Course review
Review each learning objective in this topic, then open its concept explanation or question set.
Learning objective
• Ecological system composed of individuals, populations, communities, ecosystems • Parts of Earth where life exists
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Learning objective
• Individual organism is member of a species • Biological species concept: can interbreed and produce fertile offspring
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Learning objective
• Allows efficient identification and prediction of characteristics • Binomial nomenclature: genus (capitalized) + species (lowercase)
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Learning objective
• Dichotomous keys, specimen comparison, DNA surveys
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Learning objective
• Same species in same area at same time, capable of interbreeding
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Learning objective
• Abiotic: non-living physical factors • Biotic: living components
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Learning objective
• Temperature, sunlight, pH, salinity, dissolved oxygen, soil texture
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Learning objective
• A niche describes the particular set of abiotic and biotic conditions and resources upon which an organism or a population depends • An ecological niche is the role of a species in an ecosystem • The niche comprises all biotic and abiotic interactions that influence the growth, survival and reproduction of a population, including how food is obtained • Include: some of the parameters of a niche for a named species
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Learning objective
• Populations interact in ecosystems by herbivory, predation, parasitism, mutualism, disease and competition, with ecological, behavioural and evolutionary consequences • Consider: one example of each relationship and consider how the relationships influence the population dynamics of the interacting populations and the selective pressures involved
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Learning objective
• Carrying capacity is the maximum size of a population determined by competition for limited resources • Include: examples of resources that may affect carrying capacity, including biotic and abiotic factors
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Learning objective
• Population size is regulated by density-dependent factors and negative feedback mechanisms • Density-independent factors may influence population size, but density-dependent factors tend to regulate populations around carrying capacity • In addition to competition for limited resources, include the increased risk of predation and the transfer of pathogens in dense populations • These are examples of negative feedback returning a population to equilibrium
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Learning objective
• Population growth can either be exponential or limited by carrying capacity • If there are no limiting factors, population growth follows a J-curve (exponential growth) • When density-dependent limiting factors start to operate, the curve becomes S-shaped • Consider S-curves and boom-and-bust patterns, such as reindeer on St Matthew Island
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Learning objective
• Limiting factors on the growth of human populations have increasingly been eliminated, resulting in consequences for sustainability of ecosystems • Include: the effects of elimination of natural predators, technological advances, and degradation of the environment
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Learning objective
• Carrying capacity cannot be easily assessed for human populations • This is because of the broad and changing ecological niche of humans • Include: the idea of populations achieving equilibrium within ecosystems, but human populations being less limited due to mobility of resources • The expansion of the human niche also takes place through technological advances and changes in consumption
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Learning objective
• Population abundance can be estimated using random sampling, systematic sampling or transect sampling
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Learning objective
• Estimate population size for non-mobile organisms • Measures: percentage cover, frequency, abundance
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Learning objective
• Estimate population size for mobile organisms • Lincoln index: Population = (M × N) / R
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Learning objective
• Collection of interacting populations within ecosystem
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Learning objective
• Location where community, species, population, or organism lives
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Learning objective
• Energy and matter can enter and exit • Community + physical environment interactions
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Learning objective
• Natural property of ecosystems • Inputs balanced by outputs in steady-state • Some persist for millions of years (e.g., tropical rainforests)
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Learning objective
• Can lead to tipping points • Example: Amazon deforestation reduces transpiration → reduced rainfall
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Learning objective
• Keystone species have a role in the sustainability of ecosystems • There is a disproportionate impact on community structure of keystone species and the risk of ecosystem collapse if they are removed • Consider: two examples • For example, purple sea stars controlling mussel populations on the North Pacific coast that would otherwise overwhelm the ecosystem; elephants feeding on shrubs and trees
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Learning objective
• The planetary boundaries model indicates that changes to biosphere integrity have passed a critical threshold • There is an interrelationship between ecosystems and species diversity • Disturbance of ecosystems due to human activity has led to loss of biosphere integrity • Extinction rates provide evidence that the planetary boundary for biosphere integrity has been crossed
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Learning objective
• To avoid critical tipping points, loss of biosphere integrity needs to be reversed • Ecosystem damage and loss of species can be slowed by protecting the integrity of ecosystems • Protecting ecosystems ensures the preservation of the niche requirements essential for the ongoing survival of a species
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Learning objective
• Clades show evolutionary relationships within a taxonomic group • All clade members evolved from a common ancestor
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Learning objective
• Traditional hierarchy: kingdom, phylum, class, order, family, genus, species • This hierarchy does not always match evolutionary divergence patterns
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Learning objective
• Fundamental niche: conditions/resources where a species could survive and reproduce without limiting factors • Realized niche: actual mode of existence shaped by adaptations and competition • Examples: Connell barnacle species; brown and green anoles
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Learning objective
• Life cycles vary in reproductive behaviour and lifespan • K-strategists: stable communities, few offspring, high survival chance • r-strategists: rapid colonization, many offspring, limited survival provision
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Learning objective
• Classification, niche requirements and life cycles help explain human impacts • Examples: climate-driven plant life-cycle changes affecting animal life cycles
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