Ch. 53 Communities Assembly of species living close enough together for possible interaction Differ...
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Transcript of Ch. 53 Communities Assembly of species living close enough together for possible interaction Differ...
Ch. 53
Communities
Assembly of species living close enough together for possible interaction
Differ in species richness
Coevolution
• describes interactions involving reciprocal evolutionary adaptations in 2 species
Table 53.1 Interspecific Interactions
Interspecific Interactions
• Occur between populations of different species living together within a community
• Predation
• Parasitism
Interspecific Interactions - Predation
Community interactions where one species eats another species
Plant defenses
• whole plant is rarely consumed
• mechanical (thorns, hooks, spines)
• chemical (bad taste, produce abnormal development in insects that feed upon them)
Interspecific Interactions - Predation
Animal defenses• passive
– hiding
• active– escaping, fleeing, self-defense,
mobbing, alarm calls
• chemical– toxins (skunk, poisonous toads)
Figure 53.5 Camouflage: Poor-will (left), lizard (right)
Figure 53.6 Aposematic (warning) coloration in a poisonous blue frog
Interspecific Interactions - Predation
Animal defenses
Adaptive coloration
• cryptic (camouflage)
• aposematic (bright; coloring acts as a warning of another physical or chemical defense)
Figure 53.x1 Deceptive coloration: moth with "eyeballs"
Figure 53.7 Batesian mimicry
Figure 53.8 Müllerian mimicry: Cuckoo bee (left), yellow jacket (right)
Interspecific Interactions - PredationMimicry• bears a superficial resemblance to another
species• batesian: a palatable species mimics a bad
tasting model• mullerian: 2 or more unpalatable species,
aposematically colored species resemble each other
• luring prey– tongue of snapping turtle looks like a worm
Interspecific Interactions - Parasitism
Host is harmed in some way
Endoparasites
• live within host’s tissues or body cavities
• tapeworms, Ascaris
Ectoparasites
• attach or briefly feed on the external surface of the host
• mosquito, aphid
Interspecific Competitions
Occurs when 2 or more species in a community rely on similar limiting resources
2 ways competition occurs
• interference (actual fighting over resources)
• exploitative (consumption or use of similar resources)
Interspecific Competitions
Competitive exclusion principle
• predicts that 2 species competing for the same limiting resources cannot coexist in the same community
• one uses resources more efficiently so it reproduces faster
Interspecific Competitions
Ecological niches
• sum of the total of an organism’s use of biotic and abiotic resources in its environment
• how an organism “fits” into its environment
Interspecific CompetitionsFundamental niche• resources a population is theoretically
capable of using under ideal conditionsRealized niche• resources a population actually uses• biological constraints
– competition, predation, resource limitation
Interspecific Competitions
• If niches are identical for 2 species, cannot coexist
• Ecologically similar species can coexist
Interspecific Competitions
Evidence for competition• should be rare if competitive exclusion
principle applies• weaker competitor becomes extinct• one of the species will evolve to use
another set of resources• huge impact on shaping niches
Interspecific Competitions
Speciation• Sympatric• Allopatric
Interspecific CompetitionsCharacter displacement• tendency for characteristics to be more
divergent in sympatric populations of 2 species than in allopatric populations of the same species
Figure 53.x3 Commensalism between a bird and mammal
SymbiosisForm of interspecific interaction in which a
host species and a symbiont maintain a close association
Commensalism• symbiont benefits/host unaffected
• cowbirds and cattle egrets
This shows the symbiotic relationship commensalism, the bird getsfood from the back of the cow but the cow is not affected
SymbiosisMutualism
• a change in the symbiont affects the host
• root nodules of legumes
• Ants and acacia trees
(video clip)
When coyotes and badgers team up, the pairs track small, burrowing animals such as prairie dogs and ground squirrels. If the prey is above ground, the coyote usually chases it down, and the badger takes over the hunt if the prey descends underground. And not only do they find food together, but coyotes also have more success in this partnership than if they go it alone.
SymbiosisParasitism
• host is
harmed
Disturbance & NonequilibriumDisturbances
• events that disrupt communities
• humans (most widespread agent)
Succession
• process of change that results from disturbances in communities
• ecological
• primary
• secondary
SuccessionEcological• transition in species composition over timePrimary• begins in areas eventually barren of life
due to lack of formed soil or on rubbleSecondary• if an existing community has been created
by some disturbance that leaves the soil in tact
Disturbance and Nonequilibrium
Recruitment
• colonization by species from distant areas not directly associated with the disturbed patch or its immediate vicinity