PLANT COMPETITION EXPERIMENT
Wear appropriate clothing, you’ll get dirty
Memory Stick or Floppy Disk
Today’s lab is a continuation of Lab 1.
your memory, we set up an experiment to reveal
the competitive effects of a weed (Bermuda grass)
on the growth of a common landscaping plant
(e.g. marigolds) with or without the addition of an
important nutrient (nitrogen).
Our goal is to
determine whether nitrogen addition alters
competitive interactions between Bermuda grass
and the flower. We will also use our results to
infer whether removal of Bermuda grass is
necessary to cultivate healthy looking flowers.
Organisms may interact with each other in a
number of ways.
These interactions are generally
grouped into three categories: consumption,
competition, and positive interactions.
consumption, one organism is harmed by another
when it is fed upon. Included in consumption are
herbivory, predation, and parasitism.
arises when two organisms require the same
resource, and that resource is in short supply.
contrast, a positive interaction occurs when at
least one species benefits from the relationship,
but neither species is harmed by the interaction.
An example of a type of positive interaction is
mutualism, where both partners benefit. Of the
three categories of interaction, competition has
probably been the most studied over the past
century, but it is not necessarily more important
than the other interactions.
There are two major types of competitive
interactions, intraspecific and interspecific.
competition occurs between
individuals of the same species, while
competition occurs between two
Because members of the same
species have identical resource needs,
intraspecific competition is in theory more severe
than interspecific competition.
Yet there are also
many examples of different species with very
similar resource needs.
states two species cannot
coexist if they share the same limiting resource.
Thus, according to this principle, similar species
usually cannot coexist because the superior
competitor drives the other species to local
extinction (if the two species had exactly the same
competitive ability then they could theoretically
coexist for a long time, but this situation is
Species need not be extremely similar
to compete with each other.
As long as two
species need the same limiting resource and
utilize it in the same way, they can be
competitors. For example, every plant, from a
grass to a cactus to an oak tree, needs phosphorus
from the soil to grow. If these species are growing
together, then they could potentially compete,
even though they have very different
morphologies and are not closely related species.
Competition, whether intraspecific or inter-