Lecture 8 Flashcards
What are biogeochemical cycles?
Cycles that regulate the movement of nutrients and elements through ecosystems.
What is nitrification?
The conversion of ammonium (NH₄⁺) to nitrate (NO₃⁻) through nitrite (NO₂⁻), requiring oxygen and mediated by bacteria.
What is denitrification?
The reduction of nitrate (NO₃⁻) to nitrogen gas (N₂) or nitrous oxide (N₂O) in anoxic conditions.
What is Michaelis-Menten kinetics?
A description of enzyme-mediated reactions where the reaction rate depends on substrate concentration until reaching a maximum rate.
What is first-order kinetics?
Reactions where the rate depends linearly on the concentration of a single reactant.
What is Henry’s Law?
A law stating that the concentration of a gas in a liquid is proportional to its partial pressure above the liquid.
What are the intrinsic and extrinsic factors affecting fish growth?
Intrinsic factors include species, size, swimming activity, maturity, and age. Extrinsic factors include abiotic (temperature, light, O₂ levels) and biotic (food availability, social hierarchy, predators) influences.
What does the metabolic growth model describe?
It describes how consumed food (C) is used for growth (B) after losses such as feces (F), excretion (U), and metabolic costs (R). Formula: B = C - F - U - R.
What are the assumptions of metabolic growth models?
Assumptions include that all consumed food has the same caloric content and that fish growth has the same composition as consumed food.
What is the URSIN metabolic model?
A model incorporating parameters for digestion (α), metabolism (m), and feeding efficiency (β). It predicts sigmoid or exponential growth depending on parameter values.
What happens if m < n in the URSIN model?
The model predicts sigmoid growth, where asymptotic weight (W∞) is large if feeding levels are high.
What are the key assumptions of the Von Bertalanffy growth model?
Assumes catabolism is proportional to body weight (W), while ingestion is proportional to body surface (W^(2/3)).
How does the Von Bertalanffy model explain fish growth?
Ingestion is proportional to body surface area (L²), while weight scales as L³. Hence, growth depends on balancing intake and metabolic costs.
What is the significance of the parameter t₀ in the Von Bertalanffy model?
t₀ represents the theoretical time when the fish’s weight was zero, shifting the growth curve along the time axis.
What does the logistic growth equation describe in population models?
It describes population growth that increases until it reaches carrying capacity (k) and follows a sigmoid curve.
