Nature Notes - TM Natural History Association

Individuality

Details: Created: Tuesday, 13 November 2012 00:00; Written by Nadia O’Carroll

It is amazing to think that billions of living organisms on Earth are discrete individuals. Even organisms which are genetically identical to their parents and siblings change over time due to environmental factors and mutations to produce tiny differences which make them unique.

For many species, sexual reproduction where the male and female parent each contribute fifty percent of molecular DNA, ensure that the offspring are genetically different from their parents and their siblings. There are exceptions where siblings have the same DNA; the most familiar is identical twins. This occurs when one fertilised egg splits into two cells. Identical twins are genetic duplicates, but even before birth they begin to develop individually and by the time they are born they have different fingerprints and are no longer exact replicas of each other. Over time environmental factors and slight physical changes and mutations cause increasing divergence between twins.

Turning down the heat

Details: Created: Tuesday, 30 October 2012 00:00; Written by Nadia O’Carroll

As the warm weather approaches many people dream of typical summer things - swimming, enjoying a cool breeze and long icy drinks, lying by the pool in the shade - its strange to think that all these symbols of summer are basically coping mechanisms that our bodies use to manage high ambient temperatures.

High temperatures and heat are not the same. Heat is energy and is measured in joules, by removing or adding heat the temperature changes according to specific heat capacity, eg it takes more heat energy to raise the temperature of water than to raise the temperature of air, so water has a higher heat capacity than air.

Marine Mammals - A life below the waves

Details: Created: Tuesday, 02 October 2012 00:00; Written by Nadia O’Carroll

Cetaceans (whales and dolphins), seals, sea lions, walrus, dugongs, manatees and sea otters are well adapted to life underwater and are capable of diving to great depths. Yet they, like us, are breath hold divers who face the challenges of drowning due to lack of air, coping with water pressure and decompression sickness.

The fundamentals of marine mammals' adaptation to survival in water are demonstrated to a lesser extent in terrestrial animals in an innate self preservation technique called mammalian diving reflex (actually this reflex also applies to birds and reptiles). If the face of a reptile, bird or mammal is submerged in water colder than 70 degrees F, the receptors in the nasal cavity trigger a response in the brain and nervous system which causes 3 main responses. It slows the heart; it slows then stops blood circulation to the extremities so that the heart brain circuit is preserved, thirdly at depth it causes a blood shift, which allows plasma and water to pass through the thoracic cavity, to protect from the effects of pressure. Consequently, even land dwellers such as humans; can survive longer underwater without oxygen, than they can on land, whether they are conscious or unconscious.

The Surf – movement and energy

Details: Created: Tuesday, 16 October 2012 00:00; Written by Nadia O’Carroll

The surf is a very powerful natural phenomenon. Many years ago the distant sound of breaking surf could sometimes even be heard on Tamborine Mountain. This is no longer possible, but from the Mountain we can still see evidence of the surf's power, when heavy surf throws plumes of salt spray high into the air along the coast.

Most ocean waves are caused by wind blowing over the surface of the ocean; friction between the air and the water transfers energy from the wind into the ocean and pushes the particles of water into a circular movement that creates the shape of a wave. Ocean waves appear to be movements of water, but they are really movements of energy, and although ocean waves can travel great distances, there is actually very little forward movement of the water particles themselves.

Spring Flowers

Details: Created: Tuesday, 18 September 2012 00:00; Written by Nadia O’Carroll

The seasonal changes that we see on Tamborine Mountain are subtler than in many parts of the world, but spring is still a time of new buds, fresh green leaves, flowers, blossoms and fragrance. How do plants sense that spring has arrived and why do many plants produce coloured and fragrant flowers?

A major key in regulating plant activity is the change in length of day (ratio of light to darkness in a 24-hour period) throughout the year.