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describes relationship between rate of consumption of a single predator, and food density. (satiation= to full compacity)
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ecology - Details
1) Chapter 1
Describes relationship between rate of consumption of a single predator, and food density. (satiation= to full compacity)
As prey density increases, so does the predator density. An increase in predator reproduction as well because they are eating enough to survive and produce plentifully.
Rate of consumption per predator is proportional to prey density. no satiation.. While density of prey increases so does the number of prey consumed. Linear upward graph
Type 1 predator
Number of prey consumed per predator increases rapidly then plateaus. Curved graph. Satiation is achieved
Type 2 predator
Predator response to prey is depressed at low prey density. satiation is achieved.
Type 3 predator
Forage in the best patches, ignore the patches with low resource levels, and remain in a patch until its profitability declines to average for the area then leave.
Marginal Value theorem
Avoid good foraging areas if predation risk is high.
Specialized herbivores evolved to feed on specific host plants. They are able to detoxify specific secondary compounds, and likely explain insect herbivore specialization.
Large conspicuous plants rely on Quantitative defenses to thwart generalized grazers.
Tannins bind to proteins and inhibit their digestion by herbivores. Most common in K-selected animals.
Cyanogenic glycosides (chemical that releases cyanide) always stored in specific parts of the plant. Mostly found in annuals or other short-lived plants.
Assumes that foraging behavior is shaped by natural selection because foraging success should be related to fitness.
Optimal foraging theory predictions
Obtain the maximum amount of energy per unit of time
Obtain as much energy as possible in the least amount of time (seems like the much more favored option of the two for natural selection.)
Where the predator preferentially consumes the most common type of prey.
Mimics that resemble a model aposematic species with defenses are benefited if predators avoid them. (can also be used as camouflage)
Defined model and harmless mimic
Batesian (aposematic mimicry)
Both species defended to mutual benefit by creating stronger selection on predators
Mullerian (aposematic mimicry)
Plants response to herbivores damage. It is a costly toxin that is only produced when the plant is attack and is sent to where the damage is.
Selective pressure on prey survival should be greater than selection for increased predatory efficiency. -a failed predation attempt results in a predator missing a meal, failing to avoid a predator means death.
-resistance and tolerance to parasites varies among hosts. (evolved defenses) -host specialization of parasites is common (evolved offensive strategies) -parasites often have high lethality rate in new hosts (host eventually evolved greater resistance to parasite.) -parasites can be generalists or specialists.
Patterns of coevolutions
-competition with other parasites -variability in abundance of host species -number of selective pressures across host species
Parasite specialization or generalization depends on ...
-they are asymbiotic. Can only be obligate. -non-producers (they feed ogg their host) -they are not very lethal and require direct contact)
General characteristics of parasites
Small and extremely numerous (bacteria, viruses, protozoans) -intracellular -multiply within the host -epidemiology is to track the # of infected hosts rather than parasites (often impossible)
Large and extracellular (complex life cycles with life stages outside the host) -epidemiology can include estimates of parasite load and # of infected hosts.
Live within the body of the host (worms, viruses, bacteria, protozoans, prions)
Live on the outside of the body of the host
Photosynthetic parasites, but with root systems poorly developed or entirely lacking.
-many human infectious diseases come from animal sources (zoonotic) -bats carry most viruses (ebola, marburg, SARS, corona) and pose the largest threat, followed by primates and rodents. -estimated 17 new viruses (per bat species) and 10 each from primates and rodents -mutations allow infection of new hosts species -environmental changes promote emergence
Emerging infectious diseases
H1N1 (bird flu)- bird to human HIV non-human primates to humans.
Mutations allow infection of new host species
White-nose syndrome in bats -snake fungal disease -chytrid fungus is amphibians
Environmental changes promote emergence
When differential indidivuals (whether intraspecific or interspecific) experience depressed fitness due to their consumption of shared resources.
Competition occurs when...
Can provide an advantage for inferior competitors -harsh abiotic conditions (fire, natural events) -disturbance
Can disproportionately impact certain species and reduce their competitive advantage. -keystone predator concept -predator susceptibility
Puts a "top down" effect on the food chain. if a dominant predator is present, than another dominant species will not be as dominant. If the top species is removed, then the other species will thrive. (example of starfish and mussels)
Keystone species influence
-by removing various components, complement synthetic-assemblage experiments in exploring the relationship between diversity and ecosystem functioning. -barnacles experiment: removed the balanus and the chthamalus barnacles could live in the lower intertidal zone, even though they are only found in the high tide zone.
How competition is demonstrated experimentally
(occurs in plants) secretion of chemicals that inhibit the germination and growth of competitor.
Consumption of common limiting resources reduces population growth of competitors
Active prevention of resource use by competitors (through aggressive interactions or crowding)
Occurs when a superior competitor drives another species to extinction
Competitive exclusion principle
Experimental manipulation of competitor densities will provide evidence of competition.
Occurs when a competitors low population density appears to be a result of competition, but is actually explained by something else. Not really what is seems because the actual story is different.
Describes a species use of resources in the absense of competition
Adjustments in resource use to avoid competition
Results from niche separation as a consequence of competition
Diversity driven by large number of feeding niches available. -an island ancestor of the honeycreeper group arrived in hawaii and evolved into a large variety of species
Communities composed of randomly assembled species with similar environmental tolerances
Community composition shaped by competition -species niches are separated along resource gradients
Niche based model
Boundaries between adjacent communities are sometimes determined by a single physical factor
Groups of coexisting species that use the same resource types.
Reducing the amount of predation on one species can cause it to grow allowing for less diversity and more abundance
Top down effect
Keystone species that affect community structure by altering habitat structure
Species by their physiological tolerances to abiotic factors.
Responses to competition and other species interaction.
-facilitation -inhibition -tolerance
How species are established and replaced...
Resident species makes conditions favorable for invasion by other species
Resident species make conditions less favorable for establishment or persistence of others.
The ability to persist in a given set of environmental conditions
Transient communities destroyed and re-established in place following frequent disturbance. (temporary ponds) In a transient succession the resources are only there for a limited time. -in an established community, the organisms compete for resources that are dependable.
How transient succession differs from succession in an established community
-early succession species are replaces by shade tolerant species (rapid growth requires high photosynthetic) -rapid succession occurs in some aquatic systems because of short generation times and rapid dispersal of dominant species.
How life history traits explain species presence in seral stages
Species have traits that facilitate colonization of open bhabitats. -transient and mobile (tand to have fast life histories) -survive in the landscape by dispersing to disturbed habitats to escape competition (fugitive species)
Final stage of succession, remaining relatively unchanged until destroyed by an event such as fire or human intervention
A sequence of stages that occur during succession, beginning with pioneer species and ending with a climax community
A community that persists (continues to do well) due to disturbance. example: after a wildfire
Destroyed and re-established in place following frequent extreme disturbance (temporary ponds)