lecture 5 Flashcards
(30 cards)
Physiological Ecology
how an individual responds to its abiotic environment – Emphasis: responses of animals to fluctuations in temperature
• Organisms live in constantly changing environments – Many temporal scales:
daily, seasonally, annually
• Variation may be predictable or unpredictable
Fitness depends on
an individual’s ability to cope with environmental change
To maximize fitness
an individual’s response to these changes must be shorter than the period of change
Individual Responses
• Responses to environmental change fall into 3 categories:
- developmental
- acclimatory
- regulatory
Developmental (years)
irreversible
• Individual alters its development to produce a phenotype most suitable to a persistent
slow change in environmental conditions
E.g. Wing length in European freshwater Water Striders (genus Gerris) –
inhabiting temporary ponds
• Eggs hatch (spring)
• Adult lifespan is short (reproduce & die during one summer)
Acclimatory
(days – weeks) - reversible • changes in response to seasonal variations
e.g. thickening of fur for winter
e.g. frost hardening in plants
= habituation of an organism’s physiological response to environmental conditions
• Acclimation – applied to laboratory
• Acclimitization – applied to nature
– Tolerances are not fixed but are preconditioned by the recent experience with environmental conditions
Regulatory
(seconds–minutes)-reversible
• Rapid changes in behaviour or rates of physiological processes
• animals vary in their responses to environmental change
- conformers
2. regulators
(1) Conformers
allow internal conditions to follow external changes
(2) Regulators
maintain constant internal conditions
homeostasis
ability to maintain constant internal conditions in a varying environment
• Always involves a negative feedback system
negative feedback system
- mechanism that senses the internal condition 2. means of comparing the actual with the desired
internal condition - apparatus that alters the internal condition in
preferred direction
Temperature Regulation
• Another way to categorize animals:
- Poikilothermy (Conforming)
* Homeothermy (Regulating)
Poikilothermy (Conforming)
cannot maintain constant body temperature
– Most amphibians, fish and insects
– Only active in a narrow range of temperatures
• Homeothermy (Regulating)
maintain constant body temperature
– most birds and mammals ~ 36 – 410C (temp. at which biochemical processes
within cells are efficient)
– Highly active under varying temperatures
• There are many ways in which organisms can regulate body temperature within a certain range…
- ectotherms
- endotherms
• Ectotherms
regulate body temperature by gaining heat from external sources (Poikilotherm)
– Adv. - energy expenditure can be low
– Disadv. – growth, reproduction and survival is limited by temperature fluctuations
• Active only in a narrow range of temps
• Endotherms
- regulate body temperature by the production of heat
(metabolism)
– Adv. – growth, reproduction & survival is not as affected by temperature
fluctuations
• Constant performance of biochemical reactions at a range of environmental
temperatures
• Active at a wide range of temperatures
– Disadv. - energy expenditure must be is high to maintain metabolic heat production
Limitations of Ectotherms
• Ectothermsmustbehaviourallygenerateheat
• Ectothermsgenerateheatwhenactive
– Every aspect of ecology and behaviour is influenced by the need to regulate body temperature
e.g. digestion in fish is strongly influenced by water temperature
Limitations of Endotherms
• Endotherm’sabilitytomaintainconstantbodytemperatureis limited under low temperatures
– Short-term – by physiological capacity to generate heat
– Long-term – by ability to gather food (or energy) to satisfy requirements for
metabolic heat production
• animals usually starve to death before they die of direct causes of cold
temperatures
• Reduceenergeticcostsbyalteringtheloss/gainofheatfrom
environment in a number of ways…
Energy Conservation - Endotherms
- Lower the regulated temperature of a portion of their body
- Lower the regulated temperature at certain times of the day
- Become larger!
- Lower the regulated temperature of a portion of their body
E.g. Birds – legs & feet
– Counter-current heat exchange
– heat loss is minimized by reducing the temperature gradient between leg and
environme nt
- Lower the regulated temperature at certain times of the day
-torpor
-hibernation
Eg. Hummingbirds
Inactive at low temps:
• body temperature is regulated around a lower temp
• reduces heat loss to environment
• Otherwise would starve to death!
