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Flashcards in Community ecology Chapter 53 Deck (108):

What are the two main outcomes due to species interactions - competition, consumption and mutualism

•(1) they affect the distribution and abundance of the interacting species, and

(2) they are agents of natural selection and thus affect the evolution of the interacting species. The nature of interactions between species frequently changes over time.


A biological commuinity changes over time, what are the primary reasons for that change


historical events


Species is richer where

and lower where

richer in large islands near continents than small isolate islands - immigration and extinction

Richer in tropics - lower in the poles


define biolobical comminity

•A biological community consists of interacting species, usually living within a defined area.


What are biologists asking about comminities

how the work, how to manage them to preserve a species so that ppl will want to live there too


define fitness

•fitness—the ability to survive and produce offspring—of the individuals involved.


due to community interactions bt species, how does that affect the fate of a population

linked to other species that share its habitiat


•A relationship between two species that provides a fitness benefit to members of one of the species is

a + interaction.


•Such a relationship that hurts members of one of the species is a

– interaction.


•A relationship that has no effect on the members of either species is a

0 interaction.


• List the four general types of interactions among species in a community:






define competition


When individuals us the same resources - resulting in lower fitness for both (--)


Define consumption


1.when one organism eats or absorbs nutrients from another, increasing the consumer’s fitness but decreasing the victim’s fitness (+/-).


define mutualism

occurs when two species interact in a way that confers fitness benefits to both (+/+).


define commensalism

1.when one species benefits but the other species is unaffected (+/0).


define coevolutionary arms race

coevolutionary arms race occurs between predators and prey, between parasites and hosts, and between other types of interacting species.


analyzing each type of species interaction - what are the three key themes


  1. Species interactions may affect the distribution and abundance of a particular species.
  2. Species act as agents of natural selection when they interact. In biology, a coevolutionary arms race occurs between predators and prey, between parasites and hosts, and between other types of interacting species
  3. The outcome of interactions among species is dynamic and conditional.


define competition

•is a –/– interaction that lowers the fitness of the individuals involved.  When competitors use resources, those resources are not available to help individuals survive better and produce more offspring.


define intraspecific competition

•occurs between members of the same species.
–Because intraspecific competition for resources intensifies as a population’s density increases, it is a major cause of density-dependent growth.


define interspecific competition

when members of different species use the same limiting resourses


define niche

•niche—the range of resources that the species is able to use or the range of conditions it can tolerate.


•Interspecific competition occurs when the ____________________

niches of two species overlap.


what is the competitive exclusion principle

it is not possible for species within the same niche to coexist.


in developing the competitive exclusion principle, what experiments were run to develop this hypothesis

•species of the unicellular pond-dweller Paramecium.
–Grown in separate cultures, both species exhibited logistic growth.
–When the two species grew in the same culture together, only one species exhibited logistic growth; the other species was driven to extinction.


define asymmetric competition

•when one species suffers a much greater fitness decline than the other.


define symmetric competition

each species experiences a roughly equal decrease in fitness.


•If _______________________occurs and the two species have completely overlapping niches, the stronger competitor is likely to drive the weaker competitor to extinction or to retreat to areas of nonoverlap.

asymmetric competition


define fundamental niche

1.A species’ fundamental niche is the resources or areas used or conditions it tolerates in the absence of competitors.


define realized niche

1.A species’ realized niche is the resources or areas used or conditions it tolerates when competition occurs.


•If _________________ occurs and the niches of the two species do not overlap completely, the weaker competitor will move from its fundamental niche to a realized niche, ceding some resources to the stronger competitor.

asymmetric competition


connell set experiments to test the competitive exclusion principle, what were they

•studies—removing one of the competitors and observing the response by the remaining species.

•exclusion of Chthamalus barnacles from the lower intertidal zone by Balanus barnacles.


define fitness trade-off

If individuals are extremely good at competing for a particular resource, they are probably less good at enduring drought conditions, warding off disease, or preventing predation


•Because competition is a ________________ interaction, there is strong natural selection on both species to avoid it.

negative negative


define niche differentiation or resource partitioining

•The predicted eventual outcome is an evolutionary change in traits that reduces the amount of niche overlap and the amount of competition.


•The change in species’ traits is called _______________

character displacement.


Peter and Rosemary Grant recently documented character displacement in Galápagos finches - what did they find after the two droughts

1977 - Only those individuals with larger beaks were able to crack open the fruits of their major food source, Tribulus cistoides

•2003; by this time the large ground finch, Geospiza magnirostris, had become established on the island. 
•this time, only the smallest-beaked G. fortis individuals survived.

•Data on feeding behaviour indicated that G. magnirostris were outcompeting G. fortis for Tribulus cistoides; only G. fortis that could eat extremely small seeds efficiently could survive.


what are one of the major threats to commuities

invasive species


•One of the goals of conservation biology is to ______________

keep biological communities intact.


experiments have shown that communities that contain a ________ number of different species are more resistant to invasion than communities with a ______ number of species




___________ is a +/– interaction that occurs when one organism eats another.



list the three major types of consumption

  •  herbivory
  • parasitism
  • predation


define herbivory

1.the consumption of plant tissues by herbivores.


define parasitism

the consumption of small amounts of tissues from another organism, or host, by a parasite


define predation

1.Predation is the killing and consumption of most or all of another individual (the prey) by a predator.


list the constitutive defences



fighting back

schooling and flocking behaviours

sposematic colouring


define aposemmatic colouring

poisonous animials exhibit bright warning colouring


•Some of the best-studied constitutive defences involve ___________—the close resemblance of one species to another.



what are the two forms of mimicry




define mullerian mimicry


1.the resemblance of two harmful prey species.


define batesian mimicry the resemblance of an innocuous prey species to a dangerous prey species.


•Many prey species have______________—defensive traits produced only in response to the presence of a predator.

inducible defences

efficient energetically, but slow

ie mussels


•The data available to date indicate that in many instances, predators are efficient enough to_____________________ ______________________________

reduce prey populations below carrying capacity.


•Biologists recently conducted a ____________—they compiled the results of more than 100 studies—and raised the question of why herbivores don’t eat more of the available plant food.



Why herbivores don’t eat more of the available plant food.

•Biologists consider two hypotheses to help answer the question:
1.The ___________ hypothesis suggests that predation or disease limits herbivores.
2.The ______________ hypothesis suggests that plants provide poor nutrition or are well-defended against herbivory.

top-down control

bottom-up limitation


•Cottonwood trees and two of their herbivores, beavers and leaf beetles, provide an example of both top-down and bottom-up controls on herbivory.
state is the top-down example

•Top-down control, nitrogen limitation, and effective defence are all important factors in limiting the impact of herbivory.

•The mix of factors that keeps the world green varies from species to species and habitat to habitat.


adaptations and arms races

When consumers and prey interact over time, a coevolutionary arms race begins - that happens


–Consumers evolve traits that increase their efficiency.

–In response, prey evolve traits that make them unpalatable or elusive.
–This leads to selection on consumers for traits that counter the prey adaptation, and so on.

•example is the interaction between the parasite Plasmodium (the consumer) and their host humans (the prey).


•Plasmodium are unicellular protists that cause __________, which kills at least a million people a year.



Recent data suggest that humans and Plasmodium are locked in a coevolutionary arms race

what is the evidence of this

–In West Africa, the HLA-B53 allele confers protection against malaria by displaying a signal that induces an immune response. 
–Individuals with at least one HLA-B53 allele are better able to fight malarial infections.
–However, some Plasmodium populations appear to have evolved resistance to these defences.


how do parasites manipulate their hosts

nematodes parasitize species of tree-dwelling ants - lay eggs in the posterior changing it`s colour

ants hold up their posterior - look like berries = birds eat them

nematodes complete their life cycle inside birds = feces = eaten by ants

increased likeliness parasite will be transmitted to a new host, whange the appearance of ants, and manipulatie their behaviour


•________________________: strategies to maximize crop and forest productivity while using a minimum of insecticides or other types of potentially harmful compounds.

integrated pest management


_____________ are +/+ interactions that involve a wide variety of organisms and rewards. 



–Flowering plants and their pollinators.
–Mycorrhizal fungi and plant roots.
–Bacteria that fix nitrogen and certain species of plants.
–Rancher ants and aphids.
–Farmer ants and fungi.
–Crematogaster ants and acacia trees.
–Cleaner shrimp and fish.


•Even though mutualisms benefit both species, the interaction does not involve individuals from different species being _______________



•The benefits received in a ____________ are a by-product of each individual pursuing its own self-interest by maximizing its ability to survive and reproduce.



mutualims - dynamic

Because the costs and benefits of species interactions are fluid, an interaction between the same two species may vary from ___________________________

parasitism to mutualism to competition


predictability of communities

Clements argued that communities develop by passing through a series of predictable stages dictated by extensive interactions among species, and that this development culminates in a stable final stage called a_______________

climax community

experimental testing suggest that Clements`position was to extreme


predictability of communities

Henry Gleason, in contrast, contended that the community found in a particular area is _______________________

neither stable nor predictable

•it is largely a matter of chance whether a similar community develops in the same area after a disturbance occurs.

experimental testing found that Gleason`s view is closer to accurate


•A study of planktonic communities in experimental ponds showed that.....

identical communities do not develop in identical habitats. Each pond had a unique species assemblage.


experimental testing has found that which species inhabit a particular site is influences by

biotice interations





mapping current and past species`distributions

•Historical data on plant communities showed that groups of species change their ranges ______________ of one another; fossil pollen studies suggest that plant community composition has always been _________________


dynamic, rather than static.


•A_________________ is a species that has a much greater impact on the surrounding species than its abundance would suggest.

keystone species


•A_____________________is any event that removes some individuals or biomass from a community.


•it alters some aspect of resource availability.


The impact of disturbance is a function of three factors

what are they





•Most communities experience a characteristic type of disturbance, and in most cases, disturbances occur with a predictable frequency and severity. 
–This is called a community's _____________

disturbance regime.


•Ecologists use two approaches to determine the pattern of disturbance in a community:
what are they

1.Obtaining data in a short-term analysis and extrapolating to predict the longer-term pattern.
2.Reconstruction of the history of a particular site.


•To maintain communities in good condition, biologists have to ensure that the ___________________occurs. Otherwise, community composition changes dramatically.

normal disturbance regime


•____________________ is the recovery and development of communities following a severe disturbance.



•_____________________ occurs when a disturbance removes the soil and its organisms, as well as organisms that live above the surface: Glaciers, floods, volcanic eruptions, and landslides.

Primary succession


•_______________________ occurs when a disturbance removes some or all of the organisms from an area but leaves the soil intact: fires and logging.

Secondary succession


•______________ are dominated by species that are short lived and small in stature, and that disperse their seeds over long distances.

Early successional communities


•_______________________________ are dominated by species that tend to be long lived, large, and good competitors for resources such as light and nutrients.

Late successional communities


•The specific sequence of species that appears over time is called the ______________


successional pathway.


•Three factors determine the pattern and rate of species replacement during succession at a particular time and place:

list them

1.The particular traits of the species involved.
2.How the species interact.
3.Historical and environmental circumstances, such as the size of the area involved and weather conditions.


•________________, the first organisms to arrive at a newly disturbed site, tend to be “weedy”; weeds are plants adapted for growth in disturbed soils.

Pioneering species


•__________________species devote most of their energy to reproduction and little to competitive ability.

Early successional

•These species have good dispersal ability, being able to tolerate severe abiotic conditions, and high reproductive rates.


role of species interactions

During succession, existing species can have one of three effects on subsequent species

what are they





________________ occurs when early-arriving species make conditions more favourable for the arrival of certain later species by providing shade or nutrients.



_________________ happens when existing species do not affect the probability that subsequent species will become established.



______________ occurs when the presence of one species inhibits the establishment of another.



•In addition to species traits and species interactions, the pattern and rate of succession depend on the _______________________ context in which they occur.

historical and environmental


•Succession is also affected by the ________________ that occur during the process. Variation in weather and climate causes different successional pathways to occur in the same place at different times.

climate conditions


•____________________ is the number of species present in a given community.

Species richness


_________________________ is a weighted measure that incorporates a species’ relative abundance, as well as its presence or absence

Species diversity


•The _______________ is usually positively correlated with habitat size.  However, islands in the ocean have smaller numbers of species than do areas of the same size on continents.

number of species


•The number of species present on an island is a product of just two events:

immigration and extinction.


•Immigration rates should decline as the number of species on the island increases because:

–Individuals that arrive are more likely to represent a species that is already present.
–Competition should prevent new species from becoming established when many species are already present on an island.


•______________________ should increase as species richness increases, because niche overlap and competition for resources will be more intense.

Extinction rates


•MacArthur and Wilson formulated the model called the theory of island biogeography.

•Their theory makes two predictions—species richness should be higher on:

1.Larger islands than smaller islands.
2.Near shore islands versus remote islands.


•The theory of island biogeography is important because:



1.It is relevant to a wide variety of island-like habitats such as alpine meadows, lakes and ponds, caves, and habitats isolated by human development.
2.It is relevant to species that have metapopulation structure.
3.It made specific predictions that could be tested.
4.It can help inform decisions about the design of natural preserves.


•Biologists have long understood that__________________tend to be species rich, and the theory of island biogeography has been successful in framing thinking about how species richness should vary among island-like habitats.

large habitat areas


Researchers have had a much more difficult time explaining what may be the most striking pattern in species richness

what was this

–In the mid-1800s, biologists recognized that communities in the tropics have more species than communities in temperate or subarctic environments.


[*] Data compiled in the intervening years have confirmed the existence of a _________________ in species diversity—for communities as a whole as well as for many taxonomic groups.

strong latitudinal gradient


latitudinal gradient in species diversity

to principles to explain the pattern

1.The causal mechanism must be abiotic.
2.The species diversity of a particular area is the sum of four processes: speciation, extinction, immigration, and emigration.


latitudinal gradient

1.The _______________hypothesis proposes that high productivity promotes high diversity.



Latitudinal Gradient

1.The____________ hypothesis contends that high temperature increases productivity and the likelihood that organisms can tolerate the physical conditions in a region.



Latitudinal Gradient

1.The___________________ hypothesis argues that the tropical regions have had more time and space for speciation than other regions.

area and age


Latitudinal Gradient

The _______________________ hypothesis states that regions with a moderate type, frequency, and severity of disturbance should have high species richness and diversity

intermediate disturbance


•You should be able to
–Explain how interactions among species affect the distribution and abundance of the interacting species.
–Describe the different interactions among species and how they act as agents of natural selection.
–Predict what might happen if a new species is introduced to an area and competes with an existing species.
–Describe the factors that influence the pattern of succession that occurs after a disturbance.
–Compare and contrast species richness and diversity.
–Calculate the Shannon index of species diversity.
–Explain why higher species richness is found in the tropics than in temperature regions.