Important words and concepts
from Chapter 53, Campbell & Reece, 2002 (3/25/2005):
by Stephen T. Abedon (abedon.1@osu.edu)
for Biology 113 at the Ohio State University
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Course-external links are
in brackets Click [index] to access site index Click here to access
text’s website Vocabulary
words
are found below |
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(1) Chapter title: Community Ecology
(a)
[community ecology (Google Search)]
[index]
(a)
A community consists of all of the organisms living within a certain
geographical area
(b)
These organisms include conspecifics as well as members of other
species
(c)
These organisms interact with each other both directly and indirectly
(d)
Numerous (pessimists might say "endless") parameters affect
what species are present and in what abundance
(e)
"Simple generalizations can rarely explain why certain species
commonly occur together in communities."
(f)
"The distributions of most populations in communities are probably
affected to some extent by both abiotic gradients and interactions [with other
species]."
(g)
[community and ecology
-"community ecology" (Google Search)]
[index]
(a)
Not only do the abiotic and biotic components of an ecosystem impact on
what species are present and in what abundance, but species also are modified
by their interactions with other species
(b)
Coevolution represents the evolutionary modification of organisms in
response to other organisms, particularly when two organisms are mutually
modified in response to modifications displayed by the other
(i)
E.g., a flower population better attracts certain insects which in turn
evolve to better exploit the flower population
(ii)
E.g., faster rabbits select for faster coyotes which in turn select for
faster rabbits
(c)
"In its broadest sense, coevolution is the term used to describe
more complex interactions involving reciprocal evolutionary adaptations in two
species: A change in one species acts as a selective force on another species,
and counteradaptation by the second species, in turn, is a selective force on
individuals in the first species. Coevolution has been studied most extensively
in predator-prey
relationships and in mutualism."
(d)
"It is difficult to sort out the importance of the various
selective forces, and the simple idea of coevolution as
adaptation-counteradaptation occurring exclusively between two species does not
often adequately describe the interactions within communities."
(e)
"Despite the problems in assessing cause and effect in the
evolution of complex ecological relationships, biologists agree that the
adaptation of organisms to other species in a community is a fundamental
characteristic of life. Put another way, interactions of species in ecological
time often translate into adaptations over evolutionary time."
(f)
Strictly, however, coevolutionary relations may be limited to
interactions between two species rather than modifications that affect a suite
of species; for example, an ability to run faster in order to escape predators
is not quite the same thing as an ability to run faster in order to escape one
predator species (which, if it wants a meal, would then be exposed to selection
to run even faster); this narrowing limits the applicability of the idea of
coevolution since it creates a criteria that is stricter then simply more
effectively interacting with other species in terms of survival and
reproduction
(g)
[coevolution (Google Search)]
[index]
(4) Interspecific interactions
(a)
Coevolution is one consequence of a more general category of ecology
called interspecific interactions (between-species interactions)
(b)
Previously we considered intraspecific interactions,
i.e., those between very similar organisms, conspecifics
(c)
Interspecific interactions range from those between fairly similar
organisms to those between very dissimilar organisms
(d)
A key distinction between intraspecific and interspecific interactions
is that the former but not the latter share a gene pool;
(i)
intraspecific interactions do not generally lead to the extinction of a
species
(ii)
In interspecific interactions, losers can go extinct
(e)
Interspecific interactions include symbioses and can be categorized as
(i)
Predation/parasitism (+/-)
(ii)
Competition (-/-)
(iii)
Commensalism (+/0)
(iv)
Mutualism (+/+)
(f)
The plusses and minuses are a notation employed by your text indicating
the relative gain each participant obtains from the interaction
(g)
See Table 53.1,
Interspecific Interactions
|
Interspecific Interactions |
|
|
+ / o |
Commensalism |
|
+ / + |
Mutualism |
|
+ / - |
Parasitism Parasitoidism Herbivory |
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+ / - - |
Predation |
|
- / - |
Competition |
(h)
[interspecific interaction
(Google Search)]
[index]
(a)
Commensalism is a relatively unexploited interspecific interaction
(b)
The reason for this has as much to do with its definition as anything,
i.e., commensalism is a relationship in which one member gains but the other
member neither gains nor loses; this places commensalism on a knife's edge
between predation and mutualism
(c)
If the "unaffected" individual is indeed affected, even just
a little, then the relationship can no longer, technically, be termed
commensalism
(d)
In the real world it is essentially impossible to determine whether the
"unaffected" member really is unaffected, so the concept is difficult
to apply
(e)
Nevertheless, in absence of evidence for mutualism or predation
then an assumption of commensalisms is a reasonable one
(f)
[commensalism (Google Search)]
[index]
(a)
Mutualisms, while not necessarily as common as predation or interspecific competition, are still enormously common
(b)
This makes some sense since a mutualistic relationship is one in which
both members gain
(c)
However, it is likely that most mutualistic relationships started out,
in evolutionary time, as exploitative (+/-) relationships which somehow were
co-opted into less exploitative relationships
(d)
Examples include everything from lichens, to bees and flowers, to
mitochondria and the already lectured on eucaryotic cell
(e)
[mutualism (Google Search)]
[index]
(7)
Predation
(a)
+/- interactions include
(i)
Predation
(ii)
Parasitism
(iii)
Parasitoidism
(iv)
Herbivory
(b)
These interactions all involve
(i)
one individual killing and then eating the other fully (predation)
(ii)
not killing and then eating the other partially (parasitism and
herbivory), or
(iii)
letting one's offspring do the eating (parasitoidism)
(c)
Note that an additional kind of +- interaction does not involve eating
but instead is the stealing of some non-food a resource from one individual by
the other: vines on trees, for example, or a cow bird's brood parasitism
(d)
[predation (Google Search)]
[index]
(a)
Prey organisms display numerous defenses against predation
(b)
That is, there exist a number of defenses
against + / - - (as well as + / -) interactions:
(i)
Secondary compounds (plants)
(ii)
Nutritional deficiencies (plants)
(iii)
Mechanical defenses (plants)
(iv)
Production of poisons (animals)
(v)
Mechanical defenses (animals)
(vi)
Running away & hiding (animals)
(vii)
Fighting back (mostly animals)
(viii)
Cryptic coloration (mostly animals)
(ix)
Batesian mimicry (animals)
(x)
Müllerian mimicry (animals)
(xi)
Immune systems (animals)
(c)
[in order for a predator to obtain benefit from prey they have to
encounter prey (i.e., be in close proximity), then detect prey (i.e., notice
that they currently are in close proximity), then capture prey, then
successfully consume the prey, and then successfully derive nutrient benefit
from the prey, and minimally more benefit must be derived than the costs of
capturing and consuming the prey – hence, it is to the potential prey’s
benefit, as an individual or as a population, to minimize their numbers so as
to be rare and therefore rarely found by predators, to be cryptic in both
coloration and behavior, to be capable of escaping if noticed, to be difficult
to consume or to digest, and to not supply necessary nutrients or to be toxin
to the predator in some manner]
(d)
[defence against predation
(Google Search)]
[index]
(9) Plant defenses against predation
(a)
Of course, plant predators are called herbivores
(b)
Typically a plant (and other stationary organisms) will not manage to
achieve complete avoidance of predation, but instead will limit their own
predation to those organisms that possess appropriate morphological or
biochemical adaptations
(c)
It is important to keep in mind that herbivores can be big (cows) as
well as small (insects, fungi, bacteria) so more than one defense is typically
necessary to defeat all possible predators
(d)
Of course, plants also tend to be eaten in pieces rather than as a
whole organism, so anything a plant can do to spare part of the plant from
being eaten can also be advantageous (this rule apparently is also true in
terms of defenses against lawn mowers)
(e)
Plant defenses against predation include
(iii)
Mechanical defenses
(f)
[plant defences (Google Search)]
[index]
(a)
(b)
One role of secondary compounds are as defenses against predation,
e.g., toxins
(c)
What is toxic to one herbivore may be useful to another; particularly
humans take great advantage of plant secondary chemicals using them as drugs
(both recreational and medicinal), spices, etc.
(d)
Some animals (e.g., monarch butterflies) can actually incorporate these
toxins into themselves to make themselves unpalatable to some of their own
predators
(e)
[secondary compounds
(Google Search)]
[index]
(a)
Plants additionally tend to lack certain nutrients (e.g., essential
amino acids)
(b)
Such nutritional deficiencies force predators to diversify what plants
they consume, thus preventing herbivores from getting too good (specialized) at
exploiting a particular plant species
(c)
[(Google Search)]
[index]
(a)
(b)
Thorns prevent larger things from comfortably eating a plant, while
hairs and other small appendages can keep small things from reaching the plant
(c)
This the trunk of a honey locust displaying its multibranched, red
thorns à
(d)
Plants also interfere with chewing by, essentially, being less than
succulent, e.g.,. the shell of a nut or silica deposited in the leaves of grass
(e)
(between nutritional deficiencies, mechanical defenses, and secondary
compounds one speaks of low forage quality and it is plants that represent
low-quality forage that tend to accumulate when herbivore pressures are high,
i.e., high animal to plant ratios)
(f)
[mechanical defenses
(Google Search)]
[index]
(13) Animal defenses against predation
(a)
Animals are a little bit more versatile behaviorally when it comes to
defending themselves against predation
(b)
For example, animals can
(i)
Run and hide (particularly the latter aided by cryptic coloration)
(ii)
Produce poisons that make them unpalatable
(iii)
Employ morphological adaptations that interfere with consumption
(iv)
Fight back using both morphological and chemical defenses (some plants,
too, can fight back using, for example, actively sprayed chemical defenses)
(v)
Not looking like prey (cryptic coloration)
(c)
[animal defenses (Google Search)]
[index]
(a)
(b)
["Camouflage, called cryptic coloration, is the quintessential
passive defense, making potential prey difficult to spot against its
background. A camouflaged animal need only remain still on an appropriate substrate
to avoid detection."]
(c)
See Figure 53.5, Camouflage: a canyon tree frog disappearing into a
background of granite
(d)
[cryptic coloration
(Google Search)]
[index]
(a)
A different approach is to taste bad (or be unpalatable for various
other reasons) and to advertise this
(b)
Aposematic coloration is how organisms advertise unpalatableness, at
least visually (humans, or course, display a distinct bias in terms of sensory
input hence we tend to notice the visual displays by animals much more so than,
for example, the olfactic displays – notice that since birds display the same
bias we often interpret these visual displays in terms strategies that
interfere with predation by birds)
(c)
For example, the black and yellow stripes on bees represent aposematic
coloration, and it works!
(d)
Aposematic coloration is so successful, in fact, that it gives rise to
mimicry
(i)
Batesian mimicry
(ii)
Müllerian mimicry
(e)
See Figure 53.6, Aposematic (warning) coloration of a poison-arrow frog
(f)
[aposematic coloration
(Google Search)]
[index]
(a)
Batesian mimicry is the tendency of palatable and otherwise succulent
prey species to pretend to be unpalatable by looking like unpalatable species
(b)
This works to a point, but limits the size of the mimic's population
since once mimics are sufficiently prevalent, predators will catch on to the
mimicry
(c)
However, when their numbers are sufficiently few, the mimic gains from
protection from predation while simultaneously not putting out the resources
needed to achieve lack of palatability, etc.
(d)
See Figure 53.7, Batesian mimicry
(e)
[Batesian mimicry (Google Search)]
[index]
(a)
(b)
Such mimicry increases the representation of lack of palatableness
among potential prey associated with a given form of aposematic coloration
(c)
Note that both Batesian and Müllerian mimicry can occur simultaneously
with the same aposematic coloration within the same communities (i.e., a group
a similarly marked organisms, some of which are harmless and others which are
not)
(d)
See Figure 53.8, Müllerian mimicry