Question

1. Describe the four different ways that heat exchange can occur between an organism and its environment. Include an explanation of how insulation, circulatory adaptations (countercurrent exchange), evaporative cooling, behavioral responses, and adjustment of metabolic heat production can help an organism balance heat loss and gain.
2. Differentiate between intracellular and extracellular digestion. For extracellular digestion, include information to compare those animals with a simple body plan and single opening to the digestive cavity to those having an alimentary canal.

Answer 1

Four different ways of heat exchange between an oraganism and its environment are:conduction,convection,radiation anmd evaporation.An oraganism can maintain a homeostasis condition,only if its body temperature is maintained within the prescribed limit.To remove excess heat from the body,the oraganism exchange heat with the environment.The four different ways are:

1.Conduction: This is the transfer of heat between two objects in contact.heat is exchanged from a hotter object to a colder object.Temperature difference between the organism and the environment,area of contact etc. are some factors that determine he ratye of heat lose.

2.Convection: This is the transfer of heat by the movement of air or fluid.The warm air which is less dense will rise up and is replaced by the dense colder air.By this way a convection gardient is established to matain the tempearature between the skin and the adjacent air.Animals usually adopt this form of heat loss when the outside temperature is very high.

3.Radiation: This is the transfer of heat by the emission of electromagnetic waves between bodies that are not in direct contact.The absorption of heat from the sun is an example for this.

4.Evaporation: Physical process in which liquid changes to gas o rvapour by the absorption of heat energy.Evaporation removes heat from the body surface.Sweating removes heat from the surface and panting increases evaporation from the respiratory system.

Insulation is the method of creating barrier between the organism and the environment such that there is no heat loss or heat gain by the organism.The layer of air that is trapped naer the skin acts as the insulator.This air layer prevents the heat loss to the environment eg:feathers in birds,thick layer of fat in marine animals etc.

Heat is lost mainly from the surface of body.The flow of blood to the skin carries the heat.So controlling the flow of blood to the skin is an effective way to control the heat loss or heat gain from the surrounding.some circulatory adaptations are :vasoconstriction and vasodilation ,countercurrent heat exchange...In vasoconstriction,the diameter of blood vessel that supply to the skin shrinks,thus reducing the blood flow to the skin and retains the heat. In Vasoconstriction, the blood vessels to the skin dilate,thus increasing blood flow to the skin and helps to loss excess heat.

In Countercurrent heat exchange,the heat from the warm blood that is carried by the descending artery is transferred to the cold blood carried by the ascending vein by conduction.Since the warm blood is cooled now,less heat will be lost to the environment.

Evaporation removes heat from the surface.Sweating and panting are examples of evaporative cooling ,if the body temoerature is very high.Only mammala can sweat.In panting,animal breathes rapidly with its mouth open.This increases evaporation from the mouth surface.

Behavioral responses are responses of the body of an oraganism to regulate the body temperature.Drinking cold water,siiting in shade,wearing light clothes in summer are some behavioral responses in humans.In deserts ,lizards bask to warm up and when they recieve the adequate heat ,they move to shade.Elephants spraying water on themselves during hot days,hibernation(winter sleep) and aestivation(summer sleep) of animals,migration etc.are some behavioral responses.

By increasing the maetabolic heat production,the temperature is regulated in organisms.By increasing the muscular activity,heat production is also increased.Shivering,rubbing the handsetc. are ways ro increase the muscular activity.

INTRACELLULAR DIGESTION

• Occurs within the cell in food vacoules.
• digestive enzymes are secreted from the cytoplasm to the food vacuoles.
• cytoplasm absorbs the digestive products through diffusion.

occurs in unicellular organisms and is less efficient.

• EXTRACELLULAR DIGESTION
• Occurs outside the cell in the cavity of ailmentary canal.
• special cells secrete digestive enzymes to the ailmentary canal.
• intestinal wall absorbs the digestive products.
• occurs in multivellular and is more efficient.
• in animals with single body plan,there is only one openig for both ingestion and ejection. In animals with tube within tube body plan,they have two openings