Competition/Predation Flashcards
what are the two definitions for interspecific competition
1) the simultaneous requirements by two or more species for a resource that occurs in limited supply
2) any use or defense of a resource by one species that reduces the availability of that resource to other species
what is a resource
any substance that leads to changes in individual or population growth if the substance is increased or decreased
was nitrogen determined to be a resource
for plants yes, major. For humans no
Liebig’s law of the minimum
growth is not dictated by the total resources available, but the scarcest resource (limiting factor)
What is the competition exclusion principle or ‘gauses’s law of competitive exclusion’
2 species with the same niche cannot coexist
Grain Beetle situation
- 2 degree difference in environment switches competitive ability of 2 beetle species
- habitat diversity
what did the ocean study discover
nitrogen-iron co-limitation
- need to add both things for organisms to grow
Evidence for interspecific competition in nature
- Habitat shifts in allopatry and sympatry
2) Character displacement
3) Habitat differences and resource partitioning
4) Allelopathy
Habitat shifts in allopatry and sympatry
- when species separated do one thing
- when put together, they will change their habitat to stay away from eachother
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
habitat differences and resource partitioning (2)
- the ghost of competitions past
2. competition in the present
the ghost of competition’s past
character displacement often is due to the competition between species in the past
competition in the present
- invasive species
- frequently leads to the displacement of native species that occupy similar habitats
- e.g. starling was introduced. very aggressive, space competition
allelopathy
chemical competition in plants and animals
- the release of chemicals by one species in order to reduce growth/survivorship of another species
example of allelopathy
black walnut trees secrete jugalone which is highly toxic and kills/injures other plant species within a 20 m radius
- some species r resistant to jugalone
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
niche
how an organism makes its living
elton’s niche
the role of a species in a community
hutchinson’s niche
all biophysical conditions that characterize the life of a species
fundamental niche
the entire multidimensional space that represents the total range of conditions within which an organism can function without limiting factors
realized niche
the actual multidimensional space that a species can occupy taking into account biotic factors such as predators, competitors and parasites (a lot smaller than fundamental niche)
how to calculate co-existance?
d/w
if d/w < 1 : no coexistance
if d/w > 3 : full coexistance
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
biogaphy
the biological consumption of things
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)
Graph. Number of prey eaten per predator over density of prey
- linear graph doesn’t often exist in nature
- usually steep slope then begins to hit a asymptote on x-axis
- predator gets full
- can also be like an S, with a low slope on the bottom
COMPENSATORY PREDATION
- at low densities, predators have a hard time finding their prey
- prey switching (go for most common type of prey)
- search image (only go for one type of prey)
- aggregated responses of predators (all predators come together, focus on areas where prey is v dense)
functional response curves for: proportion of prey population consumed over prey density
- Straight horizontal line
- straight line, negative slope
- upside down u kinda… low prey densities it is harder for predators to find prey but as it goes up more prey is consumed
what do virtually all predators target
- juveniles
- post reproductive adults
why do they target juveniles/post reproductives
low cost of injury
- exception: fishing
- graph kinda like a U - if age is x-axis
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)
- not enough prey for them?
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.
Leibig’s Law of the minimum
growth is not determined by resources available, it is determined by the MOST limiting factor
muskrat predation
most mink predation on muskrats occured on the ones that didn’t have a territory
What animals did this also happen with
Caribou when they killed the wolf predators
- numbers exceed K and then crash
- wolves limit the maximum prey density
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
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
When dingoes are absent what age class of wild pigs is most present
- under 1 year (young)
- when dingoes present more pigs are in the 2-5 range, not many young
Do predators limit prey density?
No: if leibig’s law of the minimum is acting
Yes: if carrying capacity has been exceeded
Yes: when native prey have no defenses against non-native predators
average biomass ratio of prey to predator ENDOTHERMS
0.3:100
ratio of biomass of prey to predators in ECTOTHERMS
1: 5
20: 100
exploitation rate of prey by each predator species
average ~ 5% for each predator species
what is the fastest predator exploitation rate
Human predators
- exploiting 14x higher than other predators
- because we are targeting reproductive adults
defenses against predators
- camo, crypsis, conspicuous
- speed, agility, stamina, protean behaviour
- autotomy - limb release
- armour.. spines
conspicuous defense
bright, scary colouration
- usually poisonous or noxious
- sometimes capable of producing injury
- predators learn to minimize contact
Mullerian mimicry
- poisonous species mimic eachother (similar colour patterns)
- butterflies
Batesian Mimicry
a non poisonous species mimics a poisonous/stinging species
batesian mimicry examples
- hoverfly mimics yellowjacket wasp. Hoverfly cannot sting
2. butterflies
