Tag Archives: metabolism

10: Physiological Adaptations for Survival

koala and gum leaves

Learning Intention: Students will develop an understanding of the terms and definitions used and how physiological adaptations allow organisms to survive in their environment.

Success Criteria: Students will be able to describe a range of physiological adaptations and how those adaptations allow organsims to survive in their environment.

Adaptations to an organism’s environment can usually be identified as structual (physical – how an organism is built), functional (physiological – how an organism works inside) or behavioural (what an organism does). Chapter 10 deals with physiological adaptations. The following is an interesting article created by a student at Davidson College for an Animal Physiology course.

The Australian koala (Phascolarctos cinereus) is a remarkable animal, and is one of only a few animals, that is capable of surviving on a naturally foliar diet of eucalyptus leaves. Over time, the Koala has evolved several physiological adaptations that allow it to cope with this high fibre, low protein diet. Low metabolic rates allow koalas to retain food within their digestive system for a long period of time, maximizing the amount of energy able to be extracted. Cork and Warner conducted interesting studies on the digestion and metabolism of Eucalyptus foliage in koalas. Using radioisotopic markers, they examined the passage of particulate and solute digesta through the alimentary tract of the koala. They found that the solute marker was retained for longer periods of time than the particulate marker. The mean retention times for the solute and particulate markers were 213 hours and 99 hours respectively. These times are longer than those reported in most other mammals (1983). The selective retention of solutes and fine particles maximizes the energy withdrawn, particularly from non cell-wall constituents. More importantly however, the relatively quick passage of larger fibrous particles, or plant cell-wall constituents, is thought to reduce the “gut-filling” effect of the foliar diet. This extends the upper limits of food intake and ultimately increases the availability of nutrients, partially compensating for the constraints of small body size (1983). Passage of the larger fibrous particles is also beneficial because other researchers found that only 25% of the the cell-wall constituents that enter the alimentary tract are able to be digested (Cork et al., 1983). Breakdown of the cell contents is most important in the digestive process.”

Check out the Hawkesdale Biology wiki page for more links and information about the physiological adaptations of organisms that enable them to extend their tolerance limits and therefor their distribution and abundance. One of last year’s students created this set of Chapter 10 Flashcards to assist her to remember the terms and definitions from this chapter of work.