Lecture 12 Flashcards
What role do zooplankton play in aquatic food webs?
They are primary consumers that graze on phytoplankton and serve as prey for higher trophic levels.
What is grazing rate?
The rate at which zooplankton consume phytoplankton.
What is selective feeding?
When zooplankton preferentially consume specific types or sizes of phytoplankton.
How does temperature influence zooplankton grazing?
Grazing and metabolic rates increase with temperature up to an optimal level.
What is the difference between top-down and bottom-up control?
- Top-down Control: When predation by higher trophic levels regulates zooplankton and algal populations.
- Bottom-up Control: When nutrient availability drives primary production and higher trophic level abundance.
What do power laws describe in ecology?
Power laws describe relationships where one variable scales as a power of another, often represented as f(x) = a · x^b.
How does taking the logarithm of a power law function affect its representation?
It transforms the power law into a linear form, log f(x) = log(a) + b · log(x), making it easier to visualize and interpret.
What is meant by scale invariance in ecology?
Scale invariance refers to relationships that remain consistent across different scales (e.g., from protozoans to whales).
What are some examples of typical-scale and scale-free phenomena?
Typical-scale phenomena have a characteristic size (e.g., species size ranges), while scale-free phenomena (e.g., power laws) do not.
Why are power laws significant for ecological modelling?
They provide first estimates for ecological parameters and indicate self-similarity in biological processes.
How does mass relate to metabolic rate according to scaling laws?
Metabolic rate scales with mass to the power of approximately 2/3 or 3/4, indicating that smaller organisms have higher mass-specific metabolic rates.
What is the ecological implication of exponents like 2/3 and 3/4?
These exponents describe how energy use and metabolic demands change with organism size.
What happens to the mass-specific metabolic rate when b - 1 < 1?
The rate is lower for smaller organisms, meaning that a gram of plankton metabolizes much more relative to its mass compared to larger animals like whales.
How does overfishing affect community-level power laws?
Removing slower-growing individuals first changes the scaling relationships, altering the community’s metabolic structure.
What is meant by the mass-abundance relationship?
It describes how the number of individuals at different sizes relates to their biomass, often influenced by ecological processes like fishing.
What is the significance of density in ecological equations?
Density (e.g., grams per volume) allows comparisons across different body sizes and ecosystems, facilitating scaling analyses
What does the term Q~B^α represent in trophic networks?
Q represents food consumption, B represents biomass, and α is the scaling exponent indicating how consumption changes with biomass.
What did the study of 64 networks reveal about Q~B^α?
It showed a consistent exponent (~1.11 ± 0.15), indicating that populations with higher biomass consume more per unit biomass.
How are outliers identified in scaling relationships?
Outliers are identified using methods like “box and whisker” plots and can represent anomalies due to non-trophic dynamics or specific ecological roles.
How does data quality affect scaling analyses?
Poor data quality or incomplete observations can introduce biases or misinterpretations in scaling-based models.
How do scaling-based indicators predict ecosystem dynamics?
They provide insights into energy transfer, the impact of human activities like fishing, and the successional state of ecosystems.
What are some sources for power law generation in ecosystems?
Processes like preferential attachment (e.g., “rich-get-richer” dynamics) and cascading effects (e.g., avalanches) generate power laws.
What is the significance of thermal regulation in metabolic scaling?
Endotherms and ectotherms exhibit different metabolic rates due to temperature regulation, affecting their position on scaling curves.
Why is it important to understand log transformations in ecology?
Log transformations reveal proportional relationships and help identify whether a process follows a power law.
