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20 Cards in this Set
- Front
- Back
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Exploitation |
- one organism benefits at the expense of another examples: parasites, parasitoids, pathogens |
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Two ways to understand possible outcomes of predation |
1. observation (natural history) 2. experimentation |
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Results of laboratory populations of host and parasite |
- reciprocal oscillations |
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Results of algae and caddisfly experiment |
- algal biomass increased quickly - caddisfly colonized and algal biomass declined |
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Foxes, mange, and hares |
- as mange reduced the fox population, the hare population increased dramatically |
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Three features of lynx/hare cycles |
1. 10 year cycle 2. hares feed on shrubs and small trees 3. lynx is the predator |
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Lotka-Volterra for host population |
dNh/dt=rhNh-(p)NhNp dNh/dt: rate of host population change r: host per capita rate of increase N: number of host (h) or predator (p) (p): predation rate |
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Lotka-Volterra for predator population |
dNp/dt=c(p)NhNp-dpNp dNp/dt: rate of predator population change c: host to predator conversion rate p: predation rate N: number of predator (p) or host (h) d: death rate |
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What are the predator/prey oscillations a result of? |
- predators increasing when prey are abundant - predators decreasing as prey populations become depleted - when pressure on prey population is lessened, prey can recover and cycle repeats |
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Consequences of herbivory |
- can alter allocation of energies - can affect timing and amount of reproduction - can affect transmission of disease |
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Why may predators not be very efficient in low prey densities? |
- refuges - lack of reinforcement of learned behavior - low rate of prey encounters reduces hunting efficiency - predators may switch to alternative prey |
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What happens in the absence of refuges and immigration? |
- both prey and predator populations go extinct |
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What happens when refuge is added? |
- prey population persists - predators go extinct |
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What happens when immigration from source populations is maintained? |
- oscillations are maintained |
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Vulnerability to predation |
- organisms that are larger in size may escape predation due to their large size example: mussels and starfish |
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What does the Lotka-Volterra model suggest? |
- predator population changes in direct proportion to the number of prey - response may not be immediate - predator reproductive output is less than prey and life span usually longer than prey |
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What five features dampen out predicted predator/prey population cycles? |
1. predator inefficiency 2. density dependent limitation of either population by external factors 3. alternative food sources for predator 4. prey refugia 3. time lags in predator response to prey abundance |
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What do we expect natural selection to do? |
- increase predator efficiency for food capture - increase capability of prey to escape |
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When are evolutionary pressures reduced? |
- if predators do not control the abundance of prey |
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What are three big benefits of group living? |
1. many lookouts: spend more time feeding 2. if size difference is not that large, several prey acting together may deter predator 3. fleeing in confusion may distract predator |
