morphological and physiological features change as a function of body size in a predictable way
isometric scaling consequence
relationship between the ratio of size to surface area is inversely proportional
feed on plant tissue and must overcome:
-breakdown of cellulose and lignin
-low nitrogen content of plant tissue
feed on the tissue of other animals and must overcome:
-shortage of prey
feed on both plant and animal tissues and must overcome:
-ability to manage a variety of food resources
feed on dead plant and animal matter and must overcome:
-competition with other life forms (bacteria)
ruminant mammal stomach (bovids, deer, antelope)
4-chambered stomach (rumen, reticulum, omasum & abomasum)
Anaerobic respiration (fermentation) by bacteria and protozoans to break down cellulose
lagomorph (rabbits, hares and pikas --- NOT RODENTS!)
use a form of coprophagia to retrieve the products of fermentation.
A ruminant (Beisa oryx, Oryx beisa, in Samburu National Park, Kenya) reflecting on its high cellulose, low nitrogen diet
Three essential minerals that influence distribution, behavior, growth and reproduction of grazing animals
oxygen formation - terrestrial
Insect uses air sacs, tracheal tubes and spiracles to obtain oxygen
Birds use lungs with a two phase breathing cycle
oxygen formation - aquatic
Fish use gills with gill filaments and lamellae.
Countercurrent exchange maximizes oxygen uptake from water
the organism's conductivity
ability to exchange heat with the surrounding environment
have variable body temperatures influence by ambient temperature, ectothermic (heat from outside)
maintain a fairly constant internal temperature, independent of external temperature, endothermic (heat from inside)
function either as ectotherms or endotherms, depending on external circumstances
Poikilothermic upper/lower limits
Low metabolic rate
High ability to exchange heat between body and environment
Use anaerobic respiration for energy-intense activities and thus are limited to short bursts of activity and rapid physical exhaustion
(amphibians, reptiles, and insects)
maintain high internal body temperature by oxidizing glucose and other energy rich molecules.
-High metabolic rate
-Low thermal conductance
Fur, feathers and fat to reduce heat exchange with the environment.
Shivering to produce heat when cold; panting/sweating to cool when overheated.
To save energy, the smallest (hummingbirds and shrews) have periods of torpor
Some normally homeothermic animals become ectothermic and drop their body temperatures under certain environmental conditions - Torpor
Many poikilotherms, notably insects, need to increase their metabolic rate to generate heat before they can take flight.
-Bask in sunshine
Countercurrent heat exchange prevents loss of heat to the environment in "blank"
Countercurrent exchange can also be used to keep heat out. The oryx keeps its heat sensitive brain cooler in hot desert sun using a RETE (network of blood vessels using countercurrent heat exchange).
water maintenance - terrestrial
Animals take in water by eating, drinking, & by producing metabolic water as a result of respiration.
Animals avoid drought by departing the area (ungulates & birds) or by summer dormancy (estivation)(spadefoot toad).
water maintenance - hyperosmotic
Aquatic organisms in freshwater are hyperosmotic with respect to their environment and must prevent water uptake:
Absorb and retain salts (gills)
Copious watery urine
water maintenance - hypoosmotic
Aquatic organisms in salt water are hypoosmotic with respect to their environment and must prevent desiccation:
Invertebrates are often isotonic (isoosmotic) to environment
Teleost (bony) fishes pump Na and Cl ions out of body using active transport (energy requiring) across gills
Sharks & rays balance with urea
Sea birds and sea turtles use salt-secreting nasal glands
Marine mammals (porpoises) use kidneys
a stage of arrested growth (usually over winter) in insects