth with unlimited resources.
intraspecific competetion - interferance or exploitation. mortality and reproduction are density-dependent. pop growth = reproduction - mortality. K = carrying capacity - stable density usually a range of values. area between births and deaths = net requitment which gives recruitment curve. have S shaped population growth curve.
logisitc = dN/dt= rN(K-N)/N. change in pop size per individual as a function of r. assumptions: r decreases linearly as intrasepcific competition increases. carrying capactity is constant. growth will be the same whether it is a pop of young or old individuals. all unrealistic. most populations follow logisitic growth at start then declines and fluctuates.
causes of density- dependance. negative - decrease in vital rates and population regulation - predation, competition and parasitism and disease. Positive - increase vital rates. pollination and mychorrihiza (large aggregations of inidividuals to be less likely to be predated, wolves hunt better in packs, penguins stay warm.
demography and human pop growth
growth rate per individual is constant when growth is exponential and constantly decreasing when growth is logistic but in humans its been historically increasing. shows historic growth and is slowly decreasing in some populations.
demography : the study of pop size and distributions and their spatial and/or temporal changes in response in to birth, death and migration. can predict future pop change or identify critical stages.
life tables describe mortality in a pop. 1. identify important stages in the life of species. 2. count number of individuals in each age group. 3. calculate the proportion of the original pop survining to each stage (Ix). follow group of individuals from birth to death: cohort life table. observe age structure of pop at specific time : static life table.
facundity schedules: describes births in pop. 1. identify important stages. 2. count offspring. 3. calculat the individual fecundity (Mx). intrinsic capacity for increase: net reporoductive rate R0: average number of offspring produced by an individual in its lifetime.<1 pop is decreasing. =1 no change, >1 increasing. R0= sum of Ix and Mx.
pop projections: observe past trends and find yearly growth rate
demogrpahic and interspecific competition
projection matrices: use fecundity and survival probabilty from life and fecundity tables. use leslie matrix. makes projections for populations.
historic and future growth of human pops varies with stages in the demographic transtition: high stationary, early expanding, late expanding, low stationary, decling. few group high birth and death rates, stable or slow increas, disease famine and poor medical knowledge --- low birth and death rates stable or slow increase, good health care and reliable food supply, family planning.
interspecific comp - competition, predation, parasitism and mutualism. competition - when individuals of one species suffer reduction in fecundity, growth and or survivial as a result of resource expoitation or interference by another species. e.g competition between diatoms for silicate or between paramecium, and rodents and ants for seeds. fundamental ecological niches - describes the overall potential of a species. Realised ecological niche - describes the part of the fundamental niche that an organism can use in the presence of competitors and predators.
lab cultures of diatoms: provide fundamental niches for both but only realised for one. lab cultures of paramicium: realised niches for only 2. rodents and ants fundamental and realised for both
competative exlusion principle: 1. if competeing species coexist in a stable environment then they do so as a result of niche differentiation. 2. if there is no differentation of niches then one competing species will eliminate or exclude the other. diatoms: exclusion. paranecium: exclusion in one pair, coexistance in other pair as diff food sources. rodents and ants: coexistance: niches differentiated with some overlap.
lotka-volterra model of interspecific compeition: fits the competitive exclusion principle. logistic growth equation with alhaN2 and betaN1. when species 1 is at equilibrium when gradient is 0. above line species 1 will decrease, below line it will increase. when species 1 line is lower than species 2, species 1 will go extinct, species 2 has zero growth at higher density than species 1 species 2 excludes species 1. and vice versa. if zero growth lines cross there is stable coexistance. or unstable coexistance as random fluctutation will send to either K1 or K2.
competiting species are predicted to coexist when: - niches are differentiated and competition within secies is more intense than between species.
environmental heterogeneity - how interspecific compettions influenced by an inconstant/unpredictable environment.
interspecific comp 2
coexistance due to gap formation e.g sea pam and mussels moves by waves. coexistance due to differences in colonisation timing. coexistance due to aggregation. Environmental heterogenity - realistic view of competition: doesn;t proceed in isolution but under the influence of a patchy, unpredictable environment. heterogeneous nature of the enviro can foster coexistance (without differentiation of niches). Hetergeneity may be spatial/temporal/individual.
competition for enemy free space or 'apparent competition'. e.g the venturia camescens wasp who lays eggs in other species as a parastioid. 2 species of catapillar, 1 goes extinct as slowest growing due to behaviour of predator. e.g when artemesia is removed, herb species show much better growth. due to - reduced exploitatibe comp for water or reduced grazing pressure, as rats and deer feed on and hide in them.
interspecific comp has negative effects therefore natural selection may have favoured individuals that avoid competiton. evolved charactoristics that minimise competition. called charactor displacement: evolutionary divergence of species due to competition. e.g darwins finches moves apart to stop competition as have diff beak sizes to have diff food niches.
interspecific comp 3
invasive species - argentine ant. native to south america, form individual colonies and defend territories. so succesful as fast foragers. single argentine ants such at fighting but colonies are nearly always good fighters. reduce native ant species. dont compete intraspecifically. native - multicolonal, defend territoies and therefore less efficient in fedding. invasive - unicolonal and all cooperate. (doesnt fit selfish gene theory). non-aggresive so more time to feed and are therefore present in higher numbers.
conclusion: elimination of INTRA-specific aggressoin : superior Inter-specific competion. high numbers make the argentine ant a successsful invasive species.
evidence : controlled experiment - diatoms for silicate and paramecium competing for yeast. Manipulative field experiment - rodents and ant competing for seeds, species of bromus colonisation timing. indirect evidence from evolutionary change - beak size in darwins finches, canine size in indian mongoose. 'Natural' experimnets - invasive species Argentine ants.
consumption of one organism by another where the prey is alive when attacked. taxonomic classification= herbivores: prey on gren plants or their seeds and fruits. Carnivores: on herbivores or other carnivores. Parasitoids: lay eggs on or near host which is eventually killed then eaten. Parasites: live on or in the host and depend on it for nutrition.
Functional classidication. True predators: kill their prey immediately and eat whole thing. Grazers: remove only part of prey which usually survives, attack large numbers of prey. Parasites: remove only part of prey which usually survives at least in short term, attack only one or 2 hosts.
predation is important for: distribution and abundance as restrict distributions and reduce abundance of prey. prey compensate: predators dont always cause reduction in abundance. Herbivory may lead to e.g increased photosynthesis due to decreased shading. Predation reduces intraspecific competition for resources. Predation normally attack old/weak so less effect on reproductive population. Biological controls are also used to control distribution and abundance of pests using predation. needs to be 1. host specific, 2. synchronous with pest, 3. high growth rate, 4. survive with few hosts. 5. good searching ability.
also important for species interaction/ community structure. predator-mediated coexistence: predator may hold down densities of competitors. selective predation may increase species numbers in a communiter when the preffered prey is dominant. When there is no competitive dominance, predation decreases species number. Community structure (food chains) change with changed predation e.g killer whales eating sea otters instead of sea lions has effect on sea urchin and kelp numbers. Keystone species: species that activites determine community structure, can reverse the outcome of competitive ineractions e.g sea otter.
also important for selection/adaptation: prey evolve defense mechanisms and predators evolve to be more efficient. predator/prey 'arms race'. e.g bats use ultrasound to find prey, moths learnt to listen for clicks and hide, bats evolved to have quieter clicks. can have structural defence or chemical defense, mimicry e.g butterflys and can evolve to escape hide and diversion better. aposematism (noxious chemicals stored in tissues). Predators are strong selective factors - prey evolve defenses in response.
theoretical predator-prey dynamics - exponential increase/decrease/stability/ damped stability/ instability/cycles/chaos
instability in protozoan. coupled oscilations usually. Prey isolcine: the predator density at which the prey population does not change in number. predator isocline: vice versa. for this to occur the lotka-volterra equation needs to apply. assumptions: predators are the only force limiting the increase of prey. prey are the only force limiting the increase of predators. prey refuge - predator is unable to drive prey to extinction e.g humans on deer. prey refuges e.g : hiding places, inaccessable habitats, predator behaviour, defense response. can lead to stability or extinction.
density dependance - above a certain density it is not predator which limits prey but competition amongst themselves. refuge and intrasepcific competition in prey can lead to : stable cycles, extinction of predator or stable equilibrium. however spatial heterogeneity means that more realistically prey is distributed in patches of differing density and predators are distributed non-randomly over these. prey: fluctuate but persist without predators. Predator added: unstable dynamics. A patchy habitat: patches were separated by barrier and prey could disperse easier than predators. only prey: growth and dispersial. only predator: extintion. both: prey consumer, predator extinct. overall outcome: at any time there was prey in some and predators in ther so both persist in tray. important points: coupled oscillations normal (lotka-volterra model). prey refuges, density-depednace and spatial heterogenity change this. stable cycles, equilibruim and extincition possible.
parasitism is parasitic symbiosis. more parasites than free living species. e.g plasmodium and malaria in humans. mosquitos inject sporozytes into human which go to liver then red blood cells to form gametocytes which are then sucked up by another mosquito, oocysts then form in its gut wall where sporozytes grow and go to salivary glands. schistosoma and nemotodes in humans. cercarie enter humans through water, mature in blood stream, settle in gut, pass to water and hatch to larvae, enter snail and leave as cercariae. gall wasps on oak.
infection: when a parastie colonises a host. disease: when infection gives rise to harmful symptoms. pathogen: a parasite that gives rise to a disease. microparasite: usually small, multiply in host, extremely numerous in host. e.g plasmodium. macroparasite: live on body in cavities or between cells, grow but dont multiply on host, produce specialised infective stages to infect new hosts e.g schistostoma. definite host: organism where parasite reaches sexual maturity. intermediate host: parasite undergo some development or morphological change but no sexual matrity. direct life cycle: only one host needed for life cycle. indirect life cycle: more than one host needed.
parasite can be physiologically dependant on host, can reproduce faster sometimes, can kill host, usually clumped in pop. not evenly distributed or random.
consequences - poor health, lack of growth leads to increased risk of predation, less competition and less tolerance to abiotic stress - less reproduction more death, change in pop size. epidemic outbreak - 'waves' of infection through pop where pathogen disappears because host die or become immune( usually micro). Endemic infection - host survives but doesnt get immunity (usually macro).
parasites can regulate pop size. can affect species interaction. can cause extinction. generalised not specialised pathogen that present most serious risk of extinction. increased contact between wildlife and humans/domesticated animals. management of wildlife disease: culling or immunisations. rabies jab effective, culling not. need to understand consequences of parasites in an environment that is warming, acidifying, urbanizing and becoming more connected.
reciprocally benefitial relationship. 75% of plants have mutalistic relationships with fungi (mychorrhiza). trading goods for service; food, defense, transport. reciprocal exploitations that involve net benefit. cost and benefit to both parties. e.g ants get housing in plants and plants get protection from competitors and herbivores. Cleaner and client fish. 'farmer' gets nutrition e.g honey-dew from aphids, decomposed plant material from fungi, 'crop' gets protection from competitors and predators. Pollinator mutalisms. Seed dispersal mutualisms. mutualistic gut inhabitors. mycetocyte symbiosis - animals get essential amino acids, lipids etc and microorganism in insect cell get food and enviro. Fungi in plant root tissue (mychorrihzia) - plant get nutrients from soil fungi gets carbon from plant.
temptation to cheat controlled by 1. sanctions and rewards 2. limiting opportunity to cheat 3. persuasion. 1. - ants protect leaves and shoots and get housing and food. plant grows extra for ants, ants patrol extra for plant. cheater ant doesnt patrol gets housing host plant 'punishes' ants by not growing as much by providing fewer and smaller domatia (swellings that ants live in). 2. - ant behaviour that decreases pollination could be a selective advantage but would be disadvantageous for plant as ant secrete toxins which kill pollinators. host plants avoidthe negative affects that ants may have on pollination by keeping ants away from young flowers via spatial or chemical control
3. - jellyfish get photosynthates and algae get nitrogen and inorganic nutrients. vertical transmission of symbionts - directly from host parent to offspring e.g through eggs or clonal offspring. Horizontal - via external enviro from host to another member of pop. most mutalists have horizontal transmission. Vertical transmission may strengthen relationship. jellyfish asexually reproduce by clonal budding. algae that was vertically transmitted are more benefitial to jellyfish host as 'pursuades' algae not to cheat.
explaining distribution and abundance of organisms through abiotic and biotic factors. population definition - group of interbreeding organisms found in same space or area. A functional unit that interact with each other. pops aggregate when and where resources and conditions favour reproduction and survival, groups reduce predation risk(selfish herd). regulation of pop = births - deaths - emigration + immegration.
dispersal - the spreading of individuals away from each other. Natal dispersal - movement between area of birth to area where breeding first takes place. Breeding dispersal - movement between 2 successive breeding areas. migration - mass directional movement of large numbers of individuals. passive - e,g seeds oh plants by gravity and wind. Partly active - spiders controlling take off, vertebrates drifting in water. completely active - birds and mammals.
benefits - 1. escape from transient habitats, 2. inbreeding avoidance, and 3. competition avoidance. 2. e.g antechinus, male young disperse after weaning. intermediate dispersal distances are optimal for size, lifespan and overall fitness. 3. planthoppers and song sparrows compete for food. food supplementation greatly reduced dispersal.
dispersal polymorphisms - habitats are variable and unpredictable e.g aphids whose wing formation depends on enviro.
and desert plant seed production is moisture dependant. Sex-biased dispersal - predominant dispersal by one sex to prevent close inbreeding. in birds males are territorial, in mammals primarily female-defense mating systems and so dont disperse, the defending sex benefit from familiarity with natal area.
when to leave influenced by - mode of dispersal, genetic predisposition to disperse, local pop density, habitat change, age/reproductive status. When to stop = conspecific attraction, habitat quality, physiological status.
migration - short (daily) migration in water column in response to gradients in resources, conditions and interacting species. long-distance in mammals and birds e.g red-necked ducks from NE america to florida in winter. Long distance in monarch butterflies, no single individual makes round trip, 2-4 generations. benefits - track favourable habitats, get complementary habitats. Partial migration - e.g blackcaps who do short distance and long distance. migration not necessarily include dispersal and salmon usually return to birthing spot years after migration nd so do pied flycatcher males.
demographic significance - metapopulation - group of spatially seperated subpops of the same species which interact at some level. pops go extinct and new pops established, dispersal between subpops
e.g of metapopulation - plebejus argus in north wales. source and sink pop. source : reproduction > mortality (pop has net excess of births). sink: mortality > reproduction. pops arent closed entities but can be influenced by emigration and immigration. Dispersal influences - dynamics and persistance of pops, distribution and abundance of species, community structure. has evolutionary consequences - determines level of gene flow between pops. co-existance between predator and prey possible when there were multiple seperate habitats and prey were dispersed between patches.
pops where dispersal is important - metapopulations and sink and source pops. habitat fragmentation and changs in environments: impact will be species specific and depends on dispersal ability.