Biology - Thermoregulation

Why is thermoregulation important? Thermoregulation is important as it maintains temperature at an optimal range, within tolerance limits, which allows for the most efficient environment for enzyme activity. Without thermoregulation, enzymes may denature or decrease in activity, or energy isn’t sufficient to allow chemical reactions, leading to a decrease in metabolic activity. Life is sustained by continuous chemical reactions, and if the rate at which these reactions occur is too slow, cells may die and life can’t be sustained.

All methods of Heat Transfer

1. Conduction - Transfer of heat energy from hotter object to cooler object through direct contact

2. Convection - Transfers heat when hot fluid rises and is replaced by a cooler fluid. Creates convection currents. Convection currents of air or water remove heat energy from the surface of an organism as they pass over it

3. Radiation - Movement of heat energy as infrared waves without the need for touching particles

4. Evaporation - Occurs when a liquid turns into a vapour. In sweat, heat is transferred from the skin to the liquid causing it to evaporate. As the water vapour moves off the skin and into the surroundings, it takes the transferred heat energy with it

Endotherms

Animals that use metabolic processes to generate their own heat to maintain their internal temeprataure within their tolerance range

Verterbrate classes: Aves and Mammals

NOTE: There are some species of reptile, fish and insects that are also endothermic or ‘functional endotherms’

ENDOTHERM ADVANTAGES

Decreased vulnerability to fluctuations in external temperature, increased tolerance range (thus larger range of environments it can exist in)

Can be optimally active more times of the day than ectothermic organisms

Increased active times reduce chances of predation

Can maintain high metabolic activity for longer periods of time than ectothermic organisms as they maintain optimal temperature for reactions consistently

Higher body temperatures may increase resistance to fungal infections

DISADVANTAGES:

Higher energy demand than ecotherms of similar size thus higher food intake required - more time hunting/grazing - dependant on constant food supply

Ecotherms

Animals whose internal temperature is determined by the external environment

Ectotherms use the external environment to modify their behaviour to control their internal body temperature

Most reptiles, amphibians, and invertebrates (e.g. insects, crustaceans, molluscs, echinoderms,) are ectothermic

ADVANTAGES: Lower energy demand than endotherms of similar size - environment is largely used to control/regulate temperature therefore food requirements are lower. Less time hunting/foraging, less dependent on constant food supply than endotherms

Generally tolerate higher internal fluctuations in temperature than endotherms

DISADVANTAGES:

Body temperature is dependent on the external environment - limits their distribution to areas with less temperature fluctuations to areas with less temperature fluctuation or less extreme temperatures

Less active times (may be restricted to being active only at night in warm areas or only during the day in cold areas)

May be more susceptible to fungal infections and predation

Cannot maintain optimal metabolism for periods as long as endotherms

Learning Objectives

• Outline behavioural, physiological and structural adaptations of ectothermic organisms for heat loss and heat loss and heat gain

Ectotherms

• Animals whose body temperature is determined by the external environment

• Ectotherms largely rely on behavioural and structural adaptations for thermoregulation

Ectotherms - Structural for HOT ENVIRONMENTS

• May have structures with a high surface area and low volume (High SA to volume ratio)

• When allows them to lose heat more easily in cooler areas

• Lighter colouration

Ectotherms - Behavioural for HOT ENVIRONMENT

• Seeking shade and cooler areas

• More active early in the morning or at night - rest during the day

• Moistening body with saliva or water sources

• Decrease physical activity (thus metabolic activity)

• Increasing surface area exposed to cooler air (not sun)

• Increasing evaporation from body parts (e.g. open mouths)

Ectotherms - Structural for COLD ENVIRONMENT

• Blubber and thick hides

• Darker colouration

• May have high area to volume structures (e.g. Flat body parts) for basking - This can be a negative feature, why? Increase surface area to volume ratio can increase the rate of heat loss out of the system, and can cause a negative effect

Ectotherms - Behavioural for COLD ENVIRONMENT

• Less active during colder times and months

• Increase physical activity (and thus metabolic activity)

• Basking, seeking warmer areas

• Decreasing surface area exposed to cooler air (not sun)

Learning Objectives

Outline behavioural, physiological and structural adaptations of ENDOTHERMIC organisms for heat loss and heat loss and heat gain

MENTAL SET

1) Outline a structural and behavioural adaptation of ectotherms for cold environments. Include specifix examples in your answer

Ectotherms are organisms that rely on thermoregulation via the external environment and aren’t able to produce their own heat via metabolic activity

Structural - High surface area to volume ratio on ectotherms will allow greater heat gain during basking or hotter areas

Behavioural - Sun basking - Sitting out on the sun allows the organism to gain heat via radiation, aiding in maintaining a stable internal body temperature by increasing heat gain

2) Outline a structural and behavioural adaptation of ectotherms for hot environment. Include specific examples in your answer

Structural - High surface area to volume ratio: facilitates heat loss by increasing body exposure to the cold external environment, allowing heat loss via convection or radiation

Behavioural - Seeking darker, shady areas away from the sun in order to promote heat loss via convection or radiation (with the air/breeze)

*FOR THESE QUESTIONS, MAKE SURE TO MENTION THE METHOD OF HEAT TRANSFER

Physiological - HOT ENDOTHERMS

Pilorelaxation - Relaxation of muscles attached to hair follicles (hair erector muscles). Causes hairs to flatten (rather than stand straight). Hairs no longer trap layer of air for insulation. More heat is lost/emitted as radiation and convection, lowering internal temperature

Sweating - Sweat is excreted to the surface of the skin. Heat moves from the surface of the skin into the liquid (via conduction). Liquid then evaporates into a vapour, and the molecules take the heat energy with them. Increasing heat loss via evaporation

Decrease metabolic rate - Rate of metabolic reactions decreases. As metabolic reactions produce heat as a byproduct this also reduces heat productions, which assists in lowering internal temperature (Tends to be a long term response - warmer seasons)

Structural ENDOTHERMS - Cold

Fur, hair, or feathers - traps air between hairs for insulation. When air reaches same temperature as skin there is no more net movement of heat between skin and air - reducing heat loss via radiation and convection

Blubber/Fat - Increases Insulation

Counter-current blood flows in extremities - arteries to extremities and veins from ex

Counter directional flow is important to maintain thermal gradient and thus heat transfer

BROWN ADIPOSE TISSUE - LARGE NUMBER OF MITOCHRONDRIA

PRODUCE HEAT RATHER THAN ATP

BEHAVIOURAL ENDOTHERMS - COLD

Heat seating behaviour

Active during warm periods

Burrowing

Increasing physical activity

PHYSIOLOGICAL - COLD

Shivering - Rapid contraction and relaxation of muscle fibres, requires ATP therefore cellular respiration. More heat produced as a byproduct, increasing internal temperature

Vasoconstriction of superficial (peripheral) blood vessels - Contraction of muscles in walls of skin arterioles, causes blood vessels in surface of skin to narrow. Less blood flow to surface of the skin, reducing heat lost/emitted to environment via radiation, preventing reduction of internal temperature

Piloerection - Contraction of muscles attached to hair follicles (hair erector muscles). Causes hair to stand up striahgt, trappin hair between hairs. Air acts as insulating layer - when

Increasing metabolic rate - rate of metabolic reactions increases,

Increase in metabolic rate for heat production also increases food demands. If food is scarce animals may instead enter torpor - a state of decreased metabolic rate and physical activity. Torpor reduces energy and water needs for the organism, but internal temperature can drop significantly

Hibernation is an extended period of torpor where the metabolic rate falls to a level that just sustains lfie - significantly reducing energy demands

Aestivation is another form of long term torpor, typically used in very dry conditions (More for water retention rather than heat)

Kleptothermy - Animals sharing or stealing body heat (Bunching up)

Explain how a greater bilby’s ears could help it to thermoregulate

Thermoregulation is a mechanism that allows the maintenance of an organism’s internal body body temperature at a stable, constant level, within tolerance limits.

Large, flat ears increases surface area to volume ratio. This can facilitates greater heat loss via radiation or convection (with cold air), as more skin is exposed to the environment aiding in thermoregulation when it’s hot.

Large ears provide greater vascularity. Increased vascularity to the ears allows greater blood flow, bringing heat from the core (via the blood), allowing greater heat loss through the ears.

Increase blood supply to increase heat loss or decrease blood supply to reduce heat loss

Hairless ears make heat loss more efficient or there is no insulation (to trap air close to the body) or the surface of the ears is in direct contact with the air

INVESTIGATION QUESTIONS:

a) Identify the trend shown by the python’s and eagle’s temperature and propose a reason for these trends (4 marks)

The python displays a decrease in average internal temperature as time begins to elapse, in a linear trend with no fluctuations *The python’s temperature remains relatively stable around 22 degrees for 20 minutes. After 20 minutes the pythons temperature decreases over time reaching 14.6 degrees at 60 minutes (1 mark)

An explanation for this trend is that python’s are ectotherms whose internal body temperatures are heavily reliant on the external environment. As the temperature of the enclosure was reduced to 10 degrees celcius, the internal body temperature of the python decreases to follow it, as it does not have any homeostatic mechanisms that allow it to generate heat to increase it’s body temperature.

Ectotherms also have a broader tolerance range compared to endotherms

The Eagle Owl’s temperature remains at a relatively constant average internal temperature at (40 Degrees), with small fluctuations over time

An explanation for this trend is that the Eagle Owl is an endotherm, whose internal body temperature are regulated via thermoregulatory mechanisms. As the temperature of the encloure was reduced to 10 degrees celsius, the Eagle Owl’s thermoregulatory systems acts in order to counteract the change. This leads to it increasing its internal body temperature, creating the fluctuations seen in the graph, however maintains a relatively stable, constant internal body temperature. Endotherms also have a smaller tolerance range compared to endotherms

Predict the temperature of the python at 55 minutes (1 mark) - 15.5 degrees celsius.

1) Aim: To investigate the average internal temperature of Stimson python and Eurasian Eagle Owl over 60 minutes (when temperature is reduced at 20 minutes) *CORRECT

2) IDV: Type of animal/organism experimented on - Eurasian eagle owl and Stimson Python *Correct

3) DV: Average Internal temperature of organism (over time, in degrees celsius) *Correct

4) Controlled Variable
Environmental factor e.g. (humidity of enclosure, size of enclosure, ambient sunlight, rate of cooling (or something like that))

Activity level of organisms

Relative size/mass of organisms used

Method of recording internal temperature (cloacal thermometer)

Health status of the experimentees (diseases, etc)

Ages/Developmental stage of the animals (e.g. Young adults relative to their age)

Room temperature is maintained at a constant 10 degrees celsius.

5) Hypothesis: As time elapses in a room at a temperature of 10 degrees celsius, the Eurasian Eagle Owl’s body temperature will remain relatively constant, while the Python’s body temperature will slowly decrease near 10 degrees celsius. OR the temperature of the owl will remain higher than the temperature of the python over time

Identify an ethical concern this experiment raises and discuss how it could be mitigated (2 marks)
Physical harm/stress towards the organism. A way to mitigate this is to change the temperature that’s being reduced to a higher level, within the animal’s tolerance limits.

1) Describe what is meant by the term animal ethics and state 3 considerations that should be made when undertaking research involving animals (4 marks)

• Animal ethics refers to considerations regarding procedures that may cause physical and psychological harm towards an organism/animal

• Reduction - Refers to a decrease in the quantity of animals experimented on

• Refinement - Improving experimental qualities in order to ensure less animal harm

• Replacement - Researchers must seek alternatives to replace animals with more viable and ethical methods

*CORRECT ANSWER

• Animal ethics involves consideration of respectful, fair and just treatment treatments of animals.

• The use of animals in science involves consideration of

• Replacement - substitution of insentient materials for conscious living animals

• Reduction - using only the minimum number of animals to satisfy research statistical requirements,

• Refinement decrease in the incidence or severity of ‘inhumane’ procedures applied to those animals that still have to be used.

INVESTIGATION TABLE

Temperature of water in test tubes insulated with different materials over 20 minutes

                                                                                TIME (Minutes)

Temperature of water in test tubes

Water’s most significant intermolecular force is hydrogen bonds. In order for a molecule to be soluble in water, the molecule must contain intermolecular forces that areh equal to or are stronger than hydrogen bonds, in order to break the bonds and bind to water and ‘dissolving’

1. Outline the difference between primary data and secondary data (2 marks) Primary data refers to data that has been directly collected by a person to be used by the person, while secondary data refers to data that has been received from a another reliable source/person

2. Accuracy refers to how close an experimental/measured value is to it’s actual value.

   1. Reliability refers to how repeatable an experiment’s results are. The extent an experiment returns consistent results

   2. Validity refers to whether an experiment’s results are representative of what it’s supposed to be testing - Test the hypothesis

3. Measurement error is a form of systematic error where a data value is read incorrectly. It is usually resolved by included absolute value, of +- 1 - Error caused by the difference between the measured value and the actual vallue

ACTUAL ANSWERS:

• Accuracy refers to how close an experimental/measured value is to it’s actual value.

• Reliability: The degree to which an assessment instrument or protocol consistently and repeatedly measures an attribute achieving similar results for the same population

• Validity refers to the extent to which tests measure what was intended; the extent to which data, inferences and actions produced from tests and other processes are accurate.

*Shivering is the rapid contraction and relaxation of muscles, which requires energy (ATP), increasing cellular respiration and producing heat as a byproduct

When the liquid evaporats into vapour, molecules take heat with it to the external environment, therefore causing heat loss from the body.

a) Identify which type of adaptation the outer covering is: Structural adaptation

b) Some lilijani species are born without the protective covering and steal the covering of their siblings. Classify this type of adaptation (1 mark) Behavioural

c) The function of the dense fibrous, protective outer covering on its cranium acts as a thermal insulator, trapping heat and preventing heat loss. Due to its fibrous structure, it can prevent heat transfer from the environment through radiation, which can assist in Lilijani yappinus maintaining heat in cold environments

Torpor and estivation are both states of dramatically reduces physiological activity, metabolic activity, and lowered body temperature. Torpor’s mainly to reduce energy demand, while estivation is mainly to retain water and prevent dehydration

WHAT ARE THE THREE R’S

Reduction - To only use the minimum number of organisms to satisfy research requirements

Refinement - To decrease in the incidence of severity of inhumane procedures procedures applied to organisms being experimented on

Replacement - To switch conscious, living animals with insentient objects

b, c, a, c

What are the advantages and disadvantages of urea/

• Advantages: Can be stored as a concentrated solution

• Has a low toxicity (lower than ammonia and urea)

• Can be used for development of young in eggs (because it has low toxicity)

Disadvantages:

Has a high energy cost to produce because it is more complex than ammonia and urea.