Lecture 12

Question 1

What role do zooplankton play in aquatic food webs?

Answer 1

They are primary consumers that graze on phytoplankton and serve as prey for higher trophic levels.

Question 2

What is grazing rate?

Answer 2

The rate at which zooplankton consume phytoplankton.

Question 3

What is selective feeding?

Answer 3

When zooplankton preferentially consume specific types or sizes of phytoplankton.

Question 4

How does temperature influence zooplankton grazing?

Answer 4

Grazing and metabolic rates increase with temperature up to an optimal level.

Question 5

What is the difference between top-down and bottom-up control?

Answer 5

• 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.

Question 6

What do power laws describe in ecology?

Answer 6

Power laws describe relationships where one variable scales as a power of another, often represented as f(x) = a · x^b.

Question 7

How does taking the logarithm of a power law function affect its representation?

Answer 7

It transforms the power law into a linear form, log f(x) = log(a) + b · log(x), making it easier to visualize and interpret.

Question 8

What is meant by scale invariance in ecology?

Answer 8

Scale invariance refers to relationships that remain consistent across different scales (e.g., from protozoans to whales).

Question 9

What are some examples of typical-scale and scale-free phenomena?

Answer 9

Typical-scale phenomena have a characteristic size (e.g., species size ranges), while scale-free phenomena (e.g., power laws) do not.

Question 10

Why are power laws significant for ecological modelling?

Answer 10

They provide first estimates for ecological parameters and indicate self-similarity in biological processes.

Question 11

How does mass relate to metabolic rate according to scaling laws?

Answer 11

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.

Question 12

What is the ecological implication of exponents like 2/3 and 3/4?

Answer 12

These exponents describe how energy use and metabolic demands change with organism size.

Question 13

What happens to the mass-specific metabolic rate when b - 1 < 1?

Answer 13

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.

Question 14

How does overfishing affect community-level power laws?

Answer 14

Removing slower-growing individuals first changes the scaling relationships, altering the community’s metabolic structure.

Question 15

What is meant by the mass-abundance relationship?

Answer 15

It describes how the number of individuals at different sizes relates to their biomass, often influenced by ecological processes like fishing.

Question 16

What is the significance of density in ecological equations?

Answer 16

Density (e.g., grams per volume) allows comparisons across different body sizes and ecosystems, facilitating scaling analyses

Question 17

What does the term Q~B^α represent in trophic networks?

Answer 17

Q represents food consumption, B represents biomass, and α is the scaling exponent indicating how consumption changes with biomass.

Question 18

What did the study of 64 networks reveal about Q~B^α?

Answer 18

It showed a consistent exponent (~1.11 ± 0.15), indicating that populations with higher biomass consume more per unit biomass.

Question 19

How are outliers identified in scaling relationships?

Answer 19

Outliers are identified using methods like “box and whisker” plots and can represent anomalies due to non-trophic dynamics or specific ecological roles.

Question 20

How does data quality affect scaling analyses?

Answer 20

Poor data quality or incomplete observations can introduce biases or misinterpretations in scaling-based models.

Question 21

How do scaling-based indicators predict ecosystem dynamics?

Answer 21

They provide insights into energy transfer, the impact of human activities like fishing, and the successional state of ecosystems.

Question 22

What are some sources for power law generation in ecosystems?

Answer 22

Processes like preferential attachment (e.g., “rich-get-richer” dynamics) and cascading effects (e.g., avalanches) generate power laws.

Question 23

What is the significance of thermal regulation in metabolic scaling?

Answer 23

Endotherms and ectotherms exhibit different metabolic rates due to temperature regulation, affecting their position on scaling curves.

Question 24

Why is it important to understand log transformations in ecology?

Answer 24

Log transformations reveal proportional relationships and help identify whether a process follows a power law.