BIO 263 week 10 Notes
The Hare - Lynx CycleNo lynx plotNot enough to completely prevent population crashExtra food plotsNot enough to completely prevent population crashNo lynx + extra food plotShows that both predation + food influence population flux
How Does Age Structure Affect Population Growth?Proportion of individuals at each possible ageInfluences population growthAge pyramid = depicts # of males + females of each age groupUniform vs top / bottom - heavyDeveloped countries = uniform → top (care for old people)Developing countries = bottom heavy → uniform (education + jobs)
Human PopulationSince 1970 growth rate ® is dropping1990 -1995 1.46% per year; now 1.2%1rst long - term decline ever
Zero population growth = fertility at replacement rate sustained for a generation
Replacement rate = each woman produces exactly enough offspring to replace herself and father
Lecture II : Species Interactions (community ecology)Commensalism (+/0) (effect on fitness)Interaction between 2 species where one one benefits and the other in newDriver ants(0), ant - birds (+)Competition (-/-)intraspecific competition → logistic population growth, (r decreases)Fighting wolves
BIO 263 week 10 NotesInterspecific competition(if niches overlap)Competitive exclusion principle = species with exactly the same ecological niche cannot coexist for a meaningful period of timeIncomplete niche overlapFundamental nice = occupied by a species when there are no competitors (larger)Realized niche = occupied by a species when competitors are present (smaller)Mechanisms of coexistence: resource partitioning Natural selection favors individuals that do no competeOver evolution time
Resource partitioning = niche differential
Change in resource use (as to not compete)Directional selection acting in opposite directions on each species
Character displacement = evolutionary trait change
Competition alters evolutionary changePredicted that fortis wouldn't survive along due to big beaked, but the opposite was actually observedConsumption (+/-) (herbivory)Herbivores eat most algae in water, but little of the plants on lanWhy don’t terrestrial herbivores eat everythingHypothesis
Top - down and bottom - up factors limit herbivoreBeaver + cottonwood example + beetlesFelled trees increase salicortin concentration in newly sprouted trees + beetle larvae survive better from resprouted trees
- Top - down control: predation or disease limits herbivores
- Bottom - up limitation: plants have low nutrients / defenses against herbivores
- Removal of predators or islands = fewer plants (top - down)
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BIO 263 week 10 NotesCannibalismIngestion of a member of the same species (conspecific)Heterospecific - different species = carnivory = predationExample = praying mantis → sexual cannibalismExample = spadefoot toad tadpoleProduce a cannibalistic morph during stressful situationsCosts = easier to get diseases (similar parasitism)Harder than preddation
Predation (bobbit worm)
Prey Adaptations (standing defenses = always present)Toxins + bright colors = warning = aposematismBombardier beetle = fighting = weaponsStotting and tail flagging (signaling) (honest signal)Indicates that the prey has noticed the predatorFooling the predatorMallerian mimicry → both are poisonous (monarch and viceroy)Batesian mimicry → model is toxic mimic is notBenefits of mimicry depend on abundance of the modelWhere the model is absent mimicry is not as beneficial
Inducible Defenses ( prey adaptation )
Takes time to createAnimals don’t un - necessarily produce them (energy efficient)Only produce when threatened