If you were to touch one of these, you'd die," says Karl Hansen, pointing towards the inhabitants of a small glass tank. A dozen 11-year-olds gather round, craning their necks to glimpse a monstrous creature. When they see a tiny green and black frog sitting motionless on a layer of moist soil, their wide-eyed expressions turn to disbelief. Surely this minute amphibian can't be a deadly killer?
The pupils, from Park House School, Newbury, are spending the morning at the Living Rainforest. The centre is Berkshire's answer to the Amazon, and has an extensive collection of tropical plants and animals in two large glasshouses. Karl, the director, is leading the Amazing Adaptations tour, which shows how plants and animals adapt to survive in the rainforest. He explains how the poison-dart frog makes itself toxic by eating fire ants.
The competition to survive in the rainforest is ferocious.
Though tropical forests account for only 6 per cent of the Earth's surface, half of the world's life-forms live in them. Creatures that can protect themselves from attack without going hungry have a better chance of survival.
As the tour continues, the pupils meet piranhas that can eat an animal the size of a pig in minutes; a salmon-pink bird-eating spider that flicks stinging hairs from its abdomen; and a cocky turquoise basilisk lizard, also called a Jesus Christ lizard because of its ability to run across water.
Rainforests can be considered as consisting of four layers: the forest floor, the understorey, the emergent layer and the canopy. The centre's larger greenhouse, Amazonica, represents the top two layers, while the smaller Lowland Humid glasshouse recreates the darker conditions of the understorey.
Plants, like animals, have a greater chance of success if they adapt.
"Plants are really rather clever, as they adapt over time to the conditions in which they find themselves," explains Karl. "In the rainforest, they have to endure high levels of moisture and high temperatures of around 25C."
A whole range of ingenious alterations enables plants to cope with the high levels of humidity and rain. Weeping figs have small leaves with down-turned spiky tips to help rainwater quickly drip away. Other plants have roots that hang in the air, so water can easily run down each strand.
Beside a large, shallow pool, Karl encourages the children to try to sink some floating, circular plants. As they roll up their sleeves and push the fat leaves under the water, the plants bob straight back to the top. "Their leaves are covered with tiny hairs which allow them to float back to the surface," he explains.
Some plants will do anything to get more sunlight. With only 3 per cent of the sun's rays reaching the ground in tropical rainforests, plants in the lowest layers miss out.
But many epiphytes, such as orchids and bromeliads, manage to hitch a lift to the sun by climbing up other plants. Others have learned to tolerate shadier spots. Coffee, which today is mainly grown in exposed plantations, naturally grows beneath the rainforest canopy. The plants grow faster in the sunshine, but the quality isn't as good. "We sell coffee from beneath the canopy and it tastes much better," says Karl.
As the tour draws to a close, the teachers are keen to test his theory with a cappuccino. But Tilly, a toucan taken in by the centre after being mistreated by her owner, has other ideas. She repeatedly lets out such shrill shrieks from her perch beside the cafe that a quiet cuppa is impossible. She may be a long way from the Amazon but, it seems, the fight to keep the upper hand goes on.
* ON THE MAP
Admission from pounds 3.25 for groups to pounds 4.25 for adults.
The Living Rainforest, Hampsted Norreys, Berkshire RG18 0TN. Tel: 01635 202444. Email: email@example.com. www.livingrainforest.org