eco ch 16
What are major characteristics of ectotherms? Why do ectotherms not have the same lower limit on body size as endotherms?
- Little or no internal physiological mechanism for controlling body temperature. - High thermal conductance, low internal heat production. - Depend primarily on behavior to regulate body T _ seek sun or shade; change body orientation relative to sun; - Nocturnal vs diurnal activity; active in warm season, inactive in cold season [diapause in insects; amphibians and turtles bury themselves in mud at bottom of ponds to overwinter; snakes go into dens]. - Low basal respiratory (metabolic) rate - Small body size is not a limitation (as compared to endotherms). Very small ectotherms can use tracheae for diffusion of oxygen to the body, so they are not limited by oxygen supply.
What are some of the examples shown in class of responses of different organisms to high soil surface and air temperatures?
- Lizards high stepping across the sand Ant goes out for 2 minutes max on hot sand in the middle of the day to eliminate competition. if cant find a place to cool off then they die - Australian stilt plant goes most mass at the top of roots and away from the surface heat. Beetles change the amount of light they reflect with different waxes which changes how much heat is absorbed.
Why is evaporative cooling not a major mechanism of temperature regulation for many small animals?
- Usually, endotherms have some means of reducing the energy costs of maintaining body temperature (e.g.), torpor-->lower body temperature-->lower metabolic rate-->inactivity; best examples seen in small animals. - Small animals cannot use evaporation as a main mechanism for cooling because too great a fraction of body mass is lost. small animals in hot environments keep going underground (frequently) to cool down, or they are active at night.
Endotherms have the capacity to maintain a (relatively) constant body temperature, even though they don't always do so.
- body temperature is relatively independent of the external environmental temperature. - high rate of heat production (can accomplish thermogenesis); low thermal conductance (i.e., lower rate of heat transfer with the environment) - can sustain activity for a fairly long time (whereas most ectotherms are good only for a short burst of activity). - high specific metabolic rate(rate per unit mass) (as discussed earlier for volume/surface area relationships)
What is the lower critical temperatures, with respect to metabolism and temperature?
- the animal has to spend much energy to produce heat. - By measuring the slope of the metabolic rate vs temperature curve below the lower critical temperature, one can determine the amount of insulation present. - A lower slope means more insulation is present (a lower metabolic rate is required to keep the same body temperature).
Why might ectothermy be characterized as a "low-energy" system, whereas endothermy could be called a "high-energy" system? Endotherms:
1-2% of ingested energy goes to growth and reproduction (net production); most energy goes to metabolism. have high metabolic costs, can expend much energy rapidly in capturing prey, must capture sufficient prey of high energy value to keep going. Endotherms typically use oxygen transport in solution to provide a high supply of oxygen to a large body (and have a different body plan and muscles for breathing).
What are major characteristics of endotherms?
Are generally warmer than their environments, but must also be able to keep cool in hot environments. Usually cannot tolerate as wide a range of temperatures as can ectotherms (considering groups as a whole). Warm body temperature requires a high metabolic rate (relatively), which means high energy costs for metabolic heat production, but which also allow intense physical activity.
How does Grant's gazelle survive very high temperatures, even without drinking liquid water?
Body temp goes up, heats up blood, Venus blood goes to arterial blood . cool arterial blood goes to brain and keeps brain cooler. Evaporative cooling from the nose.
Which group of plants has the greatest ability to tolerate high temperatures, and why?
Cacti, Euphorbias: with CAM, low transpiration leads to high temperatures, even with minimal surface area and large volume; these plants are among the most high-temperature tolerant of any plants; can survive temperatures of 50-60C.
How do counter-current exchange systems work?
Counter-current veins and artery flow. warm blood against cold blood, and conserves energy
What is the difference between endotherm and an ectotherm? How are these terms interrelated?
Endotherms--use physiological processes to generate heat internally (in addition to exchanges with the environment - Derive much of body heat from metabolism:but other sources still very important; birds, mammals Homeotherms Ectotherms--warm the body by absorbing heat from the environment; Regulate body T by behavior, movement among microenvironments (reptiles, amphibians, insects, etc.). Poikilotherms
What is Allen's Rule?
For hot environments: - Extremities (appendages) increase in length in hotter areas - Creates cooling areas. Convective cooling Ex: - Jackrabbits in the desert have longer ears elephants have large ears that they flap to dump heat For cold environments and where aquatic mammals live, other mechanisms are commonly used: - blubber. - counter-current heat exchangers in the flippers or extremities. animals in the boreal zone have shorter appendages: minimize heat loss
What is the difference between a homeotherm and a poikilotherm?
Homeotherms--maintain a constant body temperature even when the temperature of the environment changes. Poikilotherms--body temperature conforms to the temperature of the environment.
How does a camel regulate its temperature and water budget?
The camel lives in the same sort of environment as the kangaroo rat, but is large (so it can't hide or change microenvironment very well). The camel has several physiological or morphological mechanisms involving water, including: 1. Counter-current heat exchanger in the nose 2. It Sweats 3. Counter-current multiplier in the kidney 4.has thick fur on its back that provides insulation; the surface can get very hot, thus reradiating more heat, yet the insulation retards heat flow into the body. 5. Tolerates dehydration (it does not "store" water in the hump; the hump serves as fat storage, which creates metabolic water when used). 6. Large body mass helps minimize temperature fluctuations; takes a long time to heat up during the day, so doesn't reach too high a temperature; cools off slowly at night. Different reactions when water is/is not available: see graph p. 40
Have a general idea of the components of the water budget of a kangaroo rat in the desert.
The kangaroo rat, in deserts, does not drink liquid water; it gets its water from "preformed" water in seeds and water produced during metabolism ("metabolic water"). A counter-current heat exchanger in the nose of the kangaroo rat acts to reduce evaporative loss. Counter-current exchangers are also used in warm environments, along with other mechanisms, as a means of conserving water and staying cool
Why might ectothermy be characterized as a "low-energy" system, whereas endothermy could be called a "high-energy" system? Ectotherms:
Up to 44% of ingested energy goes to net production. Low energy costs, use little energy, gain little energy from prey, etc. Amphibians and reptiles are too large for this type of oxygen supply system. They also have low O2 supply and transport capability so they are limited to short bursts of activity fueled by anaerobic metabolism and then must rest while lactate is re-synthesized to glycogen.
How and why do kangaroo rats and camels differ in the mechanisms used for maintaining temperature and water budgets? What additional difficulties do intermediate-size organisms such as gazelles face, and how do they overcome those problems?
look at previous slides
What is the upper critical temperatures, with respect to metabolism and temperature?
metabolic rate goes up because it costs energy to get rid of heat.
