Adventure Ausrama Blog

Sharks may seem to be invincible, yet they have some significant weaknesses. While some dolphins succumb to their attacks, acting as a group they can kill a shark by ramming it. Sharks also have to keep moving otherwise they die. Now it has been discovered that fresh water is their enemy. They get dehydrated and cannot remain alert. Breeding is out of the question in non-salty water. A terrific battle for survival ensues as sharks continually keep sinking. The reason for this is that sharks do not have air bladders. This "device" enables fish to swim at mid-depths. Sharks use their oily livers to stay afloat - very inefficient. They have to work 50 per cent harder when they leave the sea. Freshwater species of shark have refined the evolution of their livers. The organs are flatter than their ocean cousins. There is a penalty for a flatter liver. A fatter body means a less sleek body which makes river and estuary species slower. Even with fatter live...

Bull ants do not feed during all daylight hours. Observation has shown that they feed at twilight. When the sun is brighter for longer for example in summer, or there is no cloud cover, bull ants forage for food later in the day. When the sun is darker, earlier, they search for food sooner in the day. It was believed that all insects fed according to circadian rhythms, but this does not seem to be the case. Activity in the nest was affected by cloud cover. Outside activity that involves feeding occurs at twilight. Obviously, they are feeding during these short intervals to avoid predators: most animals that eat ants would be inactive at twilight. Tests were done at ANU in Canberra. Bull ants were put in containers where diffused light was altered. It was found they only fed when the light was set at a particular low level. Evolution does take some winding paths. This shows though that evolution develops in a rational way. http://www.adventure--australia.blogspot.com/ http://www.t...