As many of you know, I love elephants and I'm very lucky in that working in South East Asia for a large proportion of the year means I actually get to see rescued former-tourist ellies from my front porch.
One of its most distinguising features is an elephant's nose, but what exactly does it use it for? Well, an elephant's trunk, or it's proboscis is of vital importance to an elephant. Early biologists referred to the elephant's trunk as it's 'hand', but it is infact a tool evolved from a merging of the nose and upper lip.
Breathing & Drinking
The primary use of an elephant's trunk is for breathing and drinking - without it's trunk the elephant would be able to do neither effectively. Where drinking is concerned, the elephant is able to submerge the tip of it's trunk in water, and suck up vast amounts of liquid into it's nasal cavity. From there, the elephant squirts the water back out through the trunk into it's waiting mouth to quench it's thirst. An adult Asian elephant can store 8.5 litres of water in it's trunk at one time, and over a period of 5 minutes, can drink up to 210 litres of liquid - without it's invaluable trunk, the elephant would struggle to drink at all, replying instead on small amounts of water in it's food content.The trunk can be effectively used as a snorkel for breathing underwater, and as the majority of elephants love wallowing in pools, this is an extremely handy aspect to the trunk, and it is believed that this was perhaps the original function of the trunk prior to further evolution.
Smell
As well as for breathing and drinking, an elephant's trunk has an extremely well developed sense of smell. From being able to detect the approach of predators through their scent, or being able to avoid bush fires due to smelling smoke well in advance, the trunk's skill in detecting scents and aromas make it an incredibly useful tool for an elephant.
A 'Hand'
When eating, an elephant will use it's trunk as a hand-like tool, and with over 150,000 muscles in the trunk, which work effectively in pairs, the proboscis is highly flexible; an elephant can wrap it's trunk gently around it's food - a piece of fruit or banana plant for example - an accurately pick it up and guide it straight into it's mouth using only the trunk. The tactile nature of the trunk, and it's incredibly sensitive tip which is often referred to as a lip, means that the trunk is not only capable of carrying heavy food loads, and lifting obstacles in it's path, but also of gently retrieving food or using it to comfort it's family members.
Communication
The elephant uses it's trunk in a variety of emotional ways, and it can be used to demonstrate a range of feelings and emotions, whether directed at troop members, such as young elephant calves, or at threats. The trunk is used both in gentle caresses, particularly where offspring are where offspring are concerned, and in admonitory slaps when calves are misbehaving. By raising a trunk in a family group, an elephant can be signalling for the attention of the other troop members.
As a Warning
By beating the ground violently with the trunk, an elephant can signal to aggressors that it is angry; despite using the trunk in a threatening manner to predators and too-close humans, the trunk is never used as a weapon. A charging elephant will not use it's trunk to beat predators, instead the elephant will favour using it's forehead as a battering ram, it's tusks to stab and it's forefeet to kick and trample. Such is the value of the trunk that before charging, the elephant will tuck it backwards in an attempt to keep it well out of harms way.
Testing the Land
When an elephant feels like it is on unsteady or unfamiliar ground, individuals can also be seen to beat the earth with the outside of their trunk to test the firmness of the ground. With an African adult elephant weighing between 4000-7000kg, this ability comes in particularly useful during wet seasons, where the usually stable ground can quickly be turned into treacherous bogs in which to become stuck.
Summary
Overall, the elephant's trunk has a wide range of uses, all of which are incredibly useful to the elephant. With the first true elephant belonging to the genus Primeelephas during the Pliocine era 5 million years ago, the modern day Asian and African elephants have a trunk which is perfectly designed for their current needs and is an invaluable tool in their everyday lives.
Every Elephant Needs It's Trunk! 
You certainly come up with some great review subjects here, not only that but they are beautifully well presented and written too. R. xxx