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Ecology Exam 4 Part 1 (Quiz 4)

Terms in this set (60)

With the exception of producers, obtaining nutrients is...
exploiting another species
List exploitative interactions
herbivory (consumer and producer), predation (consumer and consumer; predator and prey), parasitism (parasite and host; don't kill host until you reproduce), and disease (pathogen and host); but all these terms are too restrictive
competition is an interaction that reduces the fitness of individuals of both species, while exploitation is an interaction where...
one species benefits to the detriment of the other
Do we need to be more worried about the exploiters or the exploitees?
exploiters (polar bear that can't eat a walrus)
Acanthocephalans (spiny-headed worms) and amphipods (aquatic crustaceans)
These parasites infect the amphipods and then cause the amphipods to show positive phototaxis (normally amphipods exhibit negative phototaxis) when the parasite matures, increasing chance that they get eaten by ducks, beavers, and muskrats to complete parasite life cycle
Plagiorhynchus (acanthocephalon) and armadillidium (pillbug)
Adult plagiorhynchus lays eggs in intestines of infected Starling. Pillbug eats infected feces and eggs hatch and mature into larvae that affect pillbug behavior so that they wander in open and get eaten by Starling.
Tribolium
flower beetle that cannabalizes own species if it runs out of food; aka not all interactions are neatly defined
Cactus Opuntia and cactoblastis moth
Cactoblastis moth eat opuntia leaving open wound that fungi and bacteria infect, killing the cactus. How does cactus "run away" from moth? By the individuals that survive being the ones that grow in the poorest soil that the cactus can still survive in that makes the poorest food for caterpillars. Individuals didn't move, the population did
general ratio for prey to predator
10:1
What is the part of the theoretical predation graph that makes it mean something even though it is highly simplified and does not represent reality?
it demonstrates that all you need to turn the sigmoidal logistic growth curve (competition) into one that oscillates and tracks is predation (you don't need solar radiation, overpopulation due to disease, stress, or starvation, you don't need quantity or quality of food supply)
cycle: lots of prey leads to more predators which leads to...
less prey while leads to less predators which leads to lots of prey and the oscillation repeats itself
From the prey's perspective, what is the most important factor?
predator population size (and vise versa)
What are the three trophic levels in the wild?
producer (plant), primary consumer (hare), secondary consumer (lynx)
Do you need all three trophic levels in the predation model?
nope, just the last two
Host population grows exponentially, limited by...
predatory
List the two predatory-prey equations
prey/host population growth: dNh/dt = rhNh-pNhNp
predator or parasite population growth: dNp/dt = cpNhNp-dpNp
What are the only variables in the equations?
Ns (all others are constants)
rhNh
exponential growth by host population
pNhNp
predation; number of population that get killed by lynx
NhNp
how often do prey/predator encounter each other (predator seeing/chasing)
p
how often do encounters turn into dinner; predation rate
p of 0.5
means that every other encounter = dinner
Np
number of predators/parasites
Nh
number of hosts
rh
host per capita rate of increase
The predator population growth equation asks...
how many dead prey/hosts equal one baby predatory?
cpNhNp
conversion rate of hosts into predator offspring
c
host to predator conversion rate
c of 0.5
means have to each 2 hosts to make 1 baby predator
dp
predator death rate
dpNp
number of predator deaths (doesn't matter the cause)
What does predator population growth depend entire upon?
dead prey and how many equal a predator baby
How do you make prey according to the equations?
r
How do you lose prey according to the equations?
predation
How do you make predators according to the eqations?
prey eaten
How do you lose predators according to the equations?
death
Label axes of predation model?
time on x, number of predator and prey and y
reproduction of prey translates into...
destruction by predators
Increased predation translates into...
increased predators which increases predation
Increase in predators reduces prey,
which will lead to a decline in predators
Describe the two graphs that can depict prey-predation model?
two waves tracking each other and oscillating into infinity or elliptical oscillation
axes of elliptical oscillation model
prey numbers on x and predator numbers on y
which way do arrows go?
to the left (counterclockwise)
What factor does the elliptical oscillation eliminate?
time
Describe the linear oscillating model
From left to right, prey peaks first, then predators. Prey crash first, then predator. Prey recover first, then predator.
What factor changes the size of the ellipse?
the initial sizes of the two populations
What makes oscillating model unrealistic?
oscillations exactly the same/eternal and don't crash, all the resources that were left out/no carrying capacity, time lag always the same and too little, continues on to infinity
Is prey or predator more likely to crash to zero and die?
the predator (actually more vulnerable than the prey)
What use is such a simple model?
All it takes to turn competition graph (logistic) to oscillating one is add predation (exploitation); demonstrates that the exploitive interaction can produce population cycles by itself, without outside influences such as weather
Does predation equal competition?
no, because competition is talking about resources
refuge definition
situations in which members of the exploited population have some protection; way for exploited population to be less exploited
Predation rates should change from one environment to another that...
differs structurally, especially in there is a differences in availability of refuges
More access to refuges means...
lower p
List the three types of refuges
spatial refuges, large groups, large size
spatial refuges
opuntia cactus was hard to find or sometimes grew where cactus tissues were lower quality or temperatures were lower
large groups
three ways: (1) herd strategy where lower probability of INDIVIDUAL being eaten (e.g. gazelle) (2) active defense against predator (e.g. wildebeast) (3) predator satiation or masting (synchronous production of seeds and fruit) where LOTS of individuals being eaten, but population survives due to enormous number of individuals (invertebrates like cicadas or plants)
large size
increased handling time means some prey are too large to be profitable (elephants, giraffes and whales - energy to chase and kill outweighs energy gained); animals of this size usually are herbivorous and feed at bottom of food chain
commensalism
interactions between individuals of different species that benefit one partner and neither benefit nor harm the other; e.g. epiphytic plants
Is commensalism easily distinguishable?
no, can look like mutualism or parasitism
mutualism
interactions between individuals of different species that benefit both partners; can be facultative (individual can live without it) or obligate
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