Nature Notes

Highs and Lows

NHA General - Nature Notes

Written by Nadia O’Carroll Tuesday, 09 April 2013

Weather reports usually mention low and high pressure systems, fronts and troughs because these terms relate to atmospheric air pressure which is a major driver of wind and weather.

Air pressure at any point is the total weight of the air above that point. This is determined by the number of molecules present. Dense humid air contains more molecules than less dense, dry air and therefore exerts more pressure.

Read more: Highs and Lows

More than Slithering - Snake Locomotion

NHA General - Nature Notes

Written by Nadia O’Carroll Tuesday, 26 March 2013

Snakes live in a wide variety of habitats – terrestrial, arboreal, aquatic and fossorial (underground). They also vary in size from the world's smallest snake, a recently discovered Barbados threadsnake, which measures only 10 cm, to the world's most massive snake, the Green Anaconda, which may grow to 9m and weigh 220 kg. Apart from a few adaptations the structure of all snakes is basically the same – a limbless, cylindrical, scale covered body.

Animal locomotion is governed by Newton's third law of motion - to propel itself forward; an animal must push something backwards. In many animals limbs such as legs, fins, flippers, tails and wings are used to push against the surrounding environment of ground, air or water in order to achieve propulsion. In snakes a flexible skeleton, powerful muscles and strong scales are used to the same effect.

Read more: More than Slithering - Snake Locomotion

Manta Rays – gentle and majestic giants

NHA General - Nature Notes

Written by Nadia O’Carroll Tuesday, 12 March 2013

Manta Rays are the largest species of ray, and one of the largest living fish. The biggest specimens have a wingspan of 7 metres and can weigh over 1,300 kilos.

They have huge triangular pectoral fins which are flapped like wings to move through the water, although incredibly agile, and able to perform acrobatic breaches, flips and somersaults above the ocean surface, mantas are unable to swim backwards. To breathe they must also move constantly to keep water circulating in their 5 pairs of gill slits, these characteristics make them vulnerable to entanglement and suffocation.

Read more: Manta Rays – gentle and majestic giants

Mould – unwelcome but necessary

NHA General - Nature Notes

Written by Nadia O’Carroll Tuesday, 26 February 2013

One of the consequences of the recent wet weather is the appearance of mould. In fact mould is an ever present form of fungus; its spores are in the air and on surfaces waiting for the right conditions to germinate. The spores are microscopic eggs (3-40 microns) most float and travel great distances in the air, some species live in fresh water. The spores remain viable for decades until suitable hatching conditions are encountered. While there is variation, for many mould species ideal conditions are relative humidity above 60%, temperatures between 10-32 degrees C and pH 3-8 and when these occur and damp organic material (material that contains carbon atoms), is present the mould reproduces rapidly.

Read more: Mould – unwelcome but necessary

The End of the World Postponed – Part 2

NHA General - Nature Notes

Written by Nadia O’Carroll Tuesday, 05 February 2013

One of the most popular end of the world scenarios depicted in science fiction and Hollywood blockbusters is the impact event, when a large celestial object such as a comet, asteroid, planet or meteorite on a collision course with Earth threatens to devastate the planet. This is not pure fantasy, we are constantly bombarded from space, but fortunately there appears to be an inverse relationship between the size and frequency of impact events. Small celestial objects such as meteorites frequently collide with Earth but are either vapourised by the atmosphere or are too small to have an effect when they hit with the Earth's surface. However, when larger objects strike the planet the impact can cause abrupt, global changes that effect climate, biodiversity and even the Earth's magnetic field.

Read more: The End of the World Postponed – Part 2

The End of the World Postponed – Part 1

NHA General - Nature Notes

Written by Nadia O’Carroll Tuesday, 15 January 2013

Since time immemorial there have been predictions of Doomsday, now with instant global communication these prophecies attract international attention and have even created an end of the world industry selling trips to safe havens, bunkers, water purifiers and emergency supplies.

Apparently many end of the world events were scheduled for 2012. The most popular being on 21 December, inspired by a misinterpretation of the end of a Mayan calendar cycle. Many cataclysmic scenarios involve cosmic accidents such as collisions with rogue planets, wayward comets, reverses of Earth's rotation, polar shifts and other manifestations of cosmophobia – an irrational fear of the cosmos. Yet it is a reminder that all life on Earth is totally dependent upon the predictability of our planet's motion in relation to the universe, because this determines day, night, tides, seasons, weather, atmosphere, climate, currents, cycles etc.

Read more: The End of the World Postponed – Part 1

Clear and White

NHA General - Nature Notes

Written by Nadia O’Carroll Tuesday, 18 December 2012

In Australia Christmas occurs in midsummer and is associated with long hot days, shimmering heat, cicadas' chorus and trips to the beach, yet many of our Christmas trappings and traditions relate to frosty midwinter weather. The experience of a snowy winter is certainly entrancing with its biting, crisp air; the crunch of snow underfoot; an indescribable clear scent and the muted shades of a landscape dominated by gleaming white snow.

Ice is translucent, yet snow, which is composed of millions of ice crystals, appears white. To understand why, we have to consider light and how we perceive it.

Read more: Clear and White