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Final Exam Notes

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University of Guelph
BIOL 2060
Hafiz Maherali

Large/expanding ranges Species vulnerable to extinction  Habitat tolerance (broad vs. narrow)  Geographic range (extensive vs. restricted)  Local population size (large vs. small)  Trajectory of population (increasing or decreasing) Population dynamics – populations change over time  Prob: how can we study whether populations are changing? o Count all individuals of each age class in the population (=age distribution) o Info on life expectancy survival to reproductive age  Life tables  Cohort Life table – follow a cohort of indiv over time, recording deaths; difficult (length, tracking moving)  Static Life Table – based on age structure, record # indiv who died in each age class; need good records  Survivorship curves – summarizes pattern of survival in a population  Type I – high juvenile survivorship high, most mortality at older age, high parental care, few offspring (humans)  Type II – constant, birds, die at equal rates, regardless of age  Type III – die at high rate as juveniles, lower rates later, low parental care, many offspring, perennial  Influences – Life History – describes how over a lifetime, efforts are allocated to functions such as: o Growth o # offspring produced o Parental investment in offspring o Size at reproductive maturity o Dispersal o –influences timing of reprod b/c available energy is limited – TRADEOFF (an exchange that occurs as a compromise)  Growth & reprod  # & size of offspring  # offspring & parental care  Parent life-span & # of offspring  Growth & defense Dispersal  Permanent movement of indiv from their site of origin to a previously unoccupied location  Avoid competition, inbreeding, expand population  Lack of causes population growth to stop  Costs: o Energy expense  minimize by utilizing other organisms/media to move; produce small offspring  small, abundant offspring > low parental care (type I) o Risk of predation  minimize by disperse when mature & can defend self, when in protected stage (seed)  more parental care > type II o Risk finding a poorer habitat/variable environment  minimize by produce lots of cheap offspring  lots of offspring > small offspring > low parental care Population growth  growth rate = r = b-d (births-deaths) per capita = net # new indiv/exisiting # indiv   r>0 increasing; r<0 decreasing; r=0 constant  When new indiv added as a function of population size, grows exponentially  Overlapping Generations – plants/animals that die after reproducing once; Population growth w/  Multiple generations can contribute to births = per capita rate of increase ®  Convert Ro to r using info on the generation time (T = average amt of time from the birth of a female until the birth of her daughters  R=ln (Ro) / T Fecundity – ability to reproduce Net Reproductive Rate ( )  =1 – population is stable; >1 increases; <1 decreases  Resource limited environment  Carrying capacity (K) – the # of indiv that can be supported in a given environment  Popn grows rapidly, slows, then stops: K reached – theoretical maximum population  K=N, growth stops  Density dependence – population depends on density – influenced by disease, predation, competition, etc. o Logistic growth model can predict future popn size and K o Regulate pest popn using these factors – limited food supply, adding disease, predators keeps K at lowest point o Allee effects  Only applies to species that req mates to reproduce  Effectiveness of density independent controis: must reduce popn to the pt where growth is mate limited  Conservation: determines the min viable popn size  Density Independence – if per capita birth and death rates are unrelated to popn density o Examples: abiotic factors (temperature, rainfall) that exceed tolerance, rare extreme event (early freeze, flood, etc. o Manipulating would effect popn size – allows popn to grow at the highest rate (exponential phase of logistic growth) so must be applied multiple times Table 1 Differences between species: r- versus K- selection Rate of increase (r) r High K low Development rate Fast Slow Body size Small Large Generation time Short Long #offspring/size Many/small Few/large Type of habitat Variable Stable Population growth & life history – a conceptual framework So Far: Distribution of indiv species based on:  Abiotic tolerance  Adaptation/developmental plasticity  Popn growth and regulation Species Richness – number of species in a given area  Birds, trees, mammals, insects, gastropods, etc.  Latitude gradient – resource availability, ecological tolerance, seasonal temperature range Competition - - Predation/Paratsitism + - Mutualism + + Table 2Interactions among species Competition  Occurs when organisms in the same community seek same limiting resource (prey, water etc.  INTRA-specific comp – among indiv of SAME species  INTER-specific comp – among indiv of DIFFERENT species  Exploitative competition (resource limitation) o Occurs when indiv use same limiting resource(s) o Depletes amt of resources avail to ea indiv (-/-) o Strongly density-dependent o Short-term ecological response – reduced growth per indiv or fewer indiv o Ex. Self-thinning plant popn – size vs. density – high density-dependent mortality allows remaining indiv to grow to lrg size  Interference comp o Occurs when indiv interfere w/ the foraging, survival or reprod of others o Directly prevents the physical establishment of a competitor in a portion of habitat o Ex: purple sage – aromatic, volatile compounds leak from leaves  Competition coefficient = α o Per capita effects on the growth of one species (1), of a second species (2) o Displacement of species 1 by species 2 o =1, 1 indiv of species 1 is displaced by 1 indiv of species 2  Short-term response – exclusion based on interference competition; reduced growth/popn size (suppression)  Popn should evolve to reduce –ve effects of competition – minimize interaction Character Displacement – tolerance ranges differentiate to reduce interaction  Ex – finches – beak depth, determines size of seeds able to eat  Causes: drought in 1970 – reduced small seed abundance  Larger beaks sized birds popn decreased  Phenotypic differences must be genetic (variation)  sympatry  Phenol diff related to diff in resource use  Additional niches which can be exploited Allopatric – two species that live apart | Sympatric – species that live together Multi-dimensional resource environment defines suitable habitat (potential range) Ecological Niche – consists of all the factors necessary for a species‟ existence in terms of time, space & req resources  Fundamental Niches – all the possible dimensions in which species can survive  Realized Niche – alter the effects of interspecific competition and other biotic interactions; = abiotic tolerance - competition Determining if competition is important in nature  Removal Experiments Ecotone – transition area between two adjacent ecological communities  Ex: treeline  Place where the effect of abiotic factors on competition is most important Facilitation – pioneer species modify the environment in such a way that it becomes less suitable for themselves and more suitable for species characteristic of later successional stages  Ex: plant w/ herb cover: competition + facilitation (protection from abiotic stress)  Plant w/ opening in herb cover: competition alone Weak competition  Abiotic stress is severe  Freq disturbance and high density independent mortality  Intra-specific competition >> inter-specific competition Consumer-Resource  A trophic level interaction  Indiv of one species consume indiv of another (+/-) o Parasite – host o Predator-prey o Monophagous(eating only one kind of food)/polyphagous  Affect popn dynamics of each species is the off-set of predator-prey cycles  Prey popn are influenced by food availability, by being consumed by predators, and through non- consumptive effects of predators  Lotka-Veterra model – oscillations in popn of prey/predators  Predators high, prey lowers, predators lowers, prey increases Spatial-refuges  places where members of the exploited population have some protection from predators  burrows, trees, air, water  without this, both groups may become extinct  with refuge for prey, the popn can persist but predators become extinct Predator-prey cycles  rapid evolution can alter it – prey is well defended under intense predation; life-history trade-off between growth rate and defense  Natural selection by humans can affect prey pop‟n o Ex: fisheries o Haven‟t
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