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Chapter 55

BIO SCI 94 Chapter 55: Chapter 55

Biological Sciences
Course Code
Robin Bush

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Community: all of the species that interact in a certain area
Community Ecology
Commensalism: one species benefits, the other is unaffected
Competition: individuals use same resources, resulting in lower fitness for both
Consumption: one eats/ absorbs nutrients from another -- increases consumer's fitness but
decreases victims fitness
Mutualism: two species interact in a way that confers fitness benefits to both
General types of interactions:
Coevolution: pattern of evolution where two species influence each other's
adaptations over time
Coevolutionary arms race: repeating cycle of reciprocal adaptation
Species act as agents of natural selection when they interact
The outcome of interactions among species is dynamic and conditional
Key themes:
Intraspecific competition: within species; occurs when niches of two species overlap
Interspecific competition: between species
Niche: range of resources that species is able to use
Symmetric competition: if both species experience similar decrease in fitness due to overlap
of their niches
Asymmetric competition: when one species suffers greater fitness decline than the other
species does
Competitive exclusion principle: Two species that occupy the same niche cannot coexist
Fundamental niche: total theoretical range of environmental conditions that a species can
Realized niche: portion of fundamental niche that species actually occupies, given limiting
factors such as competition with other species
Common experimental strategy in competition studies: one of the competitors is removed,
and the response by the remaining species is observed
Fitness trade-offs: inevitable compromises in adaptation
If individuals are extremely good at competing for particular resource, then they are
probably not good at enduring drought conditions, warding off disease, or preventing
Because competition is a -/- interaction, there is strong natural selection on both species to
avoid it
Niche differentation: resource partitioning; evolutionary change in resource use caused by
competition over generations
Character displacement: evolutionary change that occurs in species traits and that enables
species to exploit different resources; makes niche differentation possible
Herbivory: herbivores consume plant tissues
Parasitism: parasite consumes relatively small amount of tissue/ nutrients from host
Predation: predator kills and consumes another individual
Natural selection strongly favors standing/ constitutive defenses traits that allow
individuals to avoid being eaten -- hide, flee, poison, threaten to poison, school together,
Species Interactions
Chapter 55
Friday, March 23, 2018
4:46 AM
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