Thermal Biology Flashcards
Metabolism
Processes that provide an organism the energy it needs to survive and respond to its surroundings.
The sum of the chemical reactions within the body that convert food to energy molecules (e.g., ATP) used for life functions (e.g., growth, reproduction) and to sustain the cellular energy demands that support life (e.g., protein synthesis).
(Currie & Evans, 2021; Fry, 1947)
Fry Paradigm
Outlines the different ways in which environment impacts an organism.
What are the six categories for effects of the environment on organisms as per Fry (1947)?
- Lethal factors
- Masking factors
- Directive factors
- Controlling factors
- Limiting factors
- Accessory factors
Lethal Factors
An environmental effect that kills the organism.
Have two components:
1. the incipient lethal level
2. the effective time
(Fry, 1947)
Incipient Lethal Level
Level of a lethal factor beyond which an organism cannot survive.
(Fry, 1947)
Effective Time of a Lethal Factor
How long it takes an organism to die when exposed to a lethal factor beyond the incipient lethal level.
(Fry, 1947)
Masking Factor
An environmental effect that prevents another environmental effect from acting on an organism either fully or partially (e.g., sweating to lower temperature).
(Fry, 1947)
Directive Factor
An environmental effect that allows or requires an organism to respond in relation to a gradient of effect (e.g., light to see prey).
(Fry, 1947)
Controlling Factor
An environmental effect that governs metabolic rate (e.g., temperature).
(Fry, 1947)
Limiting Factor
An environmental effect that limits metabolic rate even if other factors changing would normally cause an increase in metabolic rate (e.g., oxygen concentration in water being at a certain level limiting the rate at which metabolism can occur).
(Fry, 1947)
Accessory Factor
An environmental effect that when combined with another effect (that is not lethal) increases the metabolic load on the organism too much causing it to die.
(Fry, 1947)
Zone of Tolerance
Zone in which an organism will never die from the effects of a particular effect.
(Fry, 1947)
Zone of Resistance
Zone in which an organism can resist a lethal factor for a period of time but will eventually die - this zone lies outside the incipient lethal levels.
(Fry, 1947)
How does the Fry paradigm relate to my work?
I think my work will contribute to the body of knowledge relating to each of my study species’ zones of tolerance for the various habitat variables I’m measuring.
Incipient Lethal Temperature
Temperature beyond which 50% of the population cannot survive indefinitely.
(Fry, 1947)
Thermal Tolerance
All temperatures an organism can withstand indefinitely.
(Fry, 1947)
Preferred Temperature aka Preferendum
Temperature at which animals congregate when they have multiple temperature options.
(Fry, 1947)
Final Preferendum
Where preferred temperature equals acclimation temperature - where all individuals ultimately congregate.
(Fry, 1947)
What distinguishes a controlling factor from a limiting factor?
A controlling factor impacts both the minimum and maximum metabolic rate whereas a limiting factor only impacts the maximum rate.
Also, more than one controlling factor can operate at the same time.
(Fry, 1947)
Optima
Level of an effect at which an animal can perform a certain activity best.
(Fry, 1947)
Why is understanding the effects of temperature on biological processes especially important right now?
Climate change is altering global temperatures changing the biogeographic distribution of species.
(Schulte, 2015)
Thermal Performance Curve (TPC)
Describes the effects of temperature on the rate of a biochemical, physiological, or behavioural process.
(Schulte, 2015)
What are the characteristics of TPCs?
They tend to be unimodal and left-skewed with 3 distinct regions:
- A rising phase as temperature increases,
- A plateau phase that encompasses the thermal optimum (Topt) for the trait, and
- A steep falling phase at higher temperatures.
(Schulte, 2015)
Homeotherm
An endotherm that keeps its internal temperature within a narrow range.
Poikilothermic
An ectotherm that can tolerate a wide range of temperatures.
Ectotherm
An animal that cannot warm its own body and therefore has a temperature dependent upon the environment.
Endotherm
An animal that can regulate its own body temperature.
Why does temperature impact biological systems?
It alters the rate of chemical reactions and the stability of weak chemical bonds which affects key fitness-related functions.
(Currie & Evans, 2021)
What is a major site of heat exchange in fishes?
The gills.
(Currie & Evans, 2021)
Thermal Niche
The range of environmental temperatures over which a species can survive, grow, and reproduce, i.e, where its fitness is positive.
(Currie & Evans, 2021)
How does temperature impact fish development?
Developmental plasticity occurs due to thermal exposures early in development and often results in irreversible change in phenotypes that persist in the adult organism and could be passes to its offspring.
Also impacts body shape, growth, and muscle structure and function.
(Currie & Evans, 2021)
How does temperature impact fish physiology at the cellular and molecular level?
- Promotes cellular stress response.
- Changes the expression of metabolic genes as well as genes related to ion transport and biosynthesis.
- Impacts the fluidity and integrity of membranes.
- Can generate excess reactive oxygen species that can damage lipids, proteins, nucleotides.
(Currie & Evans, 2021)
What are the effects of temperature on whole fish performance?
- An increase in temperature increases the aerobic metabolic rate in fishes up to a point, after which it declines rapidly.
- Cardiac limitation results from insufficient delivery of oxygen to the muscles.
- Impacts swimming performance and behaviour.
(Currie & Evans, 2021)
Which factors have the biggest impact on metabolic rate in fishes?
Body mass, temperature, hypoxia.
(Currie & Evans, 2021)
How does temperature impact metabolic rate?
Metabolic rate slows with cooling and speeds up with heating.
(Currie & Evans, 2021)
Why are fishes especially sensitive to temperature?
Because they are ectothermic - their body temperature matches their surrounding environment.
(Currie & Evans, 2021)
How does hypoxia impact metabolic rate?
It can constrain aerobic metabolism, increase reliance on anaerobic metabolism, and in some species cause a metabolic depression.
Because of anaerobic metabolism, lactate and metabolic acid accumulate in the body, which can interfere with normal physiological function and ultimately limit the magnitude and duration of hypoxia that is survivable.
(Currie & Evans, 2021)
What are the effects of temperature on ectotherms?
The body temperature of ectotherms depends on the environment and this temperature governs an organisms metabolic rate and subsequently many important process in the organism.
For example, in turtles, temperature:
- triggers the depression (in fall) and stimulation (in spring) of gonadal growth
- aids digestion
- influences turtle sex
- influence successfulness of hibernation
And in fishes temperature:
- Impacts growth
- impacts swimming performance and behaviour.
In both cases animals are required to reduce their activity during the winter so there’s less feeding.
OCLTT
Oxygen- and capacity-limitation of thermal tolerance
What is the oxygen and capacity limitation of thermal tolerance (OCLTT) concept?
Concept that proposes that the thermal performance curve (TPC) of animals is shaped by the capacity for oxygen delivery in relation to oxygen demand (i.e., the aerobic scope).
i.e., performance along the curve is a result of oxygen limitation to organs, etc. - the peak of the curve with highest performance = highest aerobic scope = most oxygen available
(Pörtner, 2010; Verberk et al, 2016)
Aerobic Scope
The difference between the maximum and standard (resting - basal) rates of aerobic metabolism that an animal can achieve.
(Fry, 1947; Halsey et al, 2018)
What has the OCLTT been proposed to help with?
It has been proposed as a tool to help predict the impacts of climate change.
(Pörtner, 2010)
What are some issues with the OCLTT?
Mostly Portner’s own papers.
Didn’t include papers that disprove.
Many studies have failed to find a clear optimal temperature for aerobic scope.
(Jutfelt et al, 2018)
Thermal Complexity
Refers to water temperatures fluctuating in time and space, creating diverse thermal regimes across a water body.
For example, thermal fluctuations in natural rivers take place minute by minute, day to night, season to season, and across years at every point in the stream network. Thermal diversity also exists across space: surface to subsurface, hyporheic to groundwater, streambank to thalweg, pool to riffle, mainstream to side channel, upstream to downstream, across floodplains, and on the entire stream network at every moment in time.
(Steel et al, 2017)
Why is thermal complexity important?
Temperature regulates metabolism in aquatic biota, determining growth, phenology, and survival and ultimately driving food webs and community structure in aquatic ecosystems.
Spatial diversity in thermal landscapes provides aquatic organisms with options to maximize growth and survival.
(Steel et al, 2017)
What are some variables that impact thermal complexity?
Water depth, solar radiation, substrate type, groundwater upwellings.
