Ecology Flashcards
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
Intrinsic Biotic Factors
• Regulation from within the population – Genotypic changes – Physiological changes • Crowding stress – Chitty effect • Social regulation of reproduction – Disruption of pregnancy • Immunological dysfunction – Immunocompetence selection hypothesis
Extrinsic Biotic & Abiotic
Mechanisms
• Interspecific interactions
– Predation
• Climatic processes that alter food supply
Multifactor Mechanisms
• Population cycles are complex
• Vary in space and time
• Still no consensus on causes of population
cycles in small mammals
Communities
• Formed by plants and animals with similar
environmental requirements
• Generally in disequilibrium
• Communities are characterized by:
– Interspecific interactions
– Diversity
– Trophic structure
– Succession
• Diversity is determined by:
– Climatic history
– Geography
– Latitude
– Host of biotic factors
Species Diversity Patterns
• Latitudinal diversity gradient – Species richness increases toward equator • Elevational diversity gradient – Mountainous regions have higher richness – Important factors • Mountain size • Spatial constraints • Climate
Species-Area Relationships
• Habitat diversity hypothesis
– Larger areas have greater habitat diversity
and therefore more niches to be filled
• Passive sampling hypothesis
– Larger areas sample more individuals, and
therefore, more species
• Dynamic equilibrium hypothesis
– Species diversity on islands is determined by
island size, immigration, and extinction
Species Interactions
• More diverse communities have more potential species interactions – Interspecific competition – Commensalism – Mutualism – Predation – Parasitism • Interactions are often very complex
Interspecific Competition and
Community Composition
• Competition depends on degree of niche overlap • Alleviating competition – Niche differentiation – Competitive exclusion – Foraging guilds
