Monthly Archives: June 2011

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 The selective retention of solutes and fine particles maximizes the energy withdrawn, particularly from non cell-wall constituents.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.

Chapter 9: Habitats, environment and survival

leaning_tree

Author’s photo taken at the Leaning Trees of Greenough, Western Australia

Learning Intention: Students will understand the biotic and abiotic factors that affect the distribution and abundance of organisms on earth.

Success Criteria: Students will successfully complete the Chapter 9 review questions and be able to list biotic and abiotic factors that affect the survival of organisms on earth.

Buffeted by the prevailing southerly winds, these eucalypts have survived despite challenging conditions. The survival of organisms, and therefore their distribuition and abundance, depends on both biotic (living – predators, competitors, pathogens, parasites) and abiotic (physical – temperature, wind speed, pH, atmospheric gases, turbidity, salinity, solar radiation) factors. This chapter of work is about habitats and the factors that affect the survival of organisms in their environments. Learn some definitions for this chapter at Chapter 9: Habitat and Survival Flashcards.  You will also learn about niches and resource use graphs. Match some Australian species to their habitats at DECC.

Living organisms survive in their environments due to structual, functional and behavioural adaptations. Evolution is the process by which living organisms have changed over thousands of years to become more suited to their environments. Google ‘evolution’ and you will find an enormous selection of contradictory articles confirming or condemning “The Theory of Evolution”, first proposed by Charles Darwin in 1859.

To summarise Darwin’s Theory of Evolution;

1. Variation: There is variation in every population.
2. Competition: Organisms compete for limited resources.
3. Offspring: Organisms produce more offspring than can survive.
4. Genetics: Organisms pass genetic traits on to their offspring.
5. Natural Selection: Those organisms with the most beneficial traits are more likely to survive and reproduce.

Exam Revision

revision

Image Source

Next Wednesday afternoon you will have the opportunity to demonstrate your understanding of all the work we have covered during first semester. You will have 15 minutes reading time and 90 minutes writing time to answer 20 multiple choice questions and about 8 short answer questions. The following tips may assist you during your revision period:

Use flashcards to study definitions of key terms, vocabulary and concepts – there is an online program called flashcardsdb which can assist.

You may like to try creating mind maps, using lists of related terms to identify the links between different words and concepts.

Re-read your text, taking notes and highlighting key terms in your notes. Create revision notes by taking down the headings of each chapter and adding key words and concepts under each heading.

Visit the assessment guide online for lists of key concepts.

Look after yourself – don’t stay up late, eating junk food and studying all night. Try to get plenty of rest, eat healthy foods and get some fresh air. If your body is functioning at 100%, your brain will be working better too!

Do lots of past exam papers – at least two or three as timed exams under test conditions. Identify concepts you find difficult and spend more time revising those areas.

Read the questions carefully – make sure you understand the key words ‘identify’, ‘describe’, ‘compare’, etc and look out for negatives and exceptions.