Ch. 12 Competition Flashcards
Venus flytrap
- has modified leaves that attract insects with nectar
- inner surface has touch-sensitive hairs
- if an insect trips those hairs, lead snaps shut in half a second
Pitcher plants
- lure insects into a pitcher-shaped trap
- inside of the pitcher has downward-facing hairs, which make it easy for the insect to crawl in, but hard to crawl out
- about halfway down, many pitchers have a waxy layer that sticks to insects feet, causing it to tumble into a vat that contains water or digestive juices
Why do some plants eat animals?
- competition among plants can be intense where soil nutrients are scarce
- in nutrient-poor environments, carnivory in plants has evolved multiple times
Experiment with pitcher plant
- removed noncarnivorous competitor plants
- some pitcher plants were starved
- growth rates increased when competitors were removed
- with neighbors intact, and pitchers covered, growth rate was not reduced as expected.. why?
Competition
An interaction between individuals in which each is harmed by their shared use of a limited resource
Interspecific competition
Between members of different species
Intraspecific competition
Between individuals of a single species
Limited resources
- features of environment required for growth
- which can be consumed to point of deletion
Examples of resources that can be consumed to depletion:
- food
- water in terrestrial habitats
- light for plants
- space, sessile organisms
- space for refuge, nesting, mobile organisms
Species also influenced by factors that are not consumed or depleted, such as..
- temperature
- pH
- salinity
Can’t have competition if resource is not ___.
Limited
Biases for the analyses of the study of the study showing that competition had significant effects on a wide range of organisms
- researchers may not publish studies that show no significant effects
- tendency for investigators to study species they suspect will show competition
Ghosts of competition past
Don’t see competition today, but today’s interactions were shaped by competition in the past
Exploitation competition
- species compete indirectly through their mutual effects on availability of a shared resource
Interference competition
Species compete directly for access to a resource
Antagonistic actions
Ex: when two predators fight over a prey item
Ex: when voles aggressively exclude other voles from preferred habitat
- Allelopathy
Individuals of one species release toxins that harm other species
Ex: spotted knapweed
Toxin called catechin
Competitive exclusion
When one species drives another to extinction
In many cases the effects of competition are unequal, or ___.
Asymmetrical
Amensalism
Individuals of one species are harmed while individuals of the other species are not affected at all
Niche overlap
The extent of common requirements of resources between two species
Competitive refuge
Ex: semibalanus dried out and survived poorly at the top of the intertidal zone
Removal experiments
Idk
Natural experiment
A situation in nature that is similar in effect to a controlled removal experiment
Ecological niche may be considered an..
“n-dimensional hyperspace”
Resource partitioning
Two species “share” a resource.. they use it differently
Niche differentiation
Competitive exclusion principle
Two species that use a limiting resource in the same way can not coexist
Niche breadth
“Width” of niche space
Breadth is reduced when competition is present
- How might one experimentally test if distribution is due to competition or some other factor?
Idk
Two Cyanobacteria species in the Baltic Sea
- Red BS1 absorbs green wavelengths most efficiently
- Green BS2 absorbs red mist efficiently
- each species could survive when grown alone in either wavelength
- when grown together, one drove the other to extinction, depending on the wavelength used
- under white light, they both persisted
Two Cyanobacteria then studied in lakes and oceans
- only red Cyanobacteria were found in clear waters
- only green Cyanobacteria were found in turbid waters
- both were found in intermediate waters
- able to coexist because they are partitioning the light resource
Competition coefficients
Alpha and beta
Lotka-Volterra competition model
can be used to predict the outcome of competition
Supports the idea that competitive exclusion is likely when competing species require very similar resources
If competing species use the same resources in a similar fashion -> one will likely go extinct
- Competitive reversal
An inferior competitor in one habitat, or under different conditions, may become the superior competitor in another
Ex: Tansleys bedstraws
Example of competitive reversal
When ragwort flea beetles were introduced to western Oregon, biomass of ragwort, an invasive species, decreased, and its competitor species increased
In a sense of flea beetles, ragwort is superior competitor
Disturbances
Fires or storms
___ such as fires or storms can kill or damage individuals, while creating opportunities for others.
Disturbances
