Chapter 45 Community Ecology. 45.1 Fighting Foreign Fire Ants Native to Brazil, imported fire ants...
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Transcript of Chapter 45 Community Ecology. 45.1 Fighting Foreign Fire Ants Native to Brazil, imported fire ants...
![Page 1: Chapter 45 Community Ecology. 45.1 Fighting Foreign Fire Ants Native to Brazil, imported fire ants (Solenopsis invicta) nest in the ground and have painful.](https://reader035.fdocuments.in/reader035/viewer/2022081421/551b4e42550346d31b8b4e93/html5/thumbnails/1.jpg)
Chapter 45Community Ecology
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45.1 Fighting Foreign Fire Ants
• Native to Brazil, imported fire ants (Solenopsis invicta) nest in the ground and have painful stings
• Global trade and shipping brought fire ants to the US and to other countries around the world
• Fire ants have a negative impact on native species of plants, insects, birds, and other animals
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Red Imported Fire Ants
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Communities
• Species interactions such as competition or predation are one focus of community ecology
• A community is all the species that live in a region
• Species interactions and disturbances can shift community structure (types of species and their relative abundances) in small and large ways
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45.2 Which Factors Shape Community Structure?
• Community structure refers to the number and relative abundances of species in a habitat
• Habitat• The type of place where a species normally lives
• Community• All species living in a habitat
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Species Diversity
• Communities vary in their species diversity
• Two components of species diversity:• Species richness: the number of species• Species evenness: the relative abundance of each species
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Community Structure
• Many factors influence community structure• Abiotic factors such as climate• Gradients of topography• Species interactions (direct and indirect)
• Symbiosis refers to direct, long-term interactions:• Commensalism: One species benefits and the other is
neither benefited nor harmed• Mutualism: Both benefit• Parasitism: Parasite benefits, host is harmed
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Table 45-1 p810
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Commensalism
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Take-Home Message: What factors affect species in a community?
• The types and abundances of species in a community are affected by physical factors such as climate and by species interactions.
• A species can be benefited, harmed, or unaffected by its interaction with another species.
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45.3 Mutualism
• Mutualism is a species interaction in which each species benefits by associating with the other• Flowering plants and animal pollinators• Birds that disperse seeds• Lichens, mycorrhizae, and nitrogen-fixing bacteria that
help plants obtain nutrients• Animals share nutrients with mutualistic microorganisms in
their gut• Two species may protect one another
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Obligate Mutualism: Yucca and Moth
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Mutual Protection
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Take-Home Message: What are the effects of participating in a mutualism?
• A mutualism benefits both participants.
• In some cases, two species form an exclusive partnership. In others, a species provides benefits to, and receives benefits from, multiple species.
• Participating in a mutualism has both benefits and costs. Selection favors individuals who maximize their benefits while minimizing their costs.
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45.4 Competitive Interactions
• Resources are limited; individuals of different species often compete for access to them
• Interspecific competition hurts both species
• Competition among individuals of the same species is more intense than interspecific competition
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The Niche
• Each species requires specific resources and environmental conditions that we refer to as its ecological niche
• Both physical (abiotic) and biological (biotic) factors define the niche
• The more similar the niches of two species are, the more intensely the species will compete
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Interspecific Competition
• Interference competition• One species actively prevents another from accessing a
resource
• Exploitative competition• Species reduce the amount of a resource available to the
other by using that resource
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Interference Competition
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Effects of Competition
• Competitive exclusion• When two species require the same limited resource to
survive or reproduce, the better competitor will drive the less competitive species to extinction in that habitat
• Competitors can coexist when their resource needs are not exactly the same• Competition suppresses growth of both species
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Competitive Exclusion in Paramecium
Stepped Art
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P. caudatum alone
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P. aurelia alone
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Both species together
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ANIMATED FIGURE: Competitive exclusion
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Competing for Pollinators
Mimulus Lobelia
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Resource Partitioning
• Resource partitioning is an evolutionary process by which species become adapted to use a shared limiting resource in a way that minimizes competition (directional selection)
• Example: Eight species of woodpecker in Oregon feed on insects and nest in hollow trees, but the details of their foraging behavior and nesting preferences vary
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Character Displacement
• Over generations, directional selection leads to character displacement – the range of variation for one or more traits is shifted in a direction that lessens the intensity of competition for a limiting resource
• Example: Where two species of salamanders coexist, differences in body length becomes more pronounced
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Character Displacement in Salamanders
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ANIMATED FIGURE: Hairston's experiment
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Take-Home Message: What happens when species compete for resources?
• In some interactions, one species actively blocks another’s access to a resource. In other interactions, one species is simply better than another at exploiting a shared resource.
• When two species compete, selection favors individuals whose needs are least like those of the competing species.
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45.5 Predator–Prey Interactions
• Predation is an interspecific interaction in which one species (predator) captures, kills, and eats another species (prey)
• Relative abundances of predators and prey shift over time in response to species interactions and changing environmental conditions
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Predator Responses to Changes in Prey Density
• Type I response (passive predators)• Number of prey killed depends on prey density
• Type II response• Number of prey killed depends on the predator’s capacity
to capture, eat and digest prey
• Type III response• Number of kills increases only when prey density reaches
a certain level
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Responses of Predators to Prey Density
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A Type 2 Response
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Figure 45-9b2 p814
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ANIMATED FIGURE: Predator-prey interactions
To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
![Page 34: Chapter 45 Community Ecology. 45.1 Fighting Foreign Fire Ants Native to Brazil, imported fire ants (Solenopsis invicta) nest in the ground and have painful.](https://reader035.fdocuments.in/reader035/viewer/2022081421/551b4e42550346d31b8b4e93/html5/thumbnails/34.jpg)
Cyclic Changes in Abundance
• Time lag in predator response to prey density can lead to cyclic changes in abundance
• When prey density is low, predators decline, prey are safer, prey numbers increase
• When prey density is high, predator numbers increase, prey numbers decline
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Canadian Lynx and Snowshoe Hare
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Predator and Prey
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Take-Home Message: How do predator and prey populations change over time?
• Predator populations show three general patterns of response to changes in prey density.
• Population levels of prey may show recurring oscillations.
• The numbers in predator and prey populations vary in complex ways that reflect the multiple levels of interaction in a community.
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45.6 An Evolutionary Arms Race
• Predators select for better prey defenses, and prey select for more efficient predators
• Prey defenses include exoskeletons, unpleasant taste, toxic chemicals or stings, and physical adaptations such as camouflage
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Coevolution of Predators and Prey
• Predator and prey populations exert selective pressures on one another
• Genetic traits that help prey escape will increase in frequency
• Defensive improvements select for a countering improvement in predators
• Example: Spraying beetles and grasshopper mice
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Defense and Counter Defense
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Some Physical Adaptations of Prey
• Warning coloration• Many toxic or unpalatable species have bright colors and
patterns that predators learn to avoid
• Mimicry• A harmless animal looks like a dangerous one
• Camouflage• Body shape, color pattern and behavior that make an
individual blend in with its surroundings
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Warning Coloration and Mimicry
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Camouflage in Prey and Predators
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Coevolution of Herbivores and Plants
• With herbivory, an animal feeds on plants
• Two defenses have evolved in response to herbivory:• Some plants withstand and recover quickly from the loss
of their parts• Some plants have physical deterrents (spines, thorns,
tough leaves); or chemical deterrents (secondary metabolites that taste bad or sicken herbivores)
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Take-Home Message: How do predation and herbivory influence community structure?
• In any community, predators and prey coevolve, as do plants and the herbivores that feed on them.
• Defensive adaptations in plants and prey can limit the ability of predators or herbivores to exploit some species in their community.
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45.7 Parasites and Parasitoids
• With parasitism, one species (parasite) benefits by feeding on another (host), without immediately killing it
• Endoparasites such as parasitic roundworms live and feed inside their host
• An ectoparasite such as a tick feeds while attached to a host’s external surface
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Endoparasites
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Ectoparasites
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Parasite Diversity
• Parasitism has evolved in members of a diverse variety of groups
• Bacterial, fungal, protistan, and invertebrate parasites feed on vertebrates
• Lampreys attach to and feed on other fish
• Parasitic plants that withdraw nutrients from other plants
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Dodder: A Parasitic Plant
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Strangers in the Nest
• With brood parasitism, one egg-laying species benefits by having another raise its offspring• Examples: European cuckoo, cowbird
• One cowbird can parasitize 30 nests per season, decreasing the reproductive rate of the host species
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Cowbird with Foster Parent
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Parasitoids
• Parasitoids are insects that lay eggs in other insects
• Their larvae develop in the host’s body, feed on its tissues, and eventually kill it
• As many as 15 percent of all insects may be parasitoids
• Example: parasitoid wasps
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Biological Pest Controls
• Some parasites and parasitoids are raised commercially for use as biological pest control agents
• Example: Parasitoid wasps lay eggs in aphids
• Introducing a species into a community as a biological control has both advantages and risks
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Biological Pest Control Agent
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Take-Home Message: Effects of parasites, brood parasites, and parasitoids
• Parasites reduce the reproductive rate of host individuals by withdrawing nutrients from them.
• Brood parasites reduce the reproductive rate of hosts by tricking them into caring for young that are not their own.
• Parasitoids reduce the number of host organisms by preventing reproduction and eventually killing the host.
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45.8 Ecological Succession
• Ecological succession is a process in which one array of species replaces another over time
• It can occur in a barren habitat such as new volcanic land (primary succession) or a disturbed region in which a community previously existed (secondary succession)
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Pioneer Species
• Primary succession begins when pioneer species such as lichens and mosses colonize a barren habitat with no soil
• Pioneer species are opportunistic colonizers of new or newly vacated habitats
• Pioneers help build and improve soil for later successional species
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Primary Succession: Alaska’s Glacier Bay
![Page 60: Chapter 45 Community Ecology. 45.1 Fighting Foreign Fire Ants Native to Brazil, imported fire ants (Solenopsis invicta) nest in the ground and have painful.](https://reader035.fdocuments.in/reader035/viewer/2022081421/551b4e42550346d31b8b4e93/html5/thumbnails/60.jpg)
ANIMATED FIGURE: Succession
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