Animal form and function 2 Flashcards
Elements of homeostatic systems- sensor
sensor (or receptor)
perceives a change and notifies the integrator
Elements of homeostatic systems- integrator
integrator (or control centre)
compares the sensor’s input with an internal setpoint; it then gives orders to the effector
Elements of homeostatic systems- effector
brings about a response
types of control circuits- negative feedback
(most)
change in internal environment is counteracted
Change in variable -> trigers control mechanisms-> counteracts further change
types of control circuits- positive feedback
(few)
change in internal environment is augmented
Change in variable -> triggers mechanisms-> amplify change
thermoregulation
regulation of body temperature
conduction
the direct transfer of thermal motion (heat) between molecules of objects in direct contact with each other
convection
the mass movement of warmed air or liquid to or from the surface of a body or object
radiation
the emission of electromagnetic waves by all objects warmer than absolute zero (-273)
Evaporation
the removal of heat energy from the surface of a liquid that is losing some of its molecules
Evaporative cooling
the property of liquid whereby the surface become cooler during evaporation, owing to a loss of highly kinetic molecules to the gaseous state
Thermal strategies
-combination of behavioral, biochemical, and physiological response that ensure that body temp. is within an acceptable limit
Two types of thermal strategies
- Tolerance; body temp is allowed to vary with ambient temp
- Regulation; body temp does not vary with ambient temp
Sources of thermal energy
- ectotherm; environment determines body temp
- endotherm; animal generates internal heat to maintain body temp
stability of body temp
- poikilotherm; variable body temp
- homeotherm; stable body temp
How do ectotherm and endotherm maintain body temp?
- ecto; close to the environment temp
- endo; use metabolic heat to maintain fairly stable body temp
Costs of ectotherm
- inability to physically regulate body temp. (through behavioral controls)
- restrict to geographical regions with ambient temp
- limited time of high activity/energy bursts
- not good at avoiding predators through flight
Benefits of Ectotherm
- lower metabolic rate
- slower, low energy approach to life
- require less food and water (less time foraging)
- can function with muscle much smaller body masses then endotherms
Cost of Endotherm
- metabolic cost requiring high metabolic rate
- needs lots of food and water (more time need to hunt)
- dehydration in hot/dry climates
- small amount of energy for growth and reproduction
- small body is rare due to surface area constraints on heat loss
Benefits of Endotherm
- sustain long periods of activity
- enzyme function normally in narrow body temp
- active at times of day or year that are too cold for ectotherms
- no limited geographic area
- survive weather fluctuations
Vasodilation
-increase diameter of blood vessels
- elevated blood flow in the skin
- triggered by nerve signals to relax muscles of vessel walls
-in endotherm, usually warms skin, increases transfer of body heat to cool environment
^ rate of heat loss
Vasoconstriction
-decrease diameter of vessels
- reduce blood low and heat transfer.
v rate of heat losee
Countercurrent heat exchanger
- special arrangement of blood vessels
- facilitate heat transfer from arteries to veins
- help trap heat in body core
- reducing heat loss in many endotherms
Cooling by evaporative heat loss
-sweating, panting, mucus secretion
Behavioral responsnes
change in posture, or moving about in the environment
High basal metabolic rate
production of large amounts of metabolic heat that replace the flow of heat to the environment
Shivering thermogenesis (endotherm)
high muscle activity = high heat production
Nonshivering thermogenesis (endotherm)
- high metabolic rate (due to hormonal changes)
- high mitochondrial activity = produce heat instead of ATP
- brown fat specialized for rapid heat production
Body size of endotherms
large size helps retain metabolic heat
Feedback mechanisms in thermoregulation of mammals
- neurons in hypothalamus function as a thermostat
- sensory cells (warm and cold receptors in skin) signal hypothalamus when temp increases or decreases
- hypothalamus responds by activating or inhibiting appropriate mechanisms
Bioenergetics of animals
- animals are heterotrophs that harvest chemical engery (from food)
- it is used to work, store, excrete, and release as heat
- heat produced by metabolism is for doing work, or maintaining body temp
Metabolic rate
- amount of energy an animal uses as a unit of time, sum of all energy- requiring biochemical reactions occurring over a given time
- measured by animals rate of heat loss, O2 consumption, or CO2 production
Basal Metabolic rate (BMR)
-stable rate of energy metabolism measured in mammals and birds under conditions of minimum environmental and physiological stress ( (at rest with no temp stress and after fasting)
Standard Metabolic rate (SMR)
- a measure that is similar to BMR but used for animals with varying body temp that is maintained at a selected body temp
- (animals resting and fasting metabolism at a given body temp)
What influences Metabolic rate?
- size
- internal work
- external work
- tissue growth and repair
- time of the day
- season
- sex
- stress
- type of food being metabolized
Acclimatization
-production of stress induced proteins
Acclimatization - in birds and mammals
- adjusting the amount of insulation
- varying the capacity for metabolic heat production
Acclimatization - in ectotherm
- adjustments at the cellular level
- production of cryoprotectants
Torpor
- physiological state in which activity is low and metabolism decreases
Hibernation
long term torpor, evolved as an adaptation to winter cold and good scarcity (bear)
Estivation
summer torpor, also characterized by slow metabolism and inactivity (fish, invertebrates)
Daily torpor
eg. hummingbird
