Ecological Interactions Flashcards
what is a habitat?
the physical place where an organism lives
what is a niche?
how an organism makes its living
what is competition?
occurs when an organism shares one or more resources with one or more other organisms, and the use or consumption by one organism reduces the availability of at least one resource to other organisms
what is a resource?
any substance that leads to individual or population growth/decline if the substance is increased/decreased
Liebigs Law of the Minimum
population numbers can be regulated by a single resource that has the greatest relative scarcity
was nitrogen determined to be a resource
for plants yes but not humans
what did grinnell and cause study?
interspecific competiton
what did grinnell and gause do?
they gave 2 species of paramecium a fixed amount of bacteria as a food source. when grown separately, they showed sigmodal growth, but when grown together, one species overtook the other
competitive exclusion principle
two species with the same niche cannot coexist
T/F: two species with very similar resource requirements can co exist
true but uncommon
predation on arctic lemmings by foxes and owls, tree diversity in tropical forests, and the “paradox of plankton” are all example of what?
two species with very similar resource requirements co-existing
how can two species with very similar resource requirements co-exist?
subtle differences in resource use among species. predators reduce population sizes below carrying capacity allowing other species to coexist
_____ difference switches the competitive ability of two beetle species, allowing them to coexist
3.2 degree
wo beetle species occupy nearly the same niche, but thrive at different temperatures. this is an example of ____ _____
habitat diversity
evidence for interspecific competition in nature
- habitat shifts in allopatry and sympatry
- character displacement and resource partitioning
- habitat differences and resource partitioning
- alleopathy
two different species of trout living in two different lakes is an example of _____ populations
allopatric
two different species of trout living in the same lake is an example of _____ populations
sympatric
what is allopatry
‘different home’
what is sympatry
‘same home’
Character displacement (ecological and reproductive)
tendency for 2 species to diverge in form (beak) or behaviour when in sympatry.
-natural selection will favour one of the birds
Increased floral divergence in sympatric monkeyflowers:
sympatric sister species are predicted to have greater _____ in reproductive traits than _____ sister species
divergence, allopatric
Galapagos finches’ beak sizes are an example of _____ displacement in _____ populations
character, sympatric
Increased floral divergence in sympatric monkeyflowers:
this study is an example of _____…_____
reproductive character displacement
similar species living at different heights in the same environment is an indicator of _____ _____
past competiton (or niche divergence)
the ghost of competition’s past
character displacement often is due to the competition between species in the past
artificial introduction of species into habitats where they previously did not exist frequently leads to the _____ of native species that occupy _____ _____
dispalcement, similar habitats
after arrival in a Nevada forest in 1978, 8 starlings displaced 12 species of native nesting birds, primarily through _____ _____ and _____…_____
aggressive harassment, direct competition for space
scotch broom introduced from Europe has greatly expanded and is now threatening native _____ _____
garry oaks
invasive non-native plant species grow _____ and _____
quickly, aggressively
what is allelopathy?
chemical competition in animals and plants
- the release of chemicals by one species in order to reduce growth/survivorship of another species
what is an example of allelopathy
roots of black walnut tree secrete juglone, highly toxic and kills or injures other plants within 20m radius of trunk
juglone is toxic to
herbivorous insects and other plants
salvia
produces volatile terpenes. Barren zone around them. With cages seeds germinated even in the presence of terpenes; there is an animal activity sufficient enough to produce this bare zone
what is a habitat
the physical place where an organism lives
what is a nice
how an organism makes its living
what is elton’s niche
the role of a species in a community
what is hutchinson’s niche?
all biophysical conditions that characterise the life of a species
what is a fundamental niche?
the entire multidimensional space that represents the total range of conditions within which an organism can function without limiting factors
what is a realized niche?
the actual multidimensional space that a species can occupy taking into account biotic factors such as predators, competitors and parasites
what equation quantifies niche overlap?
d/w
what is d?
distance between two species in average resource use
what is w?
measure of resource spectrum breadth of a species
given 3 species, what level of co-existence is achieved if d/w is <1?
no co-existence
given 3 species, what level of co-existence is achieved if d/w is >3?
full co-existence
as different resources come into account, the niche becomes an _____ _____
n-dimensional hypervolume
what is huchinson’s concept of niche space?
- 2 dimensional (height above ground, size of prey)
- don’t want it to overlap in height or horizontally
- niche space becomes a volume
what is the equation for Lotka and Volterra’s competition model?
dN/dt = rN[(K-N)-αN₂]/K
what does Lotka and Volterra’s competition model measure?
effect of species 2 on population growth of species 1
what is α?
competition coefficient
competition coefficient
- per capita competitive effect of species 2 on species 1
- a measure of the inhibitory effect of one individual of species 2 on the population growth of species 1
total competitive effect of species 2 on species 1 = ?
α*N₂
if alpha is 1, then _____ _____ of species 2 equals _____ _____ of species 1
one individual, one individual
if alpha is 0.1, then _____ _____ of species 2 equals _____ _____ of species 1
10 individuals, one individual
what is biophagy
one organism feeding on another
Types of biogaphy
- Carnivory
- Herbivory-grazing
->browsing (eats wood) - parasitm and parasitoids (parasitic wasps)
- pathogens
- scavengers and detritivores (consumption of dead plant or animal material)
what is the main cause of curves in survivorship curves?
predation
functional response curve (FRC)
rate of food consumption and density of prey (i.e. a numerical relationship between number of prey eaten by predators in relation to abundance of prey)
which FRC types describe a predator consuming a single prey species?
FRC I, and II
which FRC types describe a predator consuming multiple prey species?
FRC III
threshold of security
minimum density under which no further predation occurs
compensatory predation
predator behaviour at low prey densities
at low prey densities:
- reduced search efficiency
- prey switching
- search image
- aggregated responses of predators
virtually all predators target ___ and _____. there is minimal predation to _____
juveniles, post-reproductive adults, reproductive adults
why dont predators target reproductive adults?
high risk of injury, takes more energy.
what happens when they killed a bunch of kingfishers on the salmon study
number of smolts getting to the ocean increased (x3) BUT: number of adults returning after 3 years were the same (50)
- supports liebigs law
Grouse predation study
forest was split in two, predators were removed from one.
- in year one the control forest with predators lost more grouse but in year two there was the same amount of grouse. ( no statistical difference after 2 yrs)
effects of wold predation of caribou density:
population increases, greatly exceeds carrying capacity and then crashes
wolves keep caribou numbers from..
exceeding k
after wolves were removed, caribou population density temporarily increased from _____ caribou/km^2 to _____ caribou/km^2
0.4, 20
isle royale study
- lake froze and wolves went to island where moose live
- when the wolf population dec. there was more homozygosity and diseases
- needed more wolves to keep the moose from carrying capacity so more wolves were introduced
what do wolves in Isle Royale and parasitic wasps have in common?
both keep prey population under control
parasitoid process
- adult wasp delives 2 stings to the cockroach. First sting causes legs to buckle, 2nd sting in brain, controlling escape reflex
- leads to burrow, wasp lays egg on cockroach
- egg hatches and larvae chews into cockroach, eats organs for 8 days
- weaves cocoon inside cockroach and grows into adult and breaks out
what do dingoes and domestic cats have in common?
both collapse prey population
why are artificial predators so hard on native prey species?
no co-evolution
dingoes affect the _____ of wild pigs by almost eliminating ____
age structure, juveniles
when dingoes are absent what age class of wild pigs is most present?
- under 1 year
- when dingoes present more pigs are in 2-5 range, not many young
do predators limit prey density?
No: if liebigs law is acting
yes: if carrying capacity has been exceeded
yes: when native prey have no defenses against non-native predators
endotherm
an animal whose body temperature is regulated by the internal heat the animal produces
average biomass ratio of prey to predator endotherms
1: 300
ratio of biomass of prey to predator ectotherms
1:5, 20:100
what is the average exploitation rate of prey by each predator species?
~5%
what is the range of exploitation rate of prey by predator species?
5-10%
what is the fastest predator exploitation rate?
human predators
- exploiting 14x higher than other predators
- because we are targeting reproductive adults
what type of prey to natural predators take?
juveniles “ biological interest “ , the weak, the post-reproductive
exploitation rate of prey per preditor species: commercial fisherman take from ____ to ____%
natural predator take from _____ to _____ %
10 - 90% (generally 50%), 0-20%
3 factors that make humans “super-predators”
competitive dominance
impact on predators
other unique predatory behaviour
defenses against predators
camo, crypsis, conspicuous
speed, agility, stamina, protean behaviour
autotomy - limb release
armour.. spines
what are the 3 stages of hunting/foraging for prey?
search, pursuit, capture
what will protect prey during the search phase?
camouflage, crypsis, warning
what will protect prey during the pursuit phase?
speed, agility, stamina, protean behaviour
what will protect prey during the capture phase?
spines, armour, behaviour, autotomy, toxicity
what stage of being hunted ends in death?
capture
what is aposematic
warning coloration
why does aposematic colouration work
predators learn to minimize contact
what is mullerian mimicry?
many poisonous species develop similar conspicuous colour patterns (mimic each other)
what is batesian mimicry?
a non-stinging or edible species mimics a stining or poisonous species
batesian mimicry:
a hoverfly is the _____
a wasp is the _____
mimic, model
defoliation
to strip a tree, bush, etc of leaves
herbivory can reduce growth rate of a plant by up to ____%
25%
plant structural defenses:
to minimize browsing by large animals, plants grow _____
spines
effects of herbivory on plants
- loss of competitive ability
- defoliation
- go for young leaves, less lignin, more nutrients
- growth rate of plant reduced by up to 25%
plant defenses
- chemical
- structural defences
plant chemical defences
- unpleasant odour
- contact irritation
- bitter taste
- neurotoxins
- proteinase inhibitors
- growth hormone mimics
- psychotropic effects
unpleasant odour example
mustard
contact irritation example
poison ivy
- contact dermatitis
bitter taste example
berries when not ripe, tannins - alkaloids
neurotoxins
dinoflagellates
proteinase inhibitors
cotton, chickpea, potato
-inhibit the metabolism of these, they don’t get broken down and animal will starve to death
growth hormone mimic
cat nip
- mimics the moulting hormone if animal eats this, moults too early/late and die
psychotropic effects
Peyote (mescaline)
- antibrowing to kangaroo rats, flips out when they eat it
Caffeine
- when spiders have caffeine or mescaline, they suck at making webs
Animal defenses against plant chemical defenses
- mixed function oxidase - oxidation, hydrolysis, reduction
- concentration of toxins
- selective browsing
Concentration of toxins
- take toxins out of leaves they eat, metabolize this toxin to the brightest part of animal
(clams - black part = neurotoxins) - frog
- ants innoculate toxic leaves with fungus.. ants eat the fungus.. they have resistance to the poison… fungus concentrates the poison
