Population Ecology Quiz

Population Ecology

• Population: A group of individuals from the same species living in the same area and time, capable of interbreeding.
• Population is described by its boundaries and size.
• Metapopulation: A group of geographically separated populations of the same species interacting at some level.
• Density: The number of individuals per unit area, resulting from immigration and emigration.
• Species range: The area where a species is found.
• Dispersion: The spacing pattern of individuals within a population's boundaries.
  • Clumped spacing: Uneven distribution of resources, leading to grouping.
  • Uniform spacing: Behavioral interactions/resource competition causing even distribution.
  • Random spacing: Individuals do not interact strongly, distribution is independent of others.
• Types of Interactions:
  • Abiotic: How organisms react with non-living components. Factors like water availability and temperature determine species range when other species are not limiting.
  • Biotic: How organisms interact with other organisms. Factors include predators, diseases, and food sources. Negative impacts include effects of predators and diseases; positive impacts are related to food sources.
  • Immigration: Movement of new individuals into a population from other areas.
  • Emigration: Movement of individuals out of a population.

Population Size Determination

• Sampling: Counting individuals with constant density.
• Mark-Recapture: Method for mobile populations.
  • Capture, mark, and release a random sample (S).
  • Wait for them to mix in the population.
  • Capture a second sample.
  • Count the marked individuals in the second sample (X) and the total number captured in the second sample (n).
  • Calculate population size (N) using the formula: N = (S * n) / X.

Population Dynamics

• Populations grow through birth and immigration, and decline through death and emigration.
• Exponential growth: Occurs when all individuals have access to abundant food and reproduce at a constant rate. Per capita rate of increase (dN/dT)=rN, where dN is the change in population size, dT is the change in time, and r is the intrinsic rate of natural increase. N is the number of individuals. Population growth is exponential when resources are unlimited.
• Logistic growth: Growth rates change as population size approaches carrying capacity. Per capita rate of increase approaches zero. Carrying capacity (K) is the maximum population size a given environment can sustain. Population size affects growth rates as the population size approaches the carrying capacity.
• Carrying capacity (K): Maximum population size a particular environment can support. Differs across space and time.

Demography

• Demography: Study of population size, structure, and dynamics over time.
• Life table: Survival pattern of a population across age classes.
• Cohort: Group of individuals of the same age.
• Survivorship curves: Graphic representation of survival rates over time.
  • Type I: Low death rates early in life.
  • Type II: Constant death rate throughout life.
  • Type III: High death rate early in life.

Ecosystem Ecology

• Ecosystem: All organisms living in a community.
• Energy flow: Energy transfer within an ecosystem; never 100% efficient.
  • Primary producers (plants) convert light energy to chemical energy.
  • Herbivores (primary consumers) eat plants.
  • Carnivores (secondary and tertiary consumers) eat other animals.
• Primary production: Amount of light energy converted to chemical energy. Gross primary production (GPP) is total primary production; net primary production (NPP) is GPP less the energy used for cellular respiration.
• Secondary production: Amount of energy consumers convert to biomass. Production efficiency (PE) is the fraction of energy stored as food that is used for secondary production.
• Assimilation: Total energy taken in by organisms; a component of Secondary Production.

Nutrient Cycling

• Nutrient cycling: Movement of nutrients between biotic (living) and abiotic (non-living) components of ecosystems. An example is the carbon cycle where photosynthetic organisms convert CO2 to organic molecules, which are used by heterotrophs.
• Anthropogenic global environmental change: Human activities have a significant impact on the environment including pollution, like excessive nutrients from fertilizers leading to eutrophication. This can cause an oxygen drop in water bodies, harming aquatic life.

Climate Change

• Climate change: Significant, lasting change in statistical weather distributions.
  • Causes: Greenhouse gas emissions (e.g., CO2, CH4) from human activities, trapping heat.
  • Impacts: Changes in species distribution; extinction risk; shifts in species ranges; phenological shifts affecting life cycle timing.
  • Solutions: Increasing energy efficiency, developing low-carbon electricity, and using carbon-neutral fuels.

Community Ecology

• Community Ecology: Study of interacting species in the same area and time.
• Ecological niche: Total use of biotic and abiotic resources by organisms.
• Interspecific interactions: Interactions between different species.
  • Competition (-/-): Competition for limited resources. Competitive exclusion results in elimination of one species. Resource partitioning allows species to coexist by using resources in different ways.
  • Predation (+/-): Predator kills and eats prey. Adaptations like camouflage/mimicry are used by prey and predators.
  • Herbivory (+/-): Herbivore eats plants. Plants evolve defenses (thorns, toxins).
  • Parasitism (+/-): A parasite derives nutrition from its host while harming it.
  • Mutualism (+/+): Both species benefit from the interaction (e.g., bacteria in the gut).
  • Commensalism (+/0): One species benefits, and the other is unaffected.
• Species diversity: Number of species and their relative abundance in a community. Species richness, relative abundance, and diversity indices like the Shannon diversity index are used to quantify biodiversity.
• Productivity: Rate of biomass generation in an ecosystem.
• Stability: Community's resistance and resilience to environmental change.
• Keystone species: Important species that have a disproportionate effect on the ecosystem despite low abundance.
• Food chains/Food webs: Energy flow through trophic levels/complex feeding interactions.
• Disturbance: Changes (e.g., storms, fires) that alter communities. A community response to disturbance can be studied through the species composition of the area exposed to the disturbance.
• Ecological succession: Change in species composition after a disturbance; leading to an established stable climax community.