Topic 7 Cold adaptation Flashcards
Define the terms cold tolerance and cold adaptation and explain the physiological differences between them
COLD TOLERANCE
The capacity of an organism to endure changing environmental conditions with out an adverse reaction
eg. Human body can tolerate a drop in temeperature however, at a certain range cells will become damaged/die as metabolic processes can not proceed at very low temperatures
However if environmental conditions are extreme, and there are survivial implictions for the inidividual then selection pressures will lead to ADAPTATIONS through selection of benficial traits
eg Cold apatation might include thick fur, thick layers of adipose tissue, Non Shivering Thermogenesis (NST) and hibernation/torpor
Physiology
Study of the functions of living organisms and thier systems
Compare some of the thermoregulation strategies adopted by different organisms
Endotherms regualte their temperature internally (eg NST or shivering) while Ectotherms gain heat externally (eg lizards sitting in the sun)
Homeotherms maintain a stable temperature despite environmental conditions while polikiotherms have variable temperatures that are affected by environmental temperature.
Organisms can be endothermic and polikiotermic (eg hummingbirds are endothrms in the day and polikiotherms at night when they enter a state of torpor)
Simiarly ectotherms can be homethermic if their temperature remains stable (eg marine invertebrate in stable temperature envornment)
Torpor
State of controlled lowered body tepmerature and metabolic rate
Endothermic
Organism that controls its temperature INTERNALLY through processes such as shivering or increased meatabolism
Exothermic
Organism that gains heat through an external source
Homeothermic
Maintains a stable temperature despite environmental conditions
Polikiothermic
Organism who’s temperature is highly variable and tends to respond to that of its environment
Outline how biological adaptation takes place in natural environments using reindeer as an example
Svalbard reindeer have evolved different adaptations to live in their cold environment as their island was in a physically isolated from other mainlans reindeer subspecies. Seasons are highly extreme (two months of dark on winter, two months of saylight in summer.) Winters are VERY cold.
They have no natural predators so have no need to gallop unlike some other reindeer species. They do not migrate. Consequenty they have short legs which are energetically less expensive to grow/use and minimise heat loss. Because they do not need to herd to protect themselves from predators they live solitarily or in small groups which also lowers competition for food. They have large amounts of subcutaneous adipose tissue which means they have extra capacity to store energy/food for when it is scarce in mid winter and also have an extra layer of insulation. They have thick fur.
The extremely seasonal variations they live in meant they have evolved adaptations to deal with variable amounts of low quality vascular plants they eat. They have differnt micro organisms in their stomachs that digest the type of food they eat and very large guts. They eat almost constantly when their food source is available
Explain how feedback and feedforward regulation takes place, using appropriate biological examples
Negative feedback Response
Is REACTIONARY
A control mechanism reacts to a change in the output of the system by initiating a restoring action
Eg. Body tempertaure drops so message is sent to brain, that activates a response (eg. shivering). Information is fedback to brain until temperature of body is restored to optimum pre-set state.
Feedforward reguation
Is ANTICIPATORY
Eg. In plants when soil starts to dry out, chemical messenger ABA is released from roots which closes leaf stomata to stop water being lost via transpiration. This happens BEFORE any there is any change to water status of plant.
Describe a range of structural and physiological adaptations to survival in cold environment
Describe nutrient flux throughout an organism and suggest ways in which BMR can be measured both directly and indirectly
Direct Measurement
Calorimetry - Measuring heat loss. Must be performed in a controlled envirmonment eg a metabolic chamber
Indirect Measurement
Gas utilisation/production - Measured O2 used or CO2 emitted
Heterotherm
Provide explanations for the use of torpor and hibernation in different groups of animals
