BIO 3400 1nd Edition Exam 6 Study Guide Lectures 25 29 Lecture 25 I Models of Population Growth and Regulation a When resources are abundant exponential i Rate of growth r max N ii Overlapping generations cannot use Ro b Population growth with limiting resources i Logistic equation ii Verhulst 1838 iii Levels of iv Carrying capacity the max number of organisms of a population that the environment can support 1 Food space water disease parasitism predation weather events etc v Rate of growth r mx N 1 N k II Limits to Growth a Biotic factors resources predation disease etc b Abiotic factors temperature major weather events etc III R and K selection a MacArthur and Wilson 1967 i R selection low population size density independent mortality favors high rate of growth ii K selection stable population size density dependent mortality favors high competitive ability Lecture 26 I Why do life histories vary among organisms i Coconut seeds versus orchid seeds b Resource allocation i Reproduction maintenance storage growth II Organisms are constrained by limited resources a Example if an organism produces many ofspring ofspring are small compared to if an organism produces few ofspring which results in larger ofspring III Early idea r and K selection a MacArthur and Wilson 1967 i R selection low population size density independent mortality favors high rate of growth produce as many ofspring as you can ii K selection stable population size density dependent mortality favors high competitive ability b How do you maximize r IV V VI VII i R ln R0 T 1 Develop fast reproduce early produce a lot of ofspring c What problems are there with Pianka s r and k selected life history trait predictions i Only focused on density other factors could be at play ii Not all predictions are justified especially K selected traits and not all predictions match up in similar experiments iii Applied without establishing cause and efect i e density dependence or independence iv Ignored all other factors except density Demographic models a Age specific extrinsic not because of density mortality i High adult mortality Early reproduction higher reproductive efortproportion allocated to reproduction doesn t need to maintain as much since going to die soon anyway ii High juvenile mortality Delayed reproduction lower reproductive efortproportion allocated to reproduction allows to focus more on growth and maintenance Guppy Life Histories a Low predation Killifish Rivulus only eat juveniles i Prediction later maturity lower reproductive efort b High predation Cichlids eat adults i Prediction early maturity higher reproductive efort Additional Complexity a What factor influenced the evolution of life history traits in guppies i Density resources environmental fluctuations age specific extrinsic mortality b Is r and K selection a useful paradigm c What are the advantages of more complex models of life history evolution Are there any disadvantages i More realistic more accurate predictions but harder to execute and harder to understand Unit 10 Interactions a The environment contains limited resources i Competition afects both parties negatively ii Exploitative competition indirect interaction stemming from utilizing the same resources iii Interference competition direct aggressive interaction between individuals or access to resources iv Intraspecific competition competition between the individuals of the same species v Interspecific competition competition between individuals of a diferent species b The log growth model assumes intraspecific competition limits population size i Carrying capacity results from competition between individuals in the population ii Performance declines with increasing density Lecture 27 I What can happen when species compete for resources a Example 1 Terrestrial salamanders i Removal experiment b Example 2 Bedstraw competitive exclusion i Can exist on each soil type alone just fine but not when the other species is present ii Fundamental versus realized niche c Example 3 Barnacles d Example 4 Anolis lizards II Interspecific competition can be asymmetric a Asymmetric competition one party is more greatly afected than the other i Barnacles ii The presence of balanus afects chthamalus iii The presence of chtamalus has little to no efect on balanus III Interspecific competition can result in coexistence a Lizards IV Competitive exclusion or coexistence Lotka Volterra models a In class activity Lecture 28 I Competition a Competitive exclusion or coexistence Lotka Volterra models b What values should you compare to figure out if intraspecific competition is stronger than interspecific competition i Both species have a larger efect on themselves than on the other species c What form of competition intra within species or inter between species would you generally expect to be stronger i Competitive exclusion principle 1 If two competing species coexist in a stable environment they cannot have identical niches 2 Niche divergence intraspecific within one species competition stronger than interspecific competition coexistence ii Bed straw example 1 Both species can thrive alone but together they exclude the other iii Another example Balanus acorn cannot live in upper zone due to dessication drying out 1 Chthamalus settles in the middle but does not persist 2 Experiment exclude balanus chthamalus thrives control chthamalus excluded d How does niche diferentiation evolve II III IV V VI i Imagine two species of birds that are using similar seed resources Consider species 1 If there is variation in beak size and individuals with larger beaks can eat seeds outside the typical range eaten by the two species how would you expect this to influence fitness What would you expect to happen over time 1 Character displacement changes in the physical characteristics of a population as a result of natural selection for reduced interspecific competition 2 Greater trait diferences in sympatry same location than in allopatry diferent location 3 Mean phenotypes of species in an assemblage tend to be evenly spaced character displacement a character displacement is difficult to demonstrate definitively b show diference observe today is from competition that occurred in the past c there are several alternative hypotheses to test i patterns are pure chance ii diferences in sympatric and allopatric populations are not genetic environmental iii patterns are outcome of species sorting biased extinction of species similar to