Ecology Flashcards
(34 cards)
Ecology:
“A study of animals and plants and their
relations to each other and their
environment”
Ecological Scales
• Geographic – Microhabitat – Globe • Organisms – Individuals – Populations – Species – Communities – Ecosystems
What determines where mammals
live?
Biotic
Abiotic
History
Abiotic: Global Climate Patterns
• Solar radiation influences climate – Not uniform over Earth’s surface • Warm air holds more moisture – Equatorial areas more humid • 25ºN to 25ºS latitude • Cooler air carries less moisture – Belt of deserts around 30ºN and 30ºS
Biomes
• Climate affects distribution of plants and animals • Biological communities described from dominant vegetation • Large-scale biological communities are called biomes – Dynamic in space and time – Grade into each other, forming ecotones
Habitat Requirements
• Niche
—the specific environmental setting
a species occupies and the functional
“role” it plays in this habitat
Habitat Requirements (small scale) • Local environment is not uniform – – • Some patches are higher in quality of resources • Microhabitats – – –
• Local environment is not uniform – Vegetation mosaics – Habitat patches • Some patches are higher in quality of resources • Microhabitats – Subnivean zone in winter – Den or lodge vs. outside temperatures – Density and type of vegetation
Habitat Requirements • Theory predicts individuals should always select best possible habitat – Environments vary, resources patchy – Best habitats may be in short supply
• Real-world scenarios – When population density is low, all members may occupy high-quality habitats – When density is high, some members are forced into marginal habitats
Habitat Requirements of Territorial Species
• Ideal despotic distribution
– Predicts that best habitats are occupied by dominant
individuals
– Subordinate animals forced to marginal habitats
– At high density, some subordinates may be forced to
disperse
• Home range
– Area traversed by an individual during its
normal activities
– May have irregular shapes and partly overlap
– Core area may be defended
• Territory
– Area occupied and actively defended by an
individual or group
• Natal dispersal
– Individuals move permanently away from birth
area
• Breeding dispersal
– Adults relocate between breeding attempts
• Philopatry
– Remaining and breeding in the natal area
Dispersal
• Polygynous mammals
– Dispersal tends to be male-biased – Males benefit by dispersing to find more mates – Females provide care and benefit from local knowledge of resources
Dispersal
• Monogamous mammals
– Female-biased dispersal may evolve
– Males secure and defend resources
• Individuals’ fitness may be increased by dispersal because: – Dispersal avoids inbreeding – Dispersal may reduce local mate competition – Dispersal may reduce competition for other resources
• Dispersal may be genetically
driven (innate behavior)
Population Regulation
– Density-dependent factors • Competition • Reproductive rate • Predation pressure • Dispersal • Disease and parasite loads – Density-independent factors • Natural disasters
• Competition
– When 2+ individuals occupy the same
habitat at the same time, using a limited
environmental resource
– May be direct or indirect
– May be intraspecific or interspecific
– Typically most intense among conspecifics
Disease & Parasitism
• Disease – Transmission rate increases with crowding – Known to be significant causes of mortality among mammals • Parasites – May also cause species extinction – Healthy animals can often tolerate a moderately heavy parasite load
Predation
• Functional response
– Higher prey density results in increased prey consumption
by each predator
• Numerical response
– Predator density increased with increasing prey density
Generalist VS Specialist Predators
• Generalist predators tend to stabilize prey
populations
• Specialist predators may destabilize
numbers of their primary prey
Population Cycles
• Occur primarily in rodents and lagomorphs
at high latitude w/ specialist predators
• Are regular, periodic, high in amplitude,
and synchronous across wide geographic
areas
Regulation in Cyclic Populations
• Hypotheses controlling cycles grouped
into categories
– Abiotic factors
– Intrinsic biotic factors
– Extrinsic biotic factors
