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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Vocabulary words are found below

 

 

(1) Chapter title: Community Ecology

(a)                    [community ecology (Google Search)] [index]

(2) Community

(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]

(3) Coevolution

(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]

 

WITHIN-COMMUNITY INTERACTIONS

 

(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

+ / - -

Predation

- / -

Competition

 

(h)                    [interspecific interaction (Google Search)] [index]

(5) Commensalism

(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]

(6) Mutualism

(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]

 

PREDATION

 

(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]

(8) Defense against predation

(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

(i)                      Secondary compounds

(ii)                    Nutritional deficiencies

(iii)                   Mechanical defenses

(f)                      [plant defences (Google Search)] [index]

(10) Secondary compounds

(a)                    Secondary compounds are chemicals that plants produce that are distinct from the primary metabolism to some extent common to all plants

(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]

(11) Nutritional deficiencies

(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]

(12) Mechanical defenses

(a)                    Anything a plant can do to keep a herbivore from reaching, biting, or deriving benefit from once a piece that has been removed can serve to protect the plant from being consumed

(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]

(14) Cryptic coloration

(a)                    Cryptic coloration is camouflage, the art of looking like something else, i.e., not hiding behind something but instead not being visible against appropriate backgrounds

(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]

(15) Aposematic coloration

(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]

(16) Batesian mimicry

(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]

(17) Müllerian mimicry

(a)                    Mimicry works in everybody's favor when unpalatable species mimic each other (e.g., both wasps and bees sharing black and yellow aposematic coloration)

(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