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Community Ecology
Chapter 54
Community
Interspecific interactions Interactions with different species Competition Predation Herbivory Symbiosis
Interspecific Competition
Two species compete for resources Competitive exclusion: One species utilizes resources
more efficiently Eliminates the other
Paramecium
Niche
Species use of resources in its environment
Abiotic & biotic Fundamental niche: Area that a species is capable of
utilizing Realized niche: Actual resources the species utilizes
Resource Partitioning
Species use similar niches Subdivide available resources Warbles (small bird)-spruce trees Lizards in Dominican republic Character displacement: Sympatric species diverge more
than allopatric species
Barnacles
Resource partitioning
Predation
Consuming of one organism by another
Predators
Animal defenses
Hide or run Chemicals (bees, wasps, scorpions,
spiders) Snakes, lizards, frogs Coloration Aposematic: warning Cryptic: blending
Aposematic
Cryptic
Animal defenses
Mimicry Batesian: Harmless animals mimic harmful
animals Mullerian: Several harmful animals look the
same (safety in numbers)
Batesian mimicry
Mullerian mimicry
(a) Mechanicaldefense
(b) Chemicaldefense
(c) Aposematic coloration:warning coloration (d) Cryptic
coloration:camouflage
(e) Batesian mimicry:A harmless speciesmimics a harmfulone.
(f) Müllerian mimicry:Two unpalatablespecies mimiceach other.
▶ Porcupine ▶ Skunk
◀ Poisondart frog
▶ Canyontree frog
◀ Nonvenomoushawkmoth larva ◀ Cuckoo bee
◀ Yellowjacket
▲ Venomous greenparrot snake
Mimic octpus(a) Mimicking a
sea snake
(b) Mimicking a flounder
(c) Mimicking a stingray
Herbivory
Organism eats part of a plant Thorns, spines, prickles Chemicals Mustard oils, milkweed, nicotine
herbivore
Symbiosis
2 or more organisms interact in a permanent relationship
Lichen Mycorrhizae Types of symbiosis Commensalism Mutualism Parasitism
Commensalism
Interaction benefits one organism But neither harms nor helps the
other Fish & sea anemones Egrets & cattle
Commensalism
Commensalism
commensalism
Mutualism
Interactions benefit both species Flowers and bees, birds or bats Ants and acacias (plant)
Mutualism
mutualism
Mutualism
Parasitism
One organism benefits at the cost of its host organism
Parasite is usually smaller than host Ectoparasites (external) Ticks. lice Endoparasites (internal) Tapeworms
Parasitism
Community structure
How these interspecific interactions work all together
1. Predation reduces competition 2. Parasitism vs competition 3. Indirect effects (rodents and ants) 4. Keystone species Species that has a strong effect on the
composition of a community
Keystone species
Succession
Communities change from simple to complex over time
Secondary succession: New community arises where an
old community was disturbed Primary succession: New community arises on bare
lifeless substrate (glacier receding)
Primary succession
Secondary succession