Course review
Review each learning objective in this topic, then open its concept explanation or question set.
Learning objective
• A population is interacting organisms of the same species in one area • Members have opportunities to interbreed and may be reproductively isolated from others
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Learning objective
• Population size is estimated when full counts are impractical • Random sampling reduces bias; stratified and systematic sampling fit different habitats
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Learning objective
• Quadrats estimate density, frequency, cover, or abundance of sessile organisms • Random coordinates and known quadrat area support representative population estimates
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Learning objective
• Capture-mark-release-recapture estimates motile animal populations • Lincoln index assumes marks persist, mixing occurs, and marking does not affect survival
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Learning objective
• Carrying capacity is the maximum population an environment can sustain • Limited food, space, mates, and other resources create competition near capacity
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Learning objective
• Density-dependent factors regulate populations by negative feedback • Competition, predation, waste, and disease intensify as population density rises
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Learning objective
• Exponential growth occurs when resources are abundant and limiting factors are weak • Sigmoid growth slows as resources limit growth near carrying capacity
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Learning objective
• Sigmoid curves can be modelled with yeast, duckweed, or other fast-growing organisms • Lag, exponential, transition, and plateau phases show changing growth rate
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Learning objective
• Intraspecific competition occurs for food, mates, space, or light • Cooperation such as social hunting or parental care can increase survival and reproduction
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Learning objective
• A community is all interacting populations in an ecosystem • Species interactions make populations interdependent within the abiotic environment
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Learning objective
• Interspecific relationships occur between different species in communities • Categories include herbivory, predation, competition, mutualism, parasitism, and pathogenicity
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Learning objective
• Mutualism benefits both species through exchanged resources or protection • Examples include legumes and Rhizobium, orchids and mycorrhizae, corals and zooxanthellae
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Learning objective
• Endemic species are native to a restricted geographic area • Invasive species can escape controls and compete with endemic species for niche resources
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Learning objective
• Competition is tested using lab experiments, field observations, or removal studies • Connell's barnacle study links removal experiments to fundamental and realized niches
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Learning objective
• Chi-squared tests association between two species from quadrat presence/absence data • Compare observed and expected counts, degrees of freedom, and critical values
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Learning objective
• Predator-prey relationships regulate populations through density-dependent feedback • Snowshoe hare and lynx cycles show time-lagged predator and prey changes
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Learning objective
• Top-down control begins with predators and cascades to lower trophic levels • Bottom-up control begins with producers or resources and affects higher trophic levels
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Learning objective
• Allelopathy releases chemicals that inhibit competitor germination or growth • Antibiotics are microbial allelochemicals, such as penicillin from Penicillium
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