Ecology Exam 3 Flashcards
iteroparity
reproduce more than once (most perennial plants, most vertebrates)
semelparity
reproduce only once (most annual plants, agave/century plants, many short-lived insects)
why be semelparous?
if favorable years for reproduction are rare, reproduce only during favorable years (harsh environment)
what conditions are needed for iteroparity?
good environment with lots of resources
life-history tradeoffs
female age at maturity vs. offspring weight
# vs. size of offspring
population growth rate vs. generation time
reproduction vs. mortality
energy expenditure per offspring
tradeoff between total # of offspring and per individual size
three types of organisms based on energy expenditure
species with live birth/well-protected young have larger offspring that develop inside parent (arctic species)
species with eggs and lots of yolk have fairly large offspring (arctic and tropical species)
species with eggs and little yolk have small offspring (tropical species)
most common clutch size in birds should be that which results in…
the most young fledged
having more eggs/offspring raised by birds can result in…
reduced offspring weight and lower parental survival
clutch size in a year is involved in a tradeoff with…
future reproductive output
r selection happens for populations that are…
far from K
K selection happens for populations that are…
close to K
why is there r and K selection?
small populations that have abundant resources select for different traits than large populations that strongly compete for resources
r-selected characteristics
rapid development
short-lived individuals
many small offspring
immediate reproduction
K-selected characteristics
slower development
long-lived individuals
fewer/larger offspring
delayed reproduction
the r-selected plants in the goldenrod experiment were…
smaller and occurred in disturbed habitats
the K-selected plants in the goldenrod experiment were…
larger and occurred in less disturbed habitats
what are the three basic plant life strategies?
ruderal
stress tolerant
competitive
ruderal
plants that can live in highly disturbed environments and may depend on disturbance to allow them to persist in competition with other plants
traits of ruderal plants
rapid growth/reproduction
invest large portions of biomass in reproduction
produce many seeds that are capable of dispersing to new areas
ruderal plants are most similar to…
r-selected species
stress tolerant
plants that can live in very stressful environments that experience low rates of disturbance (deserts, salt flats, tundras)
traits of stress tolerant plants
slow growth
often evergreens
conserve energy and nutrients for brief periods of favorable conditions
highly defended against herbivores
stress tolerant plants are…
intermediates between r and K selection
competitive
plants that specialize in environments where both stress and disturbance are low, selected for strong competitive abilities vs. other plant species
competitive plants are most similar to…
K-selected species
birds have larger clutches…
at higher latitudes
at higher elevations (altitudes)
on mainlands vs. islands
four hypotheses for latitudinal patterns
day length
predation
spring bloom
migratory effect
day length hypothesis
since birds at higher latitudes breed during a time of the year when the day length is longer, more time to feed young
problem with day length hypothesis
nocturnal birds breeding at high latitudes also have larger clutches
predation hypothesis
more potential nest predators in tropics, so fewer offspring = fewer trips to/from nest to feed offspring –> less chance of attracting predators
spring bloom hypothesis
food is more abundant during breeding season in temperate regions, allowing adults to raise more offspring
migratory effect hypothesis
migration increases risk of mortality, so birds with far-away breeding grounds should produce larger clutches when there to compensate for increased risk during longer migration
tests of clutch size hypotheses in survey of seven tropical-temperate species pairs found…
clutch sizes consistently higher in temperate vs. tropical
increased nest visitation –> increased food to nest –> increased predation
at similar nest predation rates, clutch size is greater in temperate vs. tropical
nest predation lower and food delivery higher in tropical regions
r vs. K hypothesis
more disturbance in higher latitudes, higher altitudes, and on mainlands favors r-selected traits such as increased clutch size
trends in clutch size in plants
seeds per individual higher in tropics vs. temperate
seeds per individual higher in lowlands vs. mountains
why does plant seed size (clutch size) have a different pattern than bird clutch size?
plant reproduction needs to consider entire length of growing season, which is greater in tropics and lowland regions
competition
a negative-negative interaction between species
exploitative competition
indirect interaction between individuals of species 1 and species 2 that occurs through each species’ impact on shared resources (they decrease resources available for each other)
interference competition
direct interaction between individuals of species 1 and species 2 that occurs via aggression, territorial defense, etc.
costs to both species may result from fighting/injury
competition is often asymmetric
how might stationary organisms have interference competition
they can compete by producing chemicals that harm other species
competitive exclusion
extreme overlap of resources in which species 1 wins and species 2 goes extinct (or vice versa)
this result always occurs
gause’s principle
when resources and space of a two species overlap, there will be competition
stable equilibrium (coexistence)
both species persist and neither go extinct
unstable equilibrium (coexistence)
either species 1 or species 2 wins depending on their initial abundances (more abundant species has a tendency to win)
Lotka-Volterra competition equations
dN1/dt = r1N1([K1 - N1 - α12N2] / K1)
dN2/dt = r2N2([K2 - N2 - α21N1] / K2)
meaning of variables in LK equation
in terms of species 1, species 2 is reverse:
r1 = per capita rate of increase of species 1
N1 = population size of species 1
K1 = carrying capacity of species 1
α12 = competition coefficient (per capita effect of species 2 on species 1/how much carrying capacity of species 1 that each individual of species 2 removes)
ZNGI
zero net growth isocline where dN/dt = 0
lessons from LV equation
complete competitors can’t coexist
complete exclusion is reached more slowly with higher resource abundances
stable coexistence requires niche differentiation (intraspecific > interspecific)
resource partitioning definition and types
ways in which species differ in their use of resources
types:
food, size, hardness, and type
space (habitat)
time
broad (macrohabitat)
organisms live in different ecosystems
narrow (microhabitat)
organisms live in the same vegetation type but in different places within that habitat type
daily (time)
when organisms eat during the day
seasonal (time)
when organisms eat during the year
ecological niche
set of environmental conditions within which an organism can maintain a viable population
fundamental niche
the total range of environmental conditions that are suitable for existence in the absence of interspecific competition, predation, or other interspecific interactions
realized niche
the part of the fundamental niche occupied in the presence of interspecific competition, predation, and other interspecific interactions
limiting similarity
that degree of similarity in resource use that just allows coexistence; any greater similarity would result in one of the species becoming extinct
measured in units of d/w
d
the distance between the means of the curves
w
the standard deviation or niche width
what does niche width tell us
how “fat” the curves are
generalist vs. specialist
generalists have a large w
specialists have a small w
shaded area between curves
shaded area = α of LV model
the larger the shaded area, the larger the α
small overlap of curves
more different than limiting similarity (small α, d/w > 1)
medium-sized overlap of curves
limiting similarity (d/w about equal to 1)
large overlap of curves
no coexistence (large α, d/w < 1)
competitive extinction
if species are too similar, one drives the other to extinction
co-evolution
species are initially very similar, but diverge over evolutionary time (reduce similarity)
character displacement
species are more different from each other when in sympatry (geological ranges overlap) than when in allopatry (no range overlap)
predation
predator kills prey relatively quickly (wolves, killer whales, etc.)
herbivory
plants are eaten but generally survive
pathogens
infect host, cause diseases as a means of reproduction/transmission (myxoma virus, fungi, cold, flu, ebola, AIDS, covid)
parasitism
host is not killed quickly, exploited for resources which eventually leads to health problems for host
endoparasites
inside host (tapeworms, liver flukes, etc.)
ectoparasites
outside host (ticks, lampreys, etc.)
brood parasitism
parasite lays eggs in nest of host species, host raises parasite’s young
egg mimicry
type of brood parasitism where parasite egg looks like host spp egg, parasite young can kill host spp young –> greater share of food
nestling mimicry
type of brood parasitism where parasite young look like host spp young, tricking host into feeding it
why is nestling mimicry common in tropics
tropics are older –> more time for co-evolution
tropical birds are less territorial –> more vulnerable
MAFIA BEHAVIOR
Lotka-Volterra predator-prey model
prey: dV/dt = rV - aVP
predator: dP/dt = caVP - qP
meaning of variables in the predator-prey model
V = # of prey
P = # of predators
r = intrinsic rate of increase of prey
a = capture efficiency (prob. a pred.-prey interaction leads to prey being eaten)
c = conversion constant (# of prey needed to make a single pred.)
q = death rate of predators
assumptions of LV predator-prey model
growth of prey population is limited only by predation
predator is a specialist that can persist only if prey population is present
individual predators can consume an infinite # of prey
predator and prey encounter one another randomly in homogeneous environment
equilibria of predator-prey model
when no prey are present or P = r/a
when no predators are present or V = q/ca
mutualisms
interactions between individuals of a different species that benefit both partners (a +/+ relationship)
mutualisms can…
increase birth rates
decrease death rates
increase equilibrium population densities
raise the carrying capacity for each species
degree of dependence
the necessity of the interaction for one or both partners in a mutualism
obligate mutualism
organisms can’t survive and/or reproduce without the mutualism (ex: 70% of plants rely on insect pollinators)
facultative mutualism
organisms benefit from, but can survive and/or reproduce without the mutualism (ex: cleaner fish and marine organisms)
degree of specialization
the necessity of, or involvement of, one species in the interaction
specialist (mutualism)
only two species can participate in the interaction (ex: ant/acacia symbiosis)
generalist (mutualism)
there are a variety of suitable partner species
(ex: most bee-flower pollinator mutualisms)
benefits from mutualisms
trophic
transport
protective
nutritional
energetic
tropic (benefit)
mutualists rely on each other for food (ex: honeyguides and humans)
transport (benefit)
movement of gametes or seeds of one mutualist by another (ex: pollination and/or seed disperal)
protective (benefit)
active or passive defense of one mutualist by another (ex: gobies and shrimp)
nutritional (benefit)
interactions in which nutrients such as nitrogen and phosphorus are transferred from one mutualist to another (ex: fungi in mycorrhizal symbioses)
energetic (benefit)
interactions in which energy obtained by one mutualist is made available to another mutualist (ex: transfer of photosynthate from symbiotic bacteria to coral polyps)
two important things to note about mutualisms
each partner in a mutualism may get different types of benefits
if one partner dies or goes extinct, the other may persist in doing apparently “irrational” things
what separates mutualism from parasitism or competition?
the ability to reward “friends” and punish “cheaters” (ex: Yucca plant and Yucca moth)
degree and type of density dependence
mutualistic per-capita benefits can be independent of population density, or they can increase/decrease with population density
some good case studies about mutualisms to understand
plants and mycorrhizal fungi –> fungi increase water access and nutrients to plants, plants create carbs and share them with fungi
Pseudomyrmex ants and swollen-thorn acacias –> acacias provide shelter, sugar, liquids, oils, and proteins to ants, ants defend acacia against herbivores and remove other plants from growing near it
zooxanthellae and corals –> zooxanthellae provide organic compounds to coral, coral provides nutrients like nitrogen and protection against predators to zooxanthellae
honeyguides and humans –> honeyguides help humans find well-hidden honey bee nests, humans provide honeyguides with easier access to honey (cheated honeyguides will lead humans to nasty honey badgers 0_0)
