Question

3. Being endothermic provides certain advantages to birds and mammals – they can have a much higher activity level than ectothermic taxa, and they can be active when ectotherms typically cannot, e.g. at night and in very cold areas such as those at high elevations or high latitudes. However, endothermy requires a number of changes in various body systems to work. Birds and mammals have solved the problems associated with endothermy and higher activity levels using some of the same solutions, but also different ones that achieve the same end. Give some examples of those solutions.

Answer 1

Endothermy is a charecteristic in which the temperature of the body does not change with the change of temperature in the surrounding environment . The metabolic production of heat and high, stable body temperatures was a major step in the evolution of birds and mammals.

It is believed that such stable warm bloodedness or endothermic homeothermy results from a combination of high resting, aerobically supported heat production rates in virtually all soft tissues. Combined to this is the insulation provided by the fat layers which prevent excessive heat loss.As a consequence, many temperature sensitive physiological processes in birds and mammals proceed at stable rates even if there is temperature change in the outside environment.

* Endothermy allows birds and mammals to remain active at all times i.e. throughout the day and year.

* At higher temperatures, nerve impulses travel faster, muscle strength is increased and physical endurance is greater

* The average body temperature of birds is in the range of 40 to 45 degree celcius [ 104 to 111 degree farenheit ] which is about 10% higher than the hottest of the mammal species.

* In order to maintain the igh body temperature , both birds and mammals need to eat at a higher rate than other vertebrates.

* In the case of birds, the high body temperature may result in the denaturing of proteins ! So, they need to control their body temperature by losing heat through conduction with the surrounding air.

* Some mechanisms by which birds control their body heat are-- by changing location

-- by changing their position i.e. spreading their wings to increase the body surface area.

-- by manipulating their feathers . The birds ruffle their feathers in cold climate to trap more air so that it can act as an insulator [ air being a bad conductor of heat] . They can compress their feathers close to their body at times of hot weather to facilitate body heat loss. Also, the birds erect their feathers to expose their skin to lose body heat. Some birds also shed their feathers during the hot season and grow more during winters.

-- birds can alter their breathing rates, making it slow to reduce heat loss [ since body heat is lost when warm air comes out of the body] . Panting [ as seen in dogs] can help to lose body heat.

-- birds can also lose heat by increasing their metabolism rate eg. by shivering

-- some birds, specially water birds , can adjust their heat loss by altering the blood flow to their legs and feet, making it faster when they need to lose body heat and slow when they need to conserve body heat.

Thus, we see that birds have devised quite a few ways to conserve body heat. These are different from most mammals but the basic function is the same i.e to maintain a constant body temmperature irrespective of the changes in the surrounding temperature.